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. 2021 Jul 20;6(30):20015–20025. doi: 10.1021/acsomega.1c03053

High-Performance Perovskite Betavoltaics Employing High-Crystallinity MAPbBr3 Films

Gaocai Li †,‡, Chen Zhao †, Yang Liu †,‡, Jiwei Ren †, Ziming Zhang †, Haipeng Di †, Wei Jiang †, Jun Mei ‡,*, Yiying Zhao †,*
PMCID: PMC8340384  PMID: 34368587

Abstract

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Long-life and self-powered betavoltaic batteries are extremely attractive for many fields that require a long-term power supply, such as space exploration, polar exploration, and implantable medical technology. Organic lead halide perovskites are great potential candidate materials for betavoltaic batteries due to the large attenuation coefficient and the long carrier diffusion length, which guarantee the scale match between the penetration depth of β particles and the carrier diffusion length. However, the performance of perovskite betavoltaics is limited by the fabrication process of the thick and high-crystallinity perovskite film. In this work, we demonstrated high-performance perovskite betavoltaic cells using thick, high-quality, and wide-band-gap MAPbBr3 polycrystalline films. The solvent annealing method was adopted to improve the crystallinity and eliminate the pinholes in the MAPbBr3 film. The optimal MAPbBr3 betavoltaic cell achieved a power conversion efficiency (PCE) of 5.35% and a maximum output power of 1.203 μW under radiation of electrons of 15 keV with an equivalent activity of 253 mCi. These results are a nearly 50% improvement from previous reports. Effects of the MAPbBr3 perovskite layer thickness on the device performance were also discussed. The mechanisms of film-growth processes and device physics could provide insights for the research community of perovskites and betavoltaics.

Introduction

Betavoltaic batteries have broad applications in many fields including space exploration, polar exploration, and implantable medical devices,1−4 due to their unique features of the superlong lifetime, high energy density, and environmental stability. However, the highest overall efficiency of betavoltaic batteries is still less than 4%,5 and the maximum output power is not more than 500 μW,6 which is much lower than the theoretical predictions and hinders the potential application.

The betavoltaic battery is composed of one β-radioisotope source and one semiconductor energy conversion unit such as a Schottky or a PN junction. The key to improving the betavoltaic performance lies in the semiconductor energy conversion unit, since the option of radioisotopes is limited in several elements, including tritium (3H), nickel-63 (63Ni), and promethium-147 (147Pm), considering the requirements of the β particle energy (<100 keV) and the lifetime (>0.5 year). Researchers over the world have explored many inorganic semiconductors such as silicon,7 gallium arsenide,8 gallium nitride,9,10 silicon carbide,11 and diamond.12 In 1953, Rappaport et al. used β particles emitted from a 90Sr radioactive source to bombard a silicon PN diode, demonstrated that semiconductor devices can directly convert the energy of β particles into electrical energy, and proposed the concept of betavoltaic batteries.13 From the 1970s to the 1990s, Olsen et al. fabricated147 a Pm-based prototype battery and systematically investigated the theory of betavoltaic energy conversion, proposing that wide-band-gap semiconductor materials have higher efficiency.6,14 Thomas et al. reported a highly efficient SiC betavoltaic battery using a tritium source with a conversion efficiency of 18.6%.11 Shimaoka et al. achieved an ultrahigh conversion efficiency of 28% using a diamond p–n junction under 15 keV electron irradiation.12 The progress in betavoltaic batteries is still very slow compared with other energy conversion technologies, due to the mismatch between the penetration depth of radiation particles and the carrier diffusion length. Generally speaking, most semiconductors have a penetration depth of tens of micrometers and a carrier diffusion length less than 1 μm. The penetration depth increases with the increase of the β particle energy, while the diffusion length is limited by the crystal growth technique and the material type. It is a great challenge to find proper materials satisfying the match between the electron penetration depth and the carrier diffusion length.

One strategy to minimize the mismatch is to employ micro- and nanostructures including nanotubes,5 a pyramidal shape,15 to increase the surface area of the rectifying PN junction and the Schottky junctions. In 2003, Guo’s group demonstrated a betavoltaic battery with a power conversion efficiency (PCE) of 0.23%, consisting of a silicon PN junction with a pyramidal shape and a 63Ni source.15 Ma et al. fabricated a betavoltaic battery composed of TiO2 nanotube arrays and a 63Ni source and achieved a high PCE of 3.79% in 2018.5 However, the efficiency improvement is limited due to the degradation of the device quality. Another strategy is to employ novel materials with matched penetration depth and carrier diffusion length.16 The hybrid halide perovskites obtained are ideal material because both the carrier diffusion length of the perovskites and the electron penetration length are in the scale of a few micrometers.17 The performance of perovskite cells can also be affected by the radiation of high-energy radiation particles at appropriate energy and flux.18 Furthermore, the band gap of organic lead halide perovskite materials is continuously adjustable in the range of 1.5–3.3 eV via changing the molar ratio of iodine, bromine, and chlorine.19 Our group first demonstrated a perovskite betavoltaic consisting of the (FA0.85MA0.15)0.9Cs0.1PbI2.25Br0.45 (FAMACs) layer and achieved an efficiency of 3.56% and a maximum output power of 534 nW in 2019.17 The perovskite betavoltaics can be further improved via employing a thicker perovskite film with a wider band gap, since a 400 nm thick FAMAC layer is too thin to fully absorb the energy of β particles, and a wide band gap is preferred according to the Shockley–Queisser model.20 MAPbBr3 perovskite is one of most intensively studied materials in perovskite single crystals and thin films, due to its ease of crystallization, good grain alignment, and great crystallinity.21−30 Therefore, a MAPbBr3 film is chosen in this work as the energy conversion material in betavoltaics.

In this work, fabrication processes of a MAPbBr3 film of a few micrometers were first developed to fully utilize the energy of β particles, since the thickness of the MAPbBr3 polycrystalline film is not more than 1 μm in solar cell applications.21,24−26,31,32 A combination of the conventional spin-coating process and the solvent annealing (SA) treatment was used to fabricate high-quality MAPbBr3 polycrystalline films in a thickness range of several micrometers. MAPbBr3 perovskite devices with different film thicknesses were fabricated to investigate the effect of thickness on the performance of betavoltaic batteries from both experimental and theoretical points of view. Finally, we successfully demonstrated MAPbBr3 betavoltaic batteries with optimal efficiency of 5.35%. The efficiency is a nearly 50% improvement from previous reports,17 which is mainly attributed to the wide band gap, the great alignment of crystal grains, and the high quality of the MAPbBr3 films. The conclusions drawn from this work are inspiring for the fabrication of both high-quality thick perovskite layers and high-efficiency betavoltaic batteries.

Results and Discussion

The theoretical power conversion efficiency (PCE) of the betavoltaic device is plotted as a function of the band gap of the semiconductor material, as shown in Figure 1a, marked with the most frequently used perovskite materials.20 It can be seen that the theoretical PCE increases from 20.63 to 24.95% when using MAPbBr3 instead of the FAMACs as the semiconductor layer. The theoretical PCE of a specific device is determined by the energy deposited in the perovskite layer, which can be calculated using Geant4 Monte Carlo simulations. MAPbBr3 betavoltaic batteries in this work adopt a typical solar cell structure, as shown in Figure 1b, of Au (20 nm)/Sprio-OMeTAD (150 nm)/MAPbBr3 (variable)/TiO2/FTO glass. Ten million β particles with constant energy are set to incident perpendicularly to the perovskite betavoltaic device from the gold electrode side in the simulation. The energy deposited in each layer of the perovskite betavoltaic battery is calculated via adding the energy deposited in a unit layer of 1 nm thickness.

Figure 1.

Figure 1

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(a) Theoretical PCE of betavoltaic batteries with different band gaps (based on the SQ model).20 (b) Schematic diagram of the device structure of MAPbBr3 betavoltaic devices (left) and the trajectory diagram of β particles in MAPbBr3 simulated by Geant4 (right), where the red lines represent the trace of β particles and the yellow points represent the energy-loss position. (c) Energy deposition profiles of the MAPbBr3 betavoltaic device simulated with Geant4 software. (d) Percentages of energy deposited in the MAPbBr3 layer as a function of MAPbBr3 film thickness under radiation of β particles of 10, 15, and 20 keV. (e) Maximum percentages of total energy deposited in the MAPbBr3 layer and the corresponding minimum thickness of the MAPbBr3 layers as a function of β particle energy. Here, the results in (c–e) are obtained from the simulation results of Geant4 software. The number of β particles used in the simulation is ten million.

The energy deposition profiles of the MAPbBr3 perovskite betavoltaic batteries under the radiation of β particles of 10, 15, and 20 keV are shown in Figure 1c. It can be seen that the energy deposited in the Au electrode and the Sprio-OMeTAD layer decreases and that in the MAPbBr3 layer increases with the increase of the β particle energy, resulting from the enhanced penetration ability of β particles. This indicates that improving the β particle energy is beneficial to the effective energy deposition in perovskite betavoltaics. The energy deposition ratios in the MAPbBr3 film under radiations of β particles with different energies are plotted as a function of the film thickness in Figure 1d. As expected, the energy deposition ratio in the MAPbBr3 film first increases and then reaches a saturation value with an increase of the film thickness. The minimum thicknesses that absorb 99% β particles of 10, 15, and 20 keV are 0.7, 1.2, and 2.2 μm, respectively. The saturated energy deposition ratio and the corresponding minimum thickness are plotted as a function of β particle energy in Figure 1e. It can be seen clearly that the saturated energy ratio deposited in the MAPbBr3 film first increases with the β particle energy and then flattens out when the β particle energy is larger than 20 keV. The minimum film thickness increases with the increase of the β particle energy, resulting from the enhanced penetration depth. Therefore, we can conclude that improving the β particle energy up to 20 keV is favored to improve the effective energy deposition in perovskite betavoltaics with structures in Figure 1b. Put differently, device structures have to be designed for specific radioactive sources. Meanwhile, the fabrication of high-quality perovskite films with enough thickness is critical to realize maximum energy deposition.

To fabricate thick MAPbBr3 films, the perovskite precursor solutions are prepared in dimethyl sulfoxide (DMSO) rather than N, N-dimethylformamide (DMF), due to the larger solubility of MAPbBr3 in DMSO. MAPbBr3 films in a wide thickness range can be obtained via changing the concentration of the MAPbBr3 precursor and the spin-coating rate. The conventional process, as shown in Figure 2a,33 is first adopted to fabricate the perovskite films, where samples are annealed immediately on a hot plate right after spin-coating. However, the resulting MAPbBr3 films have many pinholes at both the film surface and the interface between the perovskite and the substrate, as shown in the top and cross-sectional scanning electron microscopy (SEM) images in Figure 2b, which are probably caused by the downward growth of crystal grains during thermal annealing.34 This phenomenon became severe in our experiments where the volume of the remaining DMSO solvents in MAPbBr3 films was much larger for its low vapor pressure. To improve the film morphology and the interface quality, a solvent annealing (SA) process is introduced before thermal annealing of the MAPbBr3 perovskite films, where the as-spin-coated films are placed in a sealed Petri dish containing the DMF solvent at room temperature for 3 min. The corresponding schematic diagram of the fabrication process is shown in Figure 2a. During solvent annealing, small MAPbBr3 crystal grains dissolve and large crystal grains grow upward, leading to compact and uniform MAPbBr3 films with fewer defects, as shown in the top and cross-sectional SEM images in Figure 2c.

Figure 2.

Figure 2

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(a) Schematic diagrams of the fabrication processes of MAPbBr3 thin films using the direct annealing (DA) method and the solvent annealing (SA) method; top-view (left) and cross-sectional (right) SEM images of the resulting samples prepared with (b) DA and (c) SA process. (d–f) Characterization of MAPbBr3 films on the TiO2/FTO substrates prepared with the DA and SA methods: (d) X-ray powder diffraction (XRD) patterns, (e) UV–vis absorption spectra (inset) and their conversion using the Tauc plot method, and (f) photoluminescence (PL) spectra and time-resolved photoluminescence (TRPL) spectra (inset).

Structure and property characterizations of MAPbBr3 polycrystalline films on the TiO2/FTO substrates prepared with the direct annealing and solvent annealing processes were conducted to investigate the effects of the annealing process, and the results are shown in Figure 2d–f. From the XRD diagrams of the MAPbBr3 films in Figure 2d, it can be seen that the diffraction peaks of both MAPbBr3 films are identical. The diffraction peaks at 15.08, 30.30, 46.08, and 62.74° correspond to the (100), (200), (300), and (400) crystal planes, respectively, indicating good alignment along the (100) direction of the MAPbBr3 crystal grains. The intensity of the main diffraction peaks of the MAPbBr3 film prepared with solvent annealing is higher than those of the direct-annealed samples, which implies better crystallinity and potentially greater carrier transport properties. There is no obvious difference between the two samples in the ultraviolet–visible light absorption spectra and the corresponding Tauc plots in Figure 2e. The band gap of the MAPbBr3 films is ∼2.31 eV, which is consistent with those of previous reports.35 From the photoluminescence (PL) spectra in Figure 2f, it can be seen that the main PL peak of the solvent-annealed MAPbBr3 film is 539 nm, which slightly blue-shifts compared with the 550 nm peak of the direct annealing sample, suggesting less near band-edge energy levels of bromine vacancies in the solvent-annealed MAPbBr3 film.36 The full width at half-maximum (FWHM) of the main PL peaks is almost the same. Moreover, the direct-annealed MAPbBr3 film has a strong PL shoulder peak at 620 nm, indicating a higher density of vacancy defects.37 The time-resolved photoluminescence (TRPL) spectra are used to investigate the effects of the annealing process on the recombination dynamics of photogenerated carriers in the MAPbBr3 films on the TiO2/FTO substrates. As shown in the inset of Figure 2f, the TRPL lifetimes of the MAPbBr3 films obtained from the biexponential fitting are 547 ns for the solvent-annealed film and 651 ns for the direct-annealed film, indicating that the solvent-annealed film has better carrier transport capacity.38 From the above characterizations, we can conclude that the solvent annealing process improves the uniformity and the crystallinity of MAPbBr3 polycrystalline films, resulting from the elimination of the vacancy defects and the pinholes in the films.

A series of MAPbBr3 films of different thicknesses were fabricated by changing the concentration of the MAPbBr3 precursor and the spin-coating rate to investigate the effects of thickness on the film quality. Figure 3a shows the photographs of MAPbBr3 polycrystalline films fabricated with different conditions. The MAPbBr3 films are uniform, transparent, and orange, indicating great crystallinity. The film thickness and roughness of these samples are measured using a laser scanning confocal microscope, as shown in Figures S1 and S2. The detailed sample number, the fabrication conditions, and the corresponding thickness and roughness can be found in Table S1. The thickness of the MAPbBr3 films varies from 0.5 to 2.2 μm, and the thickness deviation is less than 150 nm, as shown in Figure 3b. The roughness of the films increases with the film thickness from the initial 46 nm to 133 nm when the film thickness increases from 0.521 to 2.142 μm. All of the optical images in Figure S3 and the top-view SEM images of the MAPbBr3 films in Figure S4 demonstrate a similar trend where the thickness and the surface roughness increase with the film thickness. No obvious grain boundaries are observed in the SEM images of all of the MAPbBr3 films, implying fewer defects in the MAPbBr3 films prepared using the solvent annealing method. The optical micrograph and the top-view SEM image in Figure 3c–d show that even the thickest MAPbBr3 film is compact and pinhole-free. The cross-sectional SEM image of the thickest MAPbBr3 film in Figure 3e implies the intact interface contact between the MAPbBr3 film and the substrate and single MAPbBr3 grains through the whole film of 2.142 μm thickness, which perfectly explains the crystal grain alignment along the (100) direction. All of the samples of different thicknesses have similar features as shown in SEM images in Figures S4–S5. It can be concluded that MAPbBr3 films prepared using the solvent annealing method are several micrometer thick, uniform, intact, and pinhole-free.

Figure 3.

Figure 3

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(a) Photographs of MAPbBr3 films fabricated with different precursor solutions and the spin-coating rate, and the thickness increases with the increase of the sample number. (b) Thicknesses and the corresponding deviation of different MAPbBr3 films. (c) Optical micrograph, (d) top-view SEM image, and (e) cross-sectional SEM image of the MAPbBr3 film of 2.142 μm thickness.

The optical properties of MAPbBr3 films of different thicknesses are also characterized and shown in Figure 4. From the ultraviolet–visible light absorption spectra in Figure 4a, it can be seen that the absorption of the MAPbBr3 film increases with the increase of the film thickness. It also can be seen that the No. 6 film of 1.246 μm thickness is thick enough to absorb 99.9% of photons with energy exceeding 2.3 eV. Figure 4b shows the PL spectra of MAPbBr3 films of different thicknesses. Both the main PL peak position and FWHM of all of these films are independent of the film thickness, as shown in Figure 4c. The slight red shift of the PL spectra in the thicker samples is caused by the self-absorption effect of the MAPbBr3 film. Figure 4d shows the TRPL decay curves of MAPbBr3 films of different thicknesses, and the calculated PL lifetime is shown in the inset. It can be seen that when the thickness of the MAPbBr3 polycrystalline film changes, the PL lifetime varies in the range of 400–600 ns and is shorter than that of the direct-annealed MAPbBr3 films, indicating the great carrier transport capacity of the thick film. All of these properties are close to those of single crystals,39 due to the large crystal grains in the MAPbBr3 films. It can be concluded from the above characterizations that MAPbBr3 films in the thickness range of 0.5–2.2 μm prepared with the solvent annealing method are uniform and of high quality.

Figure 4.

Figure 4

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(a) UV–vis absorption spectra and (b) photoluminescence (PL) spectra of MAPbBr3 films of different thicknesses. (c) Main PL peak position and full width at half-maximum (FWHM) of MAPbBr3 films. (d) Time-resolved photoluminescence (TRPL) spectra of MAPbBr3 films of different thicknesses, and the PL lifetimes of all samples are shown in the inset.

MAPbBr3 perovskite betavoltaic batteries with different film thicknesses were fabricated with the most frequently reported device structure, shown in Figure 1b, to investigate the effects of thickness on the betavoltaic performances. The energy band diagram is shown in Figure 5a. Figure 5b displays the cross-sectional SEM image of one MAPbBr3 device, showing the structure of Au (20 nm)/Sprio-OMeTAD (150 nm)/MAPbBr3 (variable)/TiO2/FTO glass. It can be seen that a single MAPbBr3 crystal grain is present through the whole film and no pinholes at the MAPbBr3/TiO2 interface are observed, suggesting the potential good quality of MAPbBr3 devices.

Figure 5.

Figure 5

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MAPbBr3 betavoltaic device: (a) energy band diagram and (b) cross-sectional SEM image.

These MAPbBr3-betavoltaic devices were first tested under radiation of an AM 1.5G solar spectrum to evaluate the carrier transport properties. The corresponding results are shown in Figure 6. It can be seen from the current density–voltage (J–V) curves in Figure 6a that the MAPbBr3 device has obvious hysteresis, caused by ion migration that is widely reported in organic–inorganic halogen perovskite solar cells and poor charge extraction between the Spiro-OMeTAD layer and the MAPbBr3 perovskite layer due to the mismatch of energy levels.40 The external quantum efficiency (EQE) is about 85% in the spectral range from 360 to 540 nm in Figure 6b, which is consistent with those of reported MAPbBr3 solar cells.21 The parameters of solar performance are plotted as a function of MAPbBr3 film thickness, as shown in Figure 6c–f, and the specific values are listed in Table S2. The highest PCE is 8.78%, comparable with the best-reported results.21 The average open-circuit voltages (Voc) of all of the devices are between 1.3 and 1.4 V, and the average fill factor (FF) value is about 70%, as shown in Figure 6c,d, respectively. The Voc and FF of the MAPbBr3 devices are the same as those of the reported results,24,26,31,32 suggesting the good quality of these MAPbBr3 devices.

Figure 6.

Figure 6

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Solar performance of MAPbBr3 betavoltaic devices under radiation of AM 1.5G sunlight. (a) Current density–voltage characteristics and (b) EQE of perovskite betavoltaic batteries with a MAPbBr3 film of 1.246 μm thickness; photograph of the MAPbBr3 device is shown in the inset of (b). (c) Open-circuit voltage (Voc), (d) fill factor (FF), (e) short-circuit current density (Jsc), and (f) power conversion efficiency (PCE) of perovskite betavoltaic batteries as a function of the MAPbBr3 film thickness.

The Voc and FF of devices first increase with the increase of the film thickness, due to the improvement of interface contacts of the thicker MAPbBr3 film, and then slightly decrease probably due to the increased internal resistance of the corresponding devices.23 The average short-circuited current density (Jsc) in Figure 6e first increases and then decreases with the increase of the layer thickness, which can be explained by the trade-off between light absorption and the carrier collection. With the increase of the MAPbBr3 film thickness, the light absorption in the MAPbBr3 film is enhanced, and correspondingly the Jsc increases, while the collection efficiency of the photogenerated charges decreases when the film thickness is larger than the carrier diffusion length. The PCE of the MAPbBr3 devices in Figure 6f shows a similar trend as Voc, FF, and Jsc of the devices. Jsc reaches the maximum value at the thickness of 1.607 μm, while the minimum thickness to absorb the whole visible light with photon energy higher than 2.3 eV is 1.246 μm from Figure 4a. Correspondingly, we can conclude that the initial increase of Jsc caused by the enhanced light absorption and the carrier diffusion length in the MAPbBr3 film prepared using the solvent annealing method is no smaller than 1.607 μm, which is very instructive for the betavoltaic device fabrication.

The MAPbBr3 betavoltaic devices were then measured under the radiation of electrons to investigate the effects of the layer thickness on the device performance. The β radioactive isotope sources are mimicked using the electron gun of SEM KYKY-EM6200 for the capability of tunable energy and flux of electrons. The details of the mimic β source and measurement system can be found in our previous work.17 MAPbBr3 perovskite betavoltaic devices with an active layer of 1.07 μm thickness are tested under different electron energies and fluxes to verify the effectiveness of our model and our measurement system. From the I–V curves in Figure 7a, it is as expected that the short-circuit current (Isc) increases with the electron beam current, and Voc is independent of the electron beam current in the range from 1 to 2 nA, suggesting neglectable recombination current under the test conditions. The Voc of the device under electron radiation of 0.5 nA is slightly smaller than those under other electron fluxes, caused by the recombination current under the small injection condition.41 The inset of Figure 7a shows that Isc has a linear relationship with the electron beam current with a slope of 940. Considering that the energy-deposited ratio in the active layer is 59.39% (seen in Table S4), we can calculate that one incident electron of 15 keV generates at least 1583 secondary electrons in the MAPbBr3 perovskite film on average.42 The I–V curves of the same device under the 1.5 nA electron beam radiation with different accelerating voltages are shown in Figure 7b. It is similar that the Voc of the device under the electron radiation with an accelerating voltage of 10 kV is slightly smaller than those under 15 and 20 kV. Isc is proportional to the energy deposition ratio (E %) in Figure 7c. The E% in the perovskite layer is the highest under 15 kV and the PCE is also the highest, reaching 5.09%. Details of all of the device performance are listed in Table S5.

Figure 7.

Figure 7

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Device performances of MAPbBr3 betavoltaic batteries with different active layer thicknesses under radiation of mimicked β radioactive sources. I–V curves of the device with a MAPbBr3 film of 1.07 μm thickness (a) under radiation of the electron beam with an accelerating voltage of 15 kV and different electron beam currents, the inset shows the short-circuit current (Isc) is plotted as a function of the electron beam current (Ie) and (b) under radiation of an electron beam with a beam current of 1.5 nA and different accelerating voltages. (c) Isc and percentages of the energy deposited in the MAPbBr3 layer under the radiation of an electron beam with a beam current of 1.5 nA and accelerating voltages of 10, 15, and 20 kV. Isc and PCE of the devices and the percentage of electron beam energy deposition in the MAPbBr3 layer as a function of the MAPbBr3 film thickness under the radiation of an electron beam of 1.5 nA and with the accelerating voltages of (d, g) 10 kV, (e, h) 15 kV, and (f, i) 20 kV.

All of the devices were tested under the electron beam of 1.5 nA and different accelerating voltages to investigate the MAPbBr3 film thickness effect on the device performance. The specific values of betavoltaic performances are listed in Table 1, and the corresponding I–V curves are shown in Figure S7. From Table 1, it can be seen that the Voc of the MAPbBr3 betavoltaic devices first increases and then decreases with the increase of the MAPbBr3 film thickness, similar to the photovoltaic performance. But there is no obvious trend of FF on the MAPbBr3 film thickness, which could be attributed to the contact quality or radiation damage during the measurement. The Isc of MAPbBr3 betavoltaic devices, as well as the percentage of energy deposited in MAPbBr3 films, is plotted as a function of layer thickness in Figure 7d–f. The beam current is 1.5 nA and the accelerating voltages of the electron gun are 10, 15, and 20 kV. In Figure 7e, Isc of the device under radiation of 15 kV first increases and then decreases with the increase of the MAPbBr3 film thickness. The Isc of devices under the radiation of 10 and 20 keV electrons has a similar trend, as shown in Figure 7d,f, respectively. The PCE of devices shows a similar trend as Isc on the MAPbBr3 film thickness, as shown in Figure 7g–i. The optimal thickness of the MAPbBr3 film in betavoltaic devices is 0.667, 1.246, and 1.607 μm, and the corresponding PCE is 4.48, 5.35, and 3.64%, under the radiation of electrons of 10, 15, and 20 keV, respectively.

Table 1. Performance of MAPbBr3-Betavoltaic Devices with Different Film Thicknesses under Radiation of the Electron Beam of 1.5 nA with Accelerating Voltages of 10, 15, and 20 kV.

samples accelerating voltages (kV) energy-deposited ratio (%) Voc (V) Isc (nA) FF (%) PCE (%)
#1 10 45.70 1.09 1084.98 56.85 4.48
  15 41.73 1.12 946.05 48.07 2.26
  20 29.03 1.13 634.53 45.18 1.08
#2 10 47.36 1.06 1139.67 54.23 4.37
  15 48.61 1.23 1001.56 53.03 2.90
  20 35.78 1.20 885.22 49.00 1.74
#3 10 47.65 1.14 886.71 45.35 3.06
  15 51.56 1.24 1101.72 50.81 3.08
  20 39.04 1.25 938.21 51.65 2.02
#4 10 47.80 1.18 833.59 43.06 2.82
  15 55.96 1.26 1222.46 50.31 3.44
  20 44.65 1.22 1162.98 48.29 3.05
#5 10 47.82 1.23 890.76 42.93 3.14
  15 59.39 1.28 1541.22 58.06 5.09
  20 50.2 1.27 1356.46 52.60 3.02
#6 10 47.82 1.22 765.94 53.00 3.30
  15 61.28 1.32 1584.17 57.61 5.35
  20 54.74 1.31 1458.88 55.57 3.54
#7 10 47.82 1.08 566.47 55.10 2.25
  15 62.21 1.19 1108.69 57.12 3.35
  20 58.81 1.26 1453.21 51.5 3.14
#8 10 47.82 0.93 285.52 50.00 0.89
  15 62.47 1.17 1088.19 52.65 2.98
  20 61.28 1.19 1592.88 57.58 3.64
#9 10 47.82 0.91 251.05 45.66 0.70
  15 62.57 1.10 415.1 60.39 1.23
  20 63.66 1.13 697.19 52.37 1.38
#10 10 47.82 0.81 81.32 59.4 0.26
  15 62.58 0.81 413.14 40.92 0.61
  20 64.86 1.14 677.04 54.92 1.41
#11 10 47.82 0.77 106.65 38.81 0.21
  15 62.58 0.74 311.31 40.61 0.42
  20 65.62 1.11 476.18 57.09 1.01
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According to our previous trade-off model between the energy deposition ratio and the charge collection efficiency, the initial increase of Isc is due to the increased energy deposition and the roll-off of Isc is caused by the reduction of the charge collection efficiency. It is very interesting to note that the optimal thickness (0.667, 1.246, and 1.607 μm for β particles of 10, 15, and 20 keV, respectively) for the highest Isc is always slightly smaller than the minimum thickness required for energy absorption (0.7, 1.4, 1.8–1.9 μm for β particles of 10, 15, and 20 keV, respectively). The expected optimal thickness for betavoltaics is the smaller value between the carrier diffusion length and the minimum thickness required for energy deposition, which is different from the experimental results. Considering the small radiation-induced current, we speculate that the recombination current plays a significant role in betavoltaics, which strongly depends on the layer thickness.41 In conclusion, the decrease of Isc of betavoltaic devices with thicker MAPbBr3 films is caused not only by the carrier diffusion length but also by the recombination loss of carriers outside the depletion zone under the small radiation-induced current.43−45

Figure 8a shows the comparison of experimental results between MAPbBr3 and FAMAC (from ref (17)) betavoltaics under radiation of 10 keV β particles. Voc and Isc of the MAPbBr3 betavoltaics are higher than those of FAMAC betavoltaics, while the FF is much smaller than that of the FAMAC device. It is as expected that Voc of the MAPbBr3 device is higher due to its larger band gap and the FF is smaller due to the relatively poor energy level alignment. However, unexpectedly, Isc of the MAPbBr3 device is actually higher. Considering the similar energy deposition ratio in the perovskite layer, Isc of the MAPbBr3 device is supposed to be smaller due to the large band gap. The only explanation for this is the larger grain size of MAPbBr3 films and the better crystal alignment along the carrier transport direction.

Figure 8.

Figure 8

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(a) Performance of perovskite betavoltaics with different active layers under radiation of 10 keV electrons, and the data in the green box is from Song’s article.17 (b) Theoretical PCE of perovskite betavoltaics with different band gaps when the energy-deposited ratio and FF are both set as 70%. (c) Experimental and predicted betavoltaic performance of the FTO/TiO2/MAPbBr3/Spiro-OMeTAD/Au betavoltaics under radiation of e-beam: the orange box stands for the experimental value, the green box stands for the predicted value when Voc is set as 1.58 V, the purple box stands for the predicted value when FF is set as 70%, and the blue box stands for the predicted value when Voc and FF are, respectively, set as 1.58 V and 70%.

Theoretically, the PCE of betavoltaics could be calculated using the equation6,14

graphic file with name ao1c03053_m001.jpg 1

where q is the elementary charge, Voc is the open-circuit voltage, FF is the fill factor, E% is the energy-deposited ratio, and Eg is the band gap of semiconductors. For ideal perovskite betavoltaics, Voc is equal to (0.92Eg-0.16)/q,46 and the FF and E% are set as 70% (when the energy of β particles is less than 30 keV, maximum E% is close to 70%, as shown in Figure 1e). The predicted PCE is plotted as a function of band gap Eg in Figure 8b. Theoretical PCEs of FAMACs and MAPbBr3 betavoltaics are 11.73 and 12.88%, respectively. For MAPbCl3 perovskites with a band gap of 2.9 eV, the theoretical PCE of the betavoltaic is up to 13.48%.

To identify the major cause for the differences between the predicted value and the experimental results of MAPbBr3 devices with the specific structure in Figure 1b, the upper-limit PCE of betavoltaics under the radiation of β particles of 10, 15, and 20 keV is calculated using eq 1 based on experimental results, as shown in Figure 8c, and Isc is the theoretical maximum calculated from eq 1. On improving the Voc to 1.58 V (the maximum reported value of MAPbBr3 devices),26 the highest PCEs of MAPbBr3 betavoltaics under the radiation of β particles of 10, 15, and 20 keV are improved to 5.45, 7.50, and 7.49%, respectively. On improving only the FF to 70%, the corresponding PCEs are increased to 4.72, 7.61, and 6.86%, respectively. On increasing both the Voc and FF, the PCEs of the devices can be increased to 7.04, 9.11, and 9.11%, respectively. It can be concluded that Voc is the major factor limiting the MAPbBr3 betavoltaics performance in this work when the β particle energy is 10 keV, while both Voc and FF are the limiting factors when the β particle energy is 15 and 20 keV. The above calculation will be slightly larger than the experimental results, owing to the decrease of the carrier collection efficiency in devices with thicker MAPbBr3 films. Therefore, the performance of MAPbBr3 betavoltaics can be further improved via improving the Voc and the FF by virtue of adopting the hole/electron transporting layer for better energy level alignment with the MAPbBr3 layer and improving the crystallinity of the MAPbBr3 layer.

Conclusions

In this work, we have successfully demonstrated high-performance MAPbBr3 betavoltaic batteries employing thick and high-crystallinity MAPbBr3 films. By employing the solvent annealing process, the pinholes in the MAPbBr3 films and at the MAPbBr3/TiO2 interfaces are eliminated and the crystallinity is significantly improved. A series of MAPbBr3 films in the thickness range of 0.5–2.2 μm show great properties close to those of MAPbBr3 single crystals, with an impressive carrier lifetime and a carrier diffusion length. The optimal thickness of MAPbBr3 films for betavoltaic devices is 0.667, 1.246, and 1.607 μm, and the corresponding PCE is 4.48, 5.35, and 3.64%, under radiation of β particles of 10, 15, and 20 keV, respectively. The optimal thickness for betavoltaics is slightly smaller than the corresponding minimum thickness required for the energy deposition, due to the unneglectable recombination current. Under the electron radiation of 1.5 nA (the activity of 253 mCi) with an accelerating voltage of 15 kV, the maximum output power of MAPbBr3-betavoltaic devices is 1.203 μW. The efficiency is a nearly 50% improvement from previous reports. The performance of MAPbBr3 betavoltaic can be further improved via improving the interface contacts and the alignment of the energy levels of the MAPbBr3 films. In general, organic lead halide perovskite materials have good application prospects in the field of betavoltaic batteries. The film preparation method and the mechanism discussed here provide insightful guidance for the research community of perovskites and betavoltaics.

Experimental Section

Precursor Preparation

TiO2 precursors were prepared by mixing tetrabutyl titanate (250 μL, Sigma-Aldrich), hydrochloric acid (25 μL, Chron Chemicals), and absolute ethanol (3 mL, Aladdin). Further, 1.6, 2, and 3 M MAPbBr3 perovskite precursors were prepared by dissolving PbBr2 (264.22, 330.28, and 495.42 mg; 99.999%, Alfa Aesar) and CH3NH3Br (80.4, 100.5, and 150.75 mg; >99.8%, four purifications, Xi’an Polymer Light Technology Corp) in dimethyl sulfoxide (DMSO, 250 μL, Sigma-Aldrich) and dimethylformamide (DMF, 200 μL, Sigma-Aldrich), respectively. The Spiro-OMeTAD precursors consisted of a 2,2′,7,7′-tetrakis[N, N-di(4-methoxyphenyl)amino]-9,9′-spirobiflfluorene powder (Spiro-OMeTAD, 72.3 mg, Luminescence), anhydrous 4-tert-butylpyridine (28.8 μL, Sigma-Aldrich), Co(III) TFSI salt solution (60 μL, FK209 Co(III) TFSI salt (100 mg, Luminescence) in chlorobenzene (1 mL, Alfa Aesar)), Li-TFSI solution (17.5 μL, Li-TFSI (520 mg, Sigma-Aldrich) in acetonitrile (1 mL, Alfa Aesar)), and chlorobenzene (1 mL, Alfa Aesar). All chemicals are used directly without further purification.

MAPbBr3 Device Fabrication

The compact TiO2 layer was fabricated via spin-coating TiO2 precursors on FTO glass and sintered at 450 °C for 30 min to improve the crystallinity. Then, the samples were treated with oxygen plasma for 5 min and transferred to a glovebox for the preparation of the MAPbBr3 layers and the devices. The MAPbBr3 layers were deposited via spin-coating the precursors on the FTO/TiO2 substrates, and 70 μL of chlorobenzene was rapidly injected on the spinning substrate to crystallize the MAPbBr3 film. The samples were then placed in a closed container containing DMF vapor at room temperature for 3 min and annealed at 120 °C for 10 min. When the samples were fully cooled, the Spiro-OMeTAD precursors were spin-coated on these samples at 5000 rpm for 50 s. Finally, 20 nm thick Au electrodes were deposited on these samples using vacuum thermal evaporation. MAPbBr3 layers of different thicknesses were prepared via changing the concentration of the MAPbBr3 precursors (1.6, 2, and 3 M) and the spinning rate (1500, 2000, 3000, 3500, 4000, and 5000 rpm).

Materials and Device Characterization

The thickness and roughness of MAPbBr3 films were obtained using an OLS5000-EAF confocal microscope fabricated by OLYMPUS. SEM images were obtained using two scanning electron microscopes (KYKY-EM6200 and FEI Inspect). The ultraviolet–visible light absorption spectra, XRD patterns, and PL spectra of the MAPbBr3 films were obtained using Youke’s UV-1901 UV–vis spectrometer, Dandong Tongda’s TD-3000 X-ray diffractometer, and Edinburgh’s FLS 980 spectrometer, respectively. The photovoltaic performances of the devices were studied using a Newport 94123A solar simulator and a Keithley 2400 digital source meter. External quantum efficiency was obtained using Enlitech’s QE-R3011 measurement system. The betavoltaic performances of the devices were studied using a KYKY-EM6200 scanning electron microscope, a Keithley 6487 digital source meter, and LabVIEW software.

Acknowledgments

This work was supported by the Youth Innovation Research Team Project of Science and Technology Department of Sichuan Province [grant no. 2021JDTD0021] and the National Key R&D Program of China [grant no. 2018YFF01010000].

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.1c03053.

  • Fabrication parameters of MAPbBr3 films; thickness and roughness measurements of MAPbBr3 films; optical microscopy images of MAPbBr3 films; surficial and cross-sectional SEM images of MAPbBr3 films; I–V curves of MAPbBr3 betavoltaic devices under irradiation of AM 1.5G sunlight; photovoltaic performance of MAPbBr3 betavoltaic batteries under radiation of AM 1.5G sunlight; energy deposition rate of β particles in MAPbBr3 films; I–V curves of MAPbBr3 betavoltaic devices measured in the dark and under electron beam radiation; betavoltaic performance of the betavoltaic device with a MAPbBr3 film of 1.07 μm thickness under 15 keV electron beam radiation with different electron beam currents and under electron beam radiation of 1.5 nA at different accelerating voltages; and formulas used to calculate the theoretical PCE of the betavoltaic battery (PDF)

The authors declare no competing financial interest.

Supplementary Material

ao1c03053_si_001.pdf (1.2MB, pdf)

References

  1. Olsen L. C.; Seeman S. E.; Griffifin B. I. Betavoltaic Nuclear Electric Power Sources. Trans. Am. Nucl. Soc. 1969, 12, 481–482. [Google Scholar]
  2. Knight C.; Davidson J.; Behrens S. Energy Options for Wireless Sensor Nodes. Sensors 2008, 8, 8037–8066. 10.3390/s8128037. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Huffman F. N.; Norman J. C. Nuclear-Fueled Cardiac Pacemakers. Chest 1974, 65, 667–672. 10.1378/chest.65.6.667. [DOI] [PubMed] [Google Scholar]
  4. Ko W. H.; Hynecek J. Implant Evaluation of a Nuclear Power Source Betacel Battery. IEEE Trans. Biomed. Eng. 1974, 21, 238–241. 10.1109/TBME.1974.324388. [DOI] [PubMed] [Google Scholar]
  5. Ma Y.; Wang N.; Chen J.; Chen C.; San H.; Chen J.; Cheng Z. Betavoltaic Enhancement Using Defect-Engineered TiO2 Nanotube Arrays through Electrochemical Reduction in Organic Electrolytes. ACS Appl. Mater. Interfaces 2018, 10, 22174–22181. 10.1021/acsami.8b05151. [DOI] [PubMed] [Google Scholar]
  6. Olsen L. C. Betavoltaic Energy Conversion. Energy Convers. 1973, 13, 117–127. 10.1016/0013-7480(73)90010-7. [DOI] [Google Scholar]
  7. Sun W.; Kherani N. P.; Hirschman K. D.; Gadeken L. L.; Fauchet P. M. A Three-Dimensional Porous Silicon p-n Diode for Betavoltaics and Photovoltaics. Adv. Mater. 2005, 17, 1230–1233. 10.1002/adma.200401723. [DOI] [Google Scholar]
  8. Chen H.; Jiang L.; Chen X. Design Optimization of GaAs Betavoltaic Batteries. J. Phys. D: Appl. Phys. 2011, 44, 215303 10.1088/0022-3727/44/21/215303. [DOI] [Google Scholar]
  9. Kuruoğlu N. A.; Özdemir O.; Bozkurt K. Betavoltaic Study of a GaN p-i-n Structure Grown by Metal-Organic Vapour Phase Epitaxy with a Ni-63 Source. Thin Solid Films 2017, 636, 746–750. 10.1016/j.tsf.2017.07.033. [DOI] [Google Scholar]
  10. Aydin S.; Kam E. Investigation of Nickel-63 Radioisotope-Powered GaN Betavoltaic Nuclear Battery. Int. J. Energy Res. 2019, 43, 8725–8738. 10.1002/er.4871. [DOI] [Google Scholar]
  11. Thomas C.; Portnoff S.; Spencer M. G. High Efficiency 4H-SiC Betavoltaic Power Sources Using Tritium Radioisotopes. Appl. Phys. Lett. 2016, 108, 013505 10.1063/1.4939203. [DOI] [Google Scholar]
  12. Shimaoka T.; Umezawa H.; Ichikawa K.; Pernot J.; Koizumi S. Ultrahigh Conversion Efficiency of Betavoltaic Cell Using Diamond pn Junction. Appl. Phys. Lett. 2020, 117, 103902 10.1063/5.0020135. [DOI] [Google Scholar]
  13. Rappaport P. The Electron-Voltaic Effect in p-n Junctions Induced by Beta-Particle Bombardment. Phys. Rev. 1954, 93, 246–247. 10.1103/PhysRev.93.246.2. [DOI] [Google Scholar]
  14. Olsen L. C. In Review of Betavoltaic Energy Conversion, Proceedings of the 12th Space Photovoltaic Research and Technology Conference, 1993; pp 256–267.
  15. Hang G.; Lal A. In Nanopower Betavoltaic Microbatteries, 12th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS 03), 2003; pp 36–39.
  16. Prelas M. A.; Weaver C. L.; Watermann M. L.; Lukosi E. D.; Schott R. J.; Wisniewski D. A. A review of nuclear batteries. Prog. Nucl. Energy 2014, 75, 117–148. 10.1016/j.pnucene.2014.04.007. [DOI] [Google Scholar]
  17. Song Z.; Zhao C.; Liao F.; Zhao Y. Perovskite-Betavoltaic Cells: A Novel Application of Organic-Inorganic Hybrid Halide Perovskites. ACS Appl. Mater. Interfaces 2019, 11, 32969–32977. 10.1021/acsami.9b09952. [DOI] [PubMed] [Google Scholar]
  18. Durant B. K.; Afshari H.; Singh S.; Rout B.; Eperon G. E.; Sellers I. R. Tolerance of Perovskite Solar Cells to Targeted Proton Irradiation and Electronic Ionization Induced Healing. ACS Energy Lett. 2021, 6, 2362–2368. 10.1021/acsenergylett.1c00756. [DOI] [Google Scholar]
  19. Xing G.; Mathews N.; Lim S. S.; Yantara N.; Liu X.; Sabba D.; Grtzel M.; Mhaisalkar S.; Sum T. C. Low-Temperature Solution-Processed Wavelength-Tunable Perovskites for Lasing. Nat. Mater. 2014, 13, 476–480. 10.1038/nmat3911. [DOI] [PubMed] [Google Scholar]
  20. Shockley W.; Queisser H. J. Detailed Balance Limit of Efficiency of p-n Junction Solar Cells. J. Appl. Phys. 1961, 32, 510–519. 10.1063/1.1736034. [DOI] [Google Scholar]
  21. Heo J. H.; Song D. H.; Im S. H. Planar CH3NH3PbBr3 Hybrid Solar Cells with 10.4% Power Conversion Efficiency, Fabricated by Controlled Crystallization in the Spin-Coating Process. Adv. Mater. 2014, 26, 8179–8183. 10.1002/adma.201403140. [DOI] [PubMed] [Google Scholar]
  22. Wehrenfennig C.; Eperon G. E.; Johnston M. B.; Snaith H. J.; Herz L. M. High Charge Carrier Mobilities and Lifetimes in Organolead Trihalide Perovskites. Adv. Mater. 2014, 26, 1584–1589. 10.1002/adma.201305172. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Peng W.; Wang L.; Murali B.; Ho K. T.; Bera A.; Cho N.; Kang C. F.; Burlakov V. M.; Pan J.; Sinatra L.; Ma C.; Xu W.; Shi D.; Alarousu E.; Goriely A.; He J. H.; Mohammed O. F.; Wu T.; Bakr O. M. Solution-Grown Monocrystalline Hybrid Perovskite Films for Hole-Transporter-Free Solar Cells. Adv. Mater. 2016, 28, 3383–3390. 10.1002/adma.201506292. [DOI] [PubMed] [Google Scholar]
  24. Zheng X.; Chen B.; Yang M.; Wu C.; Orler B.; Moore R. B.; Zhu K.; Priya S. The Controlling Mechanism for Potential Loss in CH3NH3PbBr3 Hybrid Solar Cells. ACS Energy Lett. 2016, 1, 424–430. 10.1021/acsenergylett.6b00215. [DOI] [Google Scholar]
  25. Swain B. S.; Sheikh M. A. K.; Singh S.; Abdur R.; Jeong D.; Lee J. CH3NH3PbBr3 Nanocubes-Array for Solar Cell Application. Mater. Sci. Semicond. Process. 2018, 74, 361–368. 10.1016/j.mssp.2017.10.050. [DOI] [Google Scholar]
  26. Aranda C.; Guerrero A.; Bisquert J. Ionic Effect Enhances Light Emission and the Photovoltage of Methylammonium Lead Bromide Perovskite Solar Cells by Reduced Surface Recombination. ACS Energy Lett. 2019, 4, 741–746. 10.1021/acsenergylett.9b00186. [DOI] [Google Scholar]
  27. Di H.; Jiang W.; Sun H.; Zhao C.; Liao F.; Zhao Y. Improving the crystallinity of CH3NH4PbBr3 single crystal thin films via controlling the evaporation of methylamine. Thin Solid Films 2021, 720, 138519 10.1016/j.tsf.2021.138519. [DOI] [Google Scholar]
  28. Jiang W.; Di H.; Sun H.; Zhao C.; Liao F.; Zhao Y. Role of DMSO concentration in the crystallization process of MAPbBr3 perovskite single crystal films. J. Cryst. Growth 2020, 550, 125880 10.1016/j.jcrysgro.2020.125880. [DOI] [Google Scholar]
  29. Ding J.; Cheng X.; Jing L.; Zhou T.; Zhao Y.; Du S. Polarization-Dependent Optoelectronic Performances in Hybrid Halide Perovskite MAPbX3 (X = Br, Cl) Single-Crystal Photodetectors. ACS Appl. Mater. Interfaces 2018, 10, 845–850. 10.1021/acsami.7b13111. [DOI] [PubMed] [Google Scholar]
  30. Zhang L.; Cui S.; Guo Q.; Ge C.; Han Q.; Lin Q.; Li C.; Zheng X.; Zhai Z.; Wang L.; Sun Q.; Xu Y.; Liu Y.; Tao X. Anisotropic Performance of High-Quality MAPbBr3 Single-Crystal Wafers. ACS Appl. Mater. Interfaces 2020, 12, 51616–51627. 10.1021/acsami.0c14582. [DOI] [PubMed] [Google Scholar]
  31. Li Z.; Boix P. P.; Xing G.; Fu K.; Kulkarni S. A.; Batabyal S. K.; Xu W.; Cao A.; Sum T. C.; Mathews N.; Wong L. H. Carbon Nanotubes as an Efficient Hole Collector for High Voltage Methylammonium Lead Bromide Perovskite Solar Cells. Nanoscale 2016, 8, 6352–6360. 10.1039/C5NR06177F. [DOI] [PubMed] [Google Scholar]
  32. Giesbrecht N.; Schlipf J.; Oesinghaus L.; Binek A.; Bein T.; Müller-Buschbaum P.; Docampo P. Synthesis of Perfectly Oriented and Micrometer-Sized MAPbBr3 Perovskite Crystals for Thin-Film Photovoltaic Applications. ACS Energy Lett. 2016, 1, 150–154. 10.1021/acsenergylett.6b00050. [DOI] [Google Scholar]
  33. Xiao M.; Huang F.; Huang W.; Dkhissi Y.; Zhu Y.; Etheridge J.; Gray-Weale A.; Bach U.; Cheng Y. B.; Spiccia L. A Fast Deposition-Crystallization Procedure for Highly Efficient Lead Iodide Perovskite Thin-film Solar Cells. Angew. Chem., Int. Ed. 2014, 53, 9898–9903. 10.1002/anie.201405334. [DOI] [PubMed] [Google Scholar]
  34. Chen S.; Xiao X.; Chen B.; Kelly L. L.; Huang J.; Zhao J.; Lin Y.; Toney M. F. Crystallization in One-Step Solution Deposition of Perovskite Films: Upward or Downward?. Sci. Adv. 2021, 7, eabb2412 10.1126/sciadv.abb2412. [DOI] [PubMed] [Google Scholar]
  35. Boopathi K. M.; Martín-García B.; Ray A.; Pina J. M.; Marras S.; Saidaminov M. I.; Bonaccorso F.; Di Stasio F.; Sargent E. H.; Manna L.; Abdelhady A. L. Permanent Lattice Compression of Lead-Halide Perovskite for Persistently Enhanced Optoelectronic Properties. ACS Energy Lett. 2020, 5, 642–649. 10.1021/acsenergylett.9b02810. [DOI] [Google Scholar]
  36. Wang K. H.; Li L. C.; Shellaiah M.; Wen Sun K. Structural and Photophysical Properties of Methylammonium Lead Tribromide (MAPbBr3) Single Crystals. Sci. Rep. 2017, 7, 13643 10.1038/s41598-017-13571-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Fang Y.; Dong Q.; Shao Y.; Yuan Y.; Huang J. Highly Narrowband Perovskite Single-Crystal Photodetectors Enabled by Surface-Charge Recombination. Nat. Photonics 2015, 9, 679–686. 10.1038/nphoton.2015.156. [DOI] [Google Scholar]
  38. Sun H.; Xie D.; Song Z.; Liang C.; Xu L.; Qu X.; Yao Y.; Li D.; Zhai H.; Zheng K.; Cui C.; Zhao Y. Interface Defects Passivation and Conductivity Improvement in Planar Perovskite Solar Cells Using Na2S-Doped Compact TiO2 Electron Transport Layers. ACS Appl. Mater. Interfaces 2020, 12, 22853–22861. 10.1021/acsami.0c03180. [DOI] [PubMed] [Google Scholar]
  39. Saidaminov M. I.; Abdelhady A. L.; Murali B.; Alarousu E.; Burlakov V. M.; Peng W.; Dursun I.; Wang L.; He Y.; Maculan G.; Goriely A.; Wu T.; Mohammed O. F.; Bakr O. M. High-Quality Bulk Hybrid Perovskite Single Crystals within Minutes by Inverse Temperature Crystallization. Nat. Commun. 2015, 6, 7586 10.1038/ncomms8586. [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. Liu P.; Wang W.; Liu S.; Yang H.; Shao Z. Fundamental Understanding of Photocurrent Hysteresis in Perovskite Solar Cells. Adv. Energy Mater. 2019, 9, 1803017 10.1002/aenm.201803017. [DOI] [Google Scholar]
  41. Zhao C.; Lei L.; Liao F.; Yuan D.; Zhao Y. Efficiency prediction of planar betavoltaic batteries basing on precise modeling of semiconductor units. Appl. Phys. Lett. 2020, 117, 263901 10.1063/5.0033052. [DOI] [Google Scholar]
  42. Klein C. A. Bandgap Dependence and Related Features of Radiation Ionization Energies in Semiconductors. J. Appl. Phys. 1968, 39, 2029–2038. 10.1063/1.1656484. [DOI] [Google Scholar]
  43. Zhao C.; Liu A.; Bai S.; Zhao Y. Understanding Efficiency Differences of Betavoltaic Batteries Measured by Electron Gun Mimicked Source and Radioactive β Source. Appl. Phys. Lett. 2020, 117, 193901 10.1063/5.0028450. [DOI] [Google Scholar]
  44. Guerrero A.; Juarez-Perez E. J.; Bisquert J.; Mora-Sero I.; Garcia-Belmonte G. Electrical field profile and doping in planar lead halide perovskite solar cells. Appl. Phys. Lett. 2014, 105, 133902 10.1063/1.4896779. [DOI] [Google Scholar]
  45. Kedem N.; Brenner T. M.; Kulbak M.; Schaefer N.; Levcenko S.; Levine I.; Abou-Ras D.; Hodes G.; Cahen D. Light-Induced Increase of Electron Diffusion Length in a p-n Junction Type CH3NH3PbBr3 Perovskite Solar Cell. J. Phys. Chem. Lett. 2015, 6, 2469–2476. 10.1021/acs.jpclett.5b00889. [DOI] [PubMed] [Google Scholar]
  46. Rühle S. Tabulated Values of the Shockley–Queisser Limit for Single Junction Solar Cells. Sol. Energy 2016, 130, 139–147. 10.1016/j.solener.2016.02.015. [DOI] [Google Scholar]

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Supplementary Materials

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