Skip to main content
NCBI home page
ACS AuthorChoice logoLink to ACS AuthorChoice
. 2024 Feb 15;9(3):992–999. doi: 10.1021/acsenergylett.4c00055

Cation Influence on Hot-Carrier Relaxation in Tin Triiodide Perovskite Thin Films

Larissa J M van de Ven 1, Eelco K Tekelenburg 1, Matteo Pitaro 1, Jacopo Pinna 1, Maria A Loi 1,*
PMCID: PMC10928715  PMID: 38482183

Abstract

graphic file with name nz4c00055_0005.jpg

Slow hot-carrier cooling may potentially allow overcoming the maximum achievable power conversion efficiency of single-junction solar cells. For formamidinium tin triiodide, an exceptional slow cooling time of a few nanoseconds was reported. However, a systematic study of the cation influence, as is present for lead compounds, is lacking. Here, we report the first comparative study on formamidinium, methylammonium, and cesium tin triiodide thin films. By investigating their photoluminescence, we observe a considerable shift of the emission peak to high energy with the increase of the excited-state population, which is more prominent in the case of the two hybrid organic–inorganic perovskites (∼45 meV vs ∼15 meV at 9 × 1017 cm–3 carrier density). The hot-carrier photoluminescence of the three tin compositions decays with a 0.6–2.8 ns time constant with slower cooling observed for the two hybrids, further indicating their importance.

Due to the outstanding optoelectronic properties of metal halide perovskites, there has been a surge in research effort for their use as active materials in solar cells, leading to an unprecedented increase in power conversion efficiency from 3.8% in 2009 to 26.1% in 2023.1,2 However, the efficiency of conventional metal halide single-junction solar cells appears to be close to saturation as it is approaching the detailed balance limit.3 The rapid relaxation of above-band gap photoexcited carriers, i.e., hot carriers, via heat dissipation is a major energy loss channel in photovoltaics and largely contributes to this limit.3,4 A sufficiently retarded hot-carrier cooling time, leading to a long-lived hot-carrier population, could allow for their extraction, circumventing energy losses related to the cooling. This is the principle behind a hot-carrier solar cell that could theoretically push the power conversion efficiency limit to 66%.5 While in typical semiconductors, such as GaAs, cooling occurs within 1 ps, significantly slower cooling times have been reported for metal halide perovskites.6−12

For lead-based perovskites cooling times of several tens to several hundreds of picoseconds have been found.6−11 Furthermore, several reports on lead-based perovskites indicate that the A-site cation plays a role in the cooling dynamics.6,7,9,13 Yang et al. reported a similar cooling time constant for MAPbI3 and FAPbI3 of about 30 ps at a carrier density of ∼6 × 1018 cm–3.6 Yang et al. showed that the all-inorganic cesium-based perovskite, on the other hand, has a relaxation lifetime 10-fold faster than that of FAPbI3 (37 ps vs 305 ps after Tc = 400 K at ∼2 × 1018 cm–3).9 This is in line with the findings of Zhu et al. on lead bromide single crystals, where a similar cooling time constant of 150 ± 30 ps and 190 ± 20 ps in the initial cooling stage was found for MAPbBr3 and FAPbBr3, respectively, but no effect in CsPbBr3 was observed, suggesting that it cooled within their experimental resolution (20 ps).7 However, Hopper et al. claimed the opposite by reporting a cooling time constant of 0.8 ps for CsPbBr3 and about 0.4 ps for the hybrids at ∼2 × 1018 cm–3, with a stronger dependence of this time constant with the carrier density for CsPbBr3.13

In 2018, an exceptional slow hot-carrier cooling (a few ns) in formamidinium (HC(NH2)2+) tin triiodide (FASnI3) was reported.11 This raises the question of whether other tin triiodide perovskites also exhibit slow hot-carrier cooling and whether there is an influence on the nature of the cation. However, such a comparative study, as described above for the lead compounds, is still lacking in tin-based perovskites. Here, we aim to bridge this gap by studying cesium tin triiodide (CsSnI3) and methylammonium (CH3NH3+) tin triiodide (MASnI3) alongside FASnI3.

One of the reasons for this gap in the literature is the difficulty in producing high-quality films of the three tin compounds and the need to independently optimize each sample processing condition. Hurdles in obtaining high-quality, stable tin perovskite thin films are the low formation energies of Sn-vacancy defects and the ease of oxidation of Sn2+ to Sn4+ that result in reduced stability and a high density of background holes.14−16 The importance of the material quality lies in the fact that it has been shown to have a profound impact on the optical properties of tin metal halide perovskites, including on the relaxation time of hot carriers.6,9,17−20 It is found that hot carriers can specifically efficiently couple with defects, providing additional cooling pathways through defect states and that a higher density of “cold” background carriers may offer rapid thermalization pathways through carrier–carrier scattering.9,18−22 This is why prior to investigating the hot-carrier cooling dynamics, we present our successful efforts in improving the thin-film quality of CsSnI3 and MASnI3.

Through the use of energy-resolved and time-resolved photoluminescence (PL) spectroscopy, we show for the first time that slow hot-carrier cooling in tin perovskites is not only limited to FASnI3 but both MASnI3 and CsSnI3 exhibit the phenomenon as well. Within our described optimization of the sample quality, the two hybrids show a stronger hot-carrier contribution and a slower decay thereof with time constants of 2.0 and 2.8 ns. Importantly, this exceeds the reported necessary time of 1 ns that is expected to promote appreciable efficiency increases.23

At first, we made an effort to improve the film quality of CsSnI3 and MASnI3 to get them to a quality similar to that of our FASnI3 films. In this endeavor, we modified, among other parameters, the solvent, the antisolvent, the concentration of the solution, the deposition timing, and the annealing procedure. After each optimization step, key performance indicators comprising intense and narrow PL and a long PL lifetime were considered, since together they signify a reduced defect density.18 Minute substitution (8 mol %) of FAI by phenylethylammonium iodide (PEAI), to obtain so-called 2D/3D thin films, has been shown to lead to smoothened grain boundaries, better coverage, and extended ordering of the crystal planes, thereby suppressing trap-assisted recombination without compromising the desirable 3D perovskite properties of the thin film.24 This served as an incentive to explore the PEAI substitution for both CsSnI3 and MASnI3 prepared under the final processing conditions. The preparation details of the films made with the starting recipe (same conditions as for FASnI3),24 the improved recipe, and the 2D/3D recipe are described in the Supporting Information.

Our meticulous optimization strategy results in substantial improvement of the PL characteristics of CsSnI3, as reported in Figure 1a,b. Interestingly, by varying just the processing conditions, i.e., without any PEAI substitution, we observe an improved PL intensity and lifetime. For MASnI3 this improvement is more prominent with about a 6-fold increase in PL intensity and an increased lifetime from hundreds of picoseconds to several nanoseconds, indicating an effective suppression of trap-assisted recombination (Figures 1c and S1). In addition, the improved MASnI3 film displays smaller pinholes, smoother grain boundaries, and a reduced polydispersity of the grains, leading to smooth films (SEM in Figure 1f,g; AFM in Figure S2).

Figure 1.

Figure 1

Open in a new tab

(a) Energy-resolved PL and (b) time-resolved PL over the course of the improvements in CsSnI3, i.e., going from the starting recipe to the improved recipe to the 2D/3D recipe. (c) Overview of the improvements in integrated PL intensity and PL lifetime for CsSnI3 and MASnI3. (d–g) SEM micrographs of starting CsSnI3, 2D/3D CsSnI3, starting MASnI3, and MASnI3 with improved processing conditions on glass substrates.

By using the 2D/3D substitution method, we were able to improve the thin-film quality of FASnI3; 2D/3D FASnI3 results in an improved PL lifetime of τ = 7.5 ns at 25 nJ cm–2, a higher degree of crystallinity, and a more compact, smooth film (Figures S3 and S4). These results are in good agreement with previous work of our group.24 For both CsSnI3 and MASnI3, minute PEA substitution results in (further) smoothening of grain boundaries and better film coverage compared to the pure 3D counterpart (Figures 1d,e, S2, and S5). We note that the films in Figure 1e,g still exhibit no full coverage. This is a commonly recognized challenge—even in high-quality tin-based perovskites—that is caused by the strong Lewis acidity of Sn2+ leading to a fast, uncontrolled crystallization.25−30 We do acknowledge that full coverage is key in obtaining solar cells with low shunt resistance, and it has been achieved in a few reports;31−33 however, solar cell fabrication is not our aim.

Apart from the morphological improvements, we investigated the effects of the 2D/3D method on the crystallinity. While no improvements in the already highly crystalline MASnI3 film is obtained through PEA substitution (Figure S3), in CsSnI3 the PEA substitution results in higher crystallinity as signified by narrow XRD peaks with increased signal-to-noise ratio (Figure S6).

As a consequence, the PL lifetime improves further from τ = 1.8 ns to τ = 4.3 ns for 2D/3D CsSnI3 (Figure 1b). In addition, the CsSnI3 2D/3D film shows enhanced PL intensity with a concomitant narrowing of the PL fwhm and a small red-shift (Figure 1a), which we attribute to reduced defect and doping density, respectively.17,18,34,35 For MASnI3 on the other hand, the 2D/3D film shows a reduced PL intensity and lifetime and an increased fwhm compared to those of the 3D film with optimized processing parameters (Figures 1c and S1).

We propose that the minute substitution of PEA for MA has a nontrivial effect on the crystallization of the thin films. To further investigate this suggestion, we performed PL measurements on both the front (perovskite surface) and back (perovskite/glass interface) of all samples, as shown in Figure S7. For 2D/3D FASnI3 and 2D/3D CsSnI3, the PL signal stemming from low-dimensional perovskite phases (PEA2An–1SnnI3n+1) is only significantly detected at the back, showing that their presence is limited to the perovskite/glass interface. In contrast, for 2D/3D MASnI3 the PL signal from low-dimensional phases is detected from both sides, showing their presence throughout the bulk, which we propose to negatively impact the order of the film.

Since material quality plays a role in extending the hot-carrier cooling time, the highest quality films of all compounds, i.e., 2D/3D for FASnI3 and CsSnI3 and optimized 3D for MASnI3, are investigated in the remaining part of the study and are denoted by their chemical formula only for brevity.6,9,18,20 The optical properties and crystal structure of these films are summarized in Figure 2. Figure 2a shows the normalized photoluminescence and absorbance spectra of all three compounds. The PL peaks exhibit a progressive redshift when exchanging FA with Cs to MA (1.37 eV, 1.28 eV, and 1.25 eV, respectively). Via Tauc plots the band gaps of FASnI3, CsSnI3, and MASnI3 are estimated to be 1.38, 1.29, and 1.28 eV, respectively, meaning that all compounds exhibit small Stokes shifts (Figure S8).

Figure 2.

Figure 2

Open in a new tab

(a) Normalized photoluminescence and normalized (at 1.8 eV) absorbance spectra of FASnI3, CsSnI3, and MASnI3. (b) Representation of the cubic crystal structure of FASnI3 and MASnI3, where the organic cations are rotationally disordered and (c) of the orthorhombic crystal structure of CsSnI3. Generated from reported structures in refs (36 and 37). (d) PL lifetime and (e) XRD patterns for all three compounds. The crystal planes are indicated for the cubic Pm3̅m and orthorhombic Pnma crystal structures of the hybrid and the inorganic perovskites, respectively.

The redshift can be readily explained considering their crystal structures, as displayed in Figure 2b,c. Both FASnI3 and MASnI3 have a cubic crystal structure, where the larger ionic radius of formamidinium (1.9–2.2 Å) with respect to methylammonium (1.8 Å) extends the Sn–I bond length.37−40 This extension leads to a reduced orbital overlap at the band edges that subsequently explains the larger band gap for FASnI3. CsSnI3, on the other hand, crystallizes in an orthorhombic crystal structure as the small ionic radius of cesium (1.67 Å) induces a rotation of the Sn–I octahedra, thereby shifting the band gap to a larger value compared to MASnI3.36,40,41

The PL decay of all compounds extends to several nanoseconds (Figure 2d). While broad PL fwhm’s (>130 meV), high absorption onsets (>1.5 eV) and low carrier lifetimes (tens to hundreds of picoseconds) have been reported for these three compounds,17,42−45 our relatively long lifetimes, narrow PL (Table S1), and narrow optical band gaps, suggest a relatively low defect- and doping density17,18 and are in good agreement with results in previous works resulting in well-performing solar cells.24,30,33,46−48

Figure 2e shows the XRD patterns for all compositions. The slightly lower diffraction angles for FASnI3 compared to MASnI3 confirm the previously described longer Sn–I bond length in FASnI3, leading to a higher octahedral volume and larger lattice spacing. The narrow and intense XRD peaks show that the final films of all three compounds are highly crystalline. Moreover, the very dominant {001} peaks in the hybrid compounds and the {020} and {101} peaks in CsSnI3 indicate strong preferential growth of the perovskite with the octahedra oriented parallel with respect to the substrate.

We underline that the results presented in this work suggest a material quality of CsSnI3 and MASnI3 that are on par with FASnI3, allowing for meaningful conclusions by comparing the photophysics of these three materials.

Figure 3a,b displays normalized photoluminescence spectra under various excitation densities for FASnI3 and CsSnI3 (see Figure S10 for MASnI3). In both compounds, the PL emission peak shifts to higher energy and broadens when excited from approximately 0.22 μJ cm–2 (∼9 × 1016 cm–3 carrier density, SI note I, Figure S15) onward, resulting in an increased emission at higher energy. The increased contribution toward higher energy indicates the presence of long-lived hot carriers, i.e., prolonged presence of carriers with excess energy with respect to the band edge, such that they radiatively recombine from their higher-energy state.7,8,11,18,49 We note that this effect is dynamic and is not caused by laser-induced doping or disorder in our samples; low-fluence measurements performed on the same spot after high-fluence excitation reveal only minute changes with respect to a “fresh” low-fluence measurement (Figure S9), whereas any degradation effects are expected to lead to a permanent Burstein–Moss effect.34,35,50

Figure 3.

Figure 3

Open in a new tab

Semilog plot of fluence-dependent photoluminescence spectra of (a) FASnI3 and (b) CsSnI3. Spectra were normalized at 1.310 eV for FASnI3 and at 1.238 eV for CsSnI3. (c) The hot-carrier PL contribution as a function of the fluence and (d) extracted blueshift of the emission peak as a function of the photocarrier density n2/3 for all three compounds.

In Figure 3c we show the contribution of the hot-carrier photoluminescence to the total emission, i.e., the relative increase in PL intensity at the high-energy side when increasing the fluence. The compounds have strikingly different trends, where the hybrid perovskites have approximately double the contribution of the inorganic perovskite, illustrating the importance of the A-site cation on the hot-carrier dynamics. In addition, in Figure 3d we observe that the blueshift extracted from the fluence-dependent PL spectra is linear to the photocarrier density to the two-thirds power (n2/3) (see Figure S11 for the blueshift as a function of the fluence). This particular relationship has been attributed to a dynamic photon-induced band-filling, also called a dynamic Burstein–Moss effect.11,51,52

As the photogenerated carriers with excess energy cool via the emission of LO phonons, band-edge states gradually fill up and saturate. This inhibits other carriers at higher energy from cooling further to the band edge. The time for which the hot-carrier population is maintained depends on the electronic density of states near the band edges, the density of photogenerated carriers, and the overall photogenerated carrier lifetime. If sufficiently long, then the hot carriers residing at higher band energies recombine radiatively, emitting a higher-energy photon. In this model, increasing the photogenerated carrier density would lead to a progressively strong filling of band-edge states, resulting in a shift of the quasi-Fermi level over the band edges and thus in an effective blueshift of the optical band gap. Furthermore, from the slope of the linear fits in Figure 3d we determine the reduced effective masses to be (0.07 ± 0.01)m0 for FASnI3, (0.08 ± 0.01)m0 for MASnI3, and (0.25 ± 0.02)m0 for CsSnI3 (SI note II). These values are in line with reported calculated and experimental values that range between 0.07m0 and 0.2m0.37,38,53−56

Time-resolved photoluminescence measurements allow us to track the evolution of the hot-carrier emission after initial high-fluence excitation (2.2 μJ cm–2, ∼9 × 1017 cm–3). Figure 4a,b shows energy-dependent photoluminescence spectra normalized at the red tail, taken at different delay times after excitation for CsSnI3 and FASnI3. We observe that the emission peak shifts to lower energy and the high-energy tail reduces, rendering a more symmetrical PL profile with time. We attribute this to the relaxation of hot carriers.11,18

Figure 4.

Figure 4

Open in a new tab

Energy-dependent PL spectra at indicated times after initial 2.2 μJ cm–2 laser pulse excitation, normalized at the red tail for (a) CsSnI3 and (b) FASnI3. (c) The hot-carrier PL contribution to the overall emission as a function of time, for all three compounds.

We note that relaxation of carriers from in-band trap states as an explanation for the observed phenomena is incompatible with the higher hot-carrier PL contribution and slower cooling observed in less defective tin-based perovskites.18,20 In addition, the optical transition cross section of the trap state would have to be unusually high to cause the pronounced blueshifts. Lastly, neither a higher-energy resonance nor saturation of the trap state is observed during 24 K carrier-dependent PL measurements.11 Carrier diffusion and subsequent self-absorption cannot explain the initial blueshift (and the much more pronounced redshift over time) upon carrier-density increase and play a minor to negligible role (SI note III, Figures S16–S20).

For CsSnI3 no further spectral changes are observed after about 1500 ps, suggesting that the hot-carrier cooling extends to 1500 ps. This is further verified by a similar shape of the spectrum late in time (1800 ps) and a low fluence measurement on the same spot (Figure S12a) and by the overlap of the PL decay at different energies across the spectrum at about 1400 ps (Figure S12b). For the latter, a faster decay at the high-energy side indicates vibrational relaxation to lower-lying states, i.e., cooling, as an additional decay channel, whereas the same decay rate across the spectrum indicates solely radiative band-to-band transition.

For FASnI3 and MASnI3, the spectral evolution took a considerably longer time and, thus, was probed over a 10 ns time range. Figure 4b exhibits that FASnI3’s emission profile redshifts on a much longer time range of about 6300 ps, indicating a slower hot-carrier cooling time in comparison to CsSnI3. This is again further checked by an overlap of the PL decay curves across the spectrum at about 6000 ps (Figure S13a). By the same analysis, we find that it takes about 4000 ps for the carriers in MASnI3 to be fully cooled (Figure S14a).

To track the decay of the hot-carrier PL contribution over time, we define a fully cooled spectrum at the end of our time range as the spectrum with zero hot-carrier PL contribution and extract the relative contribution of the high-energy emission as a function of time relative to that spectrum as a fraction of the total integrated intensity. This is shown in Figure 4c for all three compounds. Here, we observe again that the hybrid perovskites have a stronger hot-carrier PL contribution, and in addition, this contribution decays slower than in CsSnI3. Through a single-exponential fit going to zero, a decay constant of τ1 = 2.8 ± 0.1 ns, τ1 = 2.0 ± 0.1 ns, and τ1 = 0.61 ± 0.02 ns is found for FASnI3, MASnI3, and CsSnI3 respectively. Interestingly, these observations of a stronger hot-carrier contribution and a slower cooling in the hybrid perovskites as compared to the fully inorganic one have similarly been found in lead-based perovskites by Zhu et al. and Yang et al.7,9

This hot-carrier cooling lifetime is on the order of the radiative recombination lifetime. If dynamic band-filling is the dominant cause for the observed phenomena, this is not surprising; hot carriers can only relax once the carrier density is sufficiently reduced through recombination such that the lower-lying energy states get depleted.49,57 However, considering the band-filling effect, the observed difference in the hot-carrier PL contribution between CsSnI3 and FASnI3, MASnI3 is of unclear origin; it has been shown that the A-site cation only indirectly, through imposed distortions on the octahedra or octahedral volume changes, influences the electronic structure, and thus, a large variation in the electronic density of states near the band edge is not expected.58

The cation influence on hot-carrier cooling in lead-based perovskites has been linked to differences in the phonon band structure of the hybrid and inorganic perovskite, e.g., the presence of an overlap of a particular LO phonon mode of the organic cation with acoustic phonon modes facilitating phonon reabsorption to reheat carriers or differences in phonon density of states resulting in variations of the phonon decay pathways.9,13 Additionally, a difference in the defect density could lead to additional relaxation pathways for the carriers and a reduced filling of the energy states in the case of the inorganic compound. Given our described successful efforts in obtaining high-quality films for all three perovskites, we believe that the difference in behavior should be attributed to the phononic properties of the different A-site cations, but future research should clarify this further.

In conclusion, we report for the first time that exceptional slow cooling of a few nanoseconds is not limited to FASnI3; other tin triiodide perovskites exhibit the phenomenon as well. This is achieved through the substantial improvements that were made in the MASnI3 and CsSnI3 film quality, such that all final ASnI3 films exhibit long carrier lifetimes, narrow PL fwhm values, and high crystalline order. Within this film optimization, in particular MASnI3 shows a similarly pronounced carrier-density-dependent hot-carrier emission that decays with τ1 ≈ 2 ns as compared to τ1 ≈ 2.8 ns for FASnI3. The hot-carrier emission in CsSnI3, on the other hand, decays faster with τ1 ≈ 0.6 ns. These results suggest a role for the organic cation in the hot-carrier cooling of tin perovskites.

Acknowledgments

The authors kindly thank A. F. Kamp and T. Zaharia for their technical support. L.J.M. acknowledges the financial support of the photophysics and optoelectronics (POE group) of the Zernike Institute of Advanced Materials and LASERLAB-EUROPE (PID: 20263). E.K.T. acknowledges the financial support of the Zernike Institute of Advanced Materials Bonus Incentive Scheme and LASERLAB-EUROPE (PID: 20263). M.P. acknowledges the financial support of the Focus Group “Next Generation Organic Photovoltaics” participating with the Dutch Institute for Fundamental Energy Research (DIFFER), both of which are part of the research programme of the Foundation for Nederlandse Wetenschappelijk Onderzoek Instituten (NWO-I), part of the Dutch Research Council (NWO). J.P. acknowledges the financial support of the project “Metamaterials for Optoelectronics (MeMOE)” (no. 17896 of the research programme Materialen NL: Challenges 2018) financed by the Dutch Research Council (NWO).

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsenergylett.4c00055.

  • Experimental details, including sample preparation, characterization settings, XRD patterns, SEM images, AFM images, and additional results of steady-state and time-resolved PL (PDF)

The authors declare no competing financial interest.

Supplementary Material

nz4c00055_si_001.pdf (35.1MB, pdf)

References

  1. Kojima A.; Teshima K.; Shirai Y.; Miyasaka T. Organometal Halide Perovskites as Visible-light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131, 6050–6051. 10.1021/ja809598r. [DOI] [PubMed] [Google Scholar]
  2. Liang Z.; Zhang Y.; Xu H.; Chen W.; Liu B.; Zhang J.; Zhang H.; Wang Z.; Kang D.-H.; Zeng J.; et al. Homogenizing out-of-plane cation composition in perovskite solar cells. Nature 2023, 624, 557–563. 10.1038/s41586-023-06784-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. 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]
  4. Li M.; Fu J.; Xu Q.; Sum T. C. Slow Hot-Carrier Cooling in Halide Perovskites: Prospects for Hot-Carrier Solar Cells. Adv. Mater. 2019, 31, 1802486 10.1002/adma.201802486. [DOI] [PubMed] [Google Scholar]
  5. Ross R. T.; Nozik A. J. Efficiency of Hot-carrier Solar Energy Converters. J. Appl. Phys. 1982, 53, 3813–3818. 10.1063/1.331124. [DOI] [Google Scholar]
  6. Yang Y.; Ostrowski D. P.; France R. M.; Zhu K.; van de Lagemaat J. V. D.; Luther J. M.; Beard M. C. Observation of a Hot-phonon Bottleneck in Lead-iodide Perovskites. Nat. Photonics 2016, 10, 53–59. 10.1038/nphoton.2015.213. [DOI] [Google Scholar]
  7. Zhu H.; Miyata K.; Fu Y.; Wang J.; Joshi P. P.; Niesner D.; Williams K. W.; Jin S.; Zhu X. Y. Screening in Crystalline Liquids Protects Energetic Carriers in Hybrid Perovskites. Science 2016, 353, 1409–1413. 10.1126/science.aaf9570. [DOI] [PubMed] [Google Scholar]
  8. Niesner D.; Zhu H.; Miyata K.; Joshi P. P.; Evans T. J.; Kudisch B. J.; Trinh M. T.; Marks M.; Zhu X. Y. Persistent Energetic Electrons in Methylammonium Lead Iodide Perovskite Thin Films. J. Am. Chem. Soc. 2016, 138, 15717–15726. 10.1021/jacs.6b08880. [DOI] [PubMed] [Google Scholar]
  9. Yang J.; Wen X.; Xia H.; Sheng R.; Ma Q.; Kim J.; Tapping P.; Harada T.; Kee T. W.; Huang F.; et al. Acoustic-optical Phonon Up-conversion and Hot-phonon bottleneck in Lead-halide Perovskites. Nat. Commun. 2017, 8, 14120 10.1038/ncomms14120. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Shen Q.; Ripolles T. S.; Even J.; Ogomi Y.; Nishinaka K.; Izuishi T.; Nakazawa N.; Zhang Y.; Ding C.; Liu F.; et al. Slow Hot-Carrier Cooling in Cesium Lead Iodide Perovskites. Appl. Phys. Lett. 2017, 111, 153903 10.1063/1.4991993. [DOI] [Google Scholar]
  11. Fang H. H.; Adjokatse S.; Shao S.; Even J.; Loi M. A. Long-lived Hot-carrier Light Emission and Large Blue Shift in Formamidinium Tin Triiodide Perovskites. Nat. Commun. 2018, 9, 243. 10.1038/s41467-017-02684-w. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Verma S. D.; Gu Q.; Sadhanala A.; Venugopalan V.; Rao A. Slow Carrier Cooling in Hybrid Pb-Sn Halide Perovskites. ACS Energy Letters 2019, 4, 736–740. 10.1021/acsenergylett.9b00251. [DOI] [Google Scholar]
  13. Hopper T. R.; Gorodetsky A.; Frost J. M.; Müller C.; Lovrincic R.; Bakulin A. A. Ultrafast Intraband Spectroscopy of Hot-Carrier Cooling in Lead-Halide Perovskites. ACS Energy Letters 2018, 3, 2199–2205. 10.1021/acsenergylett.8b01227. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Xu P.; Chen S.; Xiang H. J.; Gong X. G.; Wei S. H. Influence of Defects and Synthesis Conditions on the Photovoltaic Performance of Perovskite Semiconductor CsSnI3. Chem. Mater. 2014, 26, 6068–6072. 10.1021/cm503122j. [DOI] [Google Scholar]
  15. Shi T.; Zhang H. S.; Meng W.; Teng Q.; Liu M.; Yang X.; Yan Y.; Yip H. L.; Zhao Y. J. Effects of Organic Cations on the Defect Physics of Tin Halide Perovskites. Journal of Materials Chemistry A 2017, 5, 15124–15129. 10.1039/C7TA02662E. [DOI] [Google Scholar]
  16. Lanzetta L.; Webb T.; Zibouche N.; Liang X.; Ding D.; Min G.; Westbrook R. J.; Gaggio B.; Macdonald T. J.; Islam M. S.; et al. Degradation Mechanism of Hybrid Tin-based Perovskite Solar Cells and the Critical Role of Tin (IV) Iodide. Nat. Commun. 2021, 12, 2853. 10.1038/s41467-021-22864-z. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Milot R. L.; Klug M. T.; Davies C. L.; Wang Z.; Kraus H.; Snaith H. J.; Johnston M. B.; Herz L. M. The Effects of Doping Density and Temperature on the Optoelectronic Properties of Formamidinium Tin Triiodide Thin Films. Adv. Mater. 2018, 30, 1804506 10.1002/adma.201804506. [DOI] [PubMed] [Google Scholar]
  18. Kahmann S.; Shao S.; Loi M. A. Cooling, Scattering, and Recombination—The Role of the Material Quality for the Physics of Tin Halide Perovskites. Adv. Funct. Mater. 2019, 29, 1902963 10.1002/adfm.201902963. [DOI] [Google Scholar]
  19. Wang T.; Jin L.; Hidalgo J.; Chu W.; Snaider J. M.; Deng S.; Zhu T.; Lai B.; Prezhdo O.; Correa-Baena J.-P.; et al. Protecting hot carriers by tuning hybrid perovskite structures with alkali cations. Science Advances 2020, 6, eabb1336 10.1126/sciadv.abb1336. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Dai L.; Ye J.; Greenham N. C. Thermalization and Relaxation Mediated by Phonon Management in Tin-Lead Perovskites. Light: Science and Applications 2023, 12, 208. 10.1038/s41377-023-01236-w. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Jiang X.; Hoffman J.; Stoumpos C. C.; Kanatzidis M. G.; Harel E. Transient Sub-Band-Gap States at Grain Boundaries of CH3NH3PbI3 Perovskite Act as Fast Temperature Relaxation Centers. ACS Energy Letters 2019, 4, 1741–1747. 10.1021/acsenergylett.9b00885. [DOI] [Google Scholar]
  22. Righetto M.; Lim S. S.; Giovanni D.; Lim J. W. M.; Zhang Q.; Ramesh S.; Tay Y. K. E.; Sum T. C. Hot carriers perspective on the nature of traps in perovskites. Nat. Commun. 2020, 11, 2712. 10.1038/s41467-020-16463-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Kahmann S.; Loi M. A. Hot Carrier Solar Cells and the Potential of Perovskites for Breaking the Shockley-Queisser Limit. Journal of Materials Chemistry C 2019, 7, 2471–2486. 10.1039/C8TC04641G. [DOI] [Google Scholar]
  24. Shao S.; Liu J.; Portale G.; Fang H. H.; Blake G. R.; ten Brink G. H.; Koster L. J. A.; Loi M. A. Highly Reproducible Sn-Based Hybrid Perovskite Solar Cells with 9% Efficiency. Adv. Energy Mater. 2018, 8, 1702019 10.1002/aenm.201702019. [DOI] [Google Scholar]
  25. Dong H.; Ran C.; Gao W.; Sun N.; Liu X.; Xia Y.; Chen Y.; Huang W. Crystallization Dynamics of Sn-Based Perovskite Thin Films: Toward Efficient and Stable Photovoltaic Devices. Adv. Energy Mater. 2022, 12, 2102213 10.1002/aenm.202102213. [DOI] [Google Scholar]
  26. Hao F.; Stoumpos C. C.; Cao D. H.; Chang R. P.; Kanatzidis M. G. Lead-free Solid-state Organic-inorganic Halide Perovskite Solar Cells. Nat. Photonics 2014, 8, 489–494. 10.1038/nphoton.2014.82. [DOI] [Google Scholar]
  27. Kumar M. H.; Dharani S.; Leong W. L.; Boix P. P.; Prabhakar R. R.; Baikie T.; Shi C.; Ding H.; Ramesh R.; Asta M.; et al. Lead-free Halide Perovskite Solar Cells with High Photocurrents Realized through Vacancy Modulation. Adv. Mater. 2014, 26, 7122–7127. 10.1002/adma.201401991. [DOI] [PubMed] [Google Scholar]
  28. Marshall K. P.; Walker M.; Walton R. I.; Hatton R. A. Enhanced Stability and Efficiency in Hole-transport-layer-free CsSnI3 Perovskite Photovoltaics. Nature Energy 2016, 1, 16178 10.1038/nenergy.2016.178. [DOI] [Google Scholar]
  29. Ke W.; Stoumpos C. C.; Spanopoulos I.; Mao L.; Chen M.; Wasielewski M. R.; Kanatzidis M. G. Efficient Lead-Free Solar Cells Based on Hollow {en}MASnI3 Perovskites. J. Am. Chem. Soc. 2017, 139, 14800–14806. 10.1021/jacs.7b09018. [DOI] [PubMed] [Google Scholar]
  30. Ye T.; Wang X.; Wang K.; Ma S.; Yang D.; Hou Y.; Yoon J.; Wang K.; Priya S. Localized Electron Density Engineering for Stabilized B-γCsSnI3-Based Perovskite Solar Cells with Efficiencies > 10. ACS Energy Letters 2021, 6, 1480–1489. 10.1021/acsenergylett.1c00342. [DOI] [Google Scholar]
  31. Hao F.; Stoumpos C. C.; Guo P.; Zhou N.; Marks T. J.; Chang R. P.; Kanatzidis M. G. Solvent-Mediated Crystallization of CH3NH3SnI3 Films for Heterojunction Depleted Perovskite Solar Cells. J. Am. Chem. Soc. 2015, 137, 11445–11452. 10.1021/jacs.5b06658. [DOI] [PubMed] [Google Scholar]
  32. Song T. B.; Yokoyama T.; Stoumpos C. C.; Logsdon J.; Cao D. H.; Wasielewski M. R.; Aramaki S.; Kanatzidis M. G. Importance of Reducing Vapor Atmosphere in the Fabrication of Tin-based Perovskite Solar Cells. J. Am. Chem. Soc. 2017, 139, 836–842. 10.1021/jacs.6b10734. [DOI] [PubMed] [Google Scholar]
  33. Li F.; Zhang C.; Huang J. H.; Fan H.; Wang H.; Wang P.; Zhan C.; Liu C. M.; Li X.; Yang L. M.; et al. A Cation-Exchange Approach for the Fabrication of Efficient Methylammonium Tin Iodide Perovskite Solar Cells. Angewandte Chemie - International Edition 2019, 58, 6688–6692. 10.1002/anie.201902418. [DOI] [PubMed] [Google Scholar]
  34. Moss T. S. The Interpretation of the Properties of Indium Antimonide. Proceedings of the Physical Society. Section B 1954, 67, 775–782. 10.1088/0370-1301/67/10/306. [DOI] [Google Scholar]
  35. Burstein E. Anomalous Optical Absorption Limit in InSb. Phys. Rev. 1954, 93, 632–633. 10.1103/PhysRev.93.632. [DOI] [Google Scholar]
  36. Chung I.; Song J. H.; Im J.; Androulakis J.; Malliakas C. D.; Li H.; Freeman A. J.; Kenney J. T.; Kanatzidis M. G. CsSnI3: Semiconductor or Metal? High Electrical Conductivity and Strong Near-Infrared Photoluminescence from a Single Material. High Hole Mobility and Phase-transitions. J. Am. Chem. Soc. 2012, 134, 8579–8587. 10.1021/ja301539s. [DOI] [PubMed] [Google Scholar]
  37. Kahmann S.; Nazarenko O.; Shao S.; Hordiichuk O.; Kepenekian M.; Even J.; Kovalenko M. V.; Blake G. R.; Loi M. A. Negative Thermal Quenching in FASnI3 Perovskite Single Crystals and Thin Films. ACS Energy Letters 2020, 5, 2512–2519. 10.1021/acsenergylett.0c01166. [DOI] [Google Scholar]
  38. Mitzi D. B.; Liang K. Synthesis, Resistivity, and Thermal Properties of the Cubic Perovskite NH2CH[d1]NH2SnI3 and Related Systems. J. Solid State Chem. 1997, 134, 376–381. 10.1006/jssc.1997.7593. [DOI] [Google Scholar]
  39. Takahashi Y.; Obara R.; Lin Z. Z.; Takahashi Y.; Naito T.; Inabe T.; Ishibashi S.; Terakura K. Charge-transport in Tin-iodide Perovskite CH3NH3SnI3: Origin of High Conductivity. Dalton Transactions 2011, 40, 5563–5568. 10.1039/c0dt01601b. [DOI] [PubMed] [Google Scholar]
  40. Chen Q.; De Marco N.; Yang Y.; Song T. B.; Chen C. C.; Zhao H.; Hong Z.; Zhou H.; Yang Y. Under The Spotlight: The Organic-Inorganic Hybrid Halide Perovskite for Optoelectronic Applications. Nano Today 2015, 10, 355–396. 10.1016/j.nantod.2015.04.009. [DOI] [Google Scholar]
  41. Yamada K.; Funabiki S.; Horimoto H.; Matsui T.; Okuda T.; Ichiba S. Structural Phase Transitions of the Polymorphs of CsSnI3 by Means of Rietveld Analysis of the X-Ray Diffraction. Chem. Lett. 1991, 20, 801–804. 10.1246/cl.1991.801. [DOI] [Google Scholar]
  42. Noel N. K.; Stranks S. D.; Abate A.; Wehrenfennig C.; Guarnera S.; Haghighirad A. A.; Sadhanala A.; Eperon G. E.; Pathak S. K.; Johnston M. B.; et al. Lead-free Organic-inorganic Tin Halide Perovskites for Photovoltaic Applications. Energy Environ. Sci. 2014, 7, 3061–3068. 10.1039/C4EE01076K. [DOI] [Google Scholar]
  43. Wu B.; Zhou Y.; Xing G.; Xu Q.; Garces H. F.; Solanki A.; Goh T. W.; Padture N. P.; Sum T. C. Long Minority-Carrier Diffusion Length and Low Surface-Recombination Velocity in Inorganic Lead-Free CsSnI3 Perovskite Crystal for Solar Cells. Adv. Funct. Mater. 2017, 27, 1604818 10.1002/adfm.201604818. [DOI] [Google Scholar]
  44. Ozaki M.; Katsuki Y.; Liu J.; Handa T.; Nishikubo R.; Yakumaru S.; Hashikawa Y.; Murata Y.; Saito T.; Shimakawa Y.; et al. Solvent-coordinated Tin Halide Complexes as Purified Precursors for Tin-based Perovskites. ACS Omega 2017, 2, 7016–7021. 10.1021/acsomega.7b01292. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Song T. B.; Yokoyama T.; Logsdon J.; Wasielewski M. R.; Aramaki S.; Kanatzidis M. G. Piperazine Suppresses Self-Doping in CsSnI3 Perovskite Solar Cells. ACS Applied Energy Materials 2018, 1, 4221–4226. 10.1021/acsaem.8b00866. [DOI] [Google Scholar]
  46. Wang Y.; Tu J.; Li T.; Tao C.; Deng X.; Li Z. Convenient Preparation of CsSnI3 Quantum Dots, Excellent Stability, and the Highest Performance of Lead-free Inorganic Perovskite Solar Cells so far. Journal of Materials Chemistry A 2019, 7, 7683–7690. 10.1039/C8TA10901J. [DOI] [Google Scholar]
  47. Handa T.; Yamada T.; Kubota H.; Ise S.; Miyamoto Y.; Kanemitsu Y. Photocarrier Recombination and Injection Dynamics in Long-Term Stable Lead-Free CH3NH3SnI3 Perovskite Thin Films and Solar Cells. J. Phys. Chem. C 2017, 121, 16158–16165. 10.1021/acs.jpcc.7b06199. [DOI] [Google Scholar]
  48. Zhao Z.; Gu F.; Li Y.; Sun W.; Ye S.; Rao H.; Liu Z.; Bian Z.; Huang C. Mixed-Organic-Cation Tin Iodide for Lead-Free Perovskite Solar Cells with an Efficiency of 8.12. Advanced Science 2017, 4, 1700204 10.1002/advs.201700204. [DOI] [PMC free article] [PubMed] [Google Scholar]
  49. Cao W.; Zhang Z.; Patterson R.; Lin Y.; Wen X.; Veetil B. P.; Zhang P.; Zhang Q.; Shrestha S.; Conibeer G.; et al. Quantification of Hot Carrier Thermalization in PbS Colloidal Quantum Dots by Power and Temperature Dependent Photoluminescence Spectroscopy. RSC Adv. 2016, 6, 90846–90855. 10.1039/C6RA20165B. [DOI] [Google Scholar]
  50. Savill K. J.; Ulatowski A. M.; Herz L. M. Optoelectronic Properties of Tin-Lead Halide Perovskites. ACS Energy Letters 2021, 6, 2413–2426. 10.1021/acsenergylett.1c00776. [DOI] [PMC free article] [PubMed] [Google Scholar]
  51. Manser J. S.; Kamat P. V. Band Filling with Free Charge Carriers in Organometal Halide Perovskites. Nat. Photonics 2014, 8, 737–743. 10.1038/nphoton.2014.171. [DOI] [Google Scholar]
  52. Kamat P. V.; Dimitrijevic N. M.; Nozik A. J. Dynamic Burstein-Moss Shift in Semiconductor Colloids. J. Phys. Chem. 1989, 93, 2873–2875. 10.1021/j100345a003. [DOI] [Google Scholar]
  53. Dyksik M.; Duim H.; Zhu X.; Yang Z.; Gen M.; Kohama Y.; Adjokatse S.; Maude D. K.; Loi M. A.; Egger D. A.; et al. Broad Tunability of Carrier Effective Masses in Two-Dimensional Halide Perovskites. ACS Energy Letters 2020, 5, 3609–3616. 10.1021/acsenergylett.0c01758. [DOI] [Google Scholar]
  54. Jiang J.; Onwudinanti C. K.; Hatton R. A.; Bobbert P. A.; Tao S. Stabilizing Lead-Free All-Inorganic Tin Halide Perovskites by Ion Exchange. J. Phys. Chem. C 2018, 122, 17660–17667. 10.1021/acs.jpcc.8b04013. [DOI] [PMC free article] [PubMed] [Google Scholar]
  55. Umari P.; Mosconi E.; De Angelis F. Relativistic GW calculations on CH3NH3PbI3 and CH3NH3SnI3 Perovskites for Solar Cell Applications. Sci. Rep. 2014, 4, 4467. 10.1038/srep04467. [DOI] [PMC free article] [PubMed] [Google Scholar]
  56. Su Y.; Song K. K.; Zhong M.; Shi L. B.; Qian P. Stability and Phonon-limited Mobility for CsSnI3 and CsPbI3. J. Alloys Compd. 2021, 889, 161723 10.1016/j.jallcom.2021.161723. [DOI] [Google Scholar]
  57. Hirst L. C.; Fujii H.; Wang Y.; Sugiyama M.; Ekins-Daukes N. J. Hot Carriers in Quantum Wells for Photovoltaic Efficiency Enhancement. IEEE Journal of Photovoltaics 2014, 4, 244–252. 10.1109/JPHOTOV.2013.2289321. [DOI] [Google Scholar]
  58. Tao S.; Schmidt I.; Brocks G.; Jiang J.; Tranca I.; Meerholz K.; Olthof S. Absolute Energy Level Positions in Tin- and Lead-based Halide Perovskites. Nat. Commun. 2019, 10, 2560. 10.1038/s41467-019-10468-7. [DOI] [PMC free article] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

nz4c00055_si_001.pdf (35.1MB, pdf)

Articles from ACS Energy Letters are provided here courtesy of American Chemical Society

RESOURCES