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. 2018 Aug 1;3(8):8514–8520. doi: 10.1021/acsomega.8b01192

Exceptional Optical Absorption of Buckled Arsenene Covering a Broad Spectral Range by Molecular Doping

Minglei Sun †,‡, Jyh-Pin Chou §, Junfeng Gao ‡, Yuan Cheng ‡, Alice Hu §, Wencheng Tang †,*, Gang Zhang ‡,*
PMCID: PMC6644618  PMID: 31458980

Abstract

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Using density functional theory calculations, we demonstrate that the electronic and optical properties of a buckled arsenene monolayer can be tuned by molecular doping. Effective p-type doping of arsenene can be realized by adsorption of tetracyanoethylene and tetracyanoquinodimethane (TCNQ) molecules, while n-doped arsenene can be obtained by adsorption of tetrathiafulvalene molecules. Moreover, owing to the charge redistribution, a dipole moment is formed between each organic molecule and arsenene, and this dipole moment can significantly tune the work function of arsenene to values within a wide range of 3.99–5.57 eV. Adsorption of TCNQ molecules on pristine arsenene can significantly improve the latter’s optical absorption in a broad (visible to near-infrared) spectral range. According to the AM 1.5 solar spectrum, two-fold enhancement is attained in the efficiency of solar-energy utilization, which can lead to great opportunities for the use of TCNQ–arsenene in renewable energy. Our work clearly demonstrates the key role of molecular doping in the application of arsenene in electronic and optoelectronic components, renewable energy, and laser protection.

Introduction

Phosphorene, a monolayer composed of puckered structures of phosphorus atoms, has attracted much attention in recent years owing to its remarkable electronic,1,2 thermal,3−5 mechanical,6 and optical7 properties. Its great potential in nanoelectronics,8−10 spintronics,11 sensors,12 and energy conversion and storage13−15 has been addressed. The fascinating properties and wide application of phosphorene have driven the search for monolayers of other group V elements. Recently, Zhang et al.16 predicted a new two-dimensional (2D) semiconducting material named buckled arsenene. It is an intrinsic semiconductor with a sizable band gap16−20 and ultrahigh mobility.19,20 Its band gap (larger than 2 eV) makes it useful for transistors with a high on/off current ratio and optoelectronic devices working under blue or ultraviolet light.16 Moreover, its stability has been demonstrated by calculations of its phonon spectrum16−19 and ab initio molecular dynamics calculations.18 Very recently, Tsai et al.21 successfully synthesized multilayered arsenene nanoribbons on InAs substrates by using a plasma-assisted process. All these investigations indicate that buckled arsenene can be a promising 2D semiconducting material in various fields.

Owing to the atomic thickness and large surface-to-volume ratio of 2D materials, molecular doping has been widely adopted to enhance their conductivity, reduce their carrier-injection barrier, and control their band gap to promote their application in electronics. For example, graphene is regarded as an ideal material for hosting the molecules.22−33 By adsorbing various types of organic molecules on graphene, the type and density of charge carriers can be controlled, which is vital for different practical applications. Solís-Fernández et al.28 found that the doping of graphene can be varied from p- to n-type by gradually increasing the concentration of piperidine. Thus, p–n junctions can be formed on a graphene sheet by controlling the coverage of organic molecules. Recently, the interaction between organic molecules and 2D semiconducting materials such as MoS234−38 and black phosphorene39,40 has also been the subject of many studies. These works showed that molecular doping not only changes the electronic properties of 2D materials, but also modifies their optical34−37 and thermoelectric38 properties. For instance, Mouri et al.34 found that the photoluminescence intensity of MoS2 can be remarkably improved by chemical doping with p-type molecules.

On the basis of these developments, we expect molecular doping to be a powerful tool for tuning the electronic and optical properties of buckled arsenene. In principle, an arsenic atom in buckled arsenene forms three σ-bonds with neighboring arsenic atoms and leaves a lone pair of electrons. A previous study indicated that such lone pairs of electrons can enhance the surface interaction between black phosphorene and dopant molecules.41 Therefore, buckled arsenene is expected to be highly suitable for hosting organic molecules owing to the presence of lone pairs of electrons. However, the effects of molecular doping on the electronic and optical properties of buckled arsenene are still not well understood.

In this paper, we investigated the impact of molecular doping on the electronic and optical properties of buckled arsenene by performing first-principles calculations. We considered three representative organic molecules—tetracyanoethylene (TCNE), tetracyanoquinodimethane (TCNQ), and tetrathiafulvalene (TTF), which have been extensively investigated in organic chemistry and widely used in fabrication of electronic devices.42−47 We found that surface doping of arsenene with organic TCNE and TCNQ can lead to effective p-doping. Meanwhile, n-doped arsenene can be obtained by adsorption of TTF. For the TCNE-doping of arsenene, because the acceptor level of TCNE is just 0.082 eV above the valance band edge of arsenene, room temperature was sufficient to thermally ionize the surface dopants. We also found that beyond enhancing the electronic properties, TCNQ doubled the optical absorption ability of arsenene in the visible and near-infrared spectral regions. The effective doping and enhancement of optical absorption are expected to result in good performance of TCNQ–arsenene in both nanoelectronics and solar-energy harvesting.

Results and Discussion

Adsorption Configurations

For each molecule, we considered several adsorption configurations. To compare their stability, we calculated their adsorption energy (Ead) on arsenene as follows

graphic file with name ao-2018-01192v_m001.jpg 1

where Emolecule, Earsenene, and Emolecule+arsenene represent the energies of the dopant molecule, pristine arsenene, and molecule-doped arsenene, respectively.

We first explored the adsorption of each molecule on arsenene by identifying the most energetically favorable configurations. Various high symmetry adsorption sites for these molecules are summarized in Figure S1, and the most favorable adsorption configurations are shown in Figure 1. Adsorption on other sites is characterized by lower adsorption energy. Hereafter, all of the results and discussions are related to the most energetically favorable configurations. For the TCNE molecule, all the cyano groups align parallel to the armchair direction of arsenene, with an Ead of 0.54 eV and an adsorption height (h) of 3.23 Å. For the TCNQ molecule, the benzene ring is located right above an arsenic atom in the upper plane, allowing high doping efficiency and a rather stable structure (Ead = 0.84 eV; h = 3.31 Å). For the TTF molecule, the two C3S2 rings are also located above the arsenic atoms of arsenene. In addition, the TTF molecule bends over the arsenene sheet, resulting in an Ead of 0.84 eV and an h of 3.08 Å.

Figure 1.

Figure 1

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Top and side views of the most stable configurations of TCNE, TCNQ, and TTF molecules adsorbed on buckled arsenene. The orange and blue sticks represent the As atoms in the upper and lower planes, respectively, of arsenene. The black, red, yellow, and white spheres represent C, N, S, and H atoms, respectively.

Effects of Doping on the Electronic Structure of Arsenene

Figure 2a–c shows the isosurface of charge-density difference after the adsorption of TCNE, TCNQ, and TTF on the arsenene monolayer, respectively. The pink and white regions denote the accumulation and depletion of electrons, respectively. For the systems with adsorbed TCNE and TCNQ, the electrons are transferred from the arsenene layer to the molecules, and both the TCNE and TCNQ molecules act as electron acceptors, primarily owing to their high adiabatic electron affinity (2.884 eV for TCNE48 and 2.80 eV for TCNQ49). The electrons donated by the arsenene layer are mainly located in the cyano groups of the molecules and the interlayer region between the molecules and arsenene sheet, suggesting that the cyano groups are the electron-accepting groups. For the TTF–arsenene adsorption system, the white regions around the TTF molecule indicate that it acts as an electron donor because of its low ionization potential of 6.83 eV.50 The transferred electrons are mainly distributed in arsenic atoms in the contact region of the arsenene host layer. The more accurate Bader analysis51−53 clearly shows that 0.22, 0.20, and −0.03 electrons are transferred from the arsenene layer to TCNE, TCNQ, and TTF molecules, respectively. Therefore, the adsorption of one organic molecule (density is 1.11 × 1014 cm–2) induces carrier injection in arsenene with concentrations of 2.44 × 1013, 2.22 × 1013, and 3.33 × 1012 cm–2, respectively, which can significantly enhance the performance of arsenene in nanoelectronics. In practical application, the carrier concentration will change with adsorption density. Moreover, owing to the charge redistribution, a dipole moment forms between the organic molecule and arsenene, and it can significantly change the work function of arsenene. As shown in Figure 2d, the adsorption of acceptor molecules (TCNE or TCNQ) results in an increase in the work function: the work functions of TCNE–arsenene and TCNQ–arsenene are 5.57 and 5.40 eV, respectively. In contrast, the donor molecules (TTF) lead to a considerable reduction in the work function from that of pristine arsenene (5.16 eV) to TTF–arsenene (3.99 eV). This large tunable range of work function from 3.99 to 5.57 eV suggests the great potential of molecular doping in arsenene-based nanoelectronics. It is worth mentioning that the charge transfer is much smaller for the TTF–arsenene systems, while the change in work function is much larger than that in the TCNE–arsenene and TCNQ–arsenene systems. Actually, the relationship between change of work function and the charge transfer is not linear in most situations. This is because the change of work function not only depends on the shift of the Fermi level but also depends on the dipole moment, and the relationship between these two items and the charge transfer are nonlinear. (Please refer to the Supporting Information).

Figure 2.

Figure 2

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Isosurface of charge-density difference with an isovalue of 0.0002 e Å–3 for (a) TCNE–arsenene, (b) TCNQ–arsenene, and (c) TTF–arsenene adsorption systems. The top and side views are shown in the upper and lower panels, respectively. The blue, black, red, yellow, and white spheres represent As, C, N, S, and H atoms, respectively. The pink and white regions denote the accumulation and depletion of electrons, respectively. (d) Work functions of pristine arsenene, TCNE–arsenene, TCNQ–arsenene, and TTF–arsenene systems.

Work function is one of the critical properties that must be evaluated for the application of 2D materials in electronic devices. It is well-known that materials with low work function can potentially be applied in field-emission devices. Several strategies were employed in previous studies to decrease the work function of nanomaterials. For example, the work function of boron-doped carbon nanotubes was found to be 1.7 eV lower than that of pristine carbon nanotubes.54 The adsorption of alkali metals on carbon nanotubes55 and graphene56 was also found to significantly lower their work functions. In our study, by adsorbing the TTF molecule on the surface of buckled arsenene, the work function can be decreased by up to 1.17 eV. Moreover, this method has the advantage of not requiring the production of vacancies in the host to anchor the impurities and also avoiding the issue of clustering of alkali metal atoms. All in all, this is a feasible and controllable method for reducing the work function of arsenene.

To assess the effect of molecular doping on the electronic properties of arsenene, we calculated the projected band structure of pristine arsenene and the TCNE–arsenene, TCNQ–arsenene, and TTF–arsenene adsorption systems; the calculated structures are shown in Figure 3. It can be clearly seen that pristine arsenene is an indirect semiconductor with a band gap of 1.59 eV (Figure 3a), which is in good agreement with a previously reported result.17 Compared with pristine arsenene, a flat band, which is dominated by the lowest unoccupied molecular orbital (LUMO) of organic molecules, appears near the Fermi level in the TCNE–arsenene and TCNQ–arsenene systems (Figure 3b,c). The impurity bands are 0.041 and 0.077 eV above the Fermi level, representing the formation of acceptor states. These empty levels could accept excited electrons and produce holes in the arsenene sheet, signifying p-type doping of arsenene. For the TTF–arsenene system, we found a flat band induced by the highest occupied molecular orbital (HOMO) of the TTF molecule at 0.061 eV below the Fermi level, which suggests that donor states are formed. As a result, the adsorption of TTF on arsenene results in n-type doping behavior. Beyond the new doping level, the main features of the band structure are not changed, and the stability of arsenene remains intact without structural breakage.

Figure 3.

Figure 3

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Projected band structures of (a) pristine arsenene, (b) TCNE–arsenene, (c) TCNQ–arsenene, and (d) TTF–arsenene systems. The black and red symbols represent the contribution of the arsenene layer and organic molecules, respectively. The Fermi level was set to zero and is indicated by the black dashed line.

To gain deeper insight into the electronic properties of arsenene systems with adsorbed organic molecules, we calculated the partial charge densities of the impurity band for the TCNE–arsenene, TCNQ–arsenene, and TTF–arsenene systems; the results are shown in Figure 4. It can be seen that the impurity band of all the adsorbed systems is dominated by the organic molecules. For TCNE and TCNQ, the profiles of the partial charge densities are similar to those of their respective LUMO (Figure S2a,b). Meanwhile, for TTF, the profile of the partial charge density is quite like that of its HOMO (Figure S2c). Therefore, the excited electrons and holes are spatially separated, which leads to good characteristics for optoelectronic applications.

Figure 4.

Figure 4

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Partial charge densities of impurity band of (a) TCNE–, (b) TCNQ–, and (c) TTF–arsenene systems. The blue, black, red, yellow, and white spheres represent As, C, N, S, and H atoms, respectively. The isosurface value was set to 0.002 e Å–3.

Semiconductor p–n junctions are essential building blocks of today’s electronic and optoelectronic devices. With the rapid development of 2D materials, they are now considered as promising material candidates for post-silicon electronics. Recently, 2D-material-based p–n junctions have attracted wide interest because of their great potential in various applications such as solar cells,57,58 diodes,59,60 and photodetectors.61 To construct p–n junctions, the key is to precisely control the type of charge carriers in 2D materials as either p-type or n-type. In this work, the doping gaps for TCNE–, TCNQ–, and TTF–arsenene systems are 0.082, 0.147, and 0.655 eV, respectively. Thus, both the TCNE and TCNQ molecules can introduce shallow acceptor states in the band gap of arsenene close to the valence band edge, while the deep donor states can be introduced in the band gap after the adsorption of the TTF molecule. The DFT calculation results show that the doping gap of TCNE–arsenene is close to the thermal active energy (kBT = 0.026 eV at 300 K), which suggests that the thermal ionization of surface dopants can happen near room temperature. Moreover, the doping gap and doping concentration can be further controlled by applying an out-of-plane electric field and in-plane strain.39 Thus, the carrier type in arsenene can be effectively tuned to p-type or n-type by molecular doping, which can be used to construct arsenene p–n junctions, as revealed recently by Gao et al.62

Effect of Molecular Doping on Optical Absorption

Next, we investigated the effect of molecular doping on the optical properties of arsenene. As a benchmark, we calculated the imaginary parts of the dielectric functions for a pristine TCNQ molecule by using both Perdew–Burke–Ernzerhof (PBE) and HSE06 functionals, as shown in Figure S3. We selected the diagonal parts (εxx2) as an example. The PBE and HSE06 methods each predicted a high adsorption peak at approximately 878 and 615 nm, respectively. The results predicted by the HSE06 method are in good agreement with the available experimental data (about 580–650 nm with different cations).63 Hereafter, all the presented results were calculated using the HSE06 method. Figure 5 shows the computed results of the imaginary parts of the dielectric functions for pristine arsenene and the adsorption systems. For pristine arsenene, many absorption peaks can be found in the ultraviolet region (<400 nm), but much weaker absorption is seen in the visible region (400–700 nm), which are consistent with previous results.64,65 For the TCNE–arsenene and TTF–arsenene systems, the imaginary parts of their dielectric functions are rather similar to that of the dielectric function of pristine arsenene. Interestingly, for TCNQ–arsenene, two peaks appear in the visible region, revealing high optical absorption as a consequence of molecular doping. Although the charge transfer is similar, the band alignment of TCNE–arsenene (Figure 3b) and TCNQ–arsenene (Figure 3c) is different because the difference in the initial position of LUMO of TCNE/TCNQ. As a result, the optical absorption of TCNE–arsenene and TCNQ–arsenene is different.

Figure 5.

Figure 5

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Imaginary parts of dielectric functions of pristine arsenene and TCNE–arsenene, TCNQ–arsenene, and TTF–arsenene systems calculated by HSE06 functional.

Figure 6 shows the optical absorption spectra of the pristine arsenene and TCNQ–arsenene systems. The absorption coefficient was obtained from the following equation66

graphic file with name ao-2018-01192v_m002.jpg 2

where ε12(ω) and ε22(ω) are the real and imaginary parts, respectively, of the dielectric constant. For pristine arsenene, many absorption peaks with intensity above 1.0 × 105 cm–1 can be found in the ultraviolet region. According to the AM 1.5 solar spectrum,67 visible and near-infrared radiation accounts for most of the solar energy arriving at the surface of the earth. Therefore, a frequently employed strategy to obtain high-efficiency photovoltaic devices is to increase the optical absorption in the visible and near-infrared regions. Obviously, pristine arsenene is not a promising candidate for photovoltaics because of its poor absorption ability in the visible and near-infrared regions. Here, we propose that the adsorption of TCNQ molecule is a feasible approach to enhance the optical-absorption ability of arsenene in the major range of the solar spectrum. The absorption peaks in the ultraviolet region are reduced slightly after the adsorption of TCNQ (Figure 6), and a new absorption peak with an intensity of about 1.90 × 104 cm–1 can be found at approximately 610 nm in the visible region. In addition, the absorption spectrum of TCNQ–arsenene is much broader (in a wide range from the ultraviolet region to the near-infrared region) than that of pristine arsenene. In fact, the optical absorption spectrum of TCNQ–arsenene almost overlaps the entire incident solar spectrum, thus suggesting that this adsorption system is a highly efficient absorber of light in the visible and near-infrared range. We can quantitatively estimate the solar absorption ability (η) of a material from the following equation

graphic file with name ao-2018-01192v_m003.jpg 3

where λ is the wavelength of the incident light, a(λ) is the absorption spectrum, and S(λ) is the incident AM 1.5G solar flux. The η of TCNQ–arsenene is 27.97 W/cm3, which is about twice that of pristine arsenene (14.24 W/cm3). Thus, it can be concluded that the TCNQ–arsenene system is a high-efficiency light-absorbing material, which is promising for application in devices for harvesting of solar energy.

Figure 6.

Figure 6

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Optical-absorption coefficient of pristine arsenene and TCNQ–arsenene systems calculated by HSE06 functional. The range of light absorption by TCNQ–arsenene system overlaps the whole wavelength range of the incident AM 1.5G solar flux.

Laser technology has been widely used in both military and civilian applications. For example, a YAG laser (wavelength: 1064 nm) is used in many important applications such as material cutting68 and drug delivery.69 However, an earlier investigation showed that the picosecond pulses of Nd:YAG laser irradiation can cause ocular damage.70 The protection of humans from unwanted laser irradiation is thus very important for wide adoption of laser technology, and the search for materials that can protect them from unwanted incident laser beams is obviously the key. Pristine arsenene can be used as a protective material for laser irradiation at wavelengths below about 500 nm. On the other hand, TCNQ–arsenene offers protection from laser beams in the ultraviolet, visible, and near-infrared regions. Moreover, the absorption intensity of TCNQ–arsenene is stronger than that of pristine arsenene. For example, the TCNQ–arsenene system’s absorption intensity of laser irradiation from a YAG laser source is about eight times stronger than that of pristine arsenene. Thus, TCNQ–arsenene is also a promising protective material against unwanted laser irradiation.

Conclusions

We performed density functional theory calculations to study the effects of molecular doping on the electronic and optical properties of buckled arsenene. TCNE and TCNQ were found to be efficient p-type dopants, while TTF was found to be an n-type dopant. Our results indicate that arsenene-based p–n junctions can be manufactured by doping arsenene with these organic molecules. In addition, the adsorption of the TTF molecule can significantly reduce the work function of arsenene. Interestingly, the ability of arsenene to absorb solar energy is doubled owing to the adsorption of TCNQ molecules on its surface. Therefore, the TCNQ–arsenene system is a promising material for application in solar-energy harvesting. Our work provides a molecular-level mechanism for tuning the electronic and optical properties of arsenene and unveils its potential for application in nanoelectronics and optoelectronic devices.

Computational Details

First-principles calculations were performed by using the plane-wave-based Vienna ab initio simulation package.71 The interactions between the ions and valence electrons were treated by the projected augmented-wave method.72 We used the generalized gradient approximation with the PBE form for the exchange–correlation functional.73 Because the PBE functional is less reliable in describing the optical properties of semiconductors, the hybrid Heyd–Scuseria–Ernzerhof (HSE06) functional74 was also selected to compute the optical properties. The zero-damping vdW-D3 correction proposed by Grimme75 was used to describe the long-range interaction between organic molecules and the arsenene layer. The kinetic-energy cutoff of 400 eV and 7 × 7 × 1 Monkhorst–Pack76k-point meshes were used. We adopted a 4 × 4 × 1 supercell containing 32 As atoms to mimic the adsorption of organic molecules on the arsenene monolayer. Moreover, to avoid interactions between periodic structures, a large vacuum region of 20 Å was adopted. The geometry was optimized until the total energy converged to 10–5 eV and the forces of all atoms are smaller than 0.01 eV/Å.

Acknowledgments

This work was supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China (2016ZX04004008) and the Scientific Research Foundation of Graduate School of Southeast University (YBPY1602). It was also supported in part by a grant from the Science and Engineering Research Council (152-70-00017). The authors gratefully acknowledge the financial support from the Agency for Science, Technology and Research (A*STAR), Singapore, and the use of computing resources at the A*STAR Computational Resource Centre, Singapore. M.S. is very grateful to Dr. Qisheng Wu for many fruitful discussions. M.S. also thanks Yujing Xu for encouragement.

Supporting Information Available

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b01192.

  • Top and side views of various configurations of TCNE, TCNQ, and TTF adsorbed on buckled arsenene; partial charge densities of frontier orbitals of TCNE, TCNQ, and TTF molecules; and imaginary parts of dielectric constants of a pristine TCNQ molecule calculated by PBE and HSE06 functionals (PDF)

The authors declare no competing financial interest.

Supplementary Material

ao8b01192_si_001.pdf (626KB, pdf)

References

  1. Liu H.; Neal A. T.; Zhu Z.; Luo Z.; Xu X.; Tománek D.; Ye P. D. Phosphorene: An Unexplored 2D Semiconductor with a High Hole Mobility. ACS Nano 2014, 8, 4033–4041. 10.1021/nn501226z. [DOI] [PubMed] [Google Scholar]
  2. Qiao J.; Kong X.; Hu Z.-X.; Yang F.; Ji W. High-mobility transport anisotropy and linear dichroism in few-layer black phosphorus. Nat. Commun. 2014, 5, 4475. 10.1038/ncomms5475. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Ong Z.-Y.; Cai Y.; Zhang G.; Zhang Y.-W. Strong Thermal Transport Anisotropy and Strain Modulation in Single-Layer Phosphorene. J. Phys. Chem. C 2014, 118, 25272–25277. 10.1021/jp5079357. [DOI] [Google Scholar]
  4. Cai Y.; Ke Q.; Zhang G.; Feng Y. P.; Shenoy V. B.; Zhang Y.-W. Giant Phononic Anisotropy and Unusual Anharmonicity of Phosphorene: Interlayer Coupling and Strain Engineering. Adv. Funct. Mater. 2015, 25, 2230–2236. 10.1002/adfm.201404294. [DOI] [Google Scholar]
  5. Zhu L.; Zhang G.; Li B. Coexistence of size-dependent and size-independent thermal conductivities in phosphorene. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 90, 214302. 10.1103/physrevb.90.214302. [DOI] [Google Scholar]
  6. Jiang J.-W.; Park H. S. Negative Poisson’s ratio in single-layer black phosphorus. Nat. Commun. 2014, 5, 4727. 10.1038/ncomms5727. [DOI] [PubMed] [Google Scholar]
  7. Tran V.; Fei R.; Yang L. Quasiparticle energies, excitons, and optical spectra of few-layer black phosphorus. 2D Mater. 2015, 2, 044014. 10.1088/2053-1583/2/4/044014. [DOI] [Google Scholar]
  8. Lin Y.-C.; Dumcenco D. O.; Komsa H.-P.; Niimi Y.; Krasheninnikov A. V.; Huang Y.-S.; Suenaga K. Properties of Individual Dopant Atoms in Single-Layer MoS2: Atomic Structure, Migration, and Enhanced Reactivity. Adv. Mater. 2014, 26, 2857–2861. 10.1002/adma.201304985. [DOI] [PubMed] [Google Scholar]
  9. Du Y.; Liu H.; Deng Y.; Ye P. D. Device Perspective for Black Phosphorus Field-Effect Transistors: Contact Resistance, Ambipolar Behavior, and Scaling. ACS Nano 2014, 8, 10035–10042. 10.1021/nn502553m. [DOI] [PubMed] [Google Scholar]
  10. Prakash A.; Cai Y.; Zhang G.; Zhang Y.-W.; Ang K.-W. Black Phosphorus N-Type Field-Effect Transistor with Ultrahigh Electron Mobility via Aluminum Adatoms Doping. Small 2016, 13, 1602909. 10.1002/smll.201602909. [DOI] [PubMed] [Google Scholar]
  11. Sui X.; Si C.; Shao B.; Zou X.; Wu J.; Gu B.-L.; Duan W. Tunable Magnetism in Transition-Metal-Decorated Phosphorene. J. Phys. Chem. C 2015, 119, 10059–10063. 10.1021/jp5129468. [DOI] [Google Scholar]
  12. Cai Y.; Ke Q.; Zhang G.; Zhang Y.-W. Energetics, Charge Transfer, and Magnetism of Small Molecules Physisorbed on Phosphorene. J. Phys. Chem. C 2015, 119, 3102–3110. 10.1021/jp510863p. [DOI] [Google Scholar]
  13. Rahman M. Z.; Kwong C. W.; Davey K.; Qiao S. Z. 2D phosphorene as a water splitting photocatalyst: fundamentals to applications. Energy Environ. Sci. 2016, 9, 1513. 10.1039/c6ee90016j. [DOI] [Google Scholar]
  14. Li W.; Yang Y.; Zhang G.; Zhang Y.-W. Ultrafast and Directional Diffusion of Lithium in Phosphorene for High-Performance Lithium-Ion Battery. Nano Lett. 2015, 15, 1691–1697. 10.1021/nl504336h. [DOI] [PubMed] [Google Scholar]
  15. Zhang Y.; Sun W.; Luo Z.-Z.; Zheng Y.; Yu Z.; Zhang D.; Yang J.; Tan H. T.; Zhu J.; Wang X.; Yan Q.; Dou S. X. Functionalized few-layer black phosphorus with super-wettability towards enhanced reaction kinetics for rechargeable batteries. Nano Energy 2017, 40, 576–586. 10.1016/j.nanoen.2017.09.002. [DOI] [Google Scholar]
  16. Zhang S.; Yan Z.; Li Y.; Chen Z.; Zeng H. Atomically Thin Arsenene and Antimonene: Semimetal–Semiconductor and Indirect–Direct Band-Gap Transitions. Angew. Chem. 2015, 127, 3155–3158. 10.1002/ange.201411246. [DOI] [PubMed] [Google Scholar]
  17. Kamal C.; Ezawa M. Arsenene: Two-dimensional buckled and puckered honeycomb arsenic systems. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 91, 085423. 10.1103/physrevb.91.085423. [DOI] [Google Scholar]
  18. Kecik D.; Durgun E.; Ciraci S. Stability of single-layer and multilayer arsenene and their mechanical and electronic properties. Phys. Rev. B 2016, 94, 205409. 10.1103/physrevb.94.205409. [DOI] [Google Scholar]
  19. Zhang S.; Xie M.; Li F.; Yan Z.; Li Y.; Kan E.; Liu W.; Chen Z.; Zeng H. Semiconducting Group 15 Monolayers: A Broad Range of Band Gaps and High Carrier Mobilities. Angew. Chem. 2016, 128, 1698–1701. 10.1002/ange.201507568. [DOI] [PubMed] [Google Scholar]
  20. Wang Y.; Huang P.; Ye M.; Quhe R.; Pan Y.; Zhang H.; Zhong H.; Shi J.; Lu J. Many-body Effect, Carrier Mobility, and Device Performance of Hexagonal Arsenene and Antimonene. Chem. Mater. 2017, 29, 2191. 10.1021/acs.chemmater.6b04909. [DOI] [Google Scholar]
  21. Tsai H.-S.; Wang S.-W.; Hsiao C.-H.; Chen C.-W.; Ouyang H.; Chueh Y.-L.; Kuo H.-C.; Liang J.-H. Direct Synthesis and Practical Bandgap Estimation of Multilayer Arsenene Nanoribbons. Chem. Mater. 2016, 28, 425–429. 10.1021/acs.chemmater.5b04949. [DOI] [Google Scholar]
  22. Hong G.; Wu Q.-H.; Ren J.; Wang C.; Zhang W.; Lee S.-T. Recent progress in organic molecule/graphene interfaces. Nano Today 2013, 8, 388–402. 10.1016/j.nantod.2013.07.003. [DOI] [Google Scholar]
  23. Dong X.; Shi Y.; Zhao Y.; Chen D.; Ye J.; Yao Y.; Gao F.; Ni Z.; Yu T.; Shen Z. Symmetry breaking of graphene monolayers by molecular decoration. Phys. Rev. Lett. 2009, 102, 135501. 10.1103/physrevlett.102.135501. [DOI] [PubMed] [Google Scholar]
  24. Zhang Z.; Huang H.; Yang X.; Zang L. Tailoring Electronic Properties of Graphene by π–π Stacking with Aromatic Molecules. J. Phys. Chem. Lett. 2011, 2, 2897–2905. 10.1021/jz201273r. [DOI] [Google Scholar]
  25. Miao X.; Tongay S.; Petterson M. K.; Berke K.; Rinzler A. G.; Appleton B. R.; Hebard A. F. High Efficiency Graphene Solar Cells by Chemical Doping. Nano Lett. 2012, 12, 2745–2750. 10.1021/nl204414u. [DOI] [PubMed] [Google Scholar]
  26. Lazar P.; Karlický F.; Jurečka P.; Kocman M.; Otyepková E.; Šafářová K.; Otyepka M. Adsorption of Small Organic Molecules on Graphene. J. Am. Chem. Soc. 2013, 135, 6372–6377. 10.1021/ja403162r. [DOI] [PubMed] [Google Scholar]
  27. Néel N.; Lattelais M.; Bocquet M.-L.; Kröger J. Depopulation of Single-Phthalocyanine Molecular Orbitals upon Pyrrolic-Hydrogen Abstraction on Graphene. ACS Nano 2016, 10, 2010–2016. 10.1021/acsnano.5b06153. [DOI] [PubMed] [Google Scholar]
  28. Solís-Fernández P.; Okada S.; Sato T.; Tsuji M.; Ago H. Gate-Tunable Dirac Point of Molecular Doped Graphene. ACS Nano 2016, 10, 2930–2939. 10.1021/acsnano.6b00064. [DOI] [PubMed] [Google Scholar]
  29. Lu Y. H.; Chen W.; Feng Y. P.; He P. M. Tuning the Electronic Structure of Graphene by an Organic Molecule. J. Phys. Chem. B 2009, 113, 2–5. 10.1021/jp806905e. [DOI] [PubMed] [Google Scholar]
  30. Zhang Y.-H.; Zhou K.-Z.; Xie K.-F.; Zeng J.; Zhang H.-L.; Peng Y. Tuning the electronic structure and transport properties of graphene by noncovalent functionalization: effects of organic donor, acceptor and metal atoms. Nanotechnology 2010, 21, 065201. 10.1088/0957-4484/21/6/065201. [DOI] [PubMed] [Google Scholar]
  31. Chen L.; Wang L.; Shuai Z.; Beljonne D. Energy Level Alignment and Charge Carrier Mobility in Noncovalently Functionalized Graphene. J. Phys. Chem. Lett. 2013, 4, 2158–2165. 10.1021/jz4010174. [DOI] [Google Scholar]
  32. Hu T.; Gerber I. C. Theoretical Study of the Interaction of Electron Donor and Acceptor Molecules with Graphene. J. Phys. Chem. C 2013, 117, 2411–2420. 10.1021/jp311584r. [DOI] [Google Scholar]
  33. de Oliveira I. S. S.; Miwa R. H. Organic molecules deposited on graphene: A computational investigation of self-assembly and electronic structure. J. Chem. Phys. 2015, 142, 044301. 10.1063/1.4906435. [DOI] [PubMed] [Google Scholar]
  34. Mouri S.; Miyauchi Y.; Matsuda K. Tunable photoluminescence of monolayer MoS2 via chemical doping. Nano Lett. 2013, 13, 5944–5948. 10.1021/nl403036h. [DOI] [PubMed] [Google Scholar]
  35. Dhakal K. P.; Duong D. L.; Lee J.; Nam H.; Kim M.; Kan M.; Lee Y. H.; Kim J. Confocal absorption spectral imaging of MoS2: optical transitions depending on the atomic thickness of intrinsic and chemically doped MoS2. Nanoscale 2014, 6, 13028–13035. 10.1039/c4nr03703k. [DOI] [PubMed] [Google Scholar]
  36. Li J.; Wierzbowski J.; Ceylan Ö.; Klein J.; Nisic F.; Anh T. L.; Meggendorfer F.; Palma C.-A.; Dragonetti C.; Barth J. V.; Finley J. J.; Margapoti E. Tuning the optical emission of MoS2 nanosheets using proximal photoswitchable azobenzene molecules. Appl. Phys. Lett. 2014, 105, 241116. 10.1063/1.4904824. [DOI] [Google Scholar]
  37. Jing Y.; Tan X.; Zhou Z.; Shen P. Tuning electronic and optical properties of MoS2 monolayer via molecular charge transfer. J. Mater. Chem. A 2014, 2, 16892–16897. 10.1039/c4ta03660c. [DOI] [Google Scholar]
  38. Cai Y.; Zhou H.; Zhang G.; Zhang Y.-W. Modulating Carrier Density and Transport Properties of MoS2 by Organic Molecular Doping and Defect Engineering. Chem. Mater. 2016, 28, 8611–8621. 10.1021/acs.chemmater.6b03539. [DOI] [Google Scholar]
  39. Zhang R.; Li B.; Yang J. A First-Principles Study on Electron Donor and Acceptor Molecules Adsorbed on Phosphorene. J. Phys. Chem. C 2015, 119, 2871–2878. 10.1021/jp5116564. [DOI] [Google Scholar]
  40. Yu Z. G.; Zhang Y.-W.; Yakobson B. I. Phosphorene-based nanogenerator powered by cyclic molecular doping. Nano Energy 2016, 23, 34–39. 10.1016/j.nanoen.2016.03.010. [DOI] [Google Scholar]
  41. Shulenburger L.; Baczewski A. D.; Zhu Z.; Guan J.; Tománek D. The Nature of the Interlayer Interaction in Bulk and Few-Layer Phosphorus. Nano Lett. 2015, 15, 8170–8175. 10.1021/acs.nanolett.5b03615. [DOI] [PubMed] [Google Scholar]
  42. Miller J. S. Tetracyanoethylene (TCNE): The Characteristic Geometries and Vibrational Absorptions of Its Numerous Structures. Angew. Chem., Int. Ed. 2006, 45, 2508–2525. 10.1002/anie.200503277. [DOI] [PubMed] [Google Scholar]
  43. Torrance J. B. The difference between metallic and insulating salts of tetracyanoquinodimethone (TCNQ): how to design an organic metal. Acc. Chem. Res. 1979, 12, 79–86. 10.1021/ar50135a001. [DOI] [Google Scholar]
  44. Zhang G.; Zhang D.; Zhou Y.; Zhu D. A New Tetrathiafulvalene–Anthracence Dyad Fusion with the Crown Ether Group:  Fluorescence Modulation with Na+ and C60, Mimicking the Performance of an “AND” Logic Gate. J. Org. Chem. 2006, 71, 3970–3972. 10.1021/jo052494u. [DOI] [PubMed] [Google Scholar]
  45. Zou L.; Xu W.; Shao X.; Zhang D.; Wang Q.; Zhu D. Novel electron donors containing multi-TTF units: synthesis and electrochemical properties. Org. & Biomol. Chem. 2003, 1, 2157–2159. 10.1039/b301587d. [DOI] [PubMed] [Google Scholar]
  46. Canevet D.; Sallé M.; Zhang G.; Zhang D.; Zhu D. Tetrathiafulvalene (TTF) derivatives: key building-blocks for switchable processes. Chem. Commun. 2009, 17, 2245–2269. 10.1039/b818607n. [DOI] [PubMed] [Google Scholar]
  47. Ding H.; Li Y.; Hu H.; Sun Y.; Wang J.; Wang C.; Wang C.; Zhang G.; Wang B.; Xu W.; Zhang D. A Tetrathiafulvalene-Based Electroactive Covalent Organic Framework. Chem.—Eur. J. 2014, 20, 14614–14618. 10.1002/chem.201405330. [DOI] [PubMed] [Google Scholar]
  48. Farragher A. L.; Page F. M. Experimental determination of electron affinities. Part 11.-Electron capture by some cyanocarbons and related compounds. Trans. Faraday Soc. 1967, 63, 2369–2378. 10.1039/tf9676302369. [DOI] [Google Scholar]
  49. Klots C. E.; Compton R. N.; Raaen V. F. Electronic and ionic properties of molecular TTF and TCNQ. J. Chem. Phys. 1974, 60, 1177–1178. 10.1063/1.1681130. [DOI] [Google Scholar]
  50. Gleiter R.; Schmidt E.; Cowan D. O.; Ferraris J. P. The electronic structure of tetrathiofulvalene. J. Electron. Spectros. Relat. Phenomena 1973, 2, 207–210. 10.1016/0368-2048(73)80012-x. [DOI] [Google Scholar]
  51. Henkelman G.; Arnaldsson A.; Jónsson H. A fast and robust algorithm for Bader decomposition of charge density. Comput. Mater. Sci. 2006, 36, 354–360. 10.1016/j.commatsci.2005.04.010. [DOI] [Google Scholar]
  52. Sanville E.; Kenny S. D.; Smith R.; Henkelman G. Improved grid-based algorithm for Bader charge allocation. J. Comput. Chem. 2007, 28, 899–908. 10.1002/jcc.20575. [DOI] [PubMed] [Google Scholar]
  53. Tang W.; Sanville E.; Henkelman G. A grid-based Bader analysis algorithm without lattice bias. J. Phys.: Condens. Matter 2009, 21, 084204. 10.1088/0953-8984/21/8/084204. [DOI] [PubMed] [Google Scholar]
  54. Charlier J. C.; Terrones M.; Baxendale M.; Meunier V.; Zacharia T.; Rupesinghe N. L.; Hsu W. K.; Grobert N.; Terrones H.; Amaratunga G. A. J. Enhanced Electron Field Emission in B-doped Carbon Nanotubes. Nano Lett. 2002, 2, 1191–1195. 10.1021/nl0256457. [DOI] [Google Scholar]
  55. Zhao J.; Han J.; Lu J. P. Work functions of pristine and alkali-metal intercalated carbon nanotubes and bundles. Phys. Rev. B: Condens. Matter Mater. Phys. 2002, 65, 193401. 10.1103/physrevb.65.193401. [DOI] [Google Scholar]
  56. Chan K. T.; Neaton J.; Cohen M. L. First-principles study of metal adatom adsorption on graphene. Phys. Rev. B: Condens. Matter Mater. Phys. 2008, 77, 235430. 10.1103/physrevb.77.235430. [DOI] [Google Scholar]
  57. Li X.; Fan L.; Li Z.; Wang K.; Zhong M.; Wei J.; Wu D.; Zhu H. Boron Doping of Graphene for Graphene–Silicon p–n Junction Solar Cells. Adv. Energy Mater. 2012, 2, 425–429. 10.1002/aenm.201100671. [DOI] [Google Scholar]
  58. Tsai M.-L.; Su S.-H.; Chang J.-K.; Tsai D.-S.; Chen C.-H.; Wu C.-I.; Li L.-J.; Chen L.-J.; He J.-H. Monolayer MoS2 Heterojunction Solar Cells. ACS Nano 2014, 8, 8317–8322. 10.1021/nn502776h. [DOI] [PubMed] [Google Scholar]
  59. Cheng R.; Li D.; Zhou H.; Wang C.; Yin A.; Jiang S.; Liu Y.; Chen Y.; Huang Y.; Duan X. Electroluminescence and Photocurrent Generation from Atomically Sharp WSe2/MoS2 Heterojunction p–n Diodes. Nano Lett. 2014, 14, 5590–5597. 10.1021/nl502075n. [DOI] [PMC free article] [PubMed] [Google Scholar]
  60. Jeon P. J.; Lee Y. T.; Lim J. Y.; Kim J. S.; Hwang D. K.; Im S. Black Phosphorus–Zinc Oxide Nanomaterial Heterojunction for p–n Diode and Junction Field-Effect Transistor. Nano Lett. 2016, 16, 1293–1298. 10.1021/acs.nanolett.5b04664. [DOI] [PubMed] [Google Scholar]
  61. Xu Z.-Q.; Wang Y.; Wang Z.; Shen Y.; Huang W.; Xia X.; Yu W.; Xue Y.; Sun L.; Zheng C.; Lu Y.; Liao L.; Bao Q. L. Atomically thin lateral p–n junction photodetector with large effective detection area. 2D Mater. 2016, 3, 041001. 10.1088/2053-1583/3/4/041001. [DOI] [Google Scholar]
  62. Gao N.; Zhu Y. F.; Jiang Q. Formation of arsenene p-n junctions via organic molecular adsorption. J. Mater. Chem. C 2017, 5, 7283–7290. 10.1039/c7tc01972f. [DOI] [Google Scholar]
  63. Iida Y. Electronic Spectra of Crystalline TCNQ Anion Radical Salts. II. Complex Salts. Chem. Soc. Jpn 1969, 42, 637–643. 10.1246/bcsj.42.637. [DOI] [Google Scholar]
  64. Kecik D.; Durgun E.; Ciraci S. Optical properties of single-layer and bilayer arsenene phases. Phys. Rev. B 2016, 94, 205410. 10.1103/physrevb.94.205410. [DOI] [Google Scholar]
  65. Xu Y.; Peng B.; Zhang H.; Shao H.; Zhang R.; Zhu H. First-principle calculations of optical properties of monolayer arsenene and antimonene allotropes. Ann. Phys. 2017, 529, 1600152. 10.1002/andp.201600152. [DOI] [Google Scholar]
  66. Guan Z.; Lian C.-S.; Hu S.; Ni S.; Li J.; Duan W. Tunable Structural, Electronic, and Optical Properties of Layered Two-Dimensional C2N and MoS2 van der Waals Heterostructure as Photovoltaic Material. J. Phys. Chem. C 2017, 121, 3654–3660. 10.1021/acs.jpcc.6b12681. [DOI] [Google Scholar]
  67. Reference Solar Spectral Irradiance: Air Mass 1.5, http://rredc.nrel.gov/solar/spectra/am1.5.
  68. Sharma A.; Yadava V. Experimental analysis of Nd-YAG laser cutting of sheet materials – A review. Opt. Laser Technol. 2018, 98, 264–280. 10.1016/j.optlastec.2017.08.002. [DOI] [Google Scholar]
  69. Sklar L. R.; Burnett C. T.; Waibel J. S.; Moy R. L.; Ozog D. M. Laser assisted drug delivery: A review of an evolving technology. Lasers Surg. Med. 2014, 46, 249–262. 10.1002/lsm.22227. [DOI] [PubMed] [Google Scholar]
  70. Ham W. T.; Mueller H. A.; Goldman A. I.; Newnam B. E.; Holland L. M.; Kuwabara T. Ocular Hazard from Picosecond Pulses of Nd: YAG Laser Radiation. Science 1974, 185, 362–363. 10.1126/science.185.4148.362. [DOI] [PubMed] [Google Scholar]
  71. Kresse G.; Furthmüller J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 1996, 6, 15–50. 10.1016/0927-0256(96)00008-0. [DOI] [PubMed] [Google Scholar]
  72. Kresse G.; Joubert D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B: Condens. Matter Mater. Phys. 1999, 59, 1758–1775. 10.1103/physrevb.59.1758. [DOI] [Google Scholar]
  73. Perdew J. P.; Burke K.; Ernzerhof M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865–3868. 10.1103/physrevlett.77.3865. [DOI] [PubMed] [Google Scholar]
  74. Heyd J.; Scuseria G. E.; Ernzerhof M. Hybrid functionals based on a screened Coulomb potential. J. Chem. Phys. 2003, 118, 8207–8215. 10.1063/1.1564060. [DOI] [Google Scholar]
  75. Grimme S.; Antony J.; Ehrlich S.; Krieg H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 2010, 132, 154104. 10.1063/1.3382344. [DOI] [PubMed] [Google Scholar]
  76. Monkhorst H. J.; Pack J. D. Special points for Brillouin-zone integrations. Phys. Rev. B: Solid State 1976, 13, 5188. 10.1103/physrevb.13.5188. [DOI] [Google Scholar]

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