Intrinsic Defect Physics in Indium-based Lead-free Halide Double

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Intrinsic Defect Physics in Indium-Based Lead-Free Halide Double Perovskites Jian Xu, Jian-Bo Liu, Bai-Xin Liu, and Bing Huang J. Phys. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.jpclett.7b02008 • Publication Date (Web): 30 Aug 2017 Downloaded from http://pubs.acs.org on August 30, 2017

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The Journal of Physical Chemistry Letters

Intrinsic Defect Physics in Indium-Based Lead-Free Halide Double Perovskites

Jian Xu a, Jian-Bo Liu a,*, Bai-Xin Liu a, Bing Huang b,* a

Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China b

Beijing Computational Science Research Center, Beijing 100094, China

* Corresponding Author: Jian-bo Liu ([email protected]) Bing Huang ([email protected])

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ABSTRACT Lead-free halide double perovskites (HDPs) are expected to be promising photovoltaic (PV) materials beyond organic-inorganic halide perovskite, which is hindered by its structural instability and toxicity. The defect and stability related properties of HDPs are critical for the use of HDPs as important PV absorbers, yet their reliability is still unclear. In this letter, taking Cs2AgInBr6 as a representative, we have systemically investigated the defect properties of HDPs by theoretical calculations. First, we have determined the stable chemical potential regions to grow stoichiometric Cs2AgInBr6 without structural decomposition. Second, we reveal that Ag-rich & Br-poor are the ideal chemical potential conditions to grow n-type Cs2AgInBr6 with shallow defect levels. Third, we find the conductivity of Cs2AgInBr6 can change from good n-type, poorer n-type to intrinsic semiconducting depending on the growth conditions. Our studies provide an important guidance for experiments to fabricate Pb-free perovskite-based solar cell devices with superior PV performances.

TOC Graphic

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Organic-inorganic halide perovskite CH3NH3PbI3 is the current standout in the photovoltaic (PV) applications, which holds the record power conversion efficiency of 22%. However, there are two major concerns existing in CH3NH3PbI3: 1) the structural instability against heat, light, and moisture,1, 2 and 2) the toxicity caused by the Pb element. Consequently, the search for Pb-free stable perovskites with suitable bandgap for PV has attracted extensive attentions. Especially, Pb-free halide double perovskites (HDPs) with a formula of A2BB’X6 (B is monovalent and B’ is trivalent element) were proposed recently3-7 as new candidates for PV absorbers. Generally speaking, besides being of good structural stability, non-toxicity, and suitable optical gap, a good PV absorber candidate should also have good defect tolerance without intrinsic deep defect levels.8 However, the understanding of the defect properties in double perovskites is still in its infancy, and thus there remain many open questions for exploration. So far, Cs2AgBiX6 (X=Cl, Br) compounds have been synthesized in several experiments9-12, but they are not ideal for PV solar absorbers because of their indirect band gaps.13 Interestingly, placing Bi with In (InBi) causes direct bandgaps to appear in Cs2AgInX6 compounds. Although Cs2AgInCl6 has a large bandgap of 2.0 eV,13, 14 Cs2AgInBr6 is found to possess a bandgap of 1.33eV, which is suitable for a PV absorber. Zhao et al5 has reported that Cs2AgInBr6 may reach an ideal solar efficiency of 28%, which is close to the values of CH3NH3PbI3 (30%). The absorption coefficient of the ideal crystal of Cs2AgInBr6 is estimated to be higher than that of silicon (with an indirect bandgap of 1.1 eV).13 However, it is still very challenging to 3



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grow high quality Cs2AgInBr6 thin films, even though several Cs2Ag(Bi1-xInx)Br6 alloys have already been synthesized in experiments.6 As a result, the development of Cs2AgInBr6 for PV absorbers has been significantly delayed. Therefore, it is highly desirable to have a comprehensive understanding on the ideal growth conditions to obtain high quality Cs2AgInBr6 thin films. Gaining insight into the defect properties of HDPs are of vital importance for improving their PV performances, including the carrier mobility, ion diffusion, open-circuit voltage (VOC), and the non-radiative recombination rate. However, few theoretical studies have been reported on the defect physics of HDPs. In this work, using advanced first principle calculations, we have made a full assessment of the intrinsic defect properties and structural stability of Cs2AgInBr6. Importantly, we identify that the Ag-rich & Br-poor chemical conditions are the ideal chemical potential region to grow n-type Cs2AgInBr6 without deep in-gap levels and the unwanted secondary phases. Our first-principle calculations were carried out using the Vienna Ab initio Simulation Package (VASP).

15

The electron-ion interactions were described by the

projector augmented wave (PAW) method,16, 17 while the exchange-correlation energy was treated both with the generalized gradient approximation (GGA) in the Perdew-Burke-Ernzerhof

(PBE)

form18

and

with

Heyd−Scuseria−Ernzerh (HSE06) hybrid density functional.19,

the 20

screened

The spin-orbit

coupling (SOC) effect is included in all calculations. In our calculations, the PBE+SOC method is used for geometry optimizations, and then the HSE+SOC 4


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method is used for self-consistent static calculations. This scheme was proved to be a reliable approach to balance the computational cost and the calculation accuracy.4, 12, 21, 22

A kinetic-energy cutoff of 400 eV was tested to be sufficient for plane-waves

expansion to achieve good convergence. In the band gap calculations for the primitive unit cell, a Γ-centered 4×4×4 k-mesh was used. To calculate the defect properties of HDPs, the 160-atom supercell with a 1×2×2 Γ-centered k-mesh and a Gaussian smearing width of 0.05eV were employed during the geometry optimizations. We used a Γ-only k-mesh in the HSE+SOC calculations for the defective supercells. The conjugate gradient algorithm was used until the total energy was converged to 10−5 eV in the electronic self-consistency loop and a force criteria of 0.02 eV·Å−1 was allowed. The computational details of the equilibrium defect concentrations are demonstrated in the Supporting Information (S1). The Cs2AgInBr6 holds the standard double perovskite structure in space group of Fm 3 m, where the [AgBr6] and [InBr6] octahedral alternates along the three crystallographic axes and form the rock-salt type ordering.4, 5 Our calculated cubic lattice parameters and the bandgap of Cs2AgInBr6 are in good agreement with the experimental values and the previous calculations. (See Table S2 in the Supporting Information) In Cs2AgInX6 (X=Cl, Br), their band gaps are direct with the VBM and CBM both at the Γ point. It is because the VBM of Cs2AgInX6 (X=Cl, Br) is mainly formed by the hybridization between cationic Ag(d) and anionic X(p) orbitals, with negligible coupling with In(s) orbitals. In particular, the HSE calculated band gap of Cs2AgInBr6 (1.33eV) is ideal for a PV absorber in terms of the Shockley-Queisser 5



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limit rule.5 For comparison, the calculated electronic band structures and projected density of states for Cs2AgBiX6 (X=Cl, Br) are also shown in Figure 1. In Cs2AgBiX6 (X=Cl, Br), the coupling between Ag(d) + Bi(s) and anionic X(p) states place the VBM off-center at the X point of the Brillouin zone, leading to an indirect band gap. In fact, the indirect band gaps reduced the optical absorption and the chemical stability, so materials with indirect band gaps were not found to be ideal for PV applications.

Figure 1. HSE+SOC calculated electronic band structures and orbital-projected density of states for (a) Cs2AgBiBr6, (b) Cs2AgBiCl6, (c) Cs2AgInBr6 and (d) Cs2AgInCl6. The values of band gap are marked in these band structures. The Fermi level is set to zero. The projected density of states of s, p, d orbitals in the bottom panels are colored in green, red and blue, respectively.

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As a quaternary compound, Cs2AgInBr6 can have more types of possible intrinsic point defects compared to that of ternary and binary compounds. For this reason, growing high quality Cs2AgInBr6 thin films is expected to be more challenging. To confirm this, we calculated stable chemical potential regions of Cs2AgInBr6. As shown in Figure 2, indeed, the stoichiometric Cs2AgInBr6 can only be grown in a very narrow area of chemical potentials to avoid the formation of all possible competitive secondary phases, including InBr3, InAg3, AgBr, Cs2AgBr3, CsInBr3 and CsBr3.

Figure 2. Calculated stability regions of Cs2AgInBr6 against ∆ and ∆ at (a) ∆ 0 eV, (b) ∆ -0.5 eV, and (c) ∆ -1.0 eV slice conditions. The green

stable polygon regions are surrounded by the main competitive secondary phases, including InBr3, InAg3, AgBr, Cs2AgBr3, CsInBr3 and CsBr3. The six representative chemical potential points A-F used for defect calculations are denoted as yellow circles.

The charge-state transition levels (CTLs) and the formation energies ( ) of all the 20 intrinsic defects in Cs2AgInBr6, namely, 4 vacancies (VCs, VAg, VIn, and VBr), 4 interstitials (Csi, Agi, Ini, and Bri), 6 cation-on-cation antisites (CsIn, CsAg, AgCs, AgIn, 7



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InCs, and InAg), 3 cation-on-anion antisites (CsBr, AgBr and InBr) and 3 anion-on-cation antisites (BrCs, BrAg and BrIn), were carefully evaluated. The defect formation energy can be evaluated as23, 24 − + ∑ + ( + ) + "#$%

(1)

where is the total energy of a supercell containing the defect X in charge state q, and is the total energy of the corresponding pristine bulk lattice. is the number of atoms being removed from ( > 0) or added to ( < 0) the supercell, and denotes the corresponding chemical potential. ∆ is referenced to the corresponding elemental phase. and

are the energy levels

corresponding to the valence band maximum (VBM) and the Fermi level measured from the VBM, respectively. Additionally, "#$% (i.e. q ∆) ) is a potential-alignment correction term to correct for the finite-size effects in the calculations of charged defects. This term was determined by aligning the core levels of atoms far from the defect center in defective cells to that of the pristine bulk.25, 26 The charge-state transition levels (CTLs) are defined as27-29 ε(+ ⁄, )

(./0/ 1 23 4.56789 1 23 ):(./0/ 1 2; 4.56789 1 2; ) ; :3

−

(2)

These CTLs correspond to the Fermi-level positions at which X changes its charge state. The six representative chemical regions in Figure 2, i.e., ∆ 0 at point A and B, ∆ -0.5 at point C, D and E, ∆ -1.0 at point F, are selected to estimate of various intrinsic defects as a function of , as shown in Figure 3a-f,

respectively. The of the system can be pinned by the lowest crossing points 8


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between the CTLs of donor-like and acceptor-like defects. Using HSE+SOC, the CTLs for intrinsic donor-like and acceptor-like defects are illustrated in Figure 4. Our test calculations show that SOC effect plays a negligible role in affecting the CTLs. (see Fig. S1 in the Supporting Information)

Figure 3. The calculated formation energies of intrinsic defects with different charge states q in Cs2AgInBr6, as a function of the at six representative chemical potential points in Figure 2: (a) ∆ 0eV point A, (b) ∆ 0eV point B, (c) ∆ -0.5eV point C, (d) ∆ -0.5eV point D, (e) ∆ -0.5eV point E and (f) ∆ -1.0eV point F. The slope of the line segments indicates the defect charge 9



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states, and the kinks (solid dots) denote the transition energy levels. The Fermi level is referenced to the host VBM. The defects with significantly high are plotted as grey dashed lines. (We have labelled those defects with high formation enthalpies in Figure S2 just for reference) The pinned positions are indicated by vertical black dashed lines in (a)-(f).

Figure 4. The calculated transition energy levels (in eV) for intrinsic donor-like (upper panel) and acceptor-like (bottom panel) defects in Cs2AgInBr6, which are referenced to the host VBM of Cs2AgInBr6. 10


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As shown in Figure 3-4, Agi and VBr have the lowest and can act as shallow donors with ε(1 +⁄0) lying only at 0.01 and 0.004 eV below the CBM, which can be recognized as the most important sources for intrinsic n-type conductivity of Cs2AgInBr6. The shallow nature of VBr is attributed to the strong ionic bonds between Br-Ag or Br-In, which makes the defect levels of VBr close to the energy levels of cation, i.e., CBM. Interestingly, the coupling between antibonding Ag-d and Br-p orbitals in the VBM of Cs2AgInBr6 makes VAg shallow acceptor with the ε(0⁄1 −) resonant in the valence band. However, it has a relative higher than that of shallow donors Agi and VBr under Ag-rich conditions (∆ 0eV), as shown in Figure 3a and 3b; thus it cannot release enough holes to compensate the electrons produced by Agi and VBr. Therefore, Cs2AgInBr6 may exhibit intrinsic good n-type conductivity under Ag-rich growth conditions with the pinned 0.05 eV below the CBM. According to Table 1, the self-consistently calculated electron density n0 in Cs2AgInBr6 is around 3.92 × 1017~7.08 × 1017 cm-3 under thermal equilibrium conditions, which is the same magnitude as that in Cu2ZnSnS4 and Cu2ZnSnSe4 (1017~1019 cm-3).30 It is note that the calculated n0 can be considered as an ideal (maximum) value and in practice n0 could be much lower than this value. For example, despite exceptionally low defect formation energies, organic-inorganic halide perovskites exhibit unusually low carrier concentrations in the region of 109~1014 cm-3,31 which is possibly because the Schottky disorder would limit the formation of charge carriers through a self-regulation mechanism (ionic compensation 11



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of charged point defects).32 In Cs2AgInBr6, the equilibrium concentrations of the dominant defects (Agi, VBr and VAg) are estimated to be 1018 cm-3 (room temperature) at the pinned Fermi level under Ag-rich growth conditions. For comparison, in CH3NH3PbI3 the dominate defects are VPb and MAi, with estimated defect densities in an order of 1021 cm-3 (room temperature) at the pinned Fermi level. 33 Whether in HDPs or in hybrid halide perovskites, a large number of intrinsic defects may certainly be introduced through simple solution based synthesizing processes. Despite the presence of defects, they can still maintain good electronic quality, since the dominant defects create only shallow levels and would not degenerate their PV performance.

Table 1. The pinned Fermi level EF (eV), the hole densities p0 (cm-3), and electron densities n0 (cm-3) in the room temperature, at six representative chemical potential points A-F in Figure 1 for Cs2AgInBr6. Chemical potential points

The pinned

>?

?

A B C D E F

1.29 1.27 1.05 0.96 0.77 0.63

8.30×10-3 1.49×10-2 8.53×101 2.50×103 4.58×106 1.02×109

7.08×1017 3.92×1017 6.87×1013 2.34×1012 1.27×109 2.73×106

Intriguingly, we also find that the conductivity of Cs2AgInBr6 can change from good n-type to, poorer n-type and to intrinsic semiconducting when the chemical potential is shifted to A/B (Ag-rich, Br-poor), C/D/E (moderate), or F (Ag-poor, 12


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Br-rich). The pinned EF, the hole densities p0, and electron densities n0, in the room temperature, at those six representative chemical potential points A-F are listed in Table 1. The shifting of the pinned EF from the CBM to VBM can be understood by the fact that the of the dominant acceptor VAg would reduce as the chemical potential of Ag becomes poorer. Remarkably, the intrinsic defect properties of Cs2AgInBr6 are distinguished from that of Cu(In, Ga)Se2 and the other double perovskite Cs2AgBiBr6, which are all intrinsic p-type materials, independent of the chemical potential region.34, 35 Under relative Ag-poor conditions, e.g., at C, D, E, and F points in Figure 2, the dominant donor InAg and dominant acceptor VAg have comparable low formation energies, as shown in Figure 3c-f. However, InAg, a deeper donor, has the ε(2 +⁄1 +) and ε(1 +⁄0) lying at 0.20 and 0.12 eV below the CBM. It is known

that the deep-level defects in the bandgap may be non-radiative recombination centers, reducing the carrier lifetime and deteriorating its PV performance. When chemical potential is moved to F point (Ag-poor, Br-rich), the p0 and n0 are both comparatively low, making the system an intrinsic semiconductor. Therefore, our calculations suggest that the formation of deep-level defects can be suppressed by synthesizing Cs2AgInBr6 under Ag-rich conditions, which means the content of Ag-containing precursor needs to be abundant during synthesis. To obtain high quality Cs2AgInBr6 thin films, it is necessary to control the elemental contents (chemical potentials) of compositions, growth temperature, and partial pressure carefully to make Cs2AgInBr6 effective n-type conductivity, and avoid the formation of unwanted secondary 13



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competing phases. We also investigated the defect properties of Cs2AgInCl6 in a similar way as that of Cs2AgInBr6. Different from the case in Cs2AgInBr6, the most dominant acceptor VAg with shallow (-1/0) CTL resonant in the conduction band has a comparable low formation energy to the dominant donors Agi and VCl with shallow (0/1+) CTL resonant in the valence band. (See Figure S3 and Figure S4 in the Supporting Information.) Although bipolar conductivity is possible in Cs2AgInCl6 dependent on the chemical potentials, its n-type or p-type conductivity would be rather poor since the pinned is near the middle of the band gap. Therefore, Cs2AgInCl6 is not expected to be a promising PV material. In summary, using ab initio calculations based on HSE+SOC, we made a full assessment of the defect physics of a promising PV absorber candidate with direct band gaps, Cs2AgInBr6, by calculating the formation energies and the transition levels of all possible native defects. We found that the conductivity of Cs2AgInBr6 can change from good n-type, poorer n-type to intrinsic semiconducting depending on the growth conditions. We revealed possible suitable chemical potential conditions (Ag-rich & Br-poor) to make Cs2AgInBr6 good n-type conductive and avoid the unwanted secondary phases. Encouragingly, our findings provide valuable guidelines for future design of novel lead-free HDPs in PV applications.

ACKNOWLEDGMENTS This work at Tsinghua University is support from the Ministry of Science and 14


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Technology of China (2017YFB0702201, 2017YFB0702301, 2017YFB0702401), the National Natural Science Foundation of China (51571129, 51631005), and the Science Challenge Project (No. TZ2016004). B.H. acknowledges the support from NSFC (Grant No. 11574024), National Key Research and Development Program of China Grant No. 2016YFB0700700, and NSAF U1530401.

ASSOCIATED CONTENT Supporting Information Available: The computational details of the equilibrium defect concentrations. Calculated effective VB and CB density of states and electron/hole effective masses for Cs2AgInX6 (X=Br, Cl). Calculated cubic equilibrium lattice parameters, the band gaps and the band gap features (Direct/Indirect) for HDPs. The calculated CTLs for the dominant intrinsic defects by using HSE non-SOC method in Cs2AgInBr6. Labelled defects with high formation enthalpies in Cs2AgInBr6. The calculated charge-state transition levels and formation energies for intrinsic donor-like and acceptor-like defects in Cs2AgInCl6.

AUTHOR INFORMATION Corresponding Author *Jian-bo Liu ([email protected]) *Bing Huang ([email protected])

ORCID

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Jianbo Liu: 0000-0001-6516-6966

REFERENCES (1) Salado, M.; Contreras-Bernal, L.; Caliò, L.; Todinova, A.; López-Santos, C.; Ahmad, S.; Borras, A.; Idígoras, J.; Anta, J.A. Impact of Moisture on Efficiency-Determining Electronic Processes in Perovskite Solar Cells. J. Mater. Chem. A 2017, 5, 10917-10927. (2) Yang, S.; Fu, W.; Zhang, Z.; Chen, H.; Li, C.-Z. Recent Advances in Perovskite Solar Cells: Efficiency, Stability and Lead-Free Perovskite. J. Mater. Chem. A 2017, 5, 11462-11482. (3) Giustino, F.; Snaith, H.J. Toward Lead-Free Perovskite Solar Cells. ACS. Energy. Lett 2016, 1, 1233-1240. (4) Zhao, X.G.; Yang, J.H.; Fu, Y.; Yang, D.; Xu, Q.; Yu, L.; Wei, S.H.; Zhang, L. Design of Lead-Free Inorganic Halide Perovskites for Solar Cells via Cation-Transmutation. J. Am. Chem. Soc 2017, 139, 2630-2638. (5) Zhao, X.G.; Yang, D.; Sun, Y.; Li, T.; Zhang, L.; Yu, L.; Zunger, A. Cu-In Halide Perovskite Solar Absorbers. J. Am. Chem. Soc 2017, 139, 6718-6725. (6) Du, K.-Z.; Meng, W.; Wang, X.; Yan, Y.; Mitzi, D.B. Bandgap Engineering of Lead-Free Double Perovskite Cs2AgBiBr6 through Trivalent Metal Alloying. Angew. Chem. Int. Ed. Engl 2017, 56, 8158-8162. (7) Shi, Z.; Guo, J.; Chen, Y.; Li, Q.; Pan, Y.; Zhang, H.; Xia, Y.; Huang, W. Lead-Free Organic– Inorganic Hybrid Perovskites for Photovoltaic Applications: Recent Advances and Perspectives. Adv. Mater. 2017, 29, 1605005. (8) Brandt, R.E.; Poindexter, J.R.; Gorai, P.; Kurchin, R.C.; Hoye, R.L.Z.; Nienhaus, L.; Wilson, M.W.B.; Polizzotti, J.A.; Sereika, R.; Žaltauskas, R., et al. Searching for “Defect-Tolerant” Photovoltaic Materials: Combined Theoretical and Experimental Screening. Chem. Mat. 2017, 29, 4667-4674. (9) McClure, E.T.; Ball, M.R.; Windl, W.; Woodward, P.M. Cs2AgBiX6(X = Br, Cl): New Visible Light Absorbing, Lead-Free Halide Perovskite Semiconductors. Chem. Mat. 2016, 28, 1348-1354. (10) Slavney, A.H.; Hu, T.; Lindenberg, A.M.; Karunadasa, H.I. A Bismuth-Halide Double Perovskite with Long Carrier Recombination Lifetime for Photovoltaic Applications. J. Am. Chem. Soc 2016, 138, 2138-2141. (11) Filip, M.R.; Hillman, S.; Haghighirad, A.A.; Snaith, H.J.; Giustino, F. Band Gaps of the Lead-Free Halide Double Perovskites Cs2BiAgCl6 and Cs2BiAgBr6 from Theory and Experiment. J. Phys. Chem. Lett 2016, 7, 2579-2585. (12) Volonakis, G.; Filip, M.R.; Haghighirad, A.A.; Sakai, N.; Wenger, B.; Snaith, H.J.; Giustino, F. Lead-Free Halide Double Perovskites via Heterovalent Substitution of Noble Metals. J. Phys. Chem. Lett 2016, 7, 1254-1259. (13) Volonakis, G.; Haghighirad, A.A.; Milot, R.L.; Sio, W.H.; Filip, M.R.; Wenger, B.; Johnston, M.B.; 16


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Herz, L.M.; Snaith, H.J.; Giustino, F. Cs2InAgCl6: A New Lead-Free Halide Double Perovskite with Direct Band Gap. J. Phys. Chem. Lett 2017, 8, 772-778. (14) Tran, T.T.; Panella, J.R.; Chamorro, J.R.; Morey, J.R.; McQueen, T.M. Designing Indirect–Direct Bandgap Transitions in Double Perovskites. Mater. Horiz. 2017, 4, 688-693. (15) Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54, 11169-11186. (16) Blöchl, P.E. Projector Augmented-Wave Method. Phys. Rev. B 1994, 50, 17953-17979. (17) Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B 1999, 59, 1758-1775. (18) Perdew, J.P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865-3868. (19) Heyd, J.; Scuseria, G.E.; Ernzerhof, M. Hybrid Functionals Based on a Screened Coulomb Potential. J. Chem. Phys. 2003, 118, 8207-8215. (20) Paier, J.; Marsman, M.; Hummer, K.; Kresse, G.; Gerber, I.C.; Ángyán, J.G. Screened Hybrid Density Functionals Applied to Solids. J. Chem. Phys. 2006, 124, 154709. (21) Hendon, C.H.; Yang, R.X.; Burton, L.A.; Walsh, A. Assessment of Polyanion (BF4−and PF6−) Substitutions in Hybrid Halide Perovskites. J. Mater. Chem. A 2015, 3, 9067-9070. (22) Yang, D.; Ming, W.; Shi, H.; Zhang, L.; Du, M.-H. Fast Diffusion of Native Defects and Impurities in Perovskite Solar Cell Material CH3NH3PbI3. Chem. Mat. 2016, 28, 4349-4357. (23) Lany, S.; Zunger, A. Assessment of Correction Methods for the Band-Gap Problem and for Finite-Size Effects in Supercell Defect Calculations: Case Studies for ZnO and GaAs. Phys. Rev. B 2008, 78, 235104. (24) Freysoldt, C.; Grabowski, B.; Hickel, T.; Neugebauer, J.; Kresse, G.; Janotti, A.; Van de Walle, C.G. First-Principles Calculations for Point Defects in Solids. Rev. Mod. Phys. 2014, 86, 253-305. (25) Lany, S.; Zunger, A. Accurate Prediction of Defect Properties in Density Functional Supercell Calculations. Model. Simul. Mater. Sci. Eng. 2009, 17, 084002. (26) Van de Walle, C.G.; Neugebauer, J. First-Principles Calculations for Defects and Impurities: Applications to III-Nitrides. J. Appl. Phys. 2004, 95, 3851-3879. (27) Freysoldt, C.; Lange, B.; Neugebauer, J.; Yan, Q.; Lyons, J.L.; Janotti, A.; Van de Walle, C.G. Electron and Chemical Reservoir Corrections for Point-Defect Formation Energies. Phys. Rev. B 2016, 93, 165206. (28) Gallino, F.; Pacchioni, G.; Di Valentin, C. Transition Levels of Defect Centers in ZnO by Hybrid Functionals and Localized Basis Set Approach. J. Chem. Phys. 2010, 133, 144512. (29) Yu, Y.G.; Zhang, X.; Zunger, A. Natural Off-Stoichiometry Causes Carrier Doping in Half-Heusler Filled Tetrahedral Structures. Phys. Rev. B 2017, 95, 085201. (30) Chen, S.; Walsh, A.; Gong, X.G.; Wei, S.H. Classification of Lattice Defects in the Kesterite Cu2ZnSnS4 and Cu2ZnSnSe4 Earth-Abundant Solar Cell Absorbers. Adv. Mater. 2013, 25, 1522-1539. (31) Stoumpos, C.C.; Malliakas, C.D.; Kanatzidis, M.G. Semiconducting Tin and Lead Iodide Perovskites with Organic Cations: Phase Transitions, High Mobilities, and Near-Infrared 17



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Photoluminescent Properties. Inorg. Chem 2013, 52, 9019-9038. (32) Walsh, A.; Scanlon, D.O.; Chen, S.; Gong, X.G.; Wei, S.H. Self-Regulation Mechanism for Charged Point Defects in Hybrid Halide Perovskites. Angew. Chem. Int. Ed. Engl 2015, 54, 1791-1794. (33) Yin, W.-J.; Shi, T.; Yan, Y. Unusual Defect Physics in CH3NH3PbI3 Perovskite Solar Cell Absorber. Appl. Phys. Lett. 2014, 104, 063903. (34) Huang, B.; Chen, S.; Deng, H.-X.; Wang, L.-W.; Contreras, M.A.; Noufi, R.; Wei, S.-H. Origin of Reduced Efficiency in Cu(In,Ga)Se2 Solar Cells With High Ga Concentration: Alloy Solubility Versus Intrinsic Defects. IEEE J. Photovolt. 2014, 4, 477-482. (35) Xiao, Z.; Meng, W.; Wang, J.; Yan, Y. Thermodynamic Stability and Defect Chemistry of Bismuth-Based Lead-Free Double Perovskites. ChemSusChem 2016, 9, 2628-2633.

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TOC Graphic 49x49mm (300 x 300 DPI)



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Figure 1 93x50mm (300 x 300 DPI)


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Figure 2 51x15mm (300 x 300 DPI)



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Figure 3 323x282mm (300 x 300 DPI)


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Figure 4 113x157mm (300 x 300 DPI)


Intrinsic Defect Physics in Indium-based Lead-free Halide Double

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