Self-Regulation Mechanism for Charged Point Defects in Hybrid Halide Perovskites**

Hybrid halide perovskites such as methylammonium lead iodide (CH3NH3PbI3) exhibit unusually low free-carrier concentrations despite being processed at low-temperatures from solution. We demonstrate, through quantum mechanical calculations, that an origin of this phenomenon is a prevalence of ionic over electronic disorder in stoichiometric materials. Schottky defect formation provides a mechanism to self-regulate the concentration of charge carriers through ionic compensation of charged point defects. The equilibrium charged vacancy concentration is predicted to exceed 0.4 % at room temperature. This behavior, which goes against established defect conventions for inorganic semiconductors, has implications for photovoltaic performance.

[1]  Robert P. H. Chang,et al.  Lead-free solid-state organic–inorganic halide perovskite solar cells , 2014, Nature Photonics.

[2]  Per Kofstad,et al.  Defect chemistry in metal oxides , 1996 .

[3]  Nakita K. Noel,et al.  Anomalous Hysteresis in Perovskite Solar Cells. , 2014, The journal of physical chemistry letters.

[4]  N. Nachtrieb,et al.  The chemistry of imperfect crystals , 1973 .

[5]  D. Weber.  CH3NH3PbX3, ein Pb(II)-System mit kubischer Perowskitstruktur / CH3NH3PbX3, a Pb(II)-System with Cubic Perovskite Structure , 1978 .

[6]  M. Islam.  Ionic transport in ABO3 perovskite oxides: a computer modelling tour , 2000 .

[7]  A. Walsh,et al.  Classification of Lattice Defects in the Kesterite Cu2ZnSnS4 and Cu2ZnSnSe4 Earth‐Abundant Solar Cell Absorbers , 2013, Advanced materials.

[8]  Shiliang Zhou,et al.  Influence of moisture on the preparation, crystal structure, and photophysical properties of organohalide perovskites. , 2014, Chemical communications.

[9]  Donald Morgan Smyth,et al.  The Defect Chemistry of Metal Oxides , 2000 .

[10]  Laura M. Herz,et al.  Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber , 2013, Science.

[11]  Aron Walsh,et al.  Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells , 2014, 1405.5810.

[12]  G. Scuseria,et al.  Restoring the density-gradient expansion for exchange in solids and surfaces. , 2007, Physical review letters.

[13]  H. Zeng,et al.  Strong covalency-induced recombination centers in perovskite solar cell material CH3NH3PbI3. , 2014, Journal of the American Chemical Society.

[14]  K. N. Dollman,et al.  - 1 , 1743 .

[15]  Michael D. McGehee,et al.  Materials science: Fast-track solar cells , 2013, Nature.

[16]  Joachim Maier,et al.  Physical Chemistry of Ionic Materials: Ions and Electrons in Solids , 2004 .

[17]  Mercouri G Kanatzidis,et al.  Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties. , 2013, Inorganic chemistry.

[18]  Oleksandr Voznyy,et al.  Materials processing routes to trap-free halide perovskites. , 2014, Nano letters.

[19]  M. Grätzel,et al.  Title: Long-Range Balanced Electron and Hole Transport Lengths in Organic-Inorganic CH3NH3PbI3 , 2017 .

[20]  Juan Bisquert,et al.  Photoinduced Giant Dielectric Constant in Lead Halide Perovskite Solar Cells. , 2014, The journal of physical chemistry letters.

[21]  Aron Walsh,et al.  Electronic structure of hybrid halide perovskite photovoltaic absorbers , 2014, 1401.6993.

[22]  Antonio Luque,et al.  Handbook of photovoltaic science and engineering , 2011 .

[23]  Aron Walsh,et al.  Structural and electronic properties of hybrid perovskites for high-efficiency thin-film photovoltaics from first-principles , 2013, 1309.4215.

[24]  Tomas Leijtens,et al.  Electronic properties of meso-superstructured and planar organometal halide perovskite films: charge trapping, photodoping, and carrier mobility. , 2014, ACS nano.

[25]  R. Rosenfeld.  Nature , 2009, Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery.

[26]  Yanfa Yan,et al.  Unusual defect physics in CH3NH3PbI3 perovskite solar cell absorber , 2014 .

[27]  Kresse,et al.  Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. , 1996, Physical review. B, Condensed matter.

[28]  David Cahen,et al.  Elucidating the charge carrier separation and working mechanism of CH3NH3PbI3−xClx perovskite solar cells , 2014, Nature Communications.

[29]  Aron Walsh,et al.  Atomistic Origins of High-Performance in Hybrid Halide Perovskite Solar Cells , 2014, Nano letters.

[30]  P. Steerenberg,et al.  Targeting pathophysiological rhythms: prednisone chronotherapy shows sustained efficacy in rheumatoid arthritis. , 2010, Annals of the rheumatic diseases.

[31]  J. Teuscher,et al.  Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites , 2012, Science.

[32]  Andrew G. Glen,et al.  APPL , 2001 .

[33]  G. Kresse,et al.  First-principles calculations for point defects in solids , 2014 .