Ab Initio Analysis of Charge Carrier Dynamics in Organic-Inorganic Lead Halide Perovskite Solar Cells
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Ab Initio Analysis of Charge Carrier Dynamics in Organic-Inorganic Lead Halide Perovskite Solar Cells Dakota Junkman1, Dayton J. Vogel1, Yulun Han1, and Dmitri S. Kilin1 1 Department of Chemistry, University of South Dakota, 414 E. Clark St., Vermillion, SD 57069, U.S.A. ABSTRACT Today’s conversion of solar energy into electricity is based on silicon, which is pure, eventually crystalline, and its most efficient transitions are away from solar radiation maximum. The continuous search of efficient photovoltaic materials has recently focused on lead-halide organic-inorganic perovskite materials due to the very flexible, sustainable, and forgiving procedure of their fabrication, which is successful even if the concentrations of precursors, and temperature regimes deviate from optimal values. In addition to simple fabrication, this class of materials provides impressively high efficiency of photovoltaic (PV) cells. Attention to these materials helps to understand the mechanisms of their high efficiencies and to identify other materials with same type of properties. This work presents computational analysis of photoinduced processes in perovskite materials at ambient temperatures. INTRODUCTION Organic inorganic perovskites are composed of anionic inorganic solid scaffold (i.e. PbI3(-) ) and small organic cations located inside such “cages”.1, 2 Structural, optical, and electronic properties of organic-inorganic perovskites are tuned by varying morphological parameters such as replacing a small fraction of iodine with bromine or chlorine.3,4,5,6 Moreover, replacing lead with tin reduces toxicity.7 Several of structural properties of perovskites depend on the procedure of fabrication which ranges from thermal crystallization of dissolved precursors8 and solvent exchange at room temperature9,10 to chemical vapor deposition.11 Synthetic protocol, temperature, and duration of crystallization affects size of single crystals in the thin film.12 Control of the thickness of a perovskite thin film of fabrication perovskites in a form of nanocrystals provides tuning of their electronic structure via quantum confinement.13,14 For PV applications, perovskite thin films are deposited in a “sandwich” architecture so that perovskite interfaces thin film layers of electron donor and electron acceptor materials, connected to contact electrodes. Tuning the interfacial materials may improve the cell efficiency by an order of magnitude.1,15,16,17,18,19,20 All promising and beneficial properties of perovskites are affected by two major challenges: (i) the stability in humid environments, i.e. decomposition of perovskites back into the original precursors21,22 and (ii) the ambiguity in the current voltage curves.23,24 Organic-inorganic perovskites hold properties of both solid semiconductors and ionic liquids, thus exhibiting intriguing and unusual properties. There is a lack of understanding of the interplay and correlation between perovskite structure and their properties, such as efficient absorption,25 giant dielectric constant,26 high pol
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