Angewandte Chemie · 2017 · 27 citations · 27 references
Natural SciencesChemistryMaterials ScienceEnergy MaterialsInorganic ChemistryMaterials ChemistryCarbon-based Energy MaterialsInorganic MaterialsPerovskite MaterialsPhotovoltaic MaterialsSolar Cell MaterialsSolar CellsCharge Carrier RecombinationCharge RecombinationDielectric RelaxationElectrochemical Impedance AnalysisHalide PerovskitesLead-free PerovskitesPerovskite Solar CellsPhotovoltaic Efficiency
Abstract We synthesized and characterized methylammonium (MA) mixed tri‐halide tin perovskites (MASnIBr 2− x Cl x ) for carbon‐based mesoscopic solar cells free of lead and hole‐transporting layers. Varied SnCl 2 /SnBr 2 ratios yielded tin perovskites with three halides (I, Br, and Cl) co‐crystallized inside the tin‐perovskite. When the SnCl 2 proportion was ≥50 % ( x ≥1), phase separation occurred to give MASnI 3− y Br y and MASnCl 3− z Br z in the stoichiometric proportions of their precursors, confirmed by XRD. A device with MASnIBr 1.8 Cl 0.2 (SnCl 2 =10 %) showed the best photovoltaic performance: J SC =14.0 mA cm −2 , V OC =380 mV, FF=0.573, and PCE=3.1 %, and long‐term stability. Electrochemical impedance spectra (EIS) show superior charge recombination and dielectric relaxation properties for the MASnIBr 1.8 Cl 0.2 cell. Transient PL decays showed the intrinsic problem of tin‐based perovskites with average lifetimes less than 100 ps.
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