Department of Chemistry and ‡Department of Materials Science and Engineering, and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
J Am Chem Soc. 2015 Sep 9;137(35):11445-52. doi: 10.1021/jacs.5b06658. Epub 2015 Aug 27.
Organo-lead halide perovskite solar cells have gained enormous significance and have now achieved power conversion efficiencies of ∼20%. However, the potential toxicity of lead in these systems raises environmental concerns for widespread deployment. Here we investigate solvent effects on the crystallization of the lead-free methylammonium tin triiodide (CH3NH3SnI3) perovskite films in a solution growth process. Highly uniform, pinhole-free perovskite films are obtained from a dimethyl sulfoxide (DMSO) solution via a transitional SnI2·3DMSO intermediate phase. This high-quality perovskite film enables the realization of heterojunction depleted solar cells based on mesoporous TiO2 layer but in the absence of any hole-transporting material with an unprecedented photocurrent up to 21 mA cm(-2). Charge extraction and transient photovoltage decay measurements reveal high carrier densities in the CH3NH3SnI3 perovskite device which are one order of magnitude larger than CH3NH3PbI3-based devices but with comparable recombination lifetimes in both devices. The relatively high background dark carrier density of the Sn-based perovskite is responsible for the lower photovoltaic efficiency in comparison to the Pb-based analogues. These results provide important progress toward achieving improved perovskite morphology control in realizing solution-processed highly efficient lead-free perovskite solar cells.
有机-铅卤钙钛矿太阳能电池已经引起了极大的关注，其功率转换效率现已达到约 20%。然而，这些体系中铅的潜在毒性对其广泛应用引起了环境方面的担忧。在此，我们研究了在溶液生长过程中溶剂对无铅甲脒锡三碘化铅（CH3NH3SnI3）钙钛矿薄膜结晶的影响。通过 SnI2·3DMSO 中间相，我们从二甲基亚砜（DMSO）溶液中获得了高度均匀、无针孔的钙钛矿薄膜。这种高质量的钙钛矿薄膜能够实现基于介孔 TiO2 层的异质结耗尽型太阳能电池，但无需任何空穴传输材料，实现了前所未有的 21 mA cm(-2) 的光电流。电荷提取和瞬态光电压衰减测量表明，CH3NH3SnI3 钙钛矿器件中的载流子密度非常高，比基于 CH3NH3PbI3 的器件高一个数量级，但两种器件的复合寿命相当。与基于 Pb 的类似物相比，Sn 基钙钛矿的相对较高的背景暗载流子密度是导致其光电转换效率较低的原因。这些结果为实现溶液处理的高效无铅钙钛矿太阳能电池提供了重要的进展，有助于更好地控制钙钛矿的形态。
