Amide-Catalyzed Phase-Selective Crystallization Reduces Defect Density in Wide-Bandgap Perovskites

作者：Kim Junghwan; Saidaminov Makhsud I; Tan Hairen; Zhao Yicheng; Kim Younghoon; Choi Jongmin; Jo Jea Woong; Fan James; Quintero Bermudez Rafael; Yang Zhenyu; Quan Li Na; Wei Mingyang; Voznyy Oleksandr; Sargent Edward H

来源：Advanced Materials, 2018, 30(13): 1706275.

DOI：10.1002/adma.201706275

• amides
• defects
• perovskite solar cells
• wide-bandgap perovskites

Wide-bandgap (WBG) formamidinium-cesium (FA-Cs) lead iodide-bromide mixed perovskites are promising materials for front cells well-matched with crystalline silicon to form tandem solar cells. They offer avenues to augment the performance of widely deployed commercial solar cells. However, phase instability, high open-circuit voltage (Voc ) deficit, and large hysteresis limit this otherwise promising technology. Here, by controlling the crystallization of FA-Cs WBG perovskite with the aid of a formamide cosolvent, light-induced phase segregation and hysteresis in perovskite solar cells are suppressed. The highly polar solvent additive formamide induces direct formation of the black perovskite phase, bypassing the yellow phases, thereby reducing the density of defects in films. As a result, the optimized WBG perovskite solar cells (PSCs) (Eg approximately 1.75 eV) exhibit a high Voc of 1.23 V, reduced hysteresis, and a power conversion efficiency (PCE) of 17.8%. A PCE of 15.2% on 1.1 cm(2) solar cells, the highest among the reported efficiencies for large-area PSCs having this bandgap is also demonstrated. These perovskites show excellent phase stability and thermal stability, as well as long-term air stability. They maintain approximately 95% of their initial PCE after 1300 h of storage in dry air without encapsulation.

• 出版日期2018-3-27