Zhou Xianyong, Zhang Luozheng, Wang Xingzhu, Liu Chang, Chen Shi, Zhang Meiqing, Li Xiangnan, Yi Wendi, Xu Baomin
Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, Guangdong Province, China.
Shenzhen Engineering Research and Development Center for Flexible Solar Cells, Southern University of Science and Technology, Shenzhen, 518055, Guangdong Province, China.
Adv Mater. 2020 Apr;32(14):e1908107. doi: 10.1002/adma.201908107. Epub 2020 Feb 25.
1.5-1.6 eV bandgap Pb-based perovskite solar cells (PSCs) with 30-31% theoretical efficiency limit by the Shockley-Queisser model achieve 21-24% power conversion efficiencies (PCEs). However, the best PCEs of reported ideal-bandgap (1.3-1.4 eV) Sn-Pb PSCs with a higher 33% theoretical efficiency limit are <18%, mainly because of their large open-circuit voltage (V ) deficits (>0.4 V). Herein, it is found that the addition of guanidinium bromide (GABr) can significantly improve the structural and photoelectric characteristics of ideal-bandgap (≈1.34 eV) Sn-Pb perovskite films. GABr introduced in the perovskite films can efficiently reduce the high defect density caused by Sn oxidation in the perovskite, which is favorable for facilitating hole transport, decreasing charge-carrier recombination, and reducing the V deficit. Therefore, the best PCE of 20.63% with a certificated efficiency of 19.8% is achieved in 1.35 eV PSCs, along with a record small V deficit of 0.33 V, which is the highest PCE among all values reported to date for ideal-bandgap Sn-Pb PSCs. Moreover, the GABr-modified PSCs exhibit significantly improved environmental and thermal stability. This work represents a noteworthy step toward the fabrication of efficient and stable ideal-bandgap PSCs.
根据肖克利-奎塞尔模型，带隙为1.5 - 1.6电子伏特的铅基钙钛矿太阳能电池（PSCs）理论效率极限为30 - 31%，其功率转换效率（PCEs）可达21 - 24%。然而，据报道，理想带隙（1.3 - 1.4电子伏特）的锡铅PSCs理论效率极限更高，为33%，但其最佳PCEs <18%，主要是因为其开路电压（V）亏损较大（>0.4伏）。在此，发现添加溴化胍（GABr）可显著改善理想带隙（≈1.34电子伏特）的锡铅钙钛矿薄膜的结构和光电特性。引入钙钛矿薄膜中的GABr可有效降低钙钛矿中由锡氧化引起的高缺陷密度，这有利于促进空穴传输、减少电荷载流子复合并降低V亏损。因此，在1.35电子伏特的PSCs中实现了20.63%的最佳PCE，认证效率为19.8%，同时V亏损创纪录地小，为0.33伏，这是迄今为止报道的所有理想带隙锡铅PSCs中最高的PCE。此外，GABr修饰的PSCs在环境和热稳定性方面有显著改善。这项工作代表了朝着制造高效稳定的理想带隙PSCs迈出的重要一步。
