CsPbCl<sub>3</sub>‐Cluster‐Widened Bandgap and Inhibited Phase Segregation in a Wide‐Bandgap Perovskite and its Application to NiO<i><sub>x</sub></i>‐Based Perovskite/Silicon Tandem Solar Cells
Renjie Li, Bingbing Chen, Ningyu Ren, Pengyang Wang, Biao Shi, Qiaojing Xu, Zhao Hua, Wei Han, Zhao Zhou Zhu, Jingjing Liu, Qian Huang, Dekun Zhang, Ying Zhao, Xiaodan Zhang
Abstract
Abstract Nickel oxide (NiO x ) is an attractive hole‐transport material for efficient and stable p–i–n metal‐halide perovskite solar cells (PSCs). However, an undesirable redox reaction occurs at the NiO x /perovskite interface, which results in a low open‐circuit voltage ( V OC ), instability, and phase separation of the NiO x ‐based wide‐bandgap perovskite (Br > 20%). In order to simultaneously address the abovementioned phase separation problem and redox chemistry at the perovskite/NiO x interface, the bandgap is widened from 1.64 to 1.67 eV by adding inorganic CsPbCl 3 ‐clusters (3 mol%) to the Cs 22 Br 15 perovskite precursor solution. Moreover, adding extra 2 mol% CsCl enriches the NiO x /perovskite interface with Cl, thereby preventing the redox reaction at the interface, while controlling the Br content to within 15% improves the photostability of the wide‐bandgap perovskite. Consequently, the power conversion efficiency (PCE) of a single‐junction p–i–n PSC increases from 17.82% to 19.76%, which leads to the fabrication of highly efficient monolithic p–i–n‐type NiO x ‐based perovskite/silicon tandem solar cells with PCEs of up to 27.26% (certified PCE: 27.15%). The perovskite to an n–i–p‐type perovskite/silicon tandem solar cell is also applied to deliver a V OC of 1.93 V and a final efficiency of 25.5%. These findings provide critical insight into the fabrication of highly efficient and stable wide‐bandgap perovskites.