Intermediate-Phase-Mediated Crystallization and A-Site Doping in CsPbI2Br Perovskite Solar Cells Enabled by Dimethylammonium Iodide
Wen Zheng, Haoran Huang, Jincheng Huang, Siyuan Zhang, Hengzhi Zuo, Qi Cui, Jianlin Chen, Zhuoyin Peng, Wei LiAbstract
CsPbI2Br perovskites are promising wide-bandgap absorbers for tandem photovoltaics but are limited by unfavorable film crystallization and high defect densities. Herein, dimethylammonium iodide is introduced as a multifunctional agent to simultaneously regulate crystallization dynamics and modulate A-site composition. In-situ photoluminescence spectroscopy reveals the formation of a transient intermediate phase that governs nucleation and growth pathways. By combining with in situ structural and spectroscopic analyses, we demonstrate that a fraction of DMA+ cations is incorporated into the perovskite lattice, forming a Cs1-xDMAxPbI2Br phase. The intermediate-phase-mediated crystallization and A-site doping result in enlarged grain size, reduced trap-state density, and suppressed nonradiative recombination. Consequently, carbon-based CsPbI2Br perovskite solar cells achieve a power conversion efficiency of 14.04% with markedly enhanced stability. This work provides mechanistic insight into synergistic crystallization control and compositional engineering in all-inorganic perovskite photovoltaics.