Ionic Liquid Bridge Assisting Bifacial Defect Passivation for Efficient All-Inorganic Perovskite Cells with High Open-Circuit Voltage
Shengcheng Wu, Shengcheng Wu, Tong Yun, Chunqiu Zheng, Xinyi Luo, Peng Qiu, Hongyang Yu, Qiwei Wang, Jinwei Gao, Xubing Lu, Xingsen Gao, Lingling Shui, Sujuan Wu, Sujuan Wu, Jun‐Ming Liu
Abstract
Serious open-circuit voltage ( V oc ) loss originating from nonradiative recombination and mismatch energy level at TiO 2 /perovskite buried interface dramatically limits the photovoltaic performance of all-inorganic CsPbI x Br 3– x ( x = 1, 2) perovskite solar cells (PSCs) fabricated through low-temperature methods. Here, an ionic liquid (IL) bridge is constructed by introducing 1-butyl-3-methylimidazolium acetate (BMIMAc) IL to treat the TiO 2 /perovskite buried interface, bilaterally passivate defects and modulate energy alignment. Therefore, the V oc of all-inorganic CsPbIBr 2 PSCs modified by BMIMAc (Target-1) significantly increases by 148 mV (from 1.213 to 1.361 V), resulting in the efficiency increasing to 10.30% from 7.87%. Unsealed Target-1 PSCs show outstanding long-term and thermal stability. During the accelerated degradation process (85 °C, RH: 50∼60%), the Target-1 PSCs achieve a champion PCE of 11.94% with a remarkable V oc of 1.403 V, while the control PSC yields a promising PCE of 10.18% with a V oc of 1.319 V. In particular, the V oc of 1.403 V is the highest V oc reported so far in carbon-electrode-based CsPbIBr 2 PSCs. Moreover, this strategy enables the modified all-inorganic CsPbI 2 Br PSCs to achieve a V oc of 1.295 V and a champion efficiency of 15.20%, which is close to the reported highest PCE of 15.48% for all-inorganic CsPbI 2 Br PSCs prepared by a low-temperature process. This study provides a simple BMIMAc IL bridge to assist bifacial defect passivation and elevate the photovoltaic performance of all-inorganic CsPbI x Br 3– x ( x = 1, 2) PSCs.