Overcoming the Limitation of Cs<sub>2</sub>AgBiBr<sub>6</sub> Double Perovskite Solar Cells Through Using Mesoporous TiO<sub>2</sub> Electron Extraction Layer
Dandan Zhao, Chao Liang, Bingzhe Wang, Tanghao Liu, Qi Wei, Kaiyang Wang, Hao Gu, Sisi Wang, Shiliang Mei, Guichuan Xing
Abstract
Lead‐free double perovskite Cs 2 AgBiBr 6 has gained increasing attention recently. However, the power conversion efficiency (PCE) of Cs 2 AgBiBr 6 perovskite solar cells (PSCs) is still low compared with their lead‐based counterparts. Here, by using photoluminescence (PL), time‐resolved photoluminescence (TRPL), and ultrafast transient absorption (TA) measurements, the unbalance between the electron and hole in diffusion and transfer, which limits the performance of the Cs 2 AgBiBr 6 PSCs, was further revealed. Considering this issue, a strategy of using the mesoporous TiO 2 electron transport layer (ETL) to construct a bulk heterojunction in Cs 2 AgBiBr 6 PSCs was proposed. Consequently, the PCE had improved by over 24% comparing with that only used compact TiO 2 ETL. Moreover, based on mesoporous TiO 2 , the unencapsulated Cs 2 AgBiBr 6 PSCs maintained 90% of their initial performance after approximately 1200 h of storage in a desiccator (humidity ~30%). This work gives further understanding of Cs 2 AgBiBr 6 perovskite and demonstrates that a proper design of balancing the electron and hole diffusion can improve device performance.