Chlorophyll Derivative-Sensitized TiO<sub>2</sub> Electron Transport Layer for Record Efficiency of Cs<sub>2</sub>AgBiBr<sub>6</sub> Double Perovskite Solar Cells
Baoning Wang, Na Li, Lin Yang, Chunxiang Dall’Agnese, Ajay Kumar Jena, Shin‐ichi Sasaki, Tsutomu Miyasaka, Hitoshi Tamiaki, Xiaofeng Wang
Abstract
The power conversion efficiency (PCE) of Cs2AgBiBr6-based perovskite solar cells (PSCs) is still low owing to the inherent defects of Cs2AgBiBr6 films. Herein, we demonstrate a carboxy-chlorophyll derivative (C-Chl)-sensitized mesoporous TiO2 (m-TiO2) film as an electron transport layer (ETL) to enhance and extend the absorption spectrum of Cs2AgBiBr6-based PSCs. The C-Chl-based device achieves a significantly improved PCE, exceeding 3% for the first time, with an increase of 27% in short-circuit current density. Optoelectronic investigations confirm that the introduction of C-Chl reduces the defects, accelerates the electron extraction, and suppresses charge recombination at the interface of ETL/perovskite. Moreover, the unencapsulated PSCs display restrained hysteresis and great stability under ambient conditions.