Chlorophyll Derivative-Sensitized TiO2 Electron Transport Layer for Record Efficiency of Cs2AgBiBr6 Double Perovskite Solar Cells

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-CM 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.

Automated summary

In this study, a carboxy-chlorophyll derivative (C-Chl) was introduced as a sensitizer to enhance the performance of Cs2AgBiBr6-based perovskite solar cells. The optimized device achieved a significantly improved power conversion efficiency (PCE) exceeding 3% for the first time, with enhanced short-circuit current density and improved stability. The introduction of C-Chl was found to reduce defects, accelerate electron extraction, and suppress charge recombination at the interface, leading to the enhanced overall performance of the solar cells.