Chlorophyll\nDerivative-Sensitized TiO₂ Electron\nTransport Layer for Record Efficiency of Cs₂AgBiBr₆ Double Perovskite Solar Cells

Abstract

The\npower conversion efficiency (PCE) of Cs₂AgBiBr₆-based perovskite solar cells (PSCs) is still low owing to\nthe inherent defects of Cs₂AgBiBr₆ films. Herein,\nwe demonstrate a carboxy-chlorophyll derivative (C-Chl)-sensitized\nmesoporous TiO₂ (m-TiO₂) film as an electron\ntransport layer (ETL) to enhance and extend the absorption spectrum\nof Cs₂AgBiBr₆-based PSCs. The C-Chl-based device\nachieves a significantly improved PCE, exceeding 3% for the first\ntime, with an increase of 27% in short-circuit current density. Optoelectronic\ninvestigations confirm that the introduction of C-Chl reduces the\ndefects, accelerates the electron extraction, and suppresses charge\nrecombination at the interface of ETL/perovskite. Moreover, the unencapsulated\nPSCs display restrained hysteresis and great stability under ambient\nconditions.