Bandgap-tunable double-perovskite thin films by solution processing

Narrowing the bandgap of lead-free double-perovskite Cs2AgBiBr6 is required for using this material in future photovoltaics. Herein, we demonstrate a bandgap engineering of Cs2AgBiBr6 by introducing Sb to substitute up to 75% of Bi via a versatile solution-processed method in dimethyl sulfoxide at 180 degrees C. The resultant Cs2AgSbxBi1-xBr6 (x = 0, 0.25, 0.50, 0.75) thin films possess high crystallinity and good thermostability. Moreover, the Sb substitution enables an obvious bandgap reduction of 0.25 eV. The fabricated solar cell using the Cs2AgSbxBi1-xBr6 (x = 0.25) thin film obtained an increased performance than the reference Cs2AgBiBr6. The effective bandgap narrowing via a facile solution method might accelerate the development of Cs2AgBiBr6-based materials for photovoltaic applications.