Effectively tuning the band gap of double perovskite Cs2Ag(BxBi1-x)Br6 (B = Sb3+, In3+) thin films

Halide double perovskite Cs 2 AgBiBr 6 hinders its wide range of optoelectronic applications due to large band gap. This work focuses on Sb 3+ /In 3+ doping to tune the band gap of Cs 2 AgBiBr 6 thin films. The influences of annealing temperature and doping amount of Cs 2 Ag(B x Bi 1-x )Br 6 (B = Sb 3+ , In 3+ ) thin films were investigated. When annealed at the optimized temperature of 150 °C, the Cs 2 Ag(B x Bi 1-x )Br 6 (B = Sb 3+ , In 3+ ) thin films accommodate up to 100% Sb 3+ and 70% In 3+ , respectively, without showing any secondary phases. The band gap of Cs 2 Ag(B x Bi 1-x )Br 6 (B = Sb 3+ , In 3+ ) thin films decreases as the increase of Sb 3+ and increases as the increase of In 3+ amount. Therefore, the band gap regulation of 0.39 eV is realized, with the smallest value of 2.25 eV for Cs 2 AgSbBr 6 and highest value of 2.64 eV for Cs 2 Ag 0.3 In 0.7 Br 6 , respectively. Our work confirms an approach to realize band gap adjustment of Cs 2 AgBiBr 6 thin films.