Lead-free Cs2Ag1−xNaxIn1 − yBiyCl6 perovskite films with broad warm-yellow emission for lighting applications

Lead-free halide double perovskite Cs 2 AgInCl 6 has been extensively studied in recent years due to the lead toxicity and poor stability of common lead halide perovskites. In this study, sodium (Na + ) and bismuth (Bi 3+ ) doped into Cs 2 AgInCl 6 double perovskite, then Cs 2 Ag 1− x Na x In 1 − y Bi y Cl 6 films with broadband warm-yellow emissions were achieved by the blade coating method. Herein, Na and Bi content were changed as variables at a series of parameter optimization experiments, respectively. In the Cs 2 Ag 1− x Na x In 1 − y Bi y Cl 6 systems, Na + broke the parity-forbidden transition of Cs 2 AgInCl 6 , and Bi 3+ suppressed non-radiative recombination. The partial replacement of Ag + with Na + ions and doping with Bi 3+ cations were crucial for increasing the intensity of the PL emission. The experimental results showed that the photoluminescence quantum yield of the Cs 2 Ag 0.4 Na 0.6 In 0.8 Bi 0.2 Cl 6 film was 66.38%, which was the highest data among all samples. It demonstrated remarkable stability under heat and ultraviolet conditions. After five thermal cycles, the PL intensity of the Cs 2 Ag 0.4 Na 0.6 In 0.8 Bi 0.2 Cl 6 film is only reduced to approximately 5.7% of the initial value. After 720 h continuous ultraviolet irradiation, there occurred 31.9% emission decay of the film.