Blue‐Light‐Excited Lead‐Free Double Perovskite Cs 2 Ag 0.6 Na 0.4 In 0.8 Bi 0.2 Cl 6 / x KBr(KI) at Room Temperature and Photovoltaic Applications

Lead‐free halide double perovskites continue to draw increasing attention in view of their nontoxicity and stability compared to lead‐based perovskites. High‐end full‐color displays and white light illumination are based on blue‐light excitation. However, the excitation of blue light of lead‐free halide double perovskites Cs 2 AgInCl 6 at room temperature faces a great challenge, which is crucial to its commercial application. In this study, Cs 2 Ag 0.6 Na 0.4 In 0.8 Bi 0.2 Cl 6 / x KBr(KI), which can be excited under blue light, have been synthesized by solid‐phase compression method. Under blue‐light excitation, Cs 2 Ag 0.6 Na 0.4 In 0.8 Bi 0.2 Cl 6 /16KBr and Cs 2 Ag 0.6 Na 0.4 In 0.8 Bi 0.2 Cl 6 /16KI emit 605 nm orange light and 665 nm red light, respectively. Based on that, orange and red light‐emitting devices are fabricated excited by blue light. The performance of blue‐light excitation can not only make the double perovskites widely used in light‐emitting devices, but also as a light‐emitting down‐shift layer in photovoltaic devices to improve the performance of photovoltaic modules. With the Cs 2 Ag 0.6 Na 0.4 In 0.8 Bi 0.2 Cl 6 /16KBr, the power conversion efficiency of the Si solar cell increases 4.80% and 8.14% under the sunlight and white light‐emitting devices, respectively. The blue‐light excitation of lead‐free double perovskites at room temperature offers greater development potential in the field of display devices and optoelectronics.