High-Efficient Blue Emission and Bandgap Engineering from Jahn–Teller Distorted Halide Double Perovskites

Decreasing the power consumption of light-emitting diodes (LEDs) and increasing the energy generation of solar cells are crucial tasks toward the mitigation of greenhouse gas emissions and Paris Agreement goals. Lead (Pb)-free halide double perovskites, identified as environmentally friendly alternatives to Pb-based perovskites, are not deemed useful thus far due to the absence of high photoluminescence quantum yield (PLQY) examples and large bandgaps. Herein, penta-cationic antimony (Sb 5+ )-doping strategy is demonstrated for the benchmark material of Cs 2 NaInCl 6 , achieving blue emission with near-unity PLQY and the lowest bandgap of 1.24 eV. The excellent PLQY observed in the material is attributed to Sb 5+ doping-induced Jahn–Teller distortion in Cs 2 NaInCl 6 and a newly emerged band structure, which has remained undisclosed in all previous reports. This groundbreaking discovery represents the first instance in the field of perovskite materials where the incorporation of a single dopant has resulted in a zero-to-one enhancement in their emission profile. This breakthrough is expected to have profound implications for advancing research in the utilization of similar dopants, such as manganese cations (Mn 6+ and Mn 7+ ), not only in halide perovskite structures but also in oxide-based perovskites and other semiconductor systems.