Synthesis of Pb‐free Double‐Perovskite Heterojunction (Cs2SnCl6‐Bi3+&Te4+/Cs2GeF6‐Mn4+) with White Emission for LED Application

Abstract Lead‐free halide double perovskites have been extensively studied for their application in the display and lighting fields. Owing to their characteristic single white luminescence, double perovskites have led to several developments in the field of white light illumination. However, most of these materials possess poor ambient stability or produce white emissions with high correlated color temperature (CCT) and low color rendering index (Ra), which hinder their application to home and commercial lighting displays. To address these challenges, a Pb‐free double perovskite heterojunction phosphor for white light is designed, namely Cs 2 SnCl 6 ‐2%Bi 3+ &4%Te 4+ /Cs 2 GeF 6 ‐0.11%Mn 4+ , which has a low CCT of 3525 K, a high Ra of 90.5, good optical moisture and thermal stability. The pattern and mechanism of epitaxial growth are derived from structural and surface tests. Analyzing the optical properties clarifies the existence of energy transfer modes in this heterojunction material, i.e., from Bi 3+ to Te 4+ , from Bi 3+ to Mn 4+ , and from Te 4+ to Mn 4+ . These results indicate the application prospects of these heterojunction phosphors in the field of white light illumination.