Heavy Chalcogen Elements in OLEDs: Advances of Sulfur and Selenium for Organic Light‐Emitting Materials

ABSTRACT The rapid development of organic light‐emitting diodes (OLEDs) has spurred extensive efforts toward the design of high‐performance organic materials. Among various molecular design strategies, the incorporation of heavy chalcogen elements has emerged as an effective approach to regulate excited‐state dynamics and enhance device performance. Owing to their unique electronic configurations, tunable oxidation states, and heavy‐atom effects, sulfur and selenium play crucial roles in modulating emission properties, strengthening spin–orbit coupling, and promoting exciton utilization of thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP) systems. In recent years, significant progress has been made in integrating these elements into diverse emissive frameworks, including donor–acceptor type TADF architectures, multiple‐resonance TADF systems, and purely organic RTP materials. Beyond emissive materials, sulfur‐containing units have also been explored as components of host materials for phosphorescent OLEDs. This review provides a comprehensive overview of recent advances in these sulfur‐ and selenium‐based purely organic materials for OLED applications, highlighting the crucial role of chalcogen‐incorporated molecular design strategies in advancing OLED technology.