Selenium-incorporated charge transfer states for room-temperature phosphorescence: A metal-free approach for high-performance OLEDs

Enhancing device efficiency is crucial for making OLED technology commercially competitive, and this relies on maximizing exciton utilization. Phosphorescent materials, capable of utilizing both singlet and triplet excitons, have been developed to achieve nearly unity internal quantum efficiency. However, conventional phosphorescent materials rely on heavy metals such as iridium and platinum, which are costly and raise environmental concerns. In response, purely organic phosphorescent materials are being explored as sustainable alternatives that are free from precious metals. This study introduces a selenium-based purely organic emitter, SeXPXSe, featuring charge transfer states that enhance spin-orbit coupling, thereby promoting efficient intersystem crossing and triplet exciton utilization. SeXPXSe achieves a high phosphorescence quantum yield of 60 % and a phosphorescence lifetime of 2.6 ms in doped film. OLED device incorporating SeXPXSe as emitter demonstrates a maximum external quantum efficiency up to 14.7 %, along with stable electroluminescence spectra and high exciton utilization, highlighting the potential of purely organic phosphorescent materials as promising candidates for environmentally friendly and high-performance OLED applications.