Efficient deep-blue fluorescent organic light-emitting diodes with high exciton utilization efficiency based on a fully twisted phenanthro[9′,10′:4,5]imidazo[1,2- f ]phenanthridine–pyrene–carbazole (A–π–D) emitter

PIPNPyCz is a deep-blue HLCT emitter with a D–π–A architecture that promotes hot-exciton RISC. Solution-processed OLEDs show deep-blue emission (CIEy = 0.06), EQE max of 5.7%, and high EUE of 50.89%, confirming excellent optoelectronic performance.