Modulation of triplet-mediated emission from selenoxanthen-9-one-based D–A–D type emitters through tuning the twist angle to realize electroluminescence efficiency over 25%

Increasing the twist angles between donor and acceptor units in 9 H -selenoxanthen-9-one-based emitters can modulate the lowest triplet excited states ( 3 LE or 3 CT), achieving pure RTP and dual emission of RTP and TADF, respectively.