Purely organic room-temperature phosphorescence sensitizers for highly efficient hyperfluorescence OLEDs

Multiresonance thermally activated delayed fluorescence (MR-TADF) emitters are promising candidates for organic light-emitting diodes (OLEDs) with high color quality. However, in most cases, noble metal-containing phosphors are required as sensitizers for MR-TADF emitters to improve their electroluminescence (EL) performances, which may lead to high cost and environmental pollution. Herein, an efficient purely organic room-temperature phosphorescence (RTP) material, 3,2-PIC-TXT, with fast phosphorescence radiation is developed. It not only exhibits impressive EL performances as an emitter with an outstanding external quantum efficiency (EQE) of 33.2%, higher than that of Ir(ppy)₃ (25.2%), but also functions remarkably as a sensitizer for green MR-TADF emitters (BN2, tCzphB-Ph, and tCzphB-Fl). The hyperfluorescence OLEDs using 3,2-PIC-TXT as a sensitizer provide ultrahigh EQEs of 40.9 to 43.8%, superior to those based on an Ir(ppy)₃ sensitizer (37.0 to 38.0%), along with superb color purity and excellent operational stability. These OLEDs are the best devices based on RTP materials reported so far.