[13p-N205-1~13] 12.4 Organic light-emitting devices and organic transistors

▼ [13p-N205-3] Role of a charge-transfer interface in blue TTU-OLEDs

〇(D)Thanh Ba Nguyen¹, Hajime Nakanotani^1,2, Chihaya Adachi^1,2 (1.OPERA, Kyushu Univ, 2.I2-CNER, Kyushu Univ)

Keywords:organic light-emitting diodes, triplet-triplet upconversion, charge-transfer interface

Two low-energy triplets can convert to one singlet via triplet-triplet upconversion (TTU), resulting in an exciton production yield in fluorescence organic light-emitting diodes (OLEDs) beyond the theoretical limit. However, TTU’s underlying mechanism still remains debated with varied viewpoints. Especially, although interfacial charge-transfer (CT) interaction has been shown to sensitize TTU before, it was claimed as a reason for external quantum efficiency (EQE) loss for blue TTU OLEDs. Herein, such interaction at the electron-blocking / emissive-layer interface is reported as an “overlooked” pathway to enhance TTU yields in OLEDs significantly. The generated interfacial triplet CT (³CT) non-radiatively decays to the localized excited triplet state (³LE) of TTU host, buliding up triplet density, and triggering efficient TTU at the interface.