Regulating the Excited States of Hybridized Local and Charge-Transfer (HLCT) Emitters for Blue OLEDs

The development of highly efficient blue emitters capable of effectively harvesting triplet excitons remains a major challenge in organic light emitting diodes (OLEDs) research. Emitters featuring hybridized local and charge-transfer (HLCT) excited states have demonstrated considerable potential for facilitating rapid high-lying triplet reverse intersystem crossing. Herein, two molecules, TRZ-p-12SIDCz and TRZ-Bp-IDCz, were synthesized by modulating the donor conjugation length to regulate their excited-state properties. Theoretical calculation and experimental results showed that they have HLCT characteristics, excellent thermal properties, and different emission colors. OLEDs devices doped with TRZ-p-12SIDCz and TRZ-Bp-IDCz achieved excellent efficiency with the the Commission internationale de l'eclairage (CIE) coordinate are (0.160, 0.126) and (0.251, 0.370) and the maximum external quantum efficiencies (EQEmax) of 0.74% and 2.85%, respectively. This study confirms that optimizing the hRISC channel of HLCT emitters by modulating the conjugation of electron donors is feasible.