Enhancing the Electroluminescent Efficiency of Acridine-Based Donor–Acceptor Materials: Quasi-Equivalent Hybridized Local and Charge-Transfer State

Abstract

Excited-state properties (characteristics and composition) play a crucial role in luminescence properties of the new-generation organic light-emitting materials. As a special excited species, the hybridized local and charge-transfer (HLCT) state is composed of locally excited (LE) state and charge-transfer (CT) state, which can harvest simultaneous high photoluminescence (PL) efficiency and high exciton utilization in organic light-emitting diodes. In this work, we designed and synthesized three donor (D)–acceptor (A) compounds with different donor units and a typical electron-deficient unit acridine as the acceptor unit to investigate the different hybridization statuses among them. As is revealed by the molecular design, the three compounds precisely show the different hybridization statuses: LE-dominated hybridization (CZP-1AC), quasi-equivalent HLCT (qHLCT, TPA-1AC), and CT-dominated hybridization (PTZ-1AC). As a result, TPA-1AC exhibits the highest PL efficiency and multifold device performance, meriting from the most effective suppression of nonradiative processes that originated from a qHLCT state due to the strong interstate coupling and the small energy gap between LE and CT states. This work not only provides a comprehensive insight into the hybridization formation and a fine modulation in HLCT state composition but also provides a valuable strategy to design new-generation, low-cost, high-performance organic electroluminescence materials based on lowly emissive chromophores of D or A.