From para to ortho: Incarnating conventional TADF molecules into AIE-TADF molecules for highly-efficient non-doped OLEDs

Abstract

Conventional thermally activated delayed fluorescence (TADF) molecules are generally constructed by planar moieties with a linear donor–acceptor (D-A) configuration but suffer from aggregation-caused quenching (ACQ). Herein, we provide a strategy to develop aggregation-induced emission TADF (AIE-TADF) emitters that are consisted of ACQ moieties through the substitute change from para-, meta- to ortho-position, which means incarnating conventional TADF molecules into AIE-TADF molecules. The ortho-substituted molecule exhibits a highly twisted conformation to hinder π-π stacking and thus avoids ACQ, while a large D-A twisted angle contributes to fast reversible intersystem crossing and low non-radiative decay, thus facilitating the AIE-TADF feature in neat film. The ortho-substituted molecule renders the non-doped devices with a high external quantum efficiency of 22.14%. These results certify that adjusting substitute position is a simple and practical strategy for the development of high-efficiency TADF materials and devices.