Realizing High-Efficiency TADF from a Low Performing Cyanopyridine Emitter via symmetric coupling

Abstract

A low-performing cyanopyridine-based emitter (tCzPyCN) is converted into a highly efficient TADF emitter using homo coupling technique. A dual-core counterpart (2tCz2Py2CN) is achieved by symmetrically connecting the single-core emitter, which significantly reduces the singlet-triplet energy gap (ΔEST) from 0.21 eV to 0.08 eV. The EQEmax increases from 0.94% to 15.02% due to this near-degenerate energy landscape. The enhancement results from the suppression of competing non-radiative triplet decay pathways (knrT=0.11×105 s−1). This effective suppression of non-radiative loss is supported by PLQY, which nearly doubles from 33.40% to 59.10%. This study demonstrates that symmetric homo-coupling is an effective method for transforming underperforming emitters into high-performing TADF systems.