Resolving the Photophysics of Nitrogen-Embedded Multiple Resonance Emitters: Origin of Color Purity and Emitting Efficiency
Yaxin Wang, Yiran Tian, Yixuan Gao, Zilong Guo, Zheng Xue, Yandong Han, Wensheng Yang, Xiaonan Ma
Abstract
The emerging nitrogen-embedded multiple resonance (MR) emitters with an indolo[3,2,1- jk ] carbazole (ICz) unit have exhibited promising performance for high-resolution organic light-emitting diode (OLED) devices, while the underlying photophysics has been rarely reported. In this work, the optical spectra, color purity, and emitting efficiency of ICz-based MR emitters were investigated by using electronic structure and thermal vibration correlation function (TVCF) calculations. Unlike B–N MR emitters, the high color purity of investigated ICz-based MR emitters was mainly contributed by considerable structural rigidity, which also greatly affects the radiative decay rate and fluorescence quantum yield of the S 1 state. For the majority of investigated emitters, potential reverse intersystem crossing (RISC) channels (T 1 → S 1 and T 2 → S 1 ) are limited by thermally inaccessible Δ E ST * or insufficient spin–orbital coupling (SOC), which can be distinguished by the calculated temperature-dependent RISC rate pattern. We provided a systematic photophysical picture for ICz-based MR emitters that might be interesting for the OLED design and application community.