TADF/RTP OLED organic emitters based on concaved N-PAHs with tunable intrinsic D-A electronic structure

Polycyclic aromatic hydrocarbons (PAHs) with centrally positioned nitrogen dopants possess a unique curved structure and strong electron-donating features. However, the lack of tools to synthetically affect their bandgap engineering and charge-transfer (CT) characteristic is detrimental to their future optoelectronics use because of usually low PLQY effi-ciency. Facing this challenge, we report on developing the first fully conjugated, curved N-PAHs containing phenazine terminus with the D-A electronic structures, which are herein studied as functional optoelectronic material. We evidence the influence of curvature on minimizing HOMO-LUMO overlap, which was severely reflected in small ΔEST values, in-dispensable to enhance the RISC rate constant. Within this approach, we evaluate the utility of the concaved system as TADF/RTP emitters which has not been explored so far in the context of non-planar N-PAHs. By variable accepting strength of phenazines employed, the photoluminescence quantum yields (ΦPL) were tuned, ranging from the lowest 9% up to the highest 86% with dinitrile terminus. As a proof of concept, solid-state OLED devices were constructed, exhibit-ing yellow to orange emission with the best maximum external EL quantum efficiency (EQE) of 12% for acceptor built up on 3-(trifluoromethyl)phenyl decorated phenazine that is demonstrated for the first time for curved D-A embedded N-PAHs.