Efficient TADF polymer with optimized molecular structure and interaction for constructing solution-processed hybrid white OLEDs with EQE above 26%

Despite the steady progress of TADF polymer research, the inter/intra-molecular interaction between TADF units is still a big factor to induce the detrimental extinction of excited excitons. Herein, a new strategy, named side-chain encapsulation and main-chain blocking (SEMB), was proposed to construct TADF polymers with minimized inter/intra-molecular interaction of TADF units. The bulky carbazole and biphenyl fluorene are deftly introduced as encapsulation and blocking units by flexible hexane chains at the periphery of the Triazin-carbazole luminance cores. Both photophysical and electro-luminance results of the four TADF polymers varied in steps along their molecular structure and interaction, which proves the effectiveness of the SEMB strategy in the macro-molecular system. Indeed, the deep-blue device based on SEMB polymer P-CzTCFu achieved a maximum external quantum efficiency (EQE) of 22.1%, which was 3 times outperforming the reference polymer without any protection. Further using such a TADF polymer as a sensitizer for hybrid white OLEDs lead to an optimized high EQE of 26.7%, which was among the highest value in previously reported solution-processed hybrid white OLEDs. We also successfully prepared the first TADF polymer-based flexible OLEDs with good bending resistance. This work reveals the potential and importance of SEMB strategy for opening a new route for TADF polymer design toward highly efficient solution-processed OLEDs.