Multi-resonance TADF non-conjugated copolymer with near-unity photoluminescence quantum yield for efficient solution-processed OLEDs

Abstract

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters have emerged as promising candidates for high-resolution OLEDs due to their near-unity exciton utilization efficiency and narrow-band emission. Highly efficient solution-processed OLEDs based on MR-TADF emitters are highly desired due to their combined advantages of cost-effective fabrication, compatibility with large-area flexible substrates, and potential to simultaneously achieve high color purity and superior device efficiency. Herein, we design and synthesis of a series of novel MR-TADF non-conjugated copolymers PBNxDPOTy by integrating MR-TADF moieties (DBNCz) and phosphine oxide moieties (DPOT) into non-conjugated polystyrene skeleton. This architecture synergistically combines narrow-band emission, through-space charge transfer (TSCT) with steric hindrance effects to achieve narrow emission (FWHM = 28-53 nm) with record-high photoluminescence quantum yields (PLQY = 99.6%). Solution-processed OLEDs employing PBN3DPOT97 emitter demonstrate exceptional performance with FWHM of 36 nm, EQE of 12.01%, and CIE coordinates of (0.16, 0.32). Theoretical calculation results show that the narrow-band emission in the copolymers PBNxDPOTy can be attributed to the MR-TADF moieties (DBNCz). Furthermore, spatial HOMO-LUMO distributions reveal enhanced TSCT for improved device performance. This work establishes a new molecular design strategy for developing highly efficient MR-TADF non-conjugated copolymers for the solution-processed OLEDs.