Navigating Precise Deuteration via Vibronic Mode Analysis to Effectively Suppress Nonradiative Decay in Organic Donor–Acceptor Emitters

Deuteration effectively modulates excited-state dynamics in organic optoelectronic materials with precise deuteration preferred over perdeuteration. In this work, we performed vibronic mode analysis to explore site-selective deuteration effects on organic donor-π-acceptor (D-π-A) emitters. Computations revealed that the dominant vibronic coupling sites of tBTAP are primarily located at the π-bridge and then acceptor. Precise deuteration at these sites amplifies the total Huang-Rhys factor (∑Sj) without significantly altering the reorganization energy, thereby suppressing the nonradiative decay rate (knr) and enhancing the photoluminescence quantum yield (PLQY). As a proof of concept, tBTd-APd1-2 with a deuterated π-bridge and acceptor halves knr from that of tBTAP (1.81 × 10⁷ s⁻¹) to 0.93 × 10⁷ s⁻¹, achieving a PLQY (95.1% at 682 nm) higher than that of tBTAP (91.7% at 687 nm) in toluene. Observed trends in knr suppression and PLQY enhancement are consistent across calculations, solution, and solid films. A nondoped near-infrared (NIR) OLED based on tBTd-APd1-2 achieved a maximum external quantum efficiency (EQEmax) of 1.30% at 868 nm, one of the best results among reported NIR TADFOLEDs with emission peaks over 850 nm. This study navigates precise deuteration through vibronic mode analysis and highlights ∑Sj as a predictive metric to suppress knr and enhance PL and electroluminescence performance for organic D-π-A emitters.