High‐Efficiency TADF‐Sensitized WOLEDs With Suppressed Efficiency Roll‐Off Enabled by an R‐G‐R Sandwich Architecture

Achieving white organic light‐emitting diodes (WOLEDs) that simultaneously deliver high efficiency, stable chromaticity, and suppressed efficiency roll‐off remains challenging. Here, we propose an exciton‐management strategy by using DBA‐DI as both a blue emitter and energy‐transfer relay in a TCTA:26DCzPPy mixed host, enabling energy‐transfer to PQ 2 Ir(dpm) and Ir(mppy) 3 . An R‐G‐R sandwich emitting layer (EML) spatially redistributes the red and green emission channels, mitigating green‐dominated spectral imbalance and improving red‐channel exciton capture. Finally, the optimized device exhibits a turn‐on voltage of 2.7 V, maximum current efficiency (CE) of 58.43 cd A −1 , power efficiency (PE) of 64.53 lm W −1 , and external quantum efficiency (EQE) of 28.00%. At 1000 cd m −2 , the EQE remains 24.56%, corresponding to a 12.3% roll‐off, with a color rendering index of 72.7. The optimized device also showed small CIE shifts of Δx = 0.025 and Δy = 0.001 over 1000–10 000 cd m −2 . Semi‐quantitative analysis of spectral overlap, transient PL/EL dynamics, and single‐carrier transport supports RISC‐assisted energy transfer and balanced multichannel exciton management. This strategy provides a framework for synergistically regulating spatial EML architecture and TADF sensitizer concentration in high‐performance WOLEDs.