An effective strategy to achieve efficient white organic light-emitting diodes based on complex molecular design of alternative novel blue exciplex

Actualizing white organic light-emitting diodes (WOLEDs) with efficient blue exciplex rather than inferior blue-emitting dyes is still a challenge. Herein, we propose a novel green exciplex system composed of 9'-Diphenyl-9H, 9'H-3, 3'-bicarbazole (BCzPh) and 2, 4-diphenyl-6-(9, 9'spirobi [9H-fluoren]-3-yl)-1, 3, 5-Triazine (SF3-TRZ). The emission peak can be transferred from 519 nm to 483 nm by precisely regulating the donor-acceptor ratio and inert material concentration of exciplex. The novel blue exciplex obtained by spectral transfer shows an external quantum efficiency (EQE) of 3.3% with current efficiency (CE) of 8.2 cd/A. Furthermore, high performance WOLED is fabricated by combining the sky blue exciplex with yellow phosphoresce, which achieves a CE of 33.7 cd/A and remained 31.8 cd/A at a luminance of 1000 cd/m 2 . The high performance of WOLED can be attributed to the increased average distance between the donor and acceptor due to molecule dilution effect, which improves the efficiency of the reverse intersystem crossing (RISC) and facilitates Förster energy transfer (FET) from exciplex to yellow dye. These results demonstrate a general approach to realize blue emission in WOLED without complex molecular design process.