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

Abstract Actualizing white organic light-emitting diodes (WOLEDs) with an 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 and 2,4-diphenyl-6-(9,9′-spirobi [9H-fluoren]-3-yl)-1, 3, 5-triazine. The emission peak can be transferred from 519 nm to 483 nm by precisely regulating the donor–acceptor ratio and inert material concentration of the exciplex. Its intrinsic mechanism is due to the distance between the electrons and holes in the charge transfer state of exciplexes, which is increased because of the increasing average distance between the donor and acceptor. The novel blue exciplex obtained by spectral transfer shows an external quantum efficiency of 3.3% with a current efficiency (CE) of 8.2 cd A −1 . Furthermore, a high-performance WOLED is fabricated by combining the sky blue exciplex with yellow phosphorescence, which achieves a CE of 33.7 cd A −1 and remained at 31.8 cd A −1 at a luminance of 1000 cd m −2 . The high performance of the WOLED can be attributed to the increased average distance between the donor and acceptor due to the molecular dilution effect, which improves the efficiency of the reverse intersystem crossing and facilitates Förster energy transfer from the exciplex to the yellow dye. These results demonstrate a general approach to realizing blue emission in a WOLED without a complex molecular design process.