Blocking energy-loss pathways for phosphorescent organic light emitting devices with novel exciplex-forming host

Abstract

Ensuring stable red and blue emission from white organic light-emitting devices (WOLEDs) with complementary colors is a major challenge. Here, a novel exciplex systems were used to solve this problem, where a thermally activated delayed fluorescence (TADF) material 10, 10, 10-(4, 4, 4-Phosphoryltris (benzene-4,1-diyl)) tris (10Hphenoxazine) (TPXZPO) and a common hole transporting material N,N′-dicarbazolyl-3,5-benzene (MCP) were mixed with an electron-transporting material (1,3,5-Triazine-2,4,6-triyl)tris(benzene-3,1-diyl)) tris(diphenylphosphineoxide) (PO-T2T) to form exciplex host for red and blue phosphorescent materials, respectively. Benefitted from the high triplet energy of donor and accepter were select to form exciplex host which ensures that excitons are excellent confined to the EMLs. Matched exciplex host-guest systems and a multichannel reverse intersystem crossing reduces energy loss during energy transfer processes and prevents triplet-triplet annihilation. The use of stepped energy transfer channels and exciplex interlayer switch ensures WOLEDs have greater stability. The devices exhibited a maximum power efficiency, current efficiency, and external quantum efficiency of 69.25 lm/W, 56.69 cd/A and 24.55%, respectively. More importantly, the devices exhibited extremely stable color rendering index ranging from 74 to 76 with luminance ranging from 102 to 104 cd/m2. These results indicate that the exciplex are promising for use in developing high performance complementary color WOLEDs.