Advanced Exciplex Sensitized Green InP-Based Quantum Dot Light Emitting Diodes for Extended Lifespan

Charge imbalance in inverted InP-based quantum dot light emitting diodes (QLEDs) due to higher electron injection is a well-known hindrance to the device's stability. To overcome this, the exciton harvesting layer (EHL) is inserted between QD and the hole transport layer to recycle overflowing electrons, form excitons, and transfer exciton energies to QD layer. This study utilized exciplex as EHL in InP-based QLEDs. The exciplex EHL is composed of 2-(5-(dibenzo[b,d]furan-4-yl)-[1,1′-biphenyl]-3-yl)-4-phenyl-6-(8-phenyldibenzo[b,d]furan-1-yl)-1,3,5-triazine (diDBFTrz) as n-type and ([1,1′-biphenyl]-4-yl).-9′-phenyl-9H,9′H-3,3′-bicarbazole (BPP-BCZ) as p-type material. The exciplex is chosen based on its compatibility with QD, which mitigates issues in QLEDs. Through the optimization of the exciplex layer, the maximum external quantum efficiency (EQE) is enhanced from 10.9% to 19.2%. The BPP-BCZ: diDBFTrz exciplex ratio of 6:4 (max EQE: 17.3%) achieves the calculated half-operation lifetime of 1881 h at 1000 cd m⁻². The findings pave the way for using exciplex as EHL in QLEDs to increase the device's operational lifetime and efficiency.