Study of p-/n-Type Co-Host System in Single Emissive White Phosphorescent Organic Light-Emitting Devices Using Glass and Flexible Substrate

The performance of co-host system including both p-type host material of N,N'-dicarbazolyl-3,5-benzene (mCP) and n-type host material of 2´,2´,2´´-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) was demonstrated for enhancing efficiency and color stability in single emissive white phosphorescent organic light-emitting devices (PHOLEDs) with three primary colors (blue, green and red) via broad expansion of the recombination region. The luminous efficiency and external quantum efficiency (EQE) of single emissive white PHOLEDs with the co-host system is higher than for devices without the co-host system due to engineering of the recombination zone. This zone occurs near the interfaces between hole transport layer and emissive layer or emissive layer and electron transport layer when only p- or n-type materials are used as host material. Additionally, we fabricated the single emissive white PHOLEDs on flexible substrate and compared with them on glass substrate.