A study on single-layered white organic light-emitting diodes based on Co-host system using solution process.

Two color white organic light-emitting diode (WOLED) that used a co-host system in a solution process method was prepared. A device configuration is ITO/PEDOT:PSS (40 nm)/emitting layer (50 nm)/TPBi (20 nm)/LiF (1 nm)/Al. The emitting layer consists of TATa+ alpha-NPB or beta-NPB + DPAVBi (blue dopant) + Rubrene (yellow dopant). The device using alpha-NPB or beta-NPB showed white color of CIE (0.30, 0.40) and (0.29, 0.39), respectively. Device efficiency of alpha-NPB was 3.85 cd/A at 100 mA/cm2, which is about 15% higher than beta-NPB's.