Influence of Thickness on Performance of Blue Single-Layer Organic Light-Emitting Device

Single-layer (SL) blue organic light-emitting devices (BOLEDs) with a bipolar transport host were fabricated. The effects of the active layer thickness on the color purity, efficiency, and efficiency roll-off were investigated. An SL BOLED with 70 nm active layer showed good color purity, high efficiency, and extremely low efficiency roll-off. The power efficiency at 1000 cd/cm² of the device was 13.1 lm/W. From the brightness at maximum external quantum efficiency to high brightness of 5000 cd/m², the efficiency roll-off was 11.8%. The excellent performance could be attributed to the broader exciton formation zone and balance of charge carrier injection and transport.