Blue top-emitting organic light-emitting devices using Alq3 as phase shift adjustment layer

Blue top-emitting organic light-emitting devices (TEOLEDs) are demonstrated by employing Alq₃ as phase shift adjustment layer (PSAL) to increase the phase shift on reflection of the top electrode within a range, which also improves the light out-coupling. By adjusting the thickness of PSAL, the CIE _x,y of devices, which utilize 2, 7-Di-pyrenyl-9, 9-spiro-bifluorene (DPSF) as emitting layer, changes from (0.16, 0.50) to (0.18, 0.37). The maximum current efficiency of 7.1 cd/A is acquired under 4.5 V with an increasing luminance of 139 cd/m². Compared with adjusting the total thickness of organic layer, it is more beneficial for achieving blue TEOLEDs with high efficiency.