Improving the performance of OLEDs by using a low-temperature-evaporable n-dopant and a high-mobility electron...

Ideal n-type layers are highly desired for high performance organic light emitting diodes (OLEDs). For the first time, we studied the combination of a low-temperature-evaporable n-dopant KBH₄ and a high mobility electron transport material 9,10-bis(3-(pyridin-3-yl)phenyl)anthracene (DPyPA). The excellent transporting property of the DPyPA: KBH₄ layer allows the fine tuning of the OLED performance by varying the thickness of the n-doped layer in a wide range (from 10 nm to 50 nm, 100 nm, 150 nm and 200 nm). The device with the optimized n-type layer thickness of 150 nm shows the best performance with a high current efficiency of 27.60 cd/A at the brightness 10,000 cd/m², which is about 40% higher than the device with a 10 nm n-type layer (19.95 cd/A at 10,000 cd/m²). The high performance is attributed to the optimization of optical path and the decrease of the loss in the organic layer/cathode interface due to the thick n-doped layer.