Interface Passivation and Hole Injection Improvement of Solution-Processed White Organic Light-Emitting Diodes through Embedding an Ultrathin Graphene Oxide Layer

To cut cost and improve device performance, expensive and acidic hole transport material (HTM) PEDOT:PSS is replaced by copper(I) thiocyanate (CuSCN) and NiOx in solution-processed white organic light-emitting diodes, respectively. However, the luminescence quenching caused by interfacial defects on the surfaces of CuSCN and NiOx limits the devices' full potential. To crack the nuts, an ultrathin graphene oxide (GO) layer is inserted between hole transport layer (HTL) and emitting layer (EML) as a passivation layer. The time-resolved photoluminescence spectra of EML intuitively prove the inhibitory effect of GO on exciton quenching. What is more, the ultraviolet photoelectron spectroscopy and impedance spectroscopy reveal that the ultrathin GO layer can also increase the work function of HTM and promote hole injection. Relative to the devices without a GO layer, the efficiency of CuSCN/GO-containing device is enhanced from 18.1 cd A(-1) (6.6 lm W-1) to 30.3 cd A(-1) (19.8 lm W-1), and the device with NiOx/GO achieves an enhancement of power efficiency by 98%, from 10.1 to 20.0 lm W-1.

Automated summary

The study replaced expensive and acidic HTM with CuSCN and NiOx in white organic light-emitting diodes to cut costs, but luminescence quenching due to interfacial defects limited device potential. By inserting an ultrathin GO layer, the inhibitory effect on exciton quenching was proven, while also increasing the work function of HTM and promoting hole injection, significantly enhancing device efficiency.