AbstractTo cut cost and improve device performance, expensive and acidic hole transport material (HTM) PEDOT:PSS is replaced by copper(I) thiocyanate (CuSCN) and NiO_x in solution‐processed white organic light‐emitting diodes, respectively. However, the luminescence quenching caused by interfacial defects on the surfaces of CuSCN and NiO_x 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 NiO_x/GO achieves an enhancement of power efficiency by 98%, from 10.1 to 20.0 lm W⁻¹.