Enhanced hole injection and transport property of thermally deposited copper thiocyanate (CuSCN) for organic light-emitting diodes

Due to its high conductivity, broad bandgap, and low manufacturing cost, copper thiocyanate (CuSCN) thin film has been considered a good hole injection layer (HIL)/transport layer in many opto/electronic devices. However, the CuSCN thin films made by the conventional wet process have limitations in terms of interfacial deterioration due to solvent incorporation and charge trap formation due to impurities. We produce a CuSCN film for HIL in organic light-emitting diode (OLED) devices using vacuum deposition and compare it to a solution-processed film. In comparison to the control device, the CuSCN HIL insertion lowers the driving voltage of fabricated OLEDs by 1.0–1.5 V. The low-voltage operation corresponds to better hole transport in hole-only devices. The vacuum-deposited CuSCN, in particular, has an impurity-free composition and a high density of band-tail states, according to chemical and electronic structural studies. Because of their outstanding quality, vacuum-deposited CuSCN films show clear advantages over solution-based films in device performance and manufacture.