Enhanced performance of GaN-based ultraviolet light emitting diodes with ITO/graphene/ITO transparent conductive layer

Abstract

In this paper, a method of indium-tin oxide /Graphene /Indium-tin oxide (ITO/Gr/ITO) structure as transparent conductive layer (TCL) to improve the current spreading of ultraviolet light-emitting diodes (UV-LEDs) is reported. The ITO/Gr/ITO structure is obtained by RF magnetron sputtering and wet-transferred. Raman spectroscopy measurement further reveal that the number of inserted graphene in the structure are single layer and few layers. It can be found that the forward voltage of optimized LEDs with ITO/Gr/ITO TCL is significantly reduced. Furthermore, the light output power (LOP) and the wall plug efficiency (WPE) of the LEDs with ITO/Gr/ITO structure have also been improved significantly compared with that of the conventional LED with ITO TCL. Light distribution analysis shows that the introduction of ITO/Gr/ITO structure as TCL in UV-LEDs is an effective method to improve the current spreading. As a result, an LED with a 45.7% increase in LOP at 100 mA, and a 52% increase in maximum WPE is obtained by the use of ITO/Gr/ITO with a single graphene interlayer.