Impact of the highest occupied molecular orbital energy level of hole transport materials on the performance of organic light-emitting devices

In order to explore the relationship between the highest occupied molecular orbital (HOMO) energy level of hole transport materials (HTM) and the performance of organic light-emitting devices (OLEDs), nine HTMs based on the triphenylamine framework were studied. It is determined through experimental and simulation methods that the device performance is optimized when the HOMO energy level is within the range of -5.40 eV to -5.45 eV. The impedance characteristics of OLEDs also verify that with the increase in the HOMO energy level, the hole injection mechanism gradually shifts from tunneling injection to thermionic emission injection. This study serves as a valuable reference and inspiration for optimizing material matching in OLEDs, thus contributing to the further development of OLED technology.