Improving The Performance Of Light Emitting Diodes By Buried Interface Modification

Abstract

Metal halide perovskite light-emitting diodes (PeLEDs) have recently emerged as a promising technology for next-generation displays and lighting applications due to their remarkable optoelectronic properties and low-cost solution-processed fabrication. Although the external quantum efficiency of PeLED in both visible and near-infrared region have attached to exceeding 20%, it still have room for improvement in terms of efficiency compared to commercially-available organic light-emitting diodes. The interfaces of PeLEDs are prone to have a multitude of defects, leading to an increase in the density of deep-level trap states. This, in turn, results in enhanced non-radiative recombination. Additionally, within the interfaces, the inhomogeneous interface contact, as well as imbalanced charge carrier injection may lead to a charge accumulation problem. These problems significantly detrimental to the performance of device. However, there are few reports on the research of buried interface modification. Herein, this work selected functional molecules of [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) as the interface modifier of ITO/hole transport layer and phenylphosphonic acid (PPA) to modify the hole transport layer/perovskite interface. The optimized device exhibits significantly enhanced luminance, accompanied with an increase in external quantum efficiency from 5.6% to 6.2%. This improvement is attributed to enhanced interfacial adhesion strength, improved film morphology properties, the balanced injection of holes and electrons, suppressed current leakage and the passivation of halogen vacancies. Notably, thanks to the above mentioned improvement, the efficiency roll-off of target devices is significantly suppressed. This work emphasizes the importance of interface optimization, and provides two more alternative modifiers of interfacial engineering in PeLED field.