High-performance polymer LED using NiOx as a hole-transport layer

Abstract

We present an investigation of polymer light-emitting diodes (PLEDs) with a nickelous oxide (NiO_x) interlayer fabricated using a radio-frequency magnetron sputtering system. The NiO_x layer has a stable conductivity, and it increases hole transport from an indium tin oxide anode to an emissive polymer relative to a poly[3,4-ethylenedioxythiophene] polystyrene sulfonate (PEDOT:PSS) interlayer. The NiO_x layer also maximizes hole–electron recombination within the emissive layer, which ultimately enhances the luminous efficiency of the PLED. It can be found that the oxygen content of the NiO_x film is an important factor for device performance. A PLED with a NiO_x interlayer obtained using gas with a 66% oxygen ratio performs better than those containing NiO_x layers obtained with other oxygen ratios or with PEDOT:PSS interlayers. It has a maximum luminance of 2737 cd m⁻² (at 6.2 V) and a maximum current efficiency of 7.00 cd A⁻¹ (at 39.0 mA cm⁻²). A PLED with a 66% oxygen-ratio NiO_x interlayer provides a 133% increase in current efficiency and a 173% increase in mean quantum efficiency compared to a PLED with a PEDOT:PSS interlayer.