Advancing beyond PEDOT:PSS: an innovative strategy for stable and efficient quantum dot light-emitting diodes

Abstract

Quantum dot light-emitting diodes (QLEDs) are promising optoelectronic devices for next-generation display applications. Poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS) has been widely utilized as the hole injection layer (HIL) in QLEDs due to its high conductivity. However, the strong acidity and hydroscopicity of the PSS component cause corrosion of the electrodes, which leads to device instability. Herein, a near-neutral pH PEDOT:PMA powder is synthesized as the HIL using phosphomolybdic acid hydrate (PMA) as an oxidizing agent, which exhibits higher chemical stability, electrical conductivity and work functions than PEDOT:PSS. Benefiting from improved hole mobility and better carrier balance, the state-of-the-art red QLEDs achieve the highest external quantum efficiency (EQE) of 32.24%. In addition, X-ray photoelectron spectroscopy results reveal that the permeation of dissociated indium from ITO to PEDOT:PMA is greatly delayed compared to that at the ITO/PEDOT:PSS interface, thereby enhancing the stability of the device. This work highlights a promising strategy for a stable PEDOT derivative, which could play a pivotal role in advancing high performance QLEDs.