Regulation of the conductivity and work function of PEDOT:PSS using MoO2 nanocrystals to achieve efficient CsPbBrxI3-x red light quantum dot light-emitting diodes

Abstract

It is well known that the balanced charge injection helps prepare high-performance red light-emitting diodes (LEDs) in the electroactive material CsPbBrxI3-x quantum dots (QDs). Employing a hydrothermal method, we synthesized MoO2 nanocrystals and doped them into Poly(3,4-ethylenedioxythiophene) /poly(styrenesulfonate) (PEDOT:PSS). The results show that the synthesized MoO2 nanocrystals can modulate the work function of PEDOT:PSS and enhance the conductivity of the PEDOT:PSS films, which is attributed to disrupting the hydrogen bond between PEDOT and PSS, and inducing the transition of PEDOT from benzoid to quinoid structure. In the PEDOT:PSS-xMoO2 film, the work function increases from 4.9 eV to 5.09 eV when the content of x is 15%, which reduces the energy barrier between the PEDOT:PSS-xMoO2 and the hole transport layer: poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzi (poly-TPD), thus promoting the hole transport and improving the Von of the devices. Additionally, the device's external quantum efficiency (EQE) reaches a maximum value of 7.53% at x = 15% enabling an improvement of 2.6 times over the base device (EQE=2.10%). This work proves that PEDOT:PSS-xMoO2 as a hole transport layer is an effective material for preparing high-performance QD-LEDs.