Tailoring Optoelectronic Properties of ZnO Films Through Synergistic Mg and B Co-Doping for Unprecedented High-Performance Transparent Electrode Applications

Abstract

The quest for indium-free transparent conductive electrodes with enhanced optical band gaps and superior electrical conductivity is imperative for the advancement of flexible electrochromic devices. This study presents a groundbreaking approach wherein composite ZnO films, incorporating Mg and/or B dopants through a facile sol–gel spin coating method, are meticulously crafted and systematically scrutinized for their optoelectrical properties. Our findings reveal that Mg doping primarily influences the optical band gap, while B doping facilitates the augmentation of free electrons by modulating morphology and electronic defect states. Optimal performance is achieved with pure Mg doping at an atomic molar concentration of 0.2, resulting in a ZnMgO film boasting an exceptional average transmittance of 98.79% and an impressively low electrical resistivity of 15.3 Ω·cm. Although pure B doping compromises the crystalline quality, it significantly reduces electrical resistivity. Intriguingly, co-doping with Mg at an atomic molar concentration of 0.2 introduces challenges to crystalline quality but enriches the composite film with additional charge carriers, leading to a reduction in bandgap and a remarkable drop in resistance to 6.2 Ω·cm. This innovative work not only sheds light on the delicate balance between Mg and B doping in ZnO films but also paves the way for unparalleled opportunities in the development of high-performance transparent conductive electrodes for flexible electrochromic devices.