Thickness and doping-dependent properties of Li-doped NiO thin films for rectification effect of <i>pn</i> junction

Transparent conducting oxides (TCOs) are crucial materials in optoelectronics, yet p-type TCOs are less studied compared to n-type TCOs. NiO as a typical p-type TCO shows promising potential for transparent optoelectronic devices. In this study, we successfully fabricated Li<i>_x</i>Ni_1-<i>x</i>O thin films with varying thicknesses and Li doping levels on MgO(001) substrates using pulsed laser deposition. The results demonstrate that both increased thickness and Li doping levels reduce the resistivity of the films, with the maximum optical bandgap observed at a thickness of 50 nm and 3% Li doping levels. Based on the control of physical properties through film thickness and Li doping, p-type Li<i>_x</i>Ni_1-<i>x</i>O with the largest bandgap were selected to construct transparent electronic devices with n-type La-doped ASnO₃ films. I-V tests confirmed the rectification properties of the heterostructures, successfully demonstrating the formation of <i>pn</i> junctions. This work enhanced the potential applications of transparent electronic devices by integrating p-type NiO with n-type ASnO₃.