Transparent conducting oxides (TCOs) are crucial materials in optoelectronics, but p-type TCOs are less studied than n-type TCOs. NiO, for typical p-type TCOs show promising potential applications in transparent optoelectronic devices. In this study, Li_xNi_1–xO thin films with varying thickness and Li doping levels on MgO(001) substrates are successfully fabricated using pulsed laser deposition. The results demonstrate that increasing both thickness and Li doping level will reduce the resistivity of the films, with the maximum optical bandgap observed at a thickness of 50 nm and 3% Li doping level. Based on the control of physical properties through film thickness and Li doping, the p-type Li_xNi_1–xO with the largest bandgap is selected to construct transparent electronic devices with n-type La-doped ASnO₃ films. The I -V tests confirm the rectification properties of the heterostructures, successfully demonstrating the formation of pn junctions. This work expands the potential applications of transparent electronic devices by integrating p-type NiO with n-type ASnO₃.