The role of MoO3 doping in tuning the optical absorption, energy gap, and photoluminescence properties of NiO nanoparticles for photodetector applications

Photodetectors are crucial optoelectronic devices that play a significant role in modern technological applications due to their unique photoresponsive properties. This study investigates the influence of molybdenum oxide (MoO₃) doping on the structural, optical, and diode characteristics of nickel oxide (NiO) nanoparticles (NPs) synthesized via a simple co-precipitation method. The XRD pattern of pure NiO NPs exhibits a cubic phase, while all MoO₃-doped NiO samples display dual crystal structures corresponding to cubic NiO and orthorhombic MoO₃. The crystallite size decreases from 20 to 14 nm with increasing MoO₃ concentration. FESEM images reveal a randomly oriented sheet-like surface morphology, and the EDX spectrum confirms the elemental composition of the MoO₃-doped NiO NPs. TEM analysis further supports the sheet-like morphology and polycrystalline nature of the samples. The optical band gap energy decreases from 3.7 to 3.1 eV upon MoO₃ incorporation. The PL spectrum exhibits three emission peaks at 414, 485, and 530 nm. All fabricated diodes demonstrate a positive photoresponse under illuminated conditions. In particular, the p-MoO₃@NiO/n-Si diode with 9-wt.% MoO₃ exhibits the highest responsivity (134.6 mA·W^-1), quantum efficiency (532.3%), and detectivity (10.3 × 10⁹ Jones). These findings suggest that the p-MoO₃@NiO/n-Si heterojunction diode is a promising candidate for next-generation optoelectronic applications.