A facile sol–gel spin-coating fabrication of Ni@WO3 thin films and highly rectifying p-Si/n-Ni@WO3 heterojunction for optoelectronic applications

The WO3 thin films and p-Si/n-Ni@WO3 junction diodes are prepared with different wt% of Ni. The XRD profiles confirm that the monoclinic crystal system with a preferential orientation of (0 2 0) plane, in which their crystallite size is reduced from 28 to 14 nm with the rise of Ni content in WO3. From SEM images, the randomly arranged plate-like grain structure was observed for grown films and grain size reduces with an increase in Ni dopant concentration. The expected elements of Ni, W, and O are confirmed by the EDX spectrum and their ratio of composition was obtained. The UV–Vis-NIR spectra reveal that the 4 wt% of Ni@WO3 film exhibits a higher transmittance (~ 80%) with a low bandgap (Eg = 2.84 eV) value. The d.c. electrical conductivity increased with an increase in temperature for each Ni-doped WO3 films. The device ideality factor (n) and barrier height (ΦB) values were found to be decreased with a rise in Ni doping concentration. The better performance of the fabricated diode is observed p-Si/n-4 wt% of Ni@WO3 heterojunction diode with n = 1.820 and ΦB = 0.759 eV values. The obtained results suggest that the p-Si/n-Ni@WO3 diode is more suitable for optoelectronic device applications.