Improvement in optoelectronics and photovoltaic properties of p-Co₃O₄/n-ZnO hetero-junction: effect of deposition time of sprayed Co₃O₄ thin films

Spinel thin films Co₃O₄ have been deposited at a temperature of approximately 400 °C using spray pyrolysis. The testimony process was carried out with different deposition times (4, 5, 6, and 8 min), indicating that the films were grown for varying durations. The objective of varying deposition times of the thin films of Co₃O₄ was to optimize the fabrication of a hetero-junction between Co₃O₄ and ZnO. XRD, SEM and Raman investigations showed that pure cubic Co₃O₄ with an irregular spindle shaped particles have been successfully obtained. The films’ thickness increased under prolonged preparation times leading to a denser surface. The optical measurements revealed that the thin layer with a deposition time of 8 min attained a total absorbance of 98% in the apparent spectrum with a band gap of 1.27 eV. The I–V characteristics recorded of FTO/ZnO/Co₃O₄/Au cells showed that all devices exhibiting a rectifying behavior with a perfect factor that varies between 3.87 and 1.64. Our results suggest that Co₃O₄ at 8 min with a carrier density of 2.414 × 10¹⁴ cm⁻³ and high absorbance is potentially a competitive hole transport material in spinel solar cells, and, the recorded characteristics of the photovoltaic phenomenon were noted a short circuit current of 1.302 mA, an open circuit voltage of 369 mV and a fill factor of 32%.