The influential role of ITO heat treatment on improving the performance of solar cell n-ITO/p-Si junction: Structural, optical, and electrical characterizations

Abstract

Electron beam evaporated film of ITO deposited on glass substrate was annealed from 100 °C to and 350 °C. The effect of the thermal treatment upon the growth, microstructural, optical, and electrical properties are studied. A cubic type of structure was observed for all the investigated films with no sign of impurities. It is found that the crystallite size increases for the film that annealed at the temperature ≤250 °C and it reduces at the temperature ≥300 °C. Furthermore, the clearness of ITO films was enhanced by the annealing due to the improvement of crystallinity. The optical energy gap Egopt is increased for the film that annealed at the temperature ≤250 °C, which is ascribed to the upgrading of the crystallinity and the increase in the crystallite size. On the other hand, at the higher annealing temperature (≥300 °C) the Egoptis decreased due to the increase of the defects. It has been observed that the optical constants, n, and k, decreased for the film that was annealed at the temperature ≤ 250 °C and it was increased at the annealing temperature ≥ 300 °C. The decrease in the refractive index is due to the observed lattice shrinking while the increase in the film density is associated with the increase in refractive index. The electrical measurements show that as the temperature increases to 250 °C, the electrical resistivity and sheet resistance decrease, which is ascribed to the enhancement of the film crystallinity and the increase of the grain size. However, the resistivity slightly increases with the further increase of the annealing temperature ≥ 300 °C due to the decrease in the grain size. It can be concluded that the post-deposition heat treatment of the ITO film improves the crystallinity, crystallite size, the transparency in the visible region. The higher conductivity of the annealed ITO allows the ITO to be the most promising candidate for optoelectronics and solar cell applications. Finally, the Ni (Al) /n-ITO/p-Si/Al heterojunction has been successfully assembled. The dark (cutting-edge-voltage) traits of fabricated heterojunctions had been suggested at distinctive different annealing ITO, as well as for voltages ranging from − 2 to 2 volts.