Photovoltaic Solar Cells With Thin Film Materials

Transparent thin layers of SnO2 and ZnO and absorbing materials like CuInSe2 and porous silicon have been deposited on glass or silicon substrates by different techniques of deposition as chemical vapour deposition (CVD), spray pyrolysis, flash evaporation and electrochemical anodization. Deposition parameters such as temperature substrate, deposition time or annealing parameters for SnO₂ or spray time, deposition temperature or solution concentration for ZnO were varied. The polycrystalline films were found to exhibit wurtzite structure for SnO₂, hexagonal structure for ZnO and chalcopyrite structure for CulnSe2. A preferential orientation of the grains appears when substrate temperature was varied. The thickness of the films was measured by Talystep instrument, interferential microscopy and from the peaks of transmission spectra. Variation of electrical conductivity with deposition parameters was analysed. The deduced activation energy depends on thermal annealing. In order to derive refractive index and coefficient absorption, reflectance R and transmittance T were measured. Heterojunction solar cell has been fabricated by deposition of tin oxide on monocrystalline silicon.