Effect of surface treatment on an n-CdSe0.6Te0.4 thin-film photoanode/polysulphide electrolyte solar cell

Polycrystalline thin films of n-CdSe0.6Te0.4 were deposited in a vacuum of 5×10−5 Torr by thermal flash evaporation with a deposition rate of 20±1 Å/s on indium oxide coated glass plates [σ=1.25×104 (Ω cm)−1] held at 200 °C. Application of surface treatment techniques such as annealing and photoelectrochemical etching on the films revealed that the films exhibit photoelectrochemical behavior with increased conversion efficiency and stability after treatment. Gärtner’s model [Phys. Rev. 116, 84 (1954)] was used in the calculation of the solid state parameters of the films like the carrier concentration ND and minority carrier diffusion length Lp for different surface treatments. Chemical etching improves the efficiency and fill factor from 1.53% and 40% to 2.72% and 50% respectively, whereas photoelectrochemical etching improves further the efficiency to 3.83% and fill factor to 59% and the stability of the photoelectrode in the polysulphide electrolyte.