Properties of ZnO thin films for solar cells grown by chemical bath deposition

摘要

Thin films of ZnO were deposited by chemical bath deposition. The “as grown” films are amorphous or polycrystalline depending upon the chemical composition of the aqueous solution and the temperature used for their deposition. After a thermal annealing at temperatures above 300° C, the films undergo a chemical phase transformation becoming ZnO. The films before and after the annealing show a bandgap around 4.2 eV and 3.3 eV, respectively. The ZnO films were used to make solar cells on CuInS₂ prepared by chemical spray pyrolysis. Under AM 1.5 illumination, these devices show a short-circuit current of the order of 10 mA/cm2, an open-circuit voltage of 350 mV and efficiency close to 2.2%