Chemical cyanide treatment of polycrystalline p-Cu2O/n-ZnO solar cell

Abstract

Cuprous oxide (Cu2O) and zinc oxide (ZnO) hold a very crucial position in the field of materials research because of their immense potential in many acoustic, electronic and optical applications. Cu2O is a direct-gap semiconducting material with forbidden energy gap around 2.0 eV. It has been considered as one of the most promising materials for photovoltaic applications, especially for use at the top in a cascade cell structure. The enchantment of Cu2O and ZnO as photovoltaic materials is due to fact that their constituent materials are nontoxic, abundantly available and of relatively low cost. In this work, Cu2O thin films in polycrystalline form were prepared in radio-frequency (rf) reactive magnetron sputtering route on glass substrates at different substrate temperatures. After the samples were prepared, these were taken through a crown-ether cyanide (CN) treatment. Presence of oxygen in excess compared to stoichiometry is the major active impurity in Cu2O and consequently holes are the majority charge carriers in it. With the aid of crown-ether cyanide treatment of the prepared samples, hole-mobility was found to increase and resistivity was found to decrease considerably. Finally, polycrystalline p-Cu2O/n-ZnO heterojunctions were fabricated for use in solar cells. Results of Hall measurement strongly support the observations made from DLTS studies and photocurrent measurements. Thus, our present study confirms the improvement of device performance of the p-Cu2O /n-ZnO heterojunctions on chemical cyanide treatment.