The influence of Cu2O crystal structure on the Cu2O/ZnO heterojunction photovoltaic performance

Cuprous oxide (Cu2O) films were potentiostatically electrodeposited onto platinum (Pt) film coated onto silicon (Si) wafer from lactic solution at pH 9. The influence of applied potential on Cu2O crystal structure was carefully examined. At higher electrochemical applied potential, a polycrystalline structure was observed, and then as the applied potential decreased, a single crystalline structure oriented along (111) was obtained. Further decrease in the applied potential leads to the formation of a polycrystalline structure and finally at much lower applied potential, a single crystalline structure growing along (200) orientation (equivalent to (100) orientation) was revealed. Cu2O/ZnO heterojunction photodiodes based on these three crystal structures were fabricated and studied under dark and illuminated conditions. The best performance of the solar cell efficiency was achieved by the heterojunction based on (111) oriented Cu2O film (approximate to 1.45%) compared to other structures (0.34% and 0.25%), which may be attributed to the formation of high quality heterojunction interface due to the heteroepitaxial-like growth of (002) oriented ZnO. (C) 2015 Elsevier Ltd. All rights reserved.