Study of the properties of heterostructures based on semiconductor metal oxides obtained by electrochemical deposition.

Abstract

The main goal of this thesis was to improve the performance of the electrodeposited Cu2O/ZnO heterojunction device by applying many strategies, such as the insertion of ZnO buffer layer, adjusting the pH of Cu2O deposition bath and engineering a back surface field architecture. At first, we deposited a p-Cu2O layer on n-ZnO (or AZO) layer by two steps electrodeposition. The properties of Cu2O/ZnO and Cu2O/Al:ZnO heterojunctions were investigated and we confirmed a good performance for Cu2O/ZnO device. To improve the performance for of this latter we deposited Cu2O/ZnO/Al:ZnO device by inserting ZnO layer, with different thickness, between Al: ZnO and Cu2O to enhance the mismatch and reduce the band offset. The device with 200nm ZnO show improvement of the performance compared to Cu2O/ZnO and Cu2O/Al: ZnO. Then, we improved the quality of Cu2O by increasing the deposition pH values and used it as an absorber layer. The Cu2O/ZnO heterojunction with 500 nm Cu2O deposited at pH 12 shows the best performance due to the low valence band offset of 1.8 eV. Finally, we fabrication Cu2O+/Cu2O/ZnO to enhance the light absorbance and the carrier collection length by the creation of back surface field devices. The 150 nm Cu2O+/300 nm Cu2O/ZnO heterojunction shows the best performance due to the low band valence offset (∆Ev) between 150 nm Cu2O+/300 nm Cu2O structure and ZnO layer.