Photon-Assisted Electrochemical Construction of <0001>-n-ZnO/<111>-p-Cu2O Photovoltaic Devices with Intermediate TiO2 Layer
The Cu2O layer was prepared by heteroepitaxial electrodeposition on <111>Au/Si wafer substrate in an alkaline solution containing copper acetate and lactic acid. The ZnO layer was stacked on the Cu2O layer by elecrodeposition in a zinc nitrate solution with light irradiation. The PV device was fabricated by stacking the top Al electrode by evaporation.
The light irradiation was needed to grow the <0001>-ZnO layer having the columnar grain morphology and 3.3 eV bandgap energy on the Cu2O layer without the reduction to metallic Cu. The thickness increased with the deposition time up to 30 min and then decreased. And the pores could be observed for the ZnO layer at the deposition time over 30 min. The <0001>-ZnO/<111>-Cu2O PV device showed a photovoltaic performance under AM1.5 illumination, and the performance changed depending on the deposition time, which strongly affected the structure of the resultant ZnO layer. The best photovoltaic performance with short-circuit current density of 2.93 mAcm2 could be obtained for the substrate-type <0001>-ZnO/<111>-Cu2O PV device prepared at 30 min for the ZnO deposition.
Ref. 1. B. M. Fariza, M. Izaki, et al., Thin Solid Films, 520(2012), 2261.