Toshihiro Miyata
Kanazawa Institute of Technology, Japan
Title: P-type Cu2O-based heterojunction solar cells fabricated with n-type ZnO thin film prepared by electrochemical deposition method
Biography
Biography: Toshihiro Miyata
Abstract
Recently, substantially improved conversion efficiency has been reported in p-type Cu2O sheet-based heterojunction solar cells with n-type oxide semiconductor thin films prepared by the pulsed laser deposition (PLD) method. However, PLD has some disadvantages as a practical preparation method, such as low deposition rate, small deposition area and high cost. On the other hand, the electrochemical deposition (ECD) method is a deposition technique that has potential to solve these problems. This paper describes the fabrication of Cu2O based heterojunction solar cells using n-type ZnO thin film prepared by the ECD method. The n-type ZnO thin film layer was prepared on a p-type Cu2O: Na sheet using the following ECD process. Initially, a zinc nitrate aqueous solution was prepared with 0.22 M zinc nitrate and de-ionized water; after that, a 0.3 M HCl or 0.1 M KOH aqueous solution was added to adjust the pH. Next, a p-Cu2O: Na sheet was immersed in the above solution. The photovoltaic properties were strongly dependent on the fabrication conditions of n-type ZnO thin films. For example; the current density-voltage (J-V) characteristics of AZO/n-ZnO/p-Cu2O: Na solar cells showed strong dependence on the pH of the zinc acetate aqueous solution, obtaining significant improvement with a pH value of 4.9 in Figure 1. Figure 2 shows typical J-V characteristics for AZO/n-ZnO/p-Cu2O solar cells prepared under optimized deposition conditions, such as film thickness of the n-ZnO thin film. The same structure of a Cu2O heterojunction solar cell using n-type ZnO thin films was prepared by PLD, and the J-V characteristics are also shown in Figure 2. It should be noted that the J-V characteristics of the AZO/n-ZnO/p-Cu2O solar cells were the same as those when using the PLD method.