AVS 51st International Symposium
    Thin Films Monday Sessions
       Session TF-MoP

Paper TF-MoP28
Effect of a Buffer Layer on the Photovoltaic Properties of AZO/Cu@sub 2@O Solar Cells

Monday, November 15, 2004, 5:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: T. Minami, Kanazawa Institute of Technology, Japan
Authors: T. Minami, Kanazawa Institute of Technology, Japan
H. Tanaka, Gunze Limited, Japan
T. Shimakawa, Kanazawa Institute of Technology, Japan
T. Miyata, Kanazawa Institute of Technology, Japan
H. Sato, Gunze Limited, Japan
Correspondent: Click to Email
We have reported recently that high energy conversion efficiencies above 1% were obtained in Al-doped ZnO (AZO)/Cu@sub 2@O heterojunction solar cells fabricated by depositing transparent conducting AZO thin films on Cu@sub 2@O sheets. However, it is well known that a Cu metal thin film can easily be created at the interface by reducing the Cu@sub 2@O; therefore, the thin film deposition method and conditions are important considerations. In this paper, we describe the effect of a buffer layer and/or interface region on the photovoltaic properties of transparent conducting oxide (TCO)/Cu@sub 2@O solar cells fabricated with TCO thin films prepared by various deposition methods; we fabricated devices by depositing TCO films on Cu@sub 2@O sheets that had been exposed to various surface treatments or that had various thin films such as ZnO deposited as a buffer layer. The polycrystalline Cu@sub 2@O sheets (thickness of approximately 0.2 mm), prepared by heat treatment of Cu sheets (purity of 99.9%), functioned as the active layer as well as the substrate in the photovoltaic devices. Hall mobility in the resulting p-type semiconducting Cu@sub 2@O sheets was typically above 90 cm@super 2@/Vs. The TCO and buffer layer thin films were deposited by pulsed laser deposition, d.c. or r.f. magnetron sputtering. The obtained dark current-voltage and photovoltaic properties in the devices were considerably affected by both the Cu@sub 2@O surface treatments and the introduced buffer layers. In addition, these properties were dependent on not only the method used in the TCO and buffer layer thin film depositions but also the deposition conditions. For example, the rectifying characteristics and the photovoltaic properties such as conversion efficiency and fill factor were found to improve in devices incorporating an undoped ZnO thin-film buffer layer. These obtained properties are mainly related to the work function and crystallinity of the deposited thin films as well as the crystallinity of the Cu@sub 2@O sheets.}