Fabrication and Photoelectrical Properties of AZO/SiO 2 /p-Si Based Device
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1123-P05-14
Fabrication and Photoelectrical Properties of AZO/SiO2/p-Si Based Device Z.Q. Ma1, B. He1, J. Xu2, L. Zhao1, F. Li1, N.S. Zhang1, X. J. Meng1, L. Shen1 and C. Shen1 1
SHU-SolarE PV Laboratory, Department of Physics, Shanghai University, Shanghai 200444, P.R.China
2
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Hubei 430070, P. R. China
ABSTRACT In order to fabricate AZO/SiO2/p-Si heterojunction device and let it be an absorber of ultraviolet response cell. Zinc oxide (ZnO) thin films doped with aluminum (AZO) were deposited on p-Si(100) substrates covered with silicon dioxide (SiO2) by radio frequency magnetron sputtering. The optical and electrical properties of the Al doped - ZnO films were characterized by UV-VIS spectrophotometer, current-voltage measurement, and four point probe technique, respectively. The results show that the device is a typical tunneling diode for minority carrier and a strong obstructing effect from majority carriers. The potential rectifying behavior and photovoltaic characteristic is present at dark current and weak light illumination, respectively. KEYWORDS: Photovoltaic, Optical properties, Electrical properties INTRODUCTION As shown in the previous work, semiconductor-insulator- semiconductor (SIS) diodes have certain features which make them more attractive for solar energy conversion than conventional Shottky, MIS, or other heterojunction devices [1]. For example, efficient SIS solar cells as indium tin oxide (ITO) on silicon have been reported, where the crystal structures and the lattice parameters of Si (diamond, a = 0.5431 nm), SnO2 (tetragonal, a = 0.4737 nm, c = 0.3185 nm), and In2O3 (cubic, a = 1.0118 nm) show that they are not particularly compatible and thus are not likely to form good photovoltaic devices. However, the SIS structure is potentially more stable and theoretically more efficient than either a Schottky or a MIS structure. The origins of this potential superiority are the tunneling suppression of majority-carrier in the high potential barrier region of SIS structure, and the existence of the thin interface layer which minimizes the amount and the impact of the interface states. This results in an extensive selection of the p-n junction partner with a matching band gap in the front layer. In addition, the multi-function of the front semiconductor film could be served as an antireflection coating [2], a low-resistance window, as well as the collector of the p-n junction. Furthermore, the semiconductor with a wide band gap as the top layer of SIS device can
eliminate the surface dead layer which often occurs within the homojunction devices. On the other side, this absence of the light absorption of visible region in a surface layer can improve the ultraviolet response of the internal quantum efficiency (IQE). Among many transparent conductive oxides (TCO) of transition metals, ZnO:Al is one the best n-type semiconductor materials. It has low resistivity, high transmittance, opt
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