| Summary: | 碩士 === 國立臺北科技大學 === 光電工程系研究所 === 103 === This study demonstrated the concept of a Metal/Oxide/Semiconductor (MOS) structure for fabricating high-efficiency silion solar cell. The reflectivity and the thickness of ITO/Al2O3/TiO2 films were simulated to obtain the best optical properties. Significantly increased in photocurrent and conversion efficiency were obtained when the cell applied with a biasing voltage. The optical and electrical properties for MOS solar cell using double layer of TiO2 and Al2O3 as passivation layer are investigated. The transparent indium tin oxide (ITO) electrode was obtained using a thermally sputtering deposition. The property Metal/Double Oxide structure exhibited a good anti-reflection (AR) property and has broadband low reflectance on visible wavelength. The depletion width of p-n junction under the ITO transparent electrode would be extended more deeply and obtained more large volume of absorption when the biased voltage increased. Thus, the short-circuit current and conversion efficiency of MOS solar cell are further enhanced. In addition, the Ti/Al metal pattern was deposited on the ceramic substrates by e-beam evaporation. Finally, the MOS solar cells and the solar cells of biasing source were die-bonding and wire bonding on the ceramic substrate. Therefore, MOS-structure and photovoltaic biasing solar cell were hybrid integrated on a ceramic substrate.
In the selection of the material and the thickness of the space layer, the cell with a 20 nm TiO2 space layer has the best performance having low reflectance and low leakage current. Under AM1.5G illumination and at temperatures of 25°C, the characteristics of the fabricated cell are characterized in following stages. (1) Bare solar cell: The open-circuit voltage (Voc) of 0.55 V, short-circuit current density (Jsc) of 26.22 mA/cm2 and conversion efficiency (η) of 10.61 % are presented. (2) Solar cell coated with TiO2 (15 nm) and Al2O3 (5 nm) layer：Voc of 0.55 V, Jsc of 29.38 mA/cm2 and η of 11.82 % are obtained. (3) Solar cell coated with TiO2 (15 nm), Al2O3 (5 nm) and ITO layer (50 nm)：Voc of 0.55 V, Jsc of 33.53 mA/cm2 and η of 13.58% are obtained. (4) Solar cell coated with TiO2 (15 nm)/Al2O3 (5 nm)/ITO layer (50 nm) and ITO electrode biased at + 3.75 V：Voc is increased from 0.55 V to 0.56 V, Jsc is increased to 53.11 mA/cm2, and η is increased to 20.05 %. Besides, the capacitance-voltage (C-V) of MOS-structure silicon solar cell was measured to confirm the depletion width as a function of the biasing voltage.
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