Performance enhancement of ITO/oxide/semiconductor MOS-structure silicon solar cells with voltage biasing
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NANO EXPRESS
Open Access
Performance enhancement of ITO/oxide/ semiconductor MOS-structure silicon solar cells with voltage biasing Wen-Jeng Ho*, Min-Chun Huang, Yi-Yu Lee, Zhong-Fu Hou and Changn-Jyun Liao
Abstract In this study, we demonstrate the photovoltaic performance enhancement of a p-n junction silicon solar cell using a transparent-antireflective ITO/oxide film deposited on the spacing of the front-side finger electrodes and with a DC voltage applied on the ITO-electrode. The depletion width of the p-n junction under the ITO-electrode was induced and extended while the absorbed volume and built-in electric field were also increased when the biasing voltage was increased. The photocurrent and conversion efficiency were increased because more photo-carriers are generated in a larger absorbed volume and because the carriers transported and collected more effectively due to higher biasing voltage effects. Compared to a reference solar cell (which was biased at 0 V), a conversion efficiency enhancement of 26.57% (from 12.42% to 15.72%) and short-circuit current density enhancement of 42.43% (from 29.51 to 42.03 mA/cm2) were obtained as the proposed MOS-structure solar cell biased at 2.5 V. In addition, the capacitance-volt (C-V) measurement was also used to examine the mechanism of photovoltaic performance enhancement due to the depletion width being enlarged by applying a DC voltage on an ITO-electrode. Keywords: Conversion efficiency; ITO; Metal oxide semiconductor; Silicon solar cell; Voltage biasing
Background To face the threat of global warming caused by fossil fuel-based energy consumption, researchers have been encouraged to search for a viable form of energy that generates minimal CO2 emissions. Photovoltaic energy can provide a good option as a renewable source in the future because it is a clean form of energy. However, the cost per unit of electricity generated from a photovoltaic system is higher than the retail price of electricity generated by more conventional means today. Presently, the dominant photovoltaic technology is based on bulk wafer-based crystalline silicon (Si) technology. Thus, reducing the cost of Si material would be one of the first options to consider in attempting to reduce the cost of electricity generated by photovoltaic systems. However, while the cost of bulk materials used in these photovoltaic cells has steadily decreased over the past 10 years, this trend cannot continue indefinitely. On the other hand, researchers have also been trying for decades to improve * Correspondence: [email protected] Department of Electro-Optical Engineering, National Taipei University of Technology, No. 1, Sec. 3, Zhongxiao E. Road, Taipei 10608, Taiwan
the efficiency of photovoltaic devices and reduce the cost of their fabrication by using novel device structures involving relatively simple fabrication methods. In fact, a number of alternate structures have been used to achieve higher efficiency, including hetero-junction [1-3], multijunction [4-6], metal-insulator-semiconductor (MIS) [
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