Temperature Dependence of Silicon-based Thin Film Solar Cells on Their Intrinsic Absorber
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0989-A24-02
Temperature Dependence of Silicon-based Thin Film Solar Cells on Their Intrinsic Absorber Kobsak Sriprapha1, Ihsanul Afdi Yunaz1, Shuichi Hiza1, Kun Ho Ahn1, Seung Yeop Myong1, Akira Yamada2, and Makoto Konagai1 1 Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1, S9-9, O-okayama, Meguro-ku, Tokyo, 152-8552, Japan 2 Quantum Nanoelectronics Research Center, Tokyo Institute of Technology, 2-12-1, S9-9, Ookayama, Meguro-ku, Tokyo, 152-8552, Japan
ABSTRACT The temperature dependence of Si-based thin film single junction solar cells on the phase of the intrinsic absorber is investigated in order to find the optimal absorber at high operating temperatures. For comparison, hydrogenated amorphous, protocrystalline and microcrystalline silicon solar cells are fabricated by plasma-enhanced chemical vapor deposition (PECVD) and hot-wired chemical vapor deposition (HWCVD) techniques. Photo J-V characteristics are measured using a solar simulator at an ambient temperature in the range of 25-75 oC. We found that the protocrystalline silicon solar cells provided the lowest temperature coefficient for the efficiency, while the microcrystalline silicon solar cells were highly sensitive to the temperature. Experimental results indicated that protocrystalline silicon is a promising material for using as an intrinsic absorber of Si-based thin film solar cells which operating in high temperature regions. INTRODUCTION In general, the solar cell performance is measured under the standard test condition (STC) at room temperature (25 oC). Under outdoor installation, in fact, the operating temperature of solar cells considerably changes according to circumstances, i.e., the climate in the installed area. In a tropical climate region, the operating temperature often reaches more than 70 oC. The increase in the operating temperature leads to the decline in solar cell efficiency (η) mainly due to the drop in the open-circuit voltage (Voc) [1-3]. In the case of silicon (Si)-based solar cells, bulk crystalline Si solar cells including single crystalline-Si (c-Si) and polycrystalline-Si (polySi) solar cells show higher η than thin film solar cells at room temperature. However, η of c-Si and poly-Si solar cells seriously decreases with an increase in the operating temperature, compared to hydrogenated amorphous Si (a-Si:H)-based thin film solar cells [5-8]. The main reason for the lower temperature coefficient (TC) for a-Si:H-based solar cells is due to their wide band gap intrinsic absorber. Taking real output power affected by the operating temperature and production cost into account [3], a-Si:H-based thin film solar cells have advantages over bulk crystalline-Si solar cells for use in high temperature area such as a tropical climate region. It is well known that a-Si:H-based thin film solar cells exhibit light-induced degradation so-called the Staebler-Wronski effect (SWE). The SWE in Si-based thin film solar cells is also a very important factor that needs to be concerned for outdoor installation. During t
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