- 學位論文
ZnO/GaP/CIGS/Mo異質結構太陽能電池之應用與特性
Characteristics of ZnO/GaP/CIGS/Mo heterostructure and its solar cell
摘要
近來年，太陽能電池是太陽能應用的重要發明，許多人將太陽能電池作為綠色能源。目前矽原料價格高漲，進而開始有人使用其它窄能隙材料作為太陽能電池之吸收層，如銅銦鎵硒(Copper Indium Gallium Diselenide，CIGS)因其能隙為1.02~1.68eV，為一直接能隙半導體材料，具有較高吸收係數，因此被視為有潛力高效率太陽能電池之吸收層材料。 本論文係以射頻反應式磁控濺鍍系統製備銅銦鎵硒薄膜太陽能電池，其結構為Al / Ti / ZnO / GaP / CIGS / Mo/ Glass。本實驗主要探討三個部分，一是探討雙層鉬與CIGS吸收層之表面形貌、電特性及結晶性，經由電子顯微鏡、霍爾量測、X-ray繞射儀分析、二是GaP緩衝層取代傳統習知的CdS緩衝層，探討GaP緩衝層對元件效率的影響。三是探討ZnO薄膜以液相化學式氣相沉積法沉積對元件效率的影響。 由實驗成功以高製程壓力及低製程壓力製備出雙層鉬，高製程壓力可提供高附著性的薄膜、低製程壓力則可提供低電阻率的薄膜，其最低電阻率為2.43x10-4Ω-cm。此外，透過I-V curve分析發現CIGS吸收層與Mo薄膜界面具有良好的歐姆接觸，而XRD量測繞射峰值約在2θ=37.5o以及43.54o。CIGS薄膜在退火400℃下有最低電阻率1.5 x 10-2Ω-cm，且由XRD量測證明在高溫退火下可有效增加CIGS黃銅礦結晶特性，其繞射峰值約在2θ=26.7o(112)、44.38o(204/220)以及52.54o(116/312)其中(112)面為此CIGS薄膜之優選取向，與SEM圖在高溫退火下形成顆粒結果相符。最後量測元件面積為0.3×0.3 cm2之最佳轉換效率，測得開路電壓170mV、短路電流密度0.556mA、填充因子0.36及效率為0.034%。
並列摘要
Recently, the solar cell is the most important inventions for solar energy applications. The solar cell was regarded as renewable energy. At present, silicon material prices rises gradually. Some people commence to find others materials as absorption layer of solar cells. For example, CIGS is a direct band gap semiconductor material with band gap ranging from 1.02 ~ 1.68 eV. It possesses higher absorption coefficient. Therefore, CIGS is regarded as the most potential absorption layer for high efficiency solar cells. In this study, the CIGS-based thin film solar cell grew by reactive magnetron sputtering system. The structure of the CIGS-based thin film solar cells is Al / Ti / ZnO / GaP / CIGS / Mo / Glass. The research discussed three parts. First, Scanning electron microscope equipped and X-ray diffraction were employed to analyze surface morphology and crystal qualities on CIGS film and bi-layer Mo film. Hall measurement was employed to analyze electrical of CIGS film and bi-layer Molybdenum film. Second, the effect of the GaP buffer layer instead of traditional CdS buffer layer on device performance. Third, the effect of ZnO thin film prepared by Ultrasonic spray pyrolsis on device performance. The bi-layer structure of Molybdenum back contact was deposited under higher working pressure and lower working pressure respectively. The former layer deposited at higher working pressure had good adhesion, and the latter one deposited at lower working pressure had low resistivity. The resistivity of bi-layer Mo electrode is 2.43x10-4Ω-cm. Furthermore, the I-V measurement analysis shows that Mo and CIGS have a good ohmic contact. In the XRD pattern, the diffraction peaks locate at 37.5o, 43.54o. The resistivity of CIGS absorption layer is 1.5 x 10-2Ω-cm at annealing temperature of 400℃. In the XRD pattern, it can be observed that annealing at high temperature can effectively increase the chalcopyrite crystal quality and grain size of CIGS films. The diffraction peaks of the chalcopyrite locate at 26.7o(112), 44.38o(204/220) and 52.54o(116/312). Finally, The fabricated cell of 0.09 cm2 active area shows an efficiency of 0.034 % with Voc = 170mV, Jsc = 0.556mA/cm2, FF = 0.36 under 100 mW/cm2 AM 1.5 illumination at 25℃.