以電鍍法分層製備CIGS薄膜太陽能電池

Cu(In,Ga)Se2半導體材料屬黃銅礦(chalcopyrite)結構，其材料為直接能隙且可因In、Ga濃度的不同而調變能隙範圍於1.04 -1.68 eV間，且光學吸收係數高，熱、電穩定性也比其他材料的太陽能電池好，因此相當適合應用於薄膜太陽能電池的吸收層。本研究以分層電鍍(Layer-by-layer Electrodeposition)的製程來製備CIGS薄膜太陽能電池中的銅銦鎵硒吸收層薄膜，針對薄膜的表面形貌及膜厚、原子組成比、晶體結構及光學性質以SEM、XRF、XRD及UV-vis進行分析。硫化鎘(CdS)緩衝層部分是以化學水浴沉積法(chemical bath deposition，CBD)沉積於ITO玻璃及CIGS吸收層上，改變的參數為持溫溫度、pH值、沉積時間，以SEM觀察其膜厚及XRD檢測其結構，找出其中的最佳值應用於吸收層，再濺鍍AZO上電極並製成元件測量電流-電壓值。由研究結果顯示，CIGS吸收層以電流密度0.16 ASD的二層結構(CuGa/InSe或 InSe/CuGa) 在熱處理後可得到平坦且緻密的薄膜，其成份接近理想組成比，呈現黃銅礦結構；而CdS緩衝層以75oC、持溫5分鐘、pH= 9.5可得所需的膜厚，由XRD檢測後可知改變持溫溫度對於CdS結構並無影響，因此pH值及沉積時間才是決定膜厚及結構的關鍵條件。關鍵詞：銅銦鎵硒、CIGS、電鍍、薄膜太陽能電池。

關鍵字

銅銦鎵硒； CIGS ；電鍍；薄膜太陽能電池

並列摘要

Chalcopyrite Cu(In,Ga)Se2 is a direct bandgap, whose energy bandgap(Eg) can be adjusted between 1.04 and 1.68 eV by varying the In/Ga ratio. Its high optical absorption coefficient as well as good thermal and electrical stability make it a suitable for thin film solar cells. In this study, layer-by-layer electrodeposition process to absorber layer for CIGS thin film solar cells. The film thickness and surface morphology, atomic percentage, crystal structure, and optical properties were characterized by SEM, XRF, ICP, XRD, and UV-vis analysis. In addition, a cadmium sulfide buffer layer was deposited by chemical bath deposition (CBD) onto glass and/or CIGS absorber layer. The thickness and structure were examined by SEM and XRD, and the processing parameters such as the temperature, pH and deposition time were optimized. Finally, an AZO layer was sputtered as the top electrode, and the current-voltage curve of the device was measured. The results showed that a flat and dense CIGS absorber layer can be obtained by two-layer electrodeposition (CuGa/InSe or InSe/CuGa) with a current density of 0.16 ASD followed by thermal annealing. The atomic percentage ratio was close to the ideal composition (Cu:In:Ga:Se= 25:17.5:7.5:50), and XRD analysis showed a chalcopyrite structure. For the CdS buffer layer, the required thickness can be obtained by CBD at 75oC and pH 9.5 for 5 min. XRD analysis indicated that temperature has no effect on the microstructure. Only the pH and deposition time are the key conditions for the film thickness and structure. Keywords: CIGS, Electrodeposition, Thin film solar cells.