利用電漿輔助式分子束磊晶系統成長硒化銅鎵 薄膜太陽能電池與特性分析

Growth and characterization of CuGaSe2 thin film solar cells by plasma-assisted molecular beam epitaxy

林弘倫(Hong-Lun Lin)

指導教授 ： 楊祝壽

大同大學/電機資訊學院/光電工程研究所/碩士(2011年)

摘要

利用電漿輔助式分子束磊晶法（PA-MBE）在砷化鎵（001）與鈉鈣玻璃基板上成長硒化銅鎵太陽能電池。由二元化合物硒化鎵作為出發點，製作出一系列不同比例的銅與鎵之硒化銅鎵薄膜，以尋找最佳的太陽能電池吸收層。在不同的銅鎵比例的樣品中利用掃瞄式電子顯微鏡(SEM) 可以觀察到樣品的表面形貌由硒化鎵岩片狀結構轉變為四方型的硒化銅鎵合金顆粒。並且利用X射線繞射儀與拉曼散射光譜證實此項轉過程。在X射線繞射譜中觀察到從多晶型態的硒化銅鎵薄膜轉變為單晶硒化銅鎵薄膜。從拉曼散射光譜可以發現到由硒化鎵主宰的光譜訊號132, 206與308 cm-1的位置相轉變到硒化銅鎵的主要訊號184與273 cm-1的位置。在光激螢光譜中觀察到螢光位置由1.55 eV逐漸藍移到硒化銅鎵的自由激子放光1.71 eV。此外，利用高品質硒化銅鎵作為吸收層來成長太陽能電池元件，並以改良式磊晶結構方式與高載子濃度之氧化鋅透明導電膜來取代以往傳統方式的上端鋁電極與透明導電層。在階段性的實驗過程中，目前硒化銅鎵太陽能電池最佳效率約為1.10 %。推就效率不佳的原因在於成長過程中的高溫環境容易造成材料有擴散之現象，導致P-N結構界面不夠銳利。也有可能是成長溫度、電極、吸收層厚度、導電率等相關問題所引起。

關鍵字

太陽能電池 ； 分子束磊晶 ； 硒化銅鎵

並列摘要

In this work, we grow CuGaSe2 solar cell on GaAs (001) and soda lime glass by plasma-assisted molecular beam epitaxy (PA-MBE). According to binary compound of GaSe basis, we produce a series of CuGaSe2 films with different [Cu]/[Cu+Ga] ratio and optimal the best absorption layer. In the different Cu/Ga ratio, scanning electron microscopy shows the surface morphology from sheet-like (GaSe-like) to square (CuGaSe2 alloy). In the X-ray diffraction (XRD) and Raman scattering results reveals that the phase transition from CuGa3Se5 to CuGaSe2 is observed in the Cu/Ga ratio from 0.23 to 0.48, respectively. In Raman scattering spectra, the phonon mode is translated from GaSe (132, 206, and 308 cm-1) to CuGaSe2 (184 and 273 cm-1). Photoluminescence (PL) shows that the GaxSey emission (1.55 eV) shifts to the free exciton emission of CuGaSe2 (1.71 eV). In addition, CuGaSe2 thin film solar cell was demonstrated in this work. In the experiment process, the best efficiency of CuGaSe2 solar cell is 1.10 %. The reason of the low efficient maybe the too high growth temperature to cause the material diffusion, interface, and metal contact problems.

並列關鍵字

solar cell ； MBE ； CuGaSe

參考文獻

[5] C. Rincón and F. J. Ramírez, J. Appl. Phys. 72, 4321 (1992).

[9] O. Madelung, Semiconductors: Data Handbook, Springer (2004).

[12] H. Hahn, W. Klinger and Z. Anorg. Chem. 259 (1949).

[13] T. T. Tsai, Growth and Physical properties of GaSe thin films by molecular beam epitaxy, Tatung University, (2010).

[14] J. E. Jaffe and Alex Zunger, Phys. Rev. B, 28, 5822 (1983).