利用熱處理探討銅銦鎵硒薄膜太陽能電池硫化鎘緩衝層性質之研究

Study on properties of CdS buffer layer of CIGS thin film solar cell by using thermal treatment

陳珮伶(PeiLing Chen)

指導教授 ： 劉宗平

元智大學/電機通訊學院/光電工程學系/碩士(2011年)

https://doi.org/10.6838/YZU.2011.00304

摘要

近年來，由於能源短缺，太陽電池的開發及使用逐漸受到重視。銅銦鎵硒(CIGS)薄膜太陽電池屬於化合物半導體太陽電池，其能隙為1.04-1.68eV，且為直接帶隙材料。為了搭配P型的CIGS吸收層，考慮同為直接帶隙的N型硫化鎘（CdS）作為緩衝層材料。
在本研究中，採用化學水浴沉積法(chemical bath deposition, CBD)來生長CdS薄膜，經退火處理改善其性質，再進行電性、光性的量測與分析。由於CdS與CIGS晶格匹配且為寬能隙材料，是製造CIGS太陽電池緩衝層的重要光窗材料。若以CBD法來沉積CdS薄膜，其製程不僅簡單、成本低廉，且膜厚相當地均勻。本研究所生長之CdS薄膜，其厚為50 nm。經由量測與分析知，若CdS前驅物薄膜通過退火處理後，則其光電性質將大幅改善。在本研究中，改變退火參數─退火溫度和退火時間，來強化CdS薄膜的光電性質。從吸收光譜量測可知，退火後的CdS薄膜在700-900 nm間之透射率提升至80%以上。由光激發螢光頻譜及霍爾量測中得知，當退火溫度為100?C、退火時間為20分鐘時，CdS薄膜的能隙最小、面電阻最低，亦即其導電性最好。分析16個樣品的退火數據，可以找到CdS薄膜一組最佳的退火參數，應用在CIGS薄膜太陽電池中。

關鍵字

硫化鎘 ； 化學水浴沉積法 ； 退火 ； 面電阻 ； 透射率

並列摘要

Since CdS material has a direct and wide band-gap, it is very potential for fabricating photovoltaic devices. Due to its wide band-gap, CdS film can be acted as a window material to combine with Cu(In, Ga)Se2 film. Therefore, CdS film grown on glass substrate is usually used to fabricate a high efficiency solar cell. To obtain a quite uniform, easily scaling-up, and inexpensive sample, the CdS thin film with a thickness of 50 nm was deposited by using chemical bath deposition (CBD) method. Through varying annealing temperatures and annealing times, the electrical and optical properties of CdS film could be obviously improved. According to measurements, the transmittance of CdS sample annealed was increased over 80% in the wavelength range of 700-900 nm. And the band gap of CdS sample annealed at 100?C with 20 min is the minimum. Its sheet resistance and band gap are the minimum, relatively, the conductivity is the best. By using those data obtained at various annealing temperatures and times, we can find an optimum condition for growing CdS thin film application on Cu(In, Ga)Se2-based solar cell.

並列關鍵字

transission ； CdS ； CBD ； annealing ； sheet resistance

參考文獻

[1] T. Mishima, M. Taguchi, H. Sakata, and E. Maruyama, "Development status of high-efficiency HIT solar cells," Solar Energy Materials & Solar Cells, Vol. 95, pp. 18-21, 2011.

[5] A. Rockett, F. Abou-Elfotouh, D. Albin, M. Bode, J. Ermer, R. Klenk, T. Lommasson, T. W. F. Russell, R.D. Tomlinson, J. Tuttle, L. Stolt, T. Walter, and T. M. Peterson, "Structure and chemistry of CuInSe2 for solar cell technology: current understanding and recommendations," Thin Solid Films, Vol. 237, pp.1–11, 1994.

[7] Johan Wennerberg, John Kessler, Lars Stolt, "Design of grided Cu(In, Ga)Se2 thin-film PV modules," Solar Energy Materials & Solar Cells, Vol.67, pp. 59-65, 2001.

[9] Nishitani M., Negami T. and Wada T., "Composition monitoring method in CuInSe2 thin film preparation", Thin Solid Films, Vol.258, pp. 313-316, 1995.

[11] A. Klein, T. Löher, Y. Tomm, C. Pettenkofer, and W. Jaegermann, "Band lineup between CdS and ultra high vacuum-cleaved CuInS2 single crystals", Applied Physics Letters, Vol.70, 1997.