Improved Amorphous Silicon Solar Cells Using RPCVD
- PDF / 642,479 Bytes
- 12 Pages / 414.72 x 648 pts Page_size
- 112 Downloads / 263 Views
IMPROVED AMORPHOUS SILICON SOLAR CELLS USING RPCVD
Kyu Chang PARK, Tae Gon KIM, Sung Ki KIM, Sung Chul KIM*, Myung Hak HWANG, Jung Mok JUN and Jin JANG Department of Physics and Research Institute of Basic Sciences, Kyung Hee University, Dongdaemoon-ku, Seoul 130-701, Korea * At present Anyang Research Lab., GoldStar Co., Anyang-shi 430-080, Korea ABSTRACT We have studied the depositions of amorphous silicon, silicon carbon alloy, doped microcrystalline silicon in order to apply these films as the component materials for the p-i-n and double stacked solar cells. We have obtained low band gap a-Si:H by decreasing the deposition rate under the proper preparation conditions and highly conductive, thin microcrystalline Si and SiC layers. We have developed a stable a-Si/a-Si double stacked solar cell with a conversion efficiency of -9% using narrow band gap a-Si:H as a i-layer of bottom cell.The performance of this cell does not degrade until 100 hrs illumination under 350 mW/cm 2. INTRODUCTION Hydrogenated amorphous silicon(a-Si:H) is one of the most suitable solar cell materials because of its high optical absorption coefficients in the visible range, high photoconductivity, and controllability of its valence electron. Therefore, there has been much work on a-Si:H solar cells since the success of the first solar cell by Carlson and Wronski [1l. However, there still remains the problems of low conversion efficiency and stability. The conversion efficiency of small area (1cm2 ) solar cell was reached nearly 12% in 1987 [2], but it did not change greatly after then. The best conversion efficiency of single p-i-n solar cell is now around 13.2% [3]. In order to obtain higher conversion efficiency, it is necessary to develop good quality, low band gap materials. Even though much work has been done on the amorphous silicon-germanium(a-SiGe:H) alloy, the density of defects in a-SiGe:H is higher than that for the pure a-Si:H. The optoelectronic properties of a-SiGe:H should be comparable to that of undoped a-Si:H. Increasing the deposition temperature (Td) is the simplest way to decrease the optical band gap 14], since the hydrogen content (Cs) in a-Si:H increases with the optical band gap and the CH in a-Si:H decreases with increasing the substrate temperature. The deposition of solar cells at high Td gives rise to the two problems [4] such as the impurity contamination in i- a-Si:H and the degradation of the interface between a-Si:H and transparent conducting oxide (TCO). The collection efficiency in the short wavelength region of a-Si:H solar cell deposited at higher temperature is lower than that for the conventional cells. Judging from these facts, the maximum deposition temperature to make a good a-Si:H p-i-n solar cell on TCO/glass is -2801C. Shimizu group developed a low band gap, small hydrogen content, a-Si:H using chemical annealing technique [5]; the repeated deposition of a few tens 'k of a-Si:H and subsequent exposure to atomic hydrogen gives rise to low band gap a-Si:H. It is known that the properties of a-Si:H
Data Loading...
