Polycrystalline Silicon Thin Film for Solar Cells Utilizing Aluminum Induced Crystallization Method

AbstractEfficient thin-film polycrystalline-silicon (pc-Si) solar cells on foreign substrates could lower the price of photovoltaic electricity. Aluminum-induced crystallization (AIC) of amorphous silicon followed by epitaxial thickening at high temperatures seems a good way to obtain efficient pc-Si solar cells. Due to its transparency and low cost, glass is well suited as substrate for pc-Si cells. However, most glass substrates do not withstand temperatures around 1000°C that are needed for high-temperature epitaxial growth. In this paper we investigate the use of experimental transparent glass-ceramics with high strain-point temperatures as substrates for pc-Si solar cells. AIC seed layers made on these substrates showed in-plane grain sizes up to 16 μm. Columnar growth was observed on these seed layers during high-temperature epitaxy. First pc-Si solar cells made on glass-ceramic substrates in substrate configuration showed efficiencies up to 4.5%, fill factors up to 75% and open-circuit voltage (Voc) values up to 536 mV. This is the highest Voc reported for pc-Si solar cells on glass and the best cell efficiency reported for cells made by AIC on glass.

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Efficiency potential of thin film polycrystalline silicon solar cells by silane-gas-free process using aluminum-induced-crystallization

Solar Energy Materials and Solar Cells ◽

10.1016/j.solmat.2004.02.015 ◽

2004 ◽

Vol 83 (1) ◽

pp. 91-99 ◽

Cited By ~ 3

Author(s):

Tadashi Ito ◽

Hideoki Fukushima ◽

Masafumi Yamaguchi

Keyword(s):

Thin Film ◽

Solar Cells ◽

Polycrystalline Silicon ◽

Silicon Solar Cells ◽

Free Process ◽

Induced Crystallization ◽

Aluminum Induced Crystallization

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Defect Study of Polycrystalline–silicon Seed Layers made by Aluminum Induced Crystallization

MRS Proceedings ◽

10.1557/proc-1153-a16-02 ◽

2009 ◽

Vol 1153 ◽

Author(s):

Srisaran Venkatachalam ◽

Dries Van Gestel ◽

Ivan Gordon

Keyword(s):

Thin Film ◽

Solar Cells ◽

Grain Boundaries ◽

Seed Layer ◽

Polycrystalline Silicon ◽

Defect Density ◽

Sem Images ◽

Induced Crystallization ◽

Seed Layers ◽

Aluminum Induced Crystallization

AbstractA polycrystalline silicon (pc-Si) thin film with large grains on a low-cost non-Si substrate is a promising material for thin-film solar cells. One possibility to grow such a pc-Si layer is by aluminum-induced crystallization (AIC) followed by epitaxial thickening. The best cell efficiency we have achieved so far with such an AIC approach is 8%. The main factor that limits the efficiency of our pc-Si solar cells at present is the presence of many intra-grain defects. These intra-grain defects originate within the AIC seed layer. The defect density of the layers can be determined by chemical defect etching. This technique is well suited for our epitaxial layers but relatively hard to execute directly on the seed layers. This paper presents a way to reveal the defects present in thin and highly-aluminum-doped AIC seed layers by using defect etching. We used diluted Schimmel and diluted Wright etching solutions. SEM pictures show the presence of intra-grain defects and grain boundaries in seed layers after defect etching, as verified by EBSD analyses. The SEM images of diluted Wright etched pc-Si seed layer shows that grain boundaries become much better visible than with diluted Schimmel etch.

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