Crystalline silicon thin-film solar cells on foreign substrates: The European project METEOR (original) (raw)
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IEE Proceedings - Circuits, Devices and Systems, 2003
Thin film polycrystalline silicon solar cells on foreign substrates are viewed as one of the most promising approaches to cost reduction in photovoltaics. To enhance the quality of the film, the use of 'seeding layers' prior to deposition of active material is being investigated. It has been shown that a phenomenon suitable to create such a seeding layer is the aluminium-induced crystallisation of amorphous silicon. Previous work mainly considered glass as the substrate of choice, thereby introducing limitations on the deposition temperature. Results concerning the application of such a technique to ceramic substrates (allowing the use of high-temperature CVD) are described. Also, the first reported results of a solar cell made in silicon deposited on these seeding layers are presented.
Influence of seed layer morphology on the epitaxial growth of polycrystalline-silicon solar cells
Thin Solid Films
Thin-film silicon solar cells on low-cost foreign substrates could lead to a large cost reduction of photovoltaic electricity if sufficiently high efficiencies could be obtained. A possible approach is to make polycrystalline-silicon solar cells by epitaxial thickening of large-grained thin seed layers made by aluminium-induced crystallization (AIC) of silicon. Until now however, obtained efficiencies are too low to lead to the desired cost reduction. We report on the influence of the AIC seed layer morphology (grain size and presence/absence of secondary crystallites on top of the surface) on the epitaxial growth of absorber layers and on the resulting cell parameters. To increase the grain size of the seed layers, we investigated the use of a nitric acid treatment to oxidize the Al layers prior to the amorphous silicon deposition. We compared seed layers oxidized by nitric acid treatment to seed layers oxidized by a short exposure to the ambient air. The nitric acid treatment led ...
Progress in Photovoltaics: Research and Applications, 2014
We fabricate thin epitaxial crystal silicon solar cells on display glass and fused silica substrates overcoated with a silicon seed layer. To confirm the quality of hot-wire chemical vapor deposition epitaxy, we grow a 2-μm-thick absorber on a (100) monocrystalline Si layer transfer seed on display glass and achieve 6.5% efficiency with an open circuit voltage (V OC ) of 586 mV without light-trapping features. This device enables the evaluation of seed layers on display glass. Using polycrystalline seeds formed from amorphous silicon by laser-induced mixed phase solidification (MPS) and electron beam crystallization, we demonstrate 2.9%, 476 mV (MPS) and 4.1%, 551 mV (electron beam crystallization) solar cells. Grain boundaries likely limit the solar cell grown on the MPS seed layer, and we establish an upper bound for the grain boundary recombination velocity (S GB ) of 1.6x10 4 cm/s.
Epitaxial Growth of Silicon Thin Films for Solar Cells
2008
Crystalline silicon thin film solar cells on glass substrates are a low cost alternative to silicon wafer cells. As an alternative to a simple furnace annealing step in which a-Si is converted to c-Si with 1 µm grains, an epitaxial crystal growth process is presented here. First a seed layer is prepared on glass by diode laser crystallization of an a-Si layer on glass to result in 100 µm grains. Then a-Si is deposited on top of the seed which is converted to c-Si by epitaxial growth. A 1.1 µm thick c-Si layer with 100 µm grains was produced in this way. The paper presents details of the epitaxial growth process.
2010
Large-grained, n + n-type polycrystalline silicon (poly-Si) films were obtained on alumina substrates by combining the aluminium induced crystallization (AIC) process of amorphous silicon and chemical vapour deposition (LPCVD) at high temperature (1000 1C) for the epitaxial thickening. The n + seed layer was obtained by phosphorus doping of the AIC layer. The electron backscattering diffraction (EBSD) technique was used for the crystallographic analysis of the poly-Si thin films. Seed layers with an average grain size of 7.6 mm were obtained on alumina substrates by exchange annealing at 475 1C for 6 h. Heterojunction emitter (HJE) solar cells were fabricated on such layers and their characteristics were monitored. IQE measurements show that n-type material based solar cells led to a much higher current collection over a large part of the spectrum compared to p-type cells. Accordingly a high effective diffusion length of about 2 mm for n-type heterojunction solar cells was obtained while it is about 0.9 mm for the p-type cell. As a result, the first n-type solar cells showed efficiencies above 5%, which is a very promising result considering that no optimization nor texturing have been applied so far.
Polycrystalline silicon on glass thin-film solar cell research at UNSW the seed layer concept
Clinical Nutrition Supplements, 2003
A novel seed layer-based poly-Si solar cell concept on glass-ALICIA (aluminium-induced crystallisation, ion-assisted deposition)-is presently being developed at the University of New South Wales (UNSW). The first key feature of ALICIA solar cells is a large-grained p/sup +/-doped poly-Si seed layer made on the glass by means of aluminium-induced crystallisation (AIC) of amorphous silicon. The other key feature is the
Epitaxial thin-film Si solar cells
Thin Solid Films, 2006
Most types of thin-film solar cells imply a radical departure from the dominant bulk crystalline Si technology. This is not the case for epitaxial thin-film solar cells. In this technology, a high quality Si layer is deposited epitaxially on a low-cost Si substrate (e.g. cast Upgraded Metallurgical Grade silicon or high-throughput Si ribbons) and processed into a solar cell. This technology combines the well-known advantages of crystalline Si (high efficiency potential, stability and reliability) with a substantial cost reduction potential. Moreover, the similarity to the traditional Si technology lowers the threshold for adoption by the PV industry. This paper gives an overview of the field of epitaxial thin-film solar cells, covering substrates, deposition techniques and solar cell processing. Achievements reported in the literature are summarized and recent results are presented. Special attention is given to the crucial issue of achieving high currents by increasing absorbance in the active layer. This can be achieved by increased absorption through material engineering and through implementation of advanced light confinement schemes.
EPJ Photovoltaics, 2013
We have previously reported on the successful deposition of heterojunction solar cells whose thin intrinsic crystalline absorber layer is grown using the standard radio frequency plasma enhanced chemical vapour deposition process at 165 • C on highly doped P-type (100) crystalline silicon substrates. The structure had an N-doped hydrogenated amorphous silicon emitter deposited on top of the intrinsic epitaxial silicon layer. However to form the basis of a solar cell, the epitaxial silicon film must be chiefly responsible for the photo-generated current of the structure and not the underlying crystalline silicon substrate. In this article we use detailed electrical-optical modelling to calculate the minimum thickness of the epitaxial silicon layer for this to happen. We have also investigated by modelling the influence of the a-Si:H/epitaxial-Si and epitaxial-Si/c-Si interface defects, the thickness of the epitaxial silicon layer and its volume defect density on cell performance. Finally by varying the input parameters and considering various light-trapping schemes, we show that it is possible to attain a conversion efficiency in excess of 13% using only a 5 micron thick epitaxial silicon layer.