ABSTRACT
The potential of polycrystalline silicon for large-scale terrestrial photovoltaic device application is well recognized. It shares with single-crystal silicon numerous desirable physical and chemical properties such as abundance, low toxicity, and stability, while also showing great promise of reduced costs by circumventing many of the complex and energy-intensive steps associated with the growth of single crystals. These facts have prompted many scientists to investigate various forms and shapes of polycrystalline silicon, with the principal objective of approaching the efficiencies obtained with single-crystal silicon (≥ 10 per cent) while minimizing the cost of the material. Several experimental 1 – 13 and theoretical 14 – 17 results have indicated that there is an increase in the efficiency of polycrystalline silicon solar cells with increasing grain sizes, and some of these results are shown in Figure 7.1. The theoretical results are based on a variety of assumptions, and the experimental results are for devices prepared under widely different conditions. There exists a gap between theory and experiment which this chapter attempts to fill. Our formulation will allow for the first time that polycrystalline silicon prepared under different conditions can be compared on the same basis. It will be shown that the differences in the photovoltaic properties of materials deposited under widely varying conditions can be understood in terms of grain size effects. Efficiency versus grain size https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315793245/fba3410f-a7b2-4207-80b4-b0645bac91bb/content/fig2_7_1.tif"/> Note: The curves are theoretical results, and the data points are experimental values obtained by different research groups. ○ Feldman et al. (Ref. 9); ▴ Chu et al. (Refs. 6 and 11); Δ Fischer and Pschunder (Ref. 2); □ Zook et al. (Ref. 7).
