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Tham khảo tài liệu 'solar cells thin film technologies part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Enhanced Diffuse Reflection of Light by Using a Periodically Textured Stainless Steel Substrate 49 In our previous study Lee et al. 2009 it was found that for a textured 430BA SS substrate the DR rate increased with the increased effectiveness of the etch-pit regions compared to that of the smooth regions. Thus the large and deeply etched areas of the textured 304BA SS indicated that they can improve the DR rate of a textured 304BA SS substrate. In order to improve the DR rate even further we design two other kinds of textured 304BA SS substrates the ridged-stripe and the pyramid texture. 3D images of the ridged-stripe and pyramid texture are shown in Figs. 16 a and b respectively. The etching depth and the width for both textured 304BA SS substrates were estimated to be 6.5 pm and 22.5 pm respectively. The aspect ratio i.e. depth width was 1 3.5 indicating that the opening angle a of the textured surface was about 120o. It should be noted that the etching depth is controlled by the PR thickness and the etching time. In general a thick PR and a long etching time can create the deeper textured 304BA SS substrate. Fig. 16. The 3D images of a ridged-stripe and b pyramid 304BA SS substrate. The TR and DR rates of the ridged-stripe and pyramid textured 304BA SS substrates are shown in Fig. 17. We found that the DR rate at the wavelength of 600 nm increased from 3.5 for the untreated 304BA SS substrate to 60.1 for the pyramid and 63.1 for the ridged-stripe textured 304BA SS substrate. In addition the DR rate also increased 1.5 times at the period depth of 6 0.3 pm for the stripe-textured 304BA SS substrate. However the textured substrates had a lower TR rate compared to the untreated 304BA SS substrate. The lowering of the TR rate for the textured surface of the 304BA SS substrate can be explained as follows a the multiple scattering is the result of the multiple reflections from the ridged-stripe or pyramid textured surface of the 304BA SS substrate and the etching pit
