Front-side Texturing of Crystalline Silicon Solar Cell by Micro-contact Printing

We give a textured front on silicon wafer for high-efficiency solar cells by using micro contact printing method which uses PDMS (polydimethylsiloxane) silicon rubber as a stamp and SAM (self assembled monolayer)s as an ink. A random pyramidal texturing have been widely used for a front-surface texturing in low cost manufacturing line although the cell with random pyramids on front surface shows relatively low efficiency than the cell with inverted pyramids patterned by normal optical lithography. In the past two decades, the micro contact printing has been intensively studied in nano technology field for high resolution patterns on silicon wafer. However, this promising printing technique has surprisingly never applied so far to silicon based solar cell industry despite their simplicity of process and attractive aspects in terms of cost competitiveness. We employ a MHA (16-mercaptohexadecanoic acid) as an ink for Au deposited $SiO_2/Si$ substrate. The $SiO_2$ pattern which is same as the pattern printed by SAM ink on Au surface and later acts as a hard resist for anisotropic silicon etching was made by HF solution, and then inverted pyramidal pattern is formed after anisotropic wet etching. We compare three textured surface with different morphology (random texture, random pyramids and inverted pyramids) and then different geometry of inverted pyramid arrays in terms of reflectivity.

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