Date

2017-12-01

Author

Es, Fırat
Turan, Raşit

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With its indirect band structure and good reflecting properties, Si is a poor absorber particularly in the infrared part of the light spectrum. Thanks to surface texturing technologies, management of light using surface structures at micro and nanometer scale can significantly improve absorption and photocurrent generation. Surface texturing is typically done by alkaline based solutions for monocrystalline Si. Pyramid structures formed by this process provides an optimum condition for minimizing the reflection from the surface and maximizing light trapping. For multi-crystalline wafers, an acid based solution is typically used to form random micro structures. However, this technique does not yield the ideal surface structure for light trapping. Moreover, the use of dangerous acidic materials and removal of excessive Si from the surface are not desirable in large scale industrial lines. It is then of high interest to develop new approaches for the texturing process of multi-crystalline Si wafers. In this work we have developed a new etching methodology based on Metal Assisted Etching (MAE) which is an electrochemical etching technique utilizing metal nanoparticles as catalyst for controlling the shape of the surface structures. Method was applied to industrial size wafers and evaluated for its applicability and performance in comparison with the standard acidic texturing process. The trade-off between optical gain due to the enhanced absorption by texturing and the electronic losses due to the high recombination at the textured surface is discussed. Gain/loss ratio is shown to improve by controlling the surface shapes with solution chemistry. It is shown that various surface shapes like nanowires, sponge-like porous structures, and pyramid-like nanostructures can be created by varying the chemical composition of the solution. Optimized nanostructures have yielded an efficiency of 5% higher than the cell fabricated by the standard recipe. We have also shown that the same solution can also be applied to mono-crystalline solar cell, which is highly desirable for industrial production lines where both wafers types can be processed without any additional equipment.

URI

https://hdl.handle.net/11511/78530
https://www.mrs.org/fall2017-symposium-sessions?Code=ES11

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Department of Physics, Conference / Seminar