Nanosecond pulsed infrared laser induced crystallization of amorphous silicon films for potential photovoltaic applications

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2018

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Çınar, Kamil

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Laser processing applied to thin film silicon is a practical tool for fabrication of thin film transistors and solar cells. Application of laser processing technologies to silicon based photovoltaics has been on the rise. Two examples out of plenty are: crystallization of amorphous Si (a-Si) thin films to produce polycrystalline Si (poly-Si) thin films; and quality improvement of poly-Si structures on the silicon wafer surface by laser annealing. Parameters for optimal crystalline silicon fabrication depend on fluence of the laser irradiation and physical conditions of the substrate where the silicon crystallization occurs. These various parameters can change the physical features of the grown poly-Si domains such as size, shape, thickness, orientation, etc. The determination and optimization of these parameters are of importance in fabrication of efficient silicon thin film solar cells. Previous works show that efficiency of the laser crystallized poly-Si solar cells exhibit enhancement of their material qualities. In this thesis, characterization of the laser induced crystallization and optimization of the nanosecond pulsed infrared laser parameters are investigated. Besides, a laser crystallization system is developed for processing a-Si thin films into poly-Si thin films for the purpose of fabrication of crystalline thin film silicon solar cells. Crystalline silicon layers with thicknesses ranging between several hundred nanometers and a micrometer are fabricated by means of the nanosecond pulsed infrared laser. The laser crystallization is performed in air at room temperature and no heating is applied to substrates. Grain sizes of up to several millimeters are found on the surface of the crystallized silicon layers. The produced crystalline silicon films are employed in fabrication of heterojunction p-n diodes and solar cells.

Subject Keywords

Lasers., Thin films., Crystallization., Photovoltaic cells., Infrared technology., Amorphous substances.

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http://etd.lib.metu.edu.tr/upload/12622578/index.pdf
https://hdl.handle.net/11511/27761

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

K. Çınar, “Nanosecond pulsed infrared laser induced crystallization of amorphous silicon films for potential photovoltaic applications,” Ph.D. - Doctoral Program, Middle East Technical University, 2018.