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

Çınar, Kamil
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.


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For silicon Heterojunction (SHJ) solar cell technology features, a thin intrinsic hydrogenated amorphous silicon (i a-Si:H) layer has inserted between the crystalline silicon and doped amorphous silicon. The state of the art SHJ solar cell structure involves low temperature depositions of a-Si:H layer by means of Plasma Enhanced Chemical Vapor Deposition (PECVD) technique. Recent developments on SHJ solar cells have been focused on increasing the passivation quality of a-Si:H layer and the formation of all ...
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.