Optimisation of doping processes for passivating contact solar cells

Date

2023-6-2

Author

Osman, Hassan Mohamed

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Polysilicon/Silicon oxide structures have garnered significant attention due to their exceptional passivation capabilities and their suitability for industrial applications. The primary deposition techniques employed for the deposition of doped polysilicon layers are plasma-enhanced chemical vapor deposition (PECVD) and low-pressure chemical vapor deposition (LPCVD). However, LPCVD suffers from the drawback of unintended double-side deposition, whereas PECVD enables precise single-side deposition. Nevertheless, when dealing with these structures, PECVD can easily result in the growth of subpar films due to the occurrence of blistering phenomena. Thus, meticulous considerations must be taken into account during the fabrication process. This thesis aims to explore various deposition parameters in order to achieve high quality films devoid of blisters. These parameters encompass the manipulation of dopant concentrations, dilution ratios, crystallization time and temperature, as well as the utilization of different oxides. To analyze the fabricated layers, characterization techniques such as photoconductance decay measurements (PCD), electrochemical capacitance voltage (ECV), and Fourier Transform Infrared spectroscopy (FTIR) are employed. Ultimately, this thesis successfully fabricates blister-free layers with low recombination currents and and low contact resistivity on Czochralski substrates. A selectivity of 13.63 is achieved corresponding to a maximum conversion efficiency of 28.18%. This achievement is realized by implementing a 50 nm doped polysilicon layer on a 1.6 nm thermal oxide as well as on a 1.3nm chemical oxide.

Subject Keywords

passivating contacts, blisters, selectivity, PECVD, LPCVD

URI

https://hdl.handle.net/11511/104415

Collections

Graduate School of Natural and Applied Sciences, Thesis