Development of n-type polycrystalline silicon thin film solar cells on glass

摘要

It is a challenge for academics and industrialists to develop solar cells with high energy conversion efficiency and low manufacturing cost. Polycrystalline silicon thin-film solar cells on glass is a competitive photovoltaic technology in that it combines the advantages of the mature crystalline silicon technology with low material usage and large-area monolithic construction typical for the thin-film approach. The focus of this thesis is on n-type polycrystalline silicon thin-film solar cells on glass prepared by electron-beam evaporation and solid-phase crystallization. It can be categorized into two parts. The first part introduces the study on material and optimization of cell structure, as well as investigation on the post-deposition treatments. Important issues are addressed, such as absorber doping control via diffused back surface field, influence of emitter doping and thickness on cell performance, influence of absorber doping on cell performance, the effect of RTA temperature on cell performance, the effect of hydrogen passivation temperature on cell performance, and the defects induced by the hydrogen passivation. The second part is a systematic study on development of a silicon nanostructure in polycrystalline silicon thin film solar cells. The silicon nanostructure is fabricated by metal-assisted wet chemical etching. Silver nanoparticles by thermal annealing of a thin silver film are used as metal catalyst. The silicon nanostructure demonstrates excellent light trapping, which is a very critical issue for thin-film solar cells. The silicon nanostructure can be passivated by atomic layer deposited aluminium oxide, in which way the electrical property of the film is improved. In the end of this thesis, 90% short-circuit current density enhancement has been achieved by application of the silicon nanostructure, resulting in the highest current density of 23.31 mA/cm2. A highest open-circuit voltage of 503 mV has been achieved for polycrystalline silicon thin-film solar cells. The silicon nanostructure is analyzed by FDTD simulation.