Untersuchung und Optimierung der Serienverschaltung von Silizium-Dünnschicht-Solarmodulen

Haas, Stefan

Book	PreJuSER-136269

Untersuchung und Optimierung der Serienverschaltung von Silizium-Dünnschicht-Solarmodulen

Haas, S. (Corresponding author)FZJ*

2010
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-680-4

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich. Reihe Energie und Umwelt / Energy und Environment 91, II, 202 S. (2010) = RWTH Aachen, Diss., 2010

This record in other databases:

Please use a persistent id in citations: http://hdl.handle.net/2128/4356

Abstract: The integrated series connection is an important and elementary part of a thin-film silicon solar module. The series connection leads to a reduction of Ohmic losses and an increase of the module voltage. After their deposition the different functional layers of a solar module must be patterned selectively to form a series connection. First the front contact, then the absorber, and finally the back contact is locally removed. The first step and the last step are needed to separate the contact layers (isolation step), the absorber patterning is used to expose the front contact and prepare the series interconnection. Usually laser ablation is used for patterning. The patterning of the front contact is overall a noncritical step. Therefore, this thesis exclusively investigates mechanisms that limit the process window of the absorber patterning and the back contact patterning. Especially for the absorber patterning on SnO$_{2}$-substrates the process window is very narrow. As too high pulse energies create a barrier layer on the SnO$_{2}$-window layer, which restricts the current flow in a series connected module. This barrier layer probably consists of SiO$_{2}$ or an alloy of (Sn,Si)O$_{2}$. It arrises from redeposition of evaporated silicon. Ablation of the absorber without creating a barrier layer is only possible, when the silicon is not evaporated. Here the ablation is induced by the explosive out-diffusion of hydrogen from the silicon layer. On ZnO-substrates no significant barrier formation occurs. For this reason the process window is very broad. Patterning the back contact is the last isolation step. It is mainly restricted by an unavoidable deterioration of the absorber as well as a possible ablation of the window layer. The deterioration of the absorber in the vicinity of the patterning groove leads to parasitic dark currents for amorphous and for microcrystalline solar cells. The parasitic dark currents decrease the efficiency $\eta$ of a patterned module. The parasitic dark currents strongly depend on the pulse duration and the wavelength of the applied laser. In general, longer pulse durations lead to larger parasitic dark currents due to a larger heat affected zone. The absorption coefficient α of the absorber depends on the wavelength $\lambda$. Wavelengths $\lambda$ of 1064 nm, 532 nm and 355 nm are used for the back contact patterning. The results for amorphous and for microcrystalline silicon solar cells differ a lot, when the wavelength is changed. In the case of amorphous solar cells shorter wavelengths lead to a [...]

Classification: