Thin-film solar technologies are very attractive due to their potential for low production costs. As in all thin-film technologies, high efficiency of small cells might be maintained with the transition to larger areas when for this purpose the areas are segmented and electrically connected in series with each other. This reduces the current load on the thin-films and the related ohmic losses. For CuIn1-xGaxSe2 (CIGS) thin film solar cells the industrial segmentation and interconnection is mostly based on mechanical scratching. Here the individual layers – front contact, absorber and back contact - are locally and slightly offset to each other removed right after their deposition. In order to meet architects’ (for e.g. BIPV applications) requirements for the shape of the module, it is beneficial to allow for a geometry adaption of the modules after the layer stack deposition. This is supported by a so-called back-end interconnection, i.e. to perform the segmentation and interconnection after the deposition of the whole layer stack. The back-end interconnection is enabled by the combination of laser-based segmentation processes and printing techniques. Furthermore, compared to mechanical scratching, laser-based interconnection promises a possible reduction of segmentation related dead area losses. In this paper we present a laser-based selective structuring of patterns for a back-end interconnection on CIGS thin film solar cells. We apply an ultrashort pulsed laser with a wavelength of 1030 nm and investigate the impact of various process parameters. Before laser processing samples were stabilized under AM1.5 at 55°C for 40 minutes to reduce metastabilities within CIGS thin film solar cells.
An analysis of the monolithical series connection of silicon thin-film modules with metal back contact fabricated by high
speed laser ablation will be presented. Optically pumped solid state lasers with wavelengths of 1064 nm and 532 nm
were used for the patterning steps. The near infrared laser is applied to pattern the TCO (P1) while the green laser is used
for the ablation of the silicon layer stack (P2) and the back contact layer stack (P3). The influence of various laser
parameters on the performance of amorphous and microcrystalline silicon modules was studied. In particular the back
contact patterning and the Si removal can significantly affect the module efficiency. Non-optimized patterning
conditions for P2 can lead to a high contact resistance, while the ablation of the ZnO/Ag back contact system can
introduce shunts at the laser scribed line. Therefore, a criterion for flakeless patterning will be briefly introduced and the
influence of flakeless back contact patterning on the electrical behavior of silicon single junction cells will be discussed.
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