B. Rau

Controlling the thermal impact of ns laser pulses for the preparation of the P2 interconnect by local phase transformation in CIGSe

The thermal impact of nanosecond laser pulses was beneficially employed and well-controlled for the preparation of the P2 interconnect by local phase transformation (i.e., by drawing conductive lines rather than removing the material) in CIGSe mini-modules, which were demonstrated to outperform their conventionally needle-patterned counterparts. Conductivity and elemental composition of the scribed lines as well as the extent of the heat-affected area were analyzed, quantified and taken into account for achieving optimal CIGSe solar module performances. This approach opens new prospects for significant simplification of the serial interconnection, since the P2 und the P3 can be scribed simultaneously after deposition of both the CIGSe and the TCO layer.

Electrical and structural functionality of CIGSe solar cells patterned with picosecond laser pulses of different wavelengths

Electrical and structural functionality of monolithic interconnection of CIGSe solar cells by P1-P3 picosecond laser ablation has been successfully established and evaluated as being competitive to conventional needle scribing. In all three patterning steps the material is selectively and completely removed yielding structurally well-defined trenches at high scribing speeds up to 1 m/s. P1 and P2 ps laser scribing clearly improves the solar cell efficiencies whereas P3 scribing is still challenging due to shunts resulting from laser-induced alteration of the absorber material.

Polycrystalline silicon thin-film solar cells on ZnO:Al-coated glass substrates

Polycrystalline Si (poly-Si) thin-film solar cells feature the potential to reach very high efficiencies at low costs. This paper addresses the development of poly-Si thin-film solar cells on ZnO:Al-coated glass substrates. This development is based on the fact that the properties of capped ZnO:Al layers stay the same (or even improve) upon annealing at temperatures far above the deposition temperature of the ZnO:Al. Three different approaches have been used to form the poly-Si films (solid phase crystallization, direct growth of poly-Si, and a ‘seed layer’ concept). Solar cells have been prepared with all three approaches. So far the best results have been obtained by direct growth of poly-Si and the ‘seed layer’ concept. Our results show that the preparation of poly-Si thin-film solar cells is compatible with the utilization of ZnO:Al-coated glass substrates.

Influence of Defect Post-deposition Treatments on poly-Si Thin-film Solar Cells on Glass grown by ECRCVD

The epitaxial thickening of a thin polycrystalline Si (poly-Si) film (seed layer) is a promising approach to realize an absorber layer of a poly-Si thin-film solar cell on glass. Such cell concept combines the benefits of crystalline Si and the high potential for cost reduction of a thin-film technology. Here, we discuss the influence of post-deposition treatments on the properties of absorber layers grown by electron-cyclotron resonance chemical vapor deposition (ECRCVD) and the solar cell performance, respectively. Defect annealing was used to improve the structural quality of the absorber layers and to increase the doping efficiency. For this, we used rapid thermal annealing (RTA) processes. Annealing times (up to 400 s) were applied at temperatures of up to 950 °C. Defect passivation treatments were carried out at temperatures of about 350 °C to passivate the remaining defects in the films by hydrogen. The impact of both treatments on the solar cell parameter will be discussed focusing on RTA. Excellent VOC’s of up to 361 mV were achieved without hydrogenation showing the high potential of ECRCVD-grown absorbers. Applying both treatments resulted so far in an increase of VOC of about 400 mV. Because of the fact, that both post-treatments (particularly hydrogenation) are still not yet optimized, further improvements can be expected.