Nt1310 Unit 3 Lab Report

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Basics of a-Si:H/uc-Si:H tandem solar cells
Figure 1.2 shows the scheme of the one of the possible configuration for the thin-film tandem solar cell, which consists out of three blocks: the upper thin-film part, the thick layer of Silicon wafer and the bottom thin-film part, which are built in stack.

Figure 1.2. The schematic view of the HIT solar cell
According to Schockley the energy of photons, which exceeds the band gap is lost due to the thermalization of the charge carriers to the band edges of the absorber material. In order to get more of the broadband edges of the broadband solar energy the thin-film layers with different absorber materials are combined.[10] For this work will be used cells with the combination of uc-Si:H with a-Si:H, which are connected in series. The uc-Si:H typically exhibits
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However, due to the disorder some atoms in a-Si have dangling bonds, which create a large number of defect states within the band gap. In order to enhance the quality of the semiconductor the dangling bonds have to be saturated by hydrogen atoms.[14] As a result, the material used for the solar cell is a-Si:H. It acts as a quasi-direct semiconductor with high absorptivity in comparison with crystalline silicon. The main minus for a-Si:H is that it has light-induced degradation, which was firstly described by Staebler-Wronski.[15] This means, that weakly strained silicon-silicon bonds can break under the illumination and induce additional dangling bonds, which create additional recombination centers that lower the