Abstract
We demonstrate an innovative CIGS-based solar cells model with a graded doping concentration absorber profile, capable of achieving high efficiency values. In detail, we start with an in-depth discussion concerning the parametrical study of conventional CIGS solar cells structures. We have used the wxAMPS software in order to numerically simulate cell electrical behaviour. By means of simulations, we have studied the variation of relevant physical and chemical parameters—characteristic of such devices—with changing energy gap and doping density of the absorber layer. Our results show that, in uniform CIGS cell, the efficiency, the open circuit voltage, and short circuit current heavily depend on CIGS band gap. Our numerical analysis highlights that the band gap value of 1.40 eV is optimal, but both the presence of Molybdenum back contact and the high carrier recombination near the junction noticeably reduce the crucial electrical parameters. For the above-mentioned reasons, we have demonstrated that the efficiency obtained by conventional CIGS cells is lower if compared to the values reached by our proposed graded carrier concentration profile structures (up to 21%).
Highlights
Quaternary chalcopyrite semiconductor alloy Cu(In,Ga)Se2 (CIGS) represents one of the most suitable materials to produce low-cost and high-efficiency photovoltaic modules and can be considered as an appropriate alternative to the silicon technology
We show a simulative analysis aimed at investigating the possible effects of both tailoring the absorber band gap and changing the carrier concentration profile on the main electrical parameters of CIGS based solar cells, in order to design graded absorber profiles that are able to increase the efficiency
We have performed some simulative campaigns by means of the wxAMPS software, to investigate on the effects of the absorber band gap on the main electrical parameters in conventional CIGS solar cells
Summary
Quaternary chalcopyrite semiconductor alloy Cu(In,Ga)Se2 (CIGS) represents one of the most suitable materials to produce low-cost and high-efficiency photovoltaic modules and can be considered as an appropriate alternative to the silicon technology. Several papers in the literature reported on CIGS solar cells presenting lateral inhomogeneities on the μm scale that affect the main parameters, in particular the local splitting of quasi-Fermi levels obtained from photoluminescence measurements and decrease the overall performance [3] Reducing or avoiding these problems is of great importance, since it is International Journal of Photoenergy worth noting that the direct conversion of sunlight into electricity, that is, photovoltaics, can be surely considered as a fundamental alternative to fossil fuels and could become, as experts say, “the biggest supplier of electricity by the end of the century” [4]. During our simulations, performed using the wxAMPS software, we have first analysed five band gap values at varying absorber thickness, and we have focused on a novel graded linear absorber profile, as will be illustrated
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