We analyzed the luminescence signal under electrical bias (Lum-V) for several Cu(In,Ga)Se2 solar cells having different absorber growth processes and different buffer layers such as CdS and ZnS. A numerical model is developed taking into account optical and electrical properties of the complete heterostructures. It appears that the absorber-buffer interface has a crucial role in explaining the different behaviors. Our interpretation is based on the quasi Fermi level splitting (QFL) linked to both the applied voltage and the luminescence intensity. Lum-V experiments and its dependence on illumination intensity are discussed and could be used to access transport properties when looking at the depth variation of the QFL and offer a classification of the possible cases.
LGEP 2011 ID = 715International audienceStructural and electronic defect-related properties of hydrogenated polymorphous silicon (pm-Si:H) films deposited at high rates of up to 9 Å/s have been investigated. Raman spectroscopy reveals the usual peaks characteristic of the amorphous nature of the material, as well as intermediate peaks associated with the effect of nanocrystallites in the amorphous matrix. These results have been correlated with infrared measurements. Transport and defect-related properties deduced from a set of complementary techniques show that hydrogenated polymorphous silicon presents better properties compared to the standard amorphous silicon (a-Si:H). In particular, capacitance measurements on Schottky diodes reveal a very low density of states at the Fermi level. Based on experimental results, band gap states modeling has been achieved for pm-Si:H and a-Si:H by means of a numerical calculation software. Some parameters that are not directly measured with experiments, such as capture cross sections, could be deduced from simulations and differences between pm-Si:H and a-Si:H could be further revealed
Soft chemical processes such as screen printing, sol-gel, electrochemical or chemical bath-deposition, enable low cost and easily scalable processes for thin layer solar cells. For the CIGSe based solar cells, with the standard Mo/Cu(In,Ga)Se2/CdS/i-ZnO/n+-ZnO structure, all layers of the p-n heterojunction and the transparent conductive oxide window can be grown by aqueous solution processes. In this work we focus on the electrochemical investigation of In-S layers. XPS analyses show the presence of both S and O. Conversion efficiencies of complete devices up to 14 % are obtained.
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