Combinational analysis with spectroscopic and optoelectronic techniques for the advanced characterization of new materials and concepts of thin-film photovoltaics

Abstract

This work proposes a simple and low-cost alternative characterization method for CIGSe thin film solar cells (TFSL) based in slope-polishing. Combining this method with conventional techniques and comparing the results with the literature, the validity of the methodology for the study of solar cells is evaluated. Different CIGSe thin film solar cells with post deposition treatment (PDT) of rubidium fluoride (RbF) at different temperatures have been in-depth studied along the thickness of the material. Sample characterization, in this work, was carried out using optical microscopy, confocal microscopy, Raman spectroscopy, electron microscopy, X-Ray fluorescence, capacitance profiling and current-voltage. The parameters of the cell have been compared before and after the polishing method to conclude that the methodology does not affect the obtained results. For the studied samples, it was found out that PDT promotes the smoothing of the existent compositional gradient of Gallium (Ga) and ordered vacancy compounds (OVC). Thus, it is found that the treatment has an improving impact not only affecting the surface but also the bulk material. These results coincide with the obtaining of higher values for the open circuit voltage (VOC) and the efficiency of the cell, so PDT can be related to a better performance of CIGSe TFSL. This project shows that the developed methodology is a powerful and promising technique that allows the in-depth characterization of TFSL, thereby revealing the impact of RbF-PDT through all the thickness of CIGSe absorbers.