Investigation of optical, structural and electrical properties of CuInSe2 thin layer by thermal spray pyrolysis method by optimizing the amount of sodium in the structure

The absorbent layer of the heart is a solar cell that plays an important role in its function. In recent years, Cu (In, Ga) Se2 has been highly regarded as an absorbent layer in chalcogenide solar cells. In this research, a cheap, fast and commercially available spray pyrolysis method has been used to make CISe layers. Then, the effect of soaking time of samples in sodium-containing solution on the electrical, optical, structural and morphological properties of the sprayed layers was investigated and the optimal amount of sodium in the structure was introduced. Analyzes performed to evaluate these features include X-ray diffraction pattern (XRD), field emission electron microscopy (FESEM) with elemental analysis (EDS), transmittance spectroscopy (UV-Vis), electrochemical analysis of Mott-Schottky and current-voltage curve measurements in the dark ambient. The results show that the change of soaking time in the solution and consequently the amount of sodium in the structure affects the crystallinity and morphological properties of the layers. The layers resulting from the soaking time of 15 minutes are finer than 5 and 10 minutes and are also porous in the cross-sectional area images. While the best crystallinity and maximum porosity of the mobility (~10-1cm2 / V.s) were obtained for a sample with a soaking time of 10 minutes. Sodium diffusion in the structure changed from ~1019cm-3 to ~1017cm-3. However, the energy levels of the band structure do not change significantly as the soaking time changes. On the other hand, by changing the soaking time of the direct band gap from 1.38 to 1.41 eV has changed. So that the expansion of the band gap with a value of 1.41 eV is visible for the optimal amount of sodium with a soaking time of 10 minutes. In general, according to the results of this study, the CISe:Na layer can be used in various optoelectronic structures by using the optimized amounts of sodium in the structure of the solar cell.