Nonlinear energy dependence of the forbidden energy band in the solid solutions CuxAg1−xBIIIC2VI

Abstract

The solid solutions CuxAg1−xGaS2 and CuxAg1−xInSe2 for x = 0.5 and their terminal compounds (x = 0; 1) have been investigated both theoretically and experimentally using x-ray emission and absorption spectroscopy. These solid solutions are advanced materials for the transformation of solar energy. The electron structure of these solutions and compounds was investigated using FEFF8 code. The calculated local densities of electron states and x-ray absorption spectra were compared with our experimental x-ray spectra and photoelectron curves taken from the literature. The good correspondence of the theory to the experiment guarantees the assumed interpretation of the results for the solid solutions CuxAg1−xGaS2 and CuxAg1−xInSe2. It was found that in these solid solutions “pushing apart” of d-states of Cu and Ag takes place, which can be explained by the splitting of p-states of the atoms CVI and d-states of AI-atom (Cu and Ag). Our calculations have proved and explained the nonlinear dependence of the energy gap Eg on x.