Structural, optical, electrical, and photovoltaic investigations of p-type Cu2MnSnSe4 thin films as a novel absorber layer for thin film solar cells

The authors in this work report the formation of high-quality Cu2MnSnSe4 thin films on glass substrates utilizing electron beam deposition. The X-ray diffraction (XRD) investigations of the Cu2MnSnSe4 samples demonstrate that the as-deposited samples are amorphous, while the films that have been annealed at 250 °C reveal a polycrystalline structure with a single tetragonal phase. The EDX spectra of these Cu2MnSnSe4 films clarified their stoichiometric composition. Moreover, various optical parameters have been calculated with the measurement of transmittance and reflectance spectroscopy in the 400–2500 nm range. The optical band gap values of the Cu2MnSnSe4 films were estimated by Tauc`s relationship, and they were reduced from 1.71 to 1.47 eV via enlarging the film thickness. The significant impact of thickness on the optical parameters of these Cu2MnSnSe4 films, such as optical conductivity, extinction coefficient, optical dielectric constant, refractive index, and absorption coefficient, was studied. Furthermore, Miller`s equations have been used to evaluate the nonlinear optical parameters such as nonlinear refractive index, first and third-order nonlinear optical susceptibility for the Cu2MnSnSe4 samples. The hot-probe approach indicated that the Cu2MnSnSe4 samples have p-type semiconductor behavior. The DC conductivity study of the Cu2MnSnSe4 samples showed that the activation energy values decreased as the film thickness rose from 174 to 459 nm, while the pre-exponential factor values enlarged. On the other hand, the ITO/CdS/Cu2MnSnSe4/Al heterojunction was prepared. This heterojunction device shows a solar conversion efficiency of 4.45%. The results showed that these Cu2MnSnSe4 samples could be used as a new absorber layer in thin-film solar cells.