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Herein, we report the structural characterization and vibrational and physical properties of Cu₂ZnSn_1−xSi_xSe₄ solid solutions synthesized using the ceramic method. X-ray diffraction analysis and Rietveld analysis of the samples indicated that by increasing the x value from 0 to 0.8, the volume of the unit cell decreased because the ionic radius of silicon is smaller than that of tin. Simultaneously, a phase transition between stannite and wurtz-stannite was observed. The Raman peaks were analyzed by fitting the spectra to identify the vibrational modes by comparison with the experimental data from Cu₂ZnSnSe₄ and Cu₂ZnSiSe₄. The spectra of Cu₂Zn(Sn_1−xSi_x)Se₄ (x = 0.2 and 0.3) show two dominant peaks at approximately 172 and 195 cm⁻¹, which are assigned to the A1 mode of the stannite structure. The optical band gaps for Cu₂Zn(Sn_0.8Si_0.2)Se₄ and Cu₂Zn(Sn_0.2Si_0.8)Se₄ were 1.30 and 1.74 eV, respectively. These values were intermediate to those of the end members. Electrical properties of Cu₂Zn(Sn_0.8Si_0.2)Se₄ revealed p-type conductivity behavior with a carrier concentration of approximately ~+3.50 × 10⁻¹⁹ cm⁻³ and electrical mobility of 2.64 cm²/V·s. Full article

Kesterite-structured Cu₂ZnSnSe₄ (CZTSe) is considered as one of the Earth-abundant and non-toxic photovoltaic materials. CZTSe films have been prepared using a single-step co-evaporation method at a relatively low temperature (i.e., below 500 °C). Due to the volatile nature of tin-selenide, the control over substrate temperature (i.e., growth temperature) is very important in terms of the deposition of high-quality CZTSe films. In this regard, the effects of growth temperatures on the CZTSe film morphology were investigated. The suitable temperature range to deposit CZTSe films with Cu-poor and Zn-rich compositions was 380–480 °C. As the temperature increased, the surface roughness of the CZTSe film decreased, which could improve p/n junction properties and associated device performances. Particularly, according to capacitance-voltage (C-V) and derived-level capacitance profiling (DLCP) measurements, the density of interfacial defects of CZTSe film grown at 480 °C showed the lowest value, of the order of ~3 × 10¹⁵ cm⁻³. Regardless of applied growth temperatures, the formation of a MoSe₂ layer was rarely observed, since the growth temperature was not high enough to have a reaction between Mo back contact layers and CZTSe absorber layers. As a result, the photovoltaic (PV) device with CZTSe film grown at 480 °C yielded the best power conversion efficiency of 6.47%. It is evident that the control over film growth temperature is a critical factor for obtaining high-quality CZTSe film prepared by one-step process. Full article