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Cu2MnSnS4 (CMTS) is a promising candidate for application in thin film for photovoltaics (PV), thanks to sustainability and low cost of its components. Nevertheless, reported efficiencies are still poor, with a current world-record of 1.13% for a solar cell with CMTS absorber layer made by sputtering and sulfurization [1]. This work reports about a simple and low-cost synthesis procedure, starting from a solution containing all the precursors, without the need of hazardous external sulfurizing agents. CMTS thin films were made by blade coating of the solution on molybdenum substrate and followed by an annealing at 550°C under argon atmosphere, without the aid of external sulphurating agents. After annealing, samples were quenched at RT, but some selected samples underwent a slow cooling inside the furnace. Some selected CMTS thin films were subjected to HCl etching (3% HCl, at 75°C for 10 minutes). Prototype devices were made with the architecture Mo/CMTS/CdS/i-ZnO/AZO/Al grid: CdS was deposited by chemical bath deposition, i-ZnO and AZO by sputtering and Al grid was thermally evaporated. Some selected devices were subjected to a thermal treatment at 260°C for 10 minutes on titanium hotplate. After measurements of photovoltaic performances, upper layers were removed and CMTS thin films were extensively studied employing the GI-XRD technique to determine the lattice constants as well as microstructural properties like microstrain and size of coherent scattering domains. These results of the evaluation of GI-XRD data and photovoltaic performances were correlated to precursor composition, cooling conditions after annealing and post deposition treatments (i.e. HCl etching of the absorber before CdS deposition and thermal treatment of the complete device). All CMTS thin films analyzed by GI-XRD exhibited stannite structure, as expected [2], with a very good crystalline quality. The impact of metal ratio in the solution of precursors was studied, keeping copper poor condi

Using spectroscopic ellipsometry we investigated and analyzed the pseudo-optical constants of Cu 2ZnSnSe4 bulk crystals, grown by the Bridgman method, over 0.8–4.5 eV photon energy range. The structures found in the spectra of the complex pseudodielectric functions were associated to E0, E1A, and E1B interband transitions and were analyzed in frame of the Adachi's model. The interband transition parameters such as strength, threshold energy, and broadening were evaluated by using the simulated annealing algorithm. In addition, the pseudo-complex refractive index, extinction coefficient, absorption coefficient, and normal-incidence reflectivity were derived over 0.8–4.5 eV photon energy range.

We report the room temperature spectroscopic ellipsometry study of Cu 2ZnGeSe4 and Cu2ZnSiSe4 crystals, grown by modified Bridgman technique. Optical measurements were performed in the range 1.2-4.6 eV. The spectral dependence of the complex pseudodielectric functions as well as pseudo- complex refractive index, extinction coefficient, absorption coefficient, and normal-incidence reflectivity of Cu 2ZnGeSe4 and Cu2ZnSiSe4 crystals were derived. The observed structures in the optical spectra were analyzed by Adachi's model and attributed to the band edge transitions and higher lying interband transitions. The parameters such as strength, threshold energy, and broadening, corresponding to the E0, E1A and E 1B interband transitions, have been determined using the simulated annealing algorithm. © 2013 Elsevier B.V. All rights reserved.

Spectroscopic ellipsometry has been used to characterize the dielectric functions of bulk Cu(In1−xGax)5Se8 crystals. Spectra were measured at room temperature over the energy range 0.74–5.2 eV. The dielectric functions as well as the complex refractive index, the absorption coefficient, and the normal-incidence reflectivity have been modeled using a modification of the Adachi model. The results are in a good agreement with the experimental data over the entire range of photon energies. The model parameters (strength, threshold energy, and broadening) have been determined using the simulated annealing algorithm. The transition energies E0 and E1A are found to shift linearly to higher energies as the gallium content increases.