Optical and morphological properties of tetragonal Cu₂ZnSnS₄ thin films grown from sulphide precursors at lower temperatures

Optical constants of Cu₂ZnSnS₄ thin films formed using thermal annealing of pre-deposited layers of copper, zinc and tin sulphides on glass substrates at different temperatures and ambient atmosphere were determined. It has been shown that films grown at lower temperatures have the tetragonal structure of kesterite, and the corresponding value of the optical band gap is 1.47 eV

Raman spectroscopy of Cu Sn S ternary compound thin films prepared by the low cost spray pyrolysis technique

Cu Sn S CTS thin films were deposited onto bare and molybdenum Mo coated glass substrates by means of the spray pyrolysis technique under different conditions. The CTS thin films obtained are shown, by means of Raman spectroscopy, to consist of two main phases Cu2SnS3 and Cu3SnS4 as well as of the secondary phase of Cu2 amp; 8722;xS. The electrical conductivity of the spray deposited p type CTS thin films under investigation is determined by two shallow acceptor levels Ev 0.07 eV at T lt; 334 K and Ev 0.1 eV at T gt; 334 K. The material of the CTS thin films was established to be a direct band semiconductor with the bandgap Eg 1.89 eV. The SEM and x ray energy dispersive analysis show the surface and cross section of the CTS thin film deposited onto molybdenum coated glass ceramics substrate with the actual atomic ratios of Cu Sn S being 2.9 1 2.64, which is in good agreement with the Raman spectra. Also, a small content of residual Cl atoms was found in the CTS thin films under investigation as the by product of the pyrolytic reaction

Graphitic carbon n CdTe Schottky type heterojunction solar cells prepared by electron beam evaporation

We report on the analysis of the electrical and photoelectrical properties of graphitic carbon n CdTe Schottky type heterojunction solar cells, which have been prepared by the deposition of transparent graphitic carbon films of nanometer thickness onto freshly cleaved n CdTe substrates by the electron beam evaporation technique. The presence of the electrically active interface states at the heterojunction interface was revealed from the analysis of the dominating current transport at forward and reverse bias and from the capacitance voltage characteristics. The unoptimized graphitic carbon n CdTe Schottky type heterojunctions possess a rectification ratio of RR 1390 and produce a maximum short circuit current density of Jsc 8.47 mA cm2, an open circuit voltage of Voc 0.435 V and fill factor of FF 0.37 under standard illumination conditions 100 mW cm2 AM 1.

Thickness dependent structural parameters of kesterite Cu2ZnSnSe4 thin films for solar cell absorbers

The influence of thickness on the structural parameters, off stoichiometry and cation disorder in kesterite Cu2ZnSnSe4 films grown by flash deposition for solar cell absorbers is investigated employing X ray diffraction, energy dispersive X ray and Raman spectroscopies. It is shown that the lattice parameters of Cu2ZnSnSe4 changed depending on film thickness the 100 nm film turned out to be weakly stretched on the molybdenum coated glass substrates, while, in the thicker films, the compressive deformation is defined. The causes of the changes in film structure are outlined. Raman spectra revealed secondary phases like Cu2SnSe3 detecting reduction of its fraction with an increment in thickness; also, the SnZn antisite defect fraction decreases. Simultaneously, the share of disordered kesterite phase associated with CuZn antisite defects rises with thickness. The obtained results can be useful for optimization of technological growth proces

Thin films of Cu₂ZnSnS₄ for solar cells: optical and structural properties

The structure of Cu₂ZnSnS₄ films was investigated by Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray spectrometry, optical reflectance and photoluminescence. The films were formed by thermal annealing layers of copper, zinc and tin sulfides on glass substrates at different substrate temperature and ambient atmosphere. It was revealed that the films have the dominant structure of kesterite with possible inclusions of stannite Cu₂ZnSnS₄ structure. Under certain growth conditions, however, segregation of Cu₂₋xS occurs, as proved by registering the characteristic peak in Raman spectra. No traces of secondary phases of zinc or tin sulphides are found

Raman study of colloidal Cu2ZnSnS4 nanocrystals obtained by “green” synthesis modified by seed nanocrystals or extra cations in the solution

The method of affordable colloidal synthesis of nanocrystalline Cu2ZnSnS4 (CZTS) is developed, which is suitable for obtaining bare CZTS nanocrystals (NCs), cation substituted CZTS NCs, and CZTS-based hetero-NCs. For the hetero-NCs, the synthesized in advance NCs of another material are introduced into the reaction solution so that the formation of CZTS takes place preferably on these “seed” NCs. Raman spectroscopy is used as the primary method of structural characterization of the NCs in this work because it is very sensitive to the CZTS structure and allows to probe NCs both in solutions and films. Raman data are corroborated by optical absorption measurements and transmission electron microscopy on selected samples. The CdTe and Ag NCs are found to be good seed NCs, resulting in a comparable or even better quality of the CZTS compound compared to bare CZTS NCs. For Au NCs, on the contrary, no hetero-NCs could be obtained under the given condition. Partial substitution of Zn for Ba during the synthesis of bare CZTS NCs results in a superior structural quality of NCs, while the introduction of Ag for partial substitution of Cu deteriorates the structural quality of the NCs