Thin films of Cu3BiS3 were prepared by coevaporation. Hall-effect, Seebeck-effect, and surface photovoltage measurements show that Cu3BiS3 is a p-type semiconductor with Hall-mobility, free carrier concentration, and thermo-electric power of 4 cm2/V s, 2×1016 cm−3, and 0.73 mV/K, respectively. The work function was determined by Kelvin probe force microscopy to be (4.37±0.04) eV before and (4.57±0.01) eV after deposition of a thin In2S3 layer. Transient surface photovoltage measurements at variable excitation wavelength showed the importance of defect states below the band gap for charge separation and the opportunity for surface defect passivation by a very thin In2S3 layer. The band bending at the Cu3BiS3/In2S3 interface was obtained. The role of grain boundaries for charge transport and charge separation is discussed.

Cu3BiS3 thin films were prepared on soda‐lime glass substrates by co‐evaporation of the precursors in a two‐step process; for that, the metallic precursors were evaporated from tungsten crucibles in the presence of elemental sulphur evaporated from a tantalum effusion cell. The films were characterized by spectral transmittance, Atomic Force Microscopy, X‐ray Photoelectron Spectroscopy, Scanning Electron Microscopy and electrical measurements to investigate the effect of growth conditions on the optical, morphological and electrical properties. The results revealed that the Cu3BiS3 films present p‐type conductivity, a high absorption coefficient (greater than 104 cm–1), and an energy band gap, Eg, of about 1.39 eV. We observed from Atomic Force Microscopy and electrical measurements that grain size and electric conductivity of the Cu3BiS3 samples are influenced by the copper mass ratio in this material. We found, in the high‐temperature range above room temperature, that carrier transport is thermally activated with activation energies fluctuating between 0.17 and 0.28 eV. This suggests that this compound has good properties to perform as absorbent layer in thin‐film solar cells. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Mo thin films have been deposited using a DC magnetron sputtering system with an S-gun configuration electrode and characterized electrically and morphologically. The influence of the sputtering gas pressure and glow discharge (GD) power, on the electrical resistivity of Mo thin films and on the contact resistivity of Mo to Cu(In,Ga)Se 2 (CIGS) films was determined through an exhaustive parameter study. This study also allowed us to find the conditions to deposit Mo films with suitable properties for its use as back contact of solar cells based on CIGS. Resistivities smaller than 1x10 −4 Ω.cm and contact resistivities smaller than 0.3 Ωcm 2 were found. Mo films with these characteristics are suitable for back contacts in solar cells based on CIGS. It was also found that the Mo thin films, deposited by DC magnetron sputtering on CIGS thin films, act effectively as ohmic contacts. The main contribution of this work was to obtain Mo thin films with adequate properties to be used as back contact for CIGS based solar cells using a DC sputtering system with S-gun configuration electrode, which allows growing the film with better surface quality and at a higher deposition rate than those deposited using the conventional planar RF sputtering system.

No abstract

No abstract