Search

Abstract: Thin films of p-type Cu3BiS3 with an orthorhombic wittichenite structure, a semiconductor with high potential for thin film solar cell absorber layers, were synthesised by thermal annealing of Cu and Bi precursors, magnetron sputtered on Mo/glass substrate, with a layer of thermo-evaporated S. The elemental composition, structural and electronic properties are studied. The Raman spectrum shows four modes with the dominant peak at 292cm−1. Photoreflectance spectra demonstrate two band gaps EgX and EgY , associated with the X and Y valence sub-bands, and their evolution with temperature. Fitting the temperature dependencies of the band-gaps gives values of 1.24 and 1.53eV for EgX and EgY at 0K as well as the average phonon energy. Photoluminescence spectra at 5K reveal two bright and broad emission bands at 0.84 and 0.99eV, which quench with an activation energy of 40meV. The photocurrent excitation measurements demonstrate a photoresponse and suggest a direct allowed nature of the band gap. [Copyright &y& Elsevier]

Abstract: Solar cells with the structure ZnO:Al/i-ZnO/CdS/Cu(In,Ga)Se2/Mo/polyimide were examined using a range of techniques. The elemental composition of the Cu(InGa)Se2 (CIGS) layers, their crystalline structure and optical properties were studied. Photoluminescence (PL) spectra of the CIGS absorber layers were studied as functions of temperature (4.2–240K) and excitation power density. The band gap energy Eg of the CIGS layers was determined by employing photoluminescence excitation (PLE) spectroscopy. The influence of sodium incorporation on the PL properties of CIGS was analysed. Correlations of the optical properties of the CIGS absorber layers and the photovoltaic parameters of the solar cells were revealed. [Copyright &y& Elsevier]

Polycrystalline CuInGaSe2 (CIGS) and CuInSe2 (CIS) thin films were synthesized on glass substrates by a two-stage selenization process. The surface morphology, phase structure and composition of the films were analyzed by scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray analysis, respectively. Photoluminescence, optical transmission and reflection spectra were measured at temperatures from 4.2 to 300 K to characterize defects and the structural quality. The structural quality and evolution of defects in the CIS films grown at different temperatures and selenization time, and dependence of the band-gap energy on the content of Ga in CIGS films at 78 K is discussed. [Copyright &y& Elsevier]

Photoluminescence (PL) and optical absorption (OA) measurements in the temperature range from 4.2 to 300 K were carried out on CuInSe2 (CIS) thin films, synthesised on soda-lime glass substrates by a two-stage selenisation process. For near stoichiometric films, intense band-to-band recombination generated a room temperature PL peak at 1.028 eV with full width at half maximum (FWHM) of approximately 50 meV. At 78 K, the A and B free exciton peaks appeared, in both PL and OA spectra, merged into a band at approximately 1.044 eV. The 4.2 K-PL spectrum contains a number of features. The A and B excitonic peaks shift to 1.0409 eV (A) and 1.0444 eV (B) and are well resolved in both the PL and OA spectra, with their FWHM reduced to 2.5 meV. Their spectral positions and FWHM are approaching those in high quality CIS single crystals. The absorption coefficient α is derived from the OA spectra. Defects responsible for the observed PL bands are discussed. [Copyright &y& Elsevier]