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Browsing by Author "Ranjbar, S."

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  • Effect of selenization conditions on the growth and properties of Cu2ZnSn(S,Se)4 thin films
    Publication . Ranjbar, S.; Menon, M. R. Rajesh; Sousa, M. G.; Fernandes, P. A.; Cunha, A. F. da
    Cu2ZnSn(S,Se)4 (CZTSSe) is a potentially cost effective candidate for future thin film solar cells (TFSCs). We report the growth of CZTSSe using a hybrid process involving the sequential evaporation of Zn and sputtering of the sulfide precursors of Cu and Sn, followed by a selenization step. Two approaches for selenization were followed, one using a tubular furnace (TF) and the other using a Rapid Thermal Processor (RTP). SEM and EDS were employed to investigate the morphology and composition of the films. Structural analyses were done using XRD and Raman spectroscopy. Structural analyses revealed the formation of CZTSSe. The effects of annealing conditions on the morphological and structural properties of the films were investigated.
    2014Conference object Open access Show more
  • Electronic Conduction Mechanisms and Defects in Polycrystalline Antimony Selenide
    Publication . Cifuentes, N.; Ghosh, Santunu; Shongolova, A.; Correia, M. R.; Salomé, P. M. P.; Fernandes, P. A.; Ranjbar, S.; Garud, S.; Vermang, B.; Ribeiro, G. M.; González, J. C.
    A study of the electronic conduction mechanisms and electrically active defects in polycrystalline Sb2Se3 is presented. It is shown that for temperatures above 200 K, the electrical transport is dominated by thermal emission of free holes, ionized from shallow acceptors, over the intergrain potential barriers. In this temperature range, the temperature dependence of the mobility of holes, limited by the intergrain potential barriers, is the main contributor to the observed thermal activation energy of the conductivity of 485 meV. However, at lower temperatures, nearest-neighbor and Mott variable range hopping transport in the bulk of the grains turn into the dominant conduction mechanisms. Important parameters of the electronic structure of the Sb2Se3 thin film such as the average intergrain potential barrier height ϕ = 391 meV, the intergrain trap density Nt = 3.4 × 1011 cm−2, the shallow acceptor ionization energy EA0 = 124 meV, the acceptor density NA = 1 × 1017 cm−3, the net donor density ND = 8.3 × 1016 cm−3, and the compensation ratio k = 0, 79 were determined from the analysis of these measurements.
    2020-02-28Journal article Restricted access Show more