Structural, Optical and Electrical Properties of CuIn 0.7 Ga 0.3 Se 2 Ingot Prepared by Direct Melting
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https://doi.org/10.1007/s11664-020-08463-6 Ó 2020 The Minerals, Metals & Materials Society
Structural, Optical and Electrical Properties of CuIn0.7Ga0.3Se2 Ingot Prepared by Direct Melting S. LAHLALI,1 M. BELAQZIZ,1 S. AMHIL,2 L. ESSALEH,2 H. CHEHOUANI ,1,5 K. DJESSAS,3 K. MEDJNOUN,3 O. ABOUNACHIT,1 M. IBANNAIN,1 and A. BOULOUFA4 1.—Laboratory of Processes for Sustainable Energy & Environment (ProcEDE), Cadi Ayyad University, Marrakech, Morocco. 2.—IMED-Lab, Faculty of Sciences and Techniques, Cadi Ayyad ´ nergie University, B.P. 549, Marrakech, Morocco. 3.—Laboratoire Proce´de´s, Mate´riaux et E Solaire (PROMES-CNRS), Universite´ de Perpignan, Rambla de la Thermodynamique, Tecnosud, 66100 Perpignan Cedex, France. 4.—Laboratory of Electrochemical and Materials, Se´tif-1 University, Se´tif 19000, Algeria. 5.—e-mail: [email protected]
CuIn0.7Ga0.3Se2 (CIGS) ingots were prepared by reaction of high-purity elements in stoichiometric proportions. The direct melting of elements was carried out using an original and low-cost process. The structural and morphological properties of the obtained material were investigated through x-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy. To detect and identify the defect chemistry of the obtained crystal, we used cathodoluminescence measurements at different temperatures. Moreover, the electrical properties of the CIGS material have been deeply investigated in this work using impedance spectroscopy. The activation energy for the conduction process was estimated. The conductivity data were found to obey the universal law of Jonsher. AC conduction is attributed to the correlated barrier hopping model. In the Nyquist diagram, two microscopic contributions to the electrical conduction were well identified. Key words: CuIn0.7Ga0.3Se2, structural properties, cathodoluminescence, electrical properties, electrical conductivity, complex impedance
INTRODUCTION It is well known that CuInSe2 and CuGaSe2 compounds and their alloys are considered the most promising photovoltaic materials. This family presents diverse physical properties which are very important for optimum device performance.1,2 Photovoltaic applications of these materials continue to make advances in economic viability and to reach high efficiencies of thin film solar cells.3–5 CuInSe2 presents a small direct band gap around 1.04 eV which is suitable for photovoltaic conversion.5 Even more significant, by partial substitution of indium with gallium (i.e. Cu (In,Ga)Se2), the band gap value can be systematically varied between 1.04 eV
(Received March 3, 2020; accepted August 29, 2020)
and 1.68 eV.6 The CuIn0.7Ga0.3Se2 (CIGS) compound presents an optimum composition and interesting electrical and optical properties.1 On a laboratory scale, the recent efficiency of CIGS-based solar cells is 22.9%.7 As is well known, the performance of CIGS solar cells is highly related to the intrinsic defects and electrical inhomogeneities introduced in the absorber material during the growth process.8 In or
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