One-step electrodeposition process of CuInSe₂: Deposition time effect

Abstract

CuInSe₂ thin films were prepared by one-step electrodeposition process using a simplified two-electrodes system. The films were deposited, during 5, 10, 15 and 20 min, from the deionized water solution consisting of CuCl₂, InCl₃ and SeO₂ onto ITO-coated glass substrates. As-deposited films have been annealed under vacuum at 300 °C during 30 min. The structural, optical band gap and electrical resistivity of elaborated films were studied, respectively, using X-ray diffraction (XRD), Raman spectroscopy, UV spectrophotometer and four-point probe method. The micro structural parameters like lattice constants, crystallite size, dislocation density and strain have been evaluated. The XRD investigation proved that the film deposited at 20 min present CuInSe₂ single phase in its chalcopyrite structure and with preferred orientation along (1 1 2) direction, whereas the films deposited at 5, 10 and 15 min show the CuInSe₂ chalcopyrite structure with the In₂Se₃ as secondary phase. We have found that the formation mechanism of CuInSe₂ depends on the In₂Se₃ phase. The optical band gap of the films is found to decrease from 1.17 to 1.04 eV with increase in deposition time. All films show Raman spectra with a dominant A₁ mode at 174 cm⁻¹, confirming the chalcopyrite crystalline quality of these films. The films exhibited a range of resistivity varying from 2.3 × 10⁻³ to 4.4 × 10⁻¹ Ω cm.