Enhanced Photosensitivity of Bi-Doped Cu 2 Se Thin Films Prepared by Chemical Synthesis for Solar Cell Application
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RESEARCH PAPER
Enhanced Photosensitivity of Bi-Doped Cu2Se Thin Films Prepared by Chemical Synthesis for Solar Cell Application J. Henry1 • T. Daniel1 • V. Balasubramanian1 • K. Mohanraj1 • G. Sivakumar2 Received: 3 February 2020 / Accepted: 20 July 2020 Ó Shiraz University 2020
Abstract In this work, pure and Bi-doped (0.01, 0.02 and 0.03) M Cu2Se thin films were deposited on glass substrate by simple chemical bath deposition method. The effect of Bi doping on Cu2Se films was analysed using their structural, morphological, optical and electrical properties recorded by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), diffuse reflectance spectra (DRS) and Hall effect analysis respectively. The XRD pattern shows cubic structure for pure and Bi-doped Cu2Se films, and peak shift confirms the incorporation of Bi into Cu2Se lattice. FESEM images show uniform homogenous particles distributed over their surface. Bi-doped films show higher optical absorption, and the band gap value is about 1.73–1.65 eV. The electrical property of the films shows high electrical conductivity. The Photo I–V measurement exhibited good photovoltaic behaviour. Keywords Thin films Materials science Photosensitivity Chemical bath deposition Cu2Se
1 Introduction Nowadays, the renewable energy source plays an important role due to an environmental impact and limited supplies of fossil fuels. The solar energy is the most widely available energy source by reducing its cost and increases in the widespread commercialization of solar cells are fabricated by novel materials and innovating technologies to be required (Korala et al. 2016). Among the absorber materials, Cu2Se has attracted much attention due to its excellent optical properties. It is a p-type semiconductor (Liu et al. 2013). Cu2Se contains Cu in the ? 1 oxidation state (Singh and Singh 2015). The optical band gap of Cu2Se is found to be 1.2–2.35 eV (Zhu et al. 2016). Doping is a simple way to enhance the light absorption ability of Cu2Se in the visible region (Kimi et al. 2015). Theoretically, the
& K. Mohanraj [email protected]; [email protected] 1
Department of Physics, Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli, Tamil Nadu 627 012, India
2
Centralised Instrumentation and Service Laboratory, Department of Physics, Annamalai University, Annamalai Nagar, Chidambaram, Tamil Nadu 608 002, India
doping elements can generate additional point defects to increase the phonon scattering and consequently to reduce the band gap. Lei Yang et al. have observed the phase transition of Cu2Se1-xTex nanoplates from b-phase to a-phase by increasing the Te doping level (Yang et al. 2016). Sedat Ballikaya et al. (2013) have reported that the doping of Ag on Cu2Se and Cu2Te reduces the density of holes and strongly suppresses the thermal conductivity. Tristan Day et al. (2014) have observed that the addition of Ag in Cu2Se reduces the carrier concentration to nearly optimum value at high temp
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