Studying the Structural, Morphological, Optical, and Electrical Properties of CdS/PbS Thin Films for Photovoltaic Applic
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Studying the Structural, Morphological, Optical, and Electrical Properties of CdS/PbS Thin Films for Photovoltaic Applications Mustafa K. A. Mohammed 1 Received: 3 April 2020 / Accepted: 29 June 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The cadmium sulfide (CdS) and lead sulfide (PbS) materials have been chosen in order to boost solar energy conversion from ultraviolet region to the near-infrared (NIR) spectral region. These materials belonging to the II–VI group have suitable direct band gaps and in solar energy conversion. CdS and PbS layers are used as window and absorber materials, respectively, in solar cells. This paper presents structural, morphological, and optical properties of PbS and CdS thin films prepared by chemical spray pyrolysis at different temperatures as well as its photovoltaic performance. The X-ray diffraction results show the PbS films have cubic structure and CdS films have hexagonal structure. FESEM measurements reveal the films have homogeneous surfaces with spherical particles. Optical analyses exhibit the optical band gap redshifts as the substrate temperature increases. Illumination current density–voltage test of ITO/CdS/PbS/Au heterojunction with different thicknesses of PbS layer has been evaluated. The optimal results are obtained in ITO/CdS/PbS/Au solar cell where thickness of PbS layer is of 0.9 μm with maximum short circuit current, open circuit voltage, and fill factor as well as highest efficiency. Keywords PbS/CdS thin film . Spray pyrolysis . X-ray diffraction . Semiconductor . Optical properties
Introduction The ever-increasing power demand has pushed the research community to find more efficient, environmentally safely, renewable, and low-cost energy sources to replace the actual dominant oil and fossil fuel [1]. Because of the inexpensive development and the moderately high theoretical power conversion efficiency, thin-film solar cells are appearing as a highly interesting kind of renewable power sources [2]. They also have versatile features such as capability of multiple exciton generation, high stability against heat, and tunable band gap because of the quantum confinement effect [3]. PbS is a significant semiconductor compound material in the manufacturing of absorber layers for photovoltaic applications due to small band gap approximately from 0.36 to 0.42 eV, appropriate exciton Bohr radius of around 18 nm, and provides electrons and holes with efficient quantum confinement, driving to a raise in the absorption of the solar spectrum in the near infrared range [4]. These features make lead sulfide plays
* Mustafa K. A. Mohammed [email protected] 1
Technical Engineering College, Middle Technical University, Baghdad, Iraq
significant role in the photovoltaic applications [5]. CdS thin films are regarded as one of the most important substances for solar cell applications [6]. It has wide band gap (2.5 eV) with high optical transmittance and high electrical conductivity [7]. For these reasons, CdS can be used as the
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