Open Access

ARTICLE

Environmentally Benign ZnS/RGO Nanocomposite Buffer Layers for High-Performance Cu₂O/CdTe Thin-Film Solar Cells

Ahmed Mostafa^1,*, Samar Al-Shehri², Azzah A. Alshehri³, A. Ashour⁴
1 Department of Physics, Faculty of Science, Suez University, Suez, Egypt
2 Department of Physics, College of Science, University of Bisha, Bisha, Saudi Arabia
3 Department of Chemistry, College of Science, University of Bisha, Bisha, Saudi Arabia
4 Department of Physics, Faculty of Science, Islamic University of Madinah, Madinah, Saudi Arabia
* Corresponding Author: Ahmed Mostafa. Email: ,
(This article belongs to the Special Issue: Chalcogenide Thin Films and Solar Cells for Optoelectronic Applications)

Chalcogenide Letters https://doi.org/10.32604/cl.2026.083336

Received 02 April 2026; Accepted 25 May 2026; Published online 29 September 2026

Abstract

ABSTRACT: Interface engineering is an effective strategy for improving the efficiency and operational stability of thin-film photovoltaic devices. In this work, zinc sulfide/reduced graphene oxide (ZnS/RGO) nanocomposites (NCs) were synthesized using environmentally benign methods and incorporated as buffer layers into Glass/ITO/Cu₂O/CdTe/ZnS–RGO/Al solar cells. X-ray diffraction (XRD) measurements confirmed the formation of phase-pure hexagonal ZnS, with crystallite sizes ranging from 18 to 26 nm. The introduction of RGO resulted in lattice microstrain values of (3.1–6.4) × 10⁻⁴, suggesting effective interfacial coupling within the composite structure. X-ray photoelectron spectroscopy (XPS) provided further evidence for the successful integration of ZnS and RGO, with the characteristic Zn 2p and S 2p core-level signals corresponding to Zn²⁺–S bonding, together with a distinct C 1s contribution from RGO and an O 1s component associated with residual oxygen-containing surface functionalities. These spectroscopic features support the presence of strong interactions at the ZnS/RGO interface. Optical characterization showed enhanced absorption throughout the 300–900 nm wavelength range and a progressive reduction in the optical band gap as the RGO content increased. This behavior was accompanied by substantial photoluminescence quenching, indicating more efficient interfacial charge transfer and reduced radiative recombination. Incorporation of the ZnS/RGO buffer layer substantially enhanced the photovoltaic response of the devices, yielding a short-circuit current density of approximately 29 mA cm⁻², an open-circuit voltage of approximately 0.82 V, and a fill factor of approximately 72%. Consequently, a maximum power conversion efficiency of approximately 17.1% was achieved. Electrochemical impedance measurements revealed a low series resistance of 2.5–4.0 Ω cm², together with a pronounced increase in recombination resistance to nearly 3.5 × 10³ Ω cm², demonstrating effective inhibition of interfacial charge recombination. In addition, temperature-dependent electrical measurements performed between 280 and 320 K revealed improved thermal stability and a lower degree of performance deterioration for the devices incorporating the ZnS/RGO buffer layer. Overall, the results demonstrate the potential of environmentally benign ZnS/RGO NCs as efficient and sustainable buffer-layer materials for advanced thin-film photovoltaic applications.

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Keywords

ZnS/RGO nanocomposites; buffer layer engineering; thin-film solar cells; interface recombination; impedance spectroscopy; external quantum efficiency; environmentally benign synthesis

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