Sputtered single-phase kesterite Cu2ZnSnS4 (CZTS) thin film for photovoltaic applications: Post annealing parameter optimization and property analysis

Afrina Sharmin,S. M. Mostafa Al Mamun,Munira Sultana,M. S. Bashar

doi:10.1063/1.5129202

Afrina Sharmin, S. M. Mostafa Al Mamun + Show 2 more

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https://doi.org/10.1063/1.5129202

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Abstract

A potential solar absorber material, sputtered kesterite Cu2ZnSnS4 (CZTS) thin film, has been extensively studied in recent years due to its advantageous properties, including the earth abundance of its constituent elements, nontoxicity, suitable band gap, and high absorption coefficient. 2000 nm CZTS thin films were deposited on soda lime glass by a sputtering technique. The prepared films underwent a postannealing treatment for crystallization in which different temperatures and pressures were applied to understand its impact on film growth, phase formation, and stoichiometry. The annealed samples were subsequently characterized by Raman and UV-visible (UV-Vis) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The thickness of each film was measured using a surface profilometer and from a cross-sectional image obtained by SEM. The XRD pattern for each film showed characteristic (112), (220), and (312) peaks, and the phase purity was confirmed via Raman studies. Film surface morphology and roughness were studied by AFM. The root mean square roughness was found to increase with annealing temperature and base pressure. The chemical compositions of the prepared samples were analyzed by EDX, and the films showed desired stoichiometry. UV-Vis absorption spectroscopy indicated that the direct band gap energies (Eg) of the films were 1.47 eV–1.51 eV, within the optimum range for use in solar cells. These attractive properties of the sputtered CZTS thin film should heighten interest in its use as a solar absorber layer in the next-generation photovoltaic cells, suggesting that it possesses substantial commercial promise.

Highlights

Photovoltaic solar power generation has grown exponentially in recent decades due to increasing energy consumption
The power conversion efficiencies (PCEs) of an amorphous silicon (a-Si) thin film can reach 13.6%,2 whereas solar cells based on copper indium selenide (CIS), copper indium gallium selenide (CIGS), and cadmium telluride (CdTe) offer higher PCEs of up to 22%
The samples annealed at 560 ○C had larger crystallites than those annealed at 470 ○C, as demonstrated by the sharper peaks in the X-ray powder diffraction (XRD) spectra of thin films annealed at 560 ○C

Summary

Introduction

Photovoltaic solar power generation has grown exponentially in recent decades due to increasing energy consumption Researchers in this field have focused on mastering low-cost and high efficient photovoltaic device manufacture. The PCE of an amorphous silicon (a-Si) thin film can reach 13.6%,2 whereas solar cells based on copper indium selenide (CIS), copper indium gallium selenide (CIGS), and cadmium telluride (CdTe) offer higher PCEs of up to 22%.3. Another potential solar absorber material is the p-type chalcogenide semiconductor Cu2ZnSnS4 (referred to as CZTS), which is derived from the chalcopyrite structure of CIGS by replacing In and Ga with less expensive and more earth-abundant elements such as Zn and Sn.. Among the various possible structures of CZTS, kesterite shows greater stability than stannite and wurzite, as kesterite possesses lower energy than those of the other two structures.

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