Study of structural and optical properties of kesterite Cu2ZnGeX4 (X = S, Se) thin films synthesized by chemical spray pyrolysis

Abstract

We report on the fabrication of polycrystalline Cu 2 ZnGeX 4 (X = S, Se) thin films using spray pyrolysis followed by post-sulfurization and post-selenization. The stoichiometric, morphological, structural and optical properties of fabricated thin films were investigated and discussed in the photovoltaic aspect. Although the as-sprayed films were observed to be grown with poor crystalline texture, the crystallinity was found to be greatly improved after post-sulfurization and post-selenization, which was confirmed by X-ray diffraction (XRD) and Raman spectroscopy. The band gap energy was estimated as 1.88-1.93 eV for post-sulfurized Cu 2 ZnGeS 4 (CZGS) films and 1.40-1.43 eV for post-selenized Cu 2 ZnGeSe 4 (CZGSe) films by UV-Vis absorption measurements. The crystal lattice parameters calculated from XRD patterns for post-sulfurized CZGS and post-selenized CZGSe films were found to be consistent with kesterite structure which is strongly supported by the band gap energy estimated from the UV-Vis absorption measurements.

Structural, optical and electrical properties of Cu2FeSnX4 (X=S, Se) thin films prepared by chemical spray pyrolysis

“…The as-sprayed films deposited on Mo-SLG were sulfurized (selenized) under sulfur or selenium vapor at 500-520 C for 25 min keeping sample inside of rectangular graphite box filled with sulfur or selenium powder (99.99%, 75 m). We followed the annealing system and pattern same as our previous report [29]. Moreover, to investigate band gaps and electrical properties by Hall effect, we also synthesized post-sulfurized and postselenized thin films on SLG substrate following exactly same procedure and condition as mentioned above.…”

“…thiourea (SC(NH 2 ) 2 ) was used to minimize oxidation and sulfur deficiency in as-sprayed thin films. The prepared solutions were deposited on soda lime glass (SLG) and molybdenum coated soda lime glass (Mo-SLG) at substrate temperature of 450 C using home-made ultrasonic spray systems in which high electrostatic field was applied between outlet of aerosol flow pipe and substrate as mentioned in spray pyrolysis report [28,29]. Nitrogen was used as carrier gas to flow the mist of precursor solution which was controlled by gas flow meter.…”

“…Chemical spray pyrolysis (CSP) is one of the simple and effective direct solution coating deposition techniques [28,29]. The cation stoichiometry of film deposited by CSP can be well controlled by dissolving required concentration of respective chemicals in spray precursor solution [8,24,28,29].…”

“…Chemical spray pyrolysis (CSP) is one of the simple and effective direct solution coating deposition techniques [28,29]. The cation stoichiometry of film deposited by CSP can be well controlled by dissolving required concentration of respective chemicals in spray precursor solution [8,24,28,29]. The fabricated CFTS (Se) films were characterized by field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, and Hall effect measurement.…”

Band Gap Tuning of Cu2ZnGeSxSe4-x Absorbers for Thin-Film Solar Cells

“…In recent years, the rather new kesterite-type Cu 2 ZnGeS x Se 4-x (CZGSSe) has gained attention as a high band gap absorber material for thin-film solar cells [1][2][3][4][5][6]. Its similarity to the extensively studied Cu 2 ZnSnS x Se 4-x (CZTSSe) offers potential for fast progress in the improvement of material properties and solar cell efficiency, with a record value of 6.0% so far [3].…”