Reactively Sputtered Cu2ZnTiS4 Thin Film as Low-Cost Earth-Abundant Absorber (original) (raw)
Related papers
Solar Energy Materials and Solar Cells, 2016
We have determined for the first time the device-relevant optical constants of 500 nm and 800 nm-thick Cu 2 ZnSnS 4 absorbers, grown on bare and Mo-coated soda-lime glass (SLG), using spectroscopic ellipsometry (SE). The composition, structure, phase purity and morphology were characterized by X-ray fluorescence, X-ray photoelectron spectroscopy depth profiling, X-ray diffraction, Raman spectroscopy, scanning-electron microscopy and atomic force microscopy. For the SE analysis, carefully determined sample characteristics were utilized to build a multilayer stack optical model, in order to derive the dielectric functions and refractive indices. The SE-derived absorption coefficients from CZTS/SLG samples were compared with those derived from complementary spectrophotometry measurements and found to be in good agreement. The bandgap determined from Tauc plots was E g ¼ 1.57 70.02 eV. The absorption coefficients just above the bandgap were found to be a few 10 4 cm À 1 and to exceed 10 5 cm À 1 at energies above $ 2.5 eV, which is much higher than previously found. The sub-bandgap k-value was found to be k $ 0.05 or less, suggesting that a moderate band tail is present. Separate device characterization performed on identical samples allowed us to assign device efficiencies of, respectively, 2.8% and 5.3% to the 500 nm and 800 nm-thick samples featured in this study.
Thin Solid Films, 2020
In this work, Cu 2 ZnSnS 4 (CZTS) absorber films were prepared by sulfurization of co-sputtered precursor films at different time periods. The influence of sulfurization time on physical characteristics of the grown films was investigated in detail. The sulfurized CZTS films exhibited the characteristic diffraction peak of the kesterite phase corresponding to the (112) crystal plane, the main Raman mode of kesterite phase at around 337 cm −1 and Cu-deficient and Zn-rich composition. From the atomic force microscopy surface and cross-sectional scanning electron microscopy images, it was revealed out that the films were uniform, compact without any cracks and consisted of micron-sized and closely packed grains. In addition, the films showed tail-to-tail, band-to-tail and band-to-band transitions at around 1.41 eV (E 1), 1.45 eV (E 2) and 1.51 eV (E 3), respectively. Secondary ion mass spectroscopy analysis showed that the sodium ions deeply diffused through the molybdenum layer into the CZTS film from the soda lime glass substrate for all samples. All of the films exhibited an optical band gap of around 1.4 eV, an absorption coefficient over 10 4 cm −1 , p-type conductivity with a high concentration of free holes in the order of 10 17-10 18 cm −3 and low mobility in the range from 0.63 cm²/V.s to 8.11 cm²/V.s.
A promising sputtering route for dense Cu2ZnSnS4 absorber films and their photovoltaic performance
Solar Energy Materials and Solar Cells, 2014
Copper zinc tin sulfide (Cu 2 ZnSnS 4 , CZTS) is highly abundant in nature. It is an important absorber material for the development of low-cost and sustainable next-generation I 2-II-IV-VI 4 thin-film solar cells because it has a the tunable direct band gap energy, inexpensive constituent elements, and a large absorption coefficient in the visible wavelength region. This work develops an efficient one-step vacuum-based approach to depositing CZTS films without the need to supply excess sulfur during/after deposition or to perform any post-sulfurization treatment. This one-step RF sputtering process produces CZTS films that are crystalline, phase-pure, dense, smooth, and continuous. Air Mass 1.5 G power conversion efficiencies of as high as 6% have been achieved with an antireflection coating, demonstrating that this new approach has great potential as a low-cost alternative for high-efficiency CZTS solar cell production.
Optics and Photonics Society of Iran, 2020
Cu2ZnSnS4 is an intriguing absorber layer in thin-film photovoltaics. Solar cells based on kesterite have made considerable progress over the past few decades. In this work, we present the fabrication of bare Cu2ZnSnS4 absorber layer through DC sputtering of Cu, Zn and Sn metallic targets with a post-sulfurization step which reached atomic ratios of 17.13%, 14.21%, 12.25% and 56.41% for Cu, Zn, Sn, and S, respectively, leading to compositional ratios of 1.16 and 0.65, respectively for Zn/Sn and Cu/(Zn+Sn). The optical bandgap of the layer was 1.48 eV. This method is a versatile and industrial technique that provides good control over the material stoichiometry and is suitable for large scale production. The CZTS layer prepared in this work demonstrates high purity, good crystallographic and desirable optical features which are confirmed by EDS, XRD, Raman measurements and UVVis analysis.
Journal of Crystal Growth, 2012
Cu 2 ZnSnS 4 (CZTS) thin films were directly grown on the heating Mo-coated glass substrate by Sputtering and Pulsed Laser Deposition (PLD) with a single quaternary sulfide target. XRD and Raman scattering confirm that both CZTS films are of kesterite structure, although the composition of CZTS film deposited by Sputtering deviates from the stoichiometry of CZTS more significantly than that deposited by PLD. However, CZTS deposited by sputtering has poor crystallintiy and small grain-sizes in contrast with the sample deposited by PLD, due to severe compositional deviation. Reflection spectroscopy and spectroscopic ellipsometry demonstrate that these CZTS films have the ideal band gap (E g E1.5 eV) and high absorption coefficient as the absorber layer of thin-film solar cells. This implies that the optical properties of CZTS film are tolerant to its compositional deviation.
AIP Advances
A potential solar absorber material, sputtered kesterite Cu 2 ZnSnS 4 (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.
MRS Proceedings, 2007
Chalcopyrite CuInS2 and the structurally related kesterite Cu2ZnSnS4 are known as photovoltaic absorber materials. In this study different precursor thin films of the quaternary Cu-Zn-Sn-S system (stacking: Mo/CuS/ZnS-SnS) and of the pentenary Cu-In-Zn-Sn-S system (stacking: Mo/CuIn/ZnS-SnS) were annealed in sulfur atmosphere. The predominant crystalline phases were detected by in-situ energy dispersive X-ray diffraction (EDXRD). Additionally the X-ray fluorescence signals of the film components were recorded to detect diffusion effects. For the quaternary system we found ZnS, CuS, Cu2-xS, Sn2S3 and SnS as main binary phases during annealing. The Sn2S3-SnS phase transition had a significant impact on the later formation of ternary/quaternary phases. A high diffusivity of copper can explain the little influence of the precursor stacking on the reaction path and may also be responsible for the poor adhesion of the films. For annealing temperatures above 450°C Cu2ZnSnS4 can be identifi...
Physical and optical properties of sprayed Cu2ZnSnS4 (CZTS) thin film: effect of Cu concentration
Journal of Materials Science: Materials in Electronics, 2019
The crystallographic microstructural and optical properties of CZTS thin film have been investigated with influence of copper concentration in spray solution. The X-ray and Raman study carried out to the prepared CZTS thin films and attained pure kesterite phase. The results of microstructural properties such as crystallite size, d-spacing, microstrain, texture coefficient and standard deviation investigated. The prepared CZTS thin film shows very high optical absorption of the order of 10 5 cm −1 in the visible region and the optical band gap energy varied between 1.45 and 1.47 eV. This optical band gap tuning is most applicable for solar cells. By using the Wemple-DiDomenico (WDD) single oscillator model, the optical parameters were calculated such as single oscillator energy (E 0), dispersion energy (E d), static refractive index (n 0), etc. Large values of optical conductivity (σ) give the promise to the solar cell application.
Study of optical and structural properties of Cu< sub> 2 ZnSnS< sub> 4 thin films
Thin Solid Films, 2011
Cu2ZnSnS4 is a promising semiconductor to be used as absorber in thin film solar cells. In this work, we investigated optical and structural properties of Cu2ZnSnS4 thin films grown by sulphurization of metallic precursors deposited on soda lime glass substrates. The crystalline phases were studied by X-ray diffraction measurements showing the presence of only the Cu2ZnSnS4 phase. The studied films were copper poor and zinc rich as shown by inductively coupled plasma mass spectroscopy. Scanning electron microscopy revealed a ...
Electrochemical and Solid-State Letters
Polycrystalline Cu 2 ZnSnS 4 (CZTS) thin film has been grown on glass substrate by RF-magnetron sputtering at substrate temperature 573 K using a commercial target of same composition. Structural and optical properties of the grown thin film have been investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy and UV-vis spectroscopy. Detailed analysis of XRD data has showed that the as-grown CZTS thin film has keserite structure (4 I , a = 5.4290 and c = 10.849Å) with preferred orientation along (112) plane. All the peaks observed in the XRD pattern have been accounted for kieserite structure, which shows the absence of additional phases such as elemental or binary or ternary systems in the grown film. SEM images recorded with different magnification have showed that the film has smooth and homogeneous surface with average crystallite size 100 nm. Raman spectrum recorded at room temperature has showed the dominant Raman shift at about 326 cm-1 which can be attributed to A 1 mode and confirms the formation of kieserite CZTS phase. From optical transmittance spectrum, the grown film is found to have direct band gap of ~1.51 eV. The above observations show that the material under investigation is suitable for solar cell application.