Properties Of CZTSSe Thin Films Research Articles

Effect of pre-deposition annealing on physical properties of CZTSSe thin films deposed by RF-sputtering based on nanoparticles synthesized by solvothermal technique

Effect of pre-deposition annealing on physical properties of CZTSSe thin films deposed by RF-sputtering based on nanoparticles synthesized by solvothermal technique

Performance improvement of Cu2ZnSn(S,Se)4 thin-film solar cells by optimizing the selenization temperature

In this work, Cu2ZnSnS4 (CZTS) precursor films were deposited using a water-based solution approach. Subsequently, selenization was performed at different temperatures in the range of 480–610 °C to prepare Cu2ZnSn(S,Se)4 (CZTSSe) absorber-layer films. The effects of the selenization temperature on the crystallinity, structure, morphology, and photoelectric properties of CZTSSe thin films, as well as the performance of solar cells constructed using these films, were systematically studied. The absorber-layer films selenized at different temperatures all formed pure-phase CZTSSe and had basically the same film thickness. It was found that application of an optimal selenization temperature can enhance the crystallinity, crystal grain size, and mobility and reduce the resistivity of CZTSSe films. Selenization at 550 °C resulted in the largest grain size (∼μm), the highest crystallinity, the highest mobility (4.29 cm2 V−1 s−1), the lowest resistivity (3.13 × 102 Ω cm), the thinner fine-grained layer, a bandgap value of 1.21 eV, and a Cu-poor, Zn-rich elemental composition [Cu/(Zn + Sn) = 0.85 and Zn/Sn = 1.16]. The power-conversion efficiency was improved from 3.04% in a CZTSSe cell device with an absorber layer selenized at 480 °C to 4.69% in a film selenized at 550 °C. This was mainly due to the improvement of the crystallinity, crystal grain growth, and reduction of the fine-grained layer of the CZTSSe film. These results show that optimizing the selenization temperature is essential for enhancing the performance and the ultimate device efficiency of CZTSSe absorber layers prepared using a water-based solution approach.

Solution transformation of SnS into Cu2ZnSnS4xSe4(1-x) for solar water splitting

Cu2ZnSnS4xSe4(1-x) (CZTSSe) has recently attracted much attention for solar water splitting due to its high absorption efficient and tunable bandgap. However, high quality CZTSSe thin films with good quality and adherence with the substrate are mainly based on physical deposition method, such as magnetron sputtering, which is expensive and energy consuming processes. Here, we have developed a novel and low-cost solution fabrication method and CZTSSe electrodes were synthesized at low temperature by hydrothermal treatment of chemical bath deposited SnS films. The quality and phase purity of CZTSSe thin films were greatly improved after annealing process and the effect of SnS thickness to the physical and photoelectrochemical (PEC) properties of CZTSSe thin films were detailedly studied. The fabrication of FTO/CZTSSe/CdS/TiO2/Pt photocathode improved the PEC properties of CZTSSe thin films greatly and the highest water splitting photocurrents of 7.2 mA/cm−2 had been achieved under simulated solar illumination. Furthermore, the electrode showed good stability and had a good incident photon-to-current efficiency (IPCE) response in the visible light range.

Efficiency Enhancement by Optimizing Selenization Time for Co-Sputtered Cu<sub>2</sub>ZnSn(S,Se)<sub>4</sub> Thin Film Solar Cells

To reveal the effects of annealing condition on CZTSSe thin film solar cells, co-sputtering and subsequent selenization were used to prepare CZTSSe thin films. Structural, morphological and optical properties of CZTSSe thin films were investigated. CZTSSe thin films with various Se/(S+Se) ratio ranging from 0.69-0.78 were obtained. Representative peaks corresponding to CZTSSe in XRD and Raman results showed a slight shift to lower diffraction angle and wavenumbers. Selenization time significantly influenced the morphologies of CZTSSe films and the gradual grown up grain size was observed. VOC deficit values down to 839 mV was achieved for the best cell. CZTSSe solar cell with the selenization time of 10 min showed a best conversion efficiency of 5.32%, which presented a 50% enhancement comparing to the solar cells with insufficient and over-selenized absorbers.

Tuning the Properties of CZTS Films by Controlling the Process Parameters in Cost-Effective Non-vacuum Technique

Highly dispersive Cu2ZnSnS4 (CZTS) nanoparticles were successfully synthesized by a simple solvothermal route. A low cost, non-vacuum method was used to deposit CZTS nanoparticle ink on glass substrates by a doctor blade process followed by selenization in a tube furnace to form Cu2ZnSn (S,Se)4 (CZTSSe) layers. Different selenization conditions and particle concentrations were considered in order to improve the crystallinity and surface morphology; the annealing temperature was varied between 400°C and 550°C and the annealing time was varied between 5 min and 20 min in a selenium-nitrogen atmosphere. The influence of annealing conditions on structural, compositional, optical and electrical properties of CZTSSe thin films was studied. An improvement in the structural and surface morphology was observed with increasing of annealing temperature (up to 500°C). An enhancement in the crystallinity and surface morphology were observed for thin films annealed for 10–15 min. Absorption study revealed that the band gap energy of as-deposited CZTS thin film was approximately 1.43 eV, while for CZTSSe thin films it ranged from 1.15 eV to 1.34 eV at different annealing temperatures, and from 1.33 eV to 1.38 eV for different annealing times.

Synthesis of Cu2ZnSn(SxSe1−x)4 thin films directly on transparent conductive glass substrates by solvothermal method

In this paper, the single-step solvothermal method was proposed to grow directly Cu2ZnSn (SxSe1−x)4 (CZTSSe) thin films on FTO substrates. The composition ‘x’ was varied by changing the molar ratios of thiourea to selenourea in the precursor solutions. The effects of the molar ratios of thiourea to selenourea on the structure, morphology and optical properties of CZTSSe thin films were investigated by X-ray diffraction, Raman spectroscopy, scanning electronic microscopy, energy dispersive spectrometry and UV–Vis spectrophotometry. The results indicated that CZTSSe thin films are composed of a large number of uniform sphere-like particles, and the diameter of particles varies from 600 to 280 nm when the molar ratios is changed from 1 to 0. The major XRD diffraction peaks shift towards lower diffraction angles, the Raman peak position of A1 mode of CZTSSe thin films moves consecutively towards the lower frequency due to the S replacement by Se. CZTS and CZTSe thin films are single kesterite structure, however, CZTSSe thin films are mixture structure of kesterite and wurtzite. By varying the molar ratios of thiourea to selenourea in the precursor solution, the atom ratios of S/Se in CZTSSe NCs thin films can be well controlled over the whole range, resulting in tunable optical band gap from 1.54 to 1.38 eV.

Influence of laser repetition rate on the Cu2ZnSn(SSe)4 thin films synthesized via pulsed laser deposition technique

Cu2ZnSn(SSe)4 (CZTSSe) thin films are considered as a viable source for the future electricity generation using solar energy. In this report, CZTSSe thin films were synthesized by pulsed laser deposition (PLD) technique as a function of laser pulse repetition rate onto the Mo coated glass substrates. Structural, surface morphological, optical and electrical properties of CZTSSe thin films have been investigated by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and UV–vis spectroscopy. The XRD and Raman analysis confirmed the phase pure polycrystalline structure of thin films of CZTSSe synthesized at high pulse repetition rate. Moreover, the presence of the XRD peak at 27.72° corresponding to (112) plane reveals the tetragonal structure of CZTSSe. The band gap energy of synthesized CZTSSe thin films is found around 1.20eV which is optimum for the solar energy harvesting. To the best of our knowledge, this is the first report on the deposition of CZTSSe via PLD technique by using different pulse repetition rate.

Controlled substitution of S by Se in reactively sputtered CZTSSe thin films for solar cells

CZTSSe thin films are considered to be future of flexible thin film solar cell. Amount of S and Se in the CZTSSe thin films controls the band gap. Therefore, control over the concentration of S/Se is very important for enhancing the efficiency. CZTS thin films were deposited on SLG substrate by sequential reactive sputtering of metal targets. The films were annealed in Se atmosphere at 550 °C for 10–25 min in order to obtain CZTSSe thin films. Elemental, surface morphological, optical and structural properties of CZTSSe thin films have been investigated in detail. Optical band gap energy of CZTSSe thin films were in the range of 1.1–1.35 eV. XRD and Raman analysis were used to analyze the structure and phase purity of CZTSSe thin films. High intense peak at 27.9° in the XRD pattern corresponding to (112) plane was observed. High intensity of XRD peak corresponding to (112) direction revealed that the growth is oriented along (112) direction. Raman analysis also showed the presence of two peaks related to Se and S anions in CZTSSe thin films. In the Raman spectra of CZTSSe thin films; peaks corresponding to Se anions were observed at 190–206 cm−1 and peaks corresponding to S anions were observed at 329–338 cm−1. Elemental analysis results showed that S/Se ratio did not change much with increase in annealing time. To the best of our knowledge, this is the first report on the deposition of CZTSSe by sequential reactive sputtering of metal targets and controlled selenization.

Effects of Se vapor annealing on water-based solution-processed Cu 2 ZnSn ( S , Se ) 4 thin-film solar cells

Among various deposition techniques to deposit Cu2ZnSn(S,Se)4 (CZTSSe) thin films, solution-based processes have attracted considerable attention because of their potentially low cost. Most of the reported solution-based methods are based on nonaqueous solvents, such as hydrazine, and organic solvents. We report the deposition of CZTSSe thin films and fabrication of CZTSSe solar cells by a water-based, solution-processed method followed by Se vapor annealing. The effects of Se vapor feeding time on the properties of CZTSSe thin films and the performance of CZTSSe solar cells are investigated. The ratio of Se/(Se+S) can be tuned by changing the Se vapor feeding time. Our results indicate that extending the Se vapor feeding time increases the band gap, slightly increases the lattice constant, and significantly improves the morphologies of the CZTSSe thin films. A remarkable enhancement in the performance was observed from the CZTSSe solar cells annealed with a longer Se vapor feeding time compared with those without Se feeding.

Improvement in the properties of CZTSSe thin films by selenizing single-step electrodeposited CZTS thin films

Cu2ZnSn(SxSe1−x)4 (CZTSSe) thin films are prepared by selenizing a single-step electrodeposited Cu–Zn–Sn–S precursor. The effect of the selenium (Se) vaporization temperature on the properties of CZTSSe thin films is systematically investigated. The position of the (112) peak is systematically shifted to lower 2θ values when the Se vaporization temperature increases. The Raman spectra of CZTSSe films show bimodal behavior. The microstructure and film thickness significantly improve with increasing Se vaporization temperature. The increased Se incorporation in CZTSSe films with the increase of the Se vaporization temperature is demonstrated using a compositional analysis. The band gap energy of CZTSSe thin films is tuned in the range of 1.40–1.08eV by varying the Se vaporization temperature.

Single-step preparation and characterization of Cu2ZnSn(SxSe1−x)4 thin films deposited by pulsed laser deposition method

Cu2ZnSn(S,Se)4 (CZTSSe) thin films have been firstly deposited on heating quartz substrates by pulsed laser deposition (PLD) method using one-step process. The results of energy dispersive X-ray (EDX) spectroscopy show that there are some discrepancies of the elemental composition between targets and thin films. However, structural and optical properties of CZTSSe thin films show good tolerance to the composition deviation from stoichiometry. Both X-ray diffraction (XRD) and Raman spectra analysis indicate the internal compressive stress exists in CZTSSe thin films. Further transmission spectra demonstrate that the band gaps of CZTSSe thin films are higher than those of CZTSSe bulks. The internal compressive stress and the deficiency of Cu content in the films contribute to the enlargement of the band gaps of CZTSSe thin films.