Papers by Keyword: Selenization

Abstract: 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. V_OC 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.

Abstract: The performance of copper indium gallium disulfoselenide (CIGSSe) solar cells strongly depends on the band bap of absorbing layer of CIGSSe. The device performance can be improved by fabricating multi band gap layer of CIGSSe. However, the fabrication of multi band gap CIGSSe using non-vacuum techniques is challenging. In this study, we fabricated solar cell devices which consisted of multi band gap Cu (In,Ga)(S,Se)₂ thin films. The CIGS thin films were prepared by the spray-pyrolysis of aqueous precursor solutions of gallium (gallium chloride; GaCl₃), copper (indium chloride; CuCl₂), indium (indium chloride; InCl₃), and Sulphur (thiourea; (SC(NH₂)₂) sources on Mo-coated glass substrate. The as-sprayed thin films were then selenized at 500 °C for 10 minutes.After selenization, CIGS films were transformed to Cu (In,Ga)(S,Se)₂ (CIGSSe). The CIGS films with different composition were deposited again on top of selenized CIGSSe films and selenization process was repeated, hence multi band gap CIGSSe films were fabricated. The Chemical bath deposition (CBD) process was used to deposit cadmium sulphide (CdS) buffer layer. The solar cell fabricated with the device configuration of glass/Mo/CIGSSe/CdS/i-ZnO/AZO showed a power conversion efficiency of 6.51%.

Abstract: Cu(In,Ga)Se₂ (CIGSe) thin films were prepared by sputtering with single CIGSe or Cu-Ga-In₂Se₃ target and subsequent selenization at 550-700°C. The one- and two-step selenization procedures and the ceramic and cermet targets were used for process comparisons. Microstructure, film growth and film composition were used to evaluate the growth performance. CIGSe films sputtered from the CIGSe target had a low Cu content. CIGSe films prepared with single Cu-Ga-In₂Se₃ target had shown different performance after the one- and two-step selenization procedures. The two-step process did not grow the dense films due to the vaporization of Se-containing species from the incomplete reaction. The high-temperature requirement is the major disadvantage for the post-selenization approach.

Abstract: In the present report, the synthesis process of CuIn_xGa_1-xSe₂ nanoparticles as an absorption layer in tetraethylene glycol using metallic chloride and Se powder for the purpose of solar cell application. Whole processes were performed under glovebox condition. Nanoparticles sizes were achieved via manipulation of reaction temperature and various precursor concentrations. CuIn_xGa_1-xSe₂ or CIGS nanoparticles with diameters in the range of about 20-50 nm were prepared via polyol route and purified through centrifugation and precipitation processes. Then nanoparticles were dispersed to obtain stable inks that could be directly used for thin-film deposition via spin coating. Then, CIGS nanoparticles were coated on soda lime glass for fabrication of inorganic thin film solar cell via spin coating as a film. In those devices, the prepared films yielded relatively dense CuInGaSe₂ films with some void spaces. For elimination of the void spaces, the nanocrystals were exposed to selenium vapor atmosphere. Filling the voids with selenium can lead to the fabrication of CIGS absorptive layers having good dense structures and high efficiency. CIGS thin films were characterized by various analytical tools, such as XRD, UV-Visible spectroscopy and SEM imaging.

Abstract: Cu (In_1-xGa_x)Se₂ (CIGS) polycrystalline thin films with Ga-gradient structures were prepared by selenization of sputtered Cu-In-Ga precursors. The Ga contents of the as-selenized CIGS thin films were measured by EDS. With greater Ga content, the peaks in the diffraction pattern become broadened. Auger electron spectroscopy was used to measure the composition distribution of the Cu, In, Ga, and Se elements in the CIGS and CuInSe₂ films. At 300°C, the diffusion coefficients D_Se was approximately (6.7±1.0) x 10^-16 m²s^-1, and D_Ga was about (4.5±1.0) x 10^-18 m²s^-1. D_Se are two orders of magnitude greater than D_Ga, which is also the reason why the selected CIGS film was almost completely selenized, but still able to keep certain Ga-grading profile. The temperature used in this work is within the low temperature range of the two-step selenization approach, which is more suitable for low-cost substrates like flexible substrates.

Abstract: Two-step growth method was used for CuInGaSe₂,(CIGS) absorption layer in this study. The layer was first deposited by thermal evaporator to use indium and gallium sauces at a vacuum of 5 × 10^-6 torr and secondly, the deposited thin film was enclosed in a quartz cartridge for the first selenization. The second selenization process was coated by copper and then annealed again in a furnace. Finding best precursor for thin film solar cells was analyzed by scanning electron microscope (SEM), X-ray diffraction analyzer (XRD) and energy dispersive spectrometer (EDS).

Abstract: CuInSe2 thin films were successfully prepared by selenization of precursor films coated on the Mo foils. The precursor films were compacted to improve surface morphology and density of CuInSe2 thin films. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The results indicate that the single-phase CuInSe2 is formed at 210 °C in selenization process and it exhibits preferred orientation along the (112) plane. The selenization temperature is above 210 °C, the selenization temperature rises to promote the crystallinity of selenized films, not to induce the occurrence of a new phase. The compact CuInSe2 film with smooth surface can be obtained by selenization of precursor films pressed with the pressure of 300 MPa.

Abstract: Cu(In_0.8Al_0.2)(SSe)₂ (CIASSe) absorber layers of thin film solar cell were prepared by selenization of Cu(In_0.8Al_0.2)S₂(CIAS) nanocrystals. The CIAS nanocrystals were synthesized by a new solution-based technique and successfully deposited on Mo-coated glass substrates in a one-step process. The phase structure, optical and electrical properties of CIASSe thin films were characterized by power X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectrophotometer and the Hall Effect Measurement system. The results showed that single-phase CIASSe solid solution was successfully obtained for a selenization temperature of above 400oC. And the diffraction peaks shifted to the lower angle with an increase in selenization time and selenization temperature. The films selenized at 500oC were found to be p-type and the resistivity was only 0.9484×10^-4Ω cm. The optical band gap of the films is 1.508eV and the optical absorption coefficient is over 10⁴cm^-1.

Abstract: The Cu2ZnSnSe4 (CZTSe) thin films were prepared by co-electroplating Cu-Zn-Sn precursors followed by selenization at different substrate temperatures. The effect of substrate temperatures on the morphologies and structures of CZTSe films were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Raman scattering spectrum respectively. The results revealed that the impurity phases in CZTSe thin films such as CuSe and SnSe disappeared when the substrate temperatures were increased. The surface morphologies of CZTSe thin films were also strongly dependent on the substrate temperature treatment in the selenization process though the selenium temperature was kept at 340°C.

Abstract: CuInSe₂ thin films were obtained by selenization of the Cu-In precursors in the atmosphere of Se vapour, which were prepared on stainless steel and titanium substrates by electrodeposition. The films were characterized by XRD, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The respective influences of composition, phases and surface morphology of Cu-In precursors on indium loss were investigated. The results indicate that the indium loss occurs in selenization process because of volatile In₂Se arising. The indium loss is less in selenization process of Cu-In precursors contained CuIn, Cu₂In and In phases.