Impurity scavenging by foreign phase in heterogeneous CuInS2

The average impurity concentration of chemical vapor transported (CVT) and vapor liquid solid (VLS) grown CuInS₂ has been determined by spark source mass spectrometry (SSMS). Transition metal impurities range between 10¹⁷ atoms cm⁻³ (Ti, V, Cr, Co, Ni, Zn) and (3–5)×10¹⁸ atoms cm⁻³ (Mn, Fe). On heterogeneous VLS grown samples, the Fe content of the CuInS₂ host material and of foreign incorporated phases has been compared by inductive coupled plasma spectrometry (ICP). The foreign phases, particularly In spheres, show a drastically increased impurity content. The results are discussed assuming impurity scavenging by metallic In.     

Thermal decomposition studies of CuInS2

Single crystals of copper indium disulphide (CuInS₂) have been successfully grown by the chemical vapour transport (CVT) technique using iodine as the transporting agent. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were carried out for the CVT grown CuInS₂ single crystals. It was revealed that the crystals are thermally stable between the ambient temperature (300 K) and 845 K and that the decomposition occurs sequentially in three steps. The kinetic parameters, e.g., activation energy, order of reaction, and frequency factor were evaluated using non-mechanistic equations for thermal decomposition.     

Electron-beam-induced effects on CuInS2 surfaces

A variety of processes occurring on a single-crystal surface of CuInS₂ subjected to electron bombardment were observed and monitored using Auger electron spectroscopy. Quantitative characterization of elemental relative concentrations (copper, indium, sulphur and oxygen) as a function of bombardment time seems to indicate two major beam-induced phenomena. Thus, when we started with a non-stoichiometric copper-rich surface, the final product had the composition Cu₂O·In₂O₃; this was produced in a vacuum of 10^?8 Torr by 70 min of 3.5 μA 3 kV electron bombardment, which gradually induced both S-O interchange and indium diffusion. Scanning Auger studies of the bombarded surface revealed an accumulation of carbon surrounding the oxygen-rich region. This seems to indicate that CO from the residual gas is involved in the processes.     

Solvothermal synthesis of CuInS2 powders and CuInS2 thin films for solar cell application

In this study, a facile solvothermal method was developed to prepare CuInS₂ powders and CuInS₂ thin films. The CuInS₂ powders and CuInS₂ thin films were prepared by solvothermal route using the precursor of Copper (II) chloride, indium (III) nitrate, thiourea, oxalic acid, hexadecyl trimethyl ammonium bromide and ethanol. The morphology, crystallographic structure, chemical composition and optical band gap of CuInS₂ powders and CuInS₂ thin films were investigated using scanning electronic microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and UV–vis spectroscopy. The results reveal that both CuInS₂ powders and CuInS₂ thin films are in chalcopyrite phase. The CuInS₂ powders are mainly composed of flower-like microspheres. Both microstructure of the sphere surface and diameter of sphere are affected by indium nitrate concentration in precursors. The CuInS₂ thin films are composed of a large number of uniform flower-like nanosheets, and the nanosheets become smaller in size and denser in distribution density with increasing concentration of thiourea. The optical band gap is found to be 1.44 and 1.52 eV for CuInS₂ powders and CuInS₂ thin films, respectively. The deposition mechanism of the CuInS₂ is discussed.     

Negative-differential-resistance effects in amorphous CuInS2 thin film

The microstructure and the optical properties of amorphous CuInS₂ thin films deposited on glass substrates by a single source thermal evaporation technique, are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission and reflection measurements. Amorphous CuInS₂ thin films sandwiched between gold and copper electrodes, show current-controlled electronic switching. The switching is believed to be associated rather with electronic processes than the thermal ones.     

纳米CuInS2光伏材料研究进展

三元系铜铟硫CuInS2(CIS)以其良好的光伏性能,成为太阳能电池领域的研究热点。从CIS结构出发,综述了CIS纳米材料合成的物理、化学方法,主要包括高温热解法、热注入法、水热和溶剂热法等化学方法以及微波加热等方法,并讨论了各方法的优缺点,最后展望了CIS纳米材料的发展趋势。     

Spray-deposited CuInS(2) solar cells

Spray deposition of CuInS(2) offers an attractive route towards industrial production of thin-film solar cells. With spray deposition it is possible to make nanocomposites of n-type TiO(2) and p-type CuInS(2). Upon application of an In(2)S(3) buffer layer, solar cells can be made with efficiencies of ～7%, being comparable to that of amorphous silicon. Rapid thermal annealing is not involved in the production of these solar cells. In order to further improve the performance, the concentration of electronic defect states in the bandgap must be reduced. Towards this end a detailed study has been undertaken to elucidate the role of associated point defects in the recombination of electron-hole pairs. Especially with transient absorption spectroscopy it is possible to make an accurate assessment of the fundamental electronic processes that are involved. We find electronic states in the bandgap related to the presence of anti-site defects. In addition, indium vacancies are also involved. State-to-state recombination occurs, indicating that the involved defects are associated. An electronic state located at 1.1?eV above the valence band, which is related to indium on a copper position, has a lifetime of about 20?μs at room temperature. The lower lying states related to copper on indium positions, and indium vacancies, are populated from this 1.1?eV state.     

Growth and properties of CuInS2 single crystals

CuInS₂ single crystals 14–16 mm in diameter and up to 40 mm in length were grown by the traveling solvent method. The crystals were found to ben-type, with a conductivity of 0.1–10 S/cm, carrier concentration of 10¹⁶–10¹⁷ cm⁻³, and carrier mobility of 150–220 cm²/(V s). The anisotropic thermal expansion of the crystals was measured.     

The optical properties of CuInS2 thin films

The optical absorption in flash-evaporated CuInS₂ thin films was studied in the photon energy range from 0.5 to about 4.2 eV. CuInS₂ was found to be a direct gap semiconductor with a gap energy of 1.524±0.005 eV at room temperature. The ground state energy of the free exciton was found to be about 8 meV. An indirect allowed transition was observed at 1.565±0.005 eV and was ascribed to an optical transition from the valence band maxima at the boundary of the Brillouin zone to the lowest conduction band minimum at the zone centre. Three further optical transitions which were probably due to the copper d states in the valence band were found at energies well above the fundamental edge.     

Growth and properties of CuInS2 thin films

Single phase copper indium disulphide (CuInS₂) thin films of thickness between 60 nm and 650 nm with the chalcopyrite structure are obtained on NaCl and glass substrates by flash evaporation. The films were found to ben-type semiconducting. The influence of the substrate temperature on the crystallinity, conductivity, activation energy and optical band gap was studied. An improvement in the film properties could be achieved up to a substrate temperature of 523 K at a molybdenum source temperature of 1873 K.     

Phase Diagram of the TlInS2–CuInS2 System

The phase diagram of the TlInS₂–CuInS₂ system is studied using differential thermal analysis, x-ray diffraction, and conductivity measurements. The system is shown to contain two restricted solid-solution series. At room temperature, CuInS₂ dissolves 0.5 mol % TlInS₂, and TlInS₂ dissolves 1.5 mol % CuInS₂.     

太阳能电池材料CuInS2的研究现状

综述了CuInS2太阳能电池的研究现状，介绍了CuInS2材料的结构性质，光学性质，电学性质及制备方法，讨论了Na与Ga对其性质的影响，并提出了目前存在的问题及其发展趋势。     

硫化时间对于固态硫化CuInS_2薄膜性能影响

采用中频交流磁控溅射方法,在玻璃基底上沉积Cu-In预制膜,采用固态硫化法制备获得了CuInS2(CIS)吸收层薄膜。考察了硫化时间对于CIS薄膜结构、形貌以及禁带宽度影响。通过XRD分析了薄膜结构,通过SEM以及XRF分析薄膜表面形貌以及薄膜成分,通过近红外透过曲线得出薄膜禁带宽度。结果表明,在400℃硫化10,15,20,25,30 min下均能制得单一黄铜矿相CIS薄膜,并且具有(112)面择优取向。以上各硫化时间下,均能形成均匀且晶粒大小为1μm的CIS薄膜,薄膜禁带宽度约为1.10~1.22 eV之间。     

铜铟硫薄膜的固态硫化法制备及其性能研究

采用中频交流磁控溅射方法沉积Cu-In预制膜,并采用固态源蒸发硫化方法制备CuInS2薄膜。考察了硫源温度对CuInS2薄膜性能的影响。采用扫描电镜(SEM)和X射线能量色散谱仪(EDS)分别观察了薄膜的表面形貌和分析了薄膜的成分,采用X射线衍射(XRD)表征了薄膜的组织结构。结果表明,在硫源温度处于280℃到360℃范围之内时,制备的CuInS2薄膜都具有单一的黄铜矿型结构,颗粒均匀,晶粒大小约为1μm。     

Optical Diagnostics of Laser Evaporation of CuInS2 Polycrystalline Compound

In the radiation spectrum of the erosion laser plasma of CuInS₂ polycrystalline compound, the presence of resonance spectral lines of CuIn and InI is revealed, as well as of spectral lines which correspond to cascade transitions and of lines from the displaced terms of the copper atom. No intense radiation of positive ions is observed in the spectral range from 200 to 600 nm. The binding energies of Cu–S, In–S, Cu–Cu, In–In, and Cu–In atoms, as well as atomic and orbital bond orders of the CuInS₂ cluster, are calculated by the Hueckel pseudoempirical method within the valent approximation. It is found that In(1, 3) atoms inversely centering the lower faces of cations Cu(6, 6 ^I), as well as cations Cu(4, 4 ^I) and In(5, 5 ^I) centering the lateral faces of the crystal, do not form strong bonds in the structure. Therefore, in the evaporation processes they must easily evolve from the structure of the CuInS₂ chalcopyrite crystal and make a predominant contribution to the radiation spectrum of laser plasma. From the standpoint of energy, the atoms of sulfur and nodal atoms of copper evaporate mainly in the form of combined complexes of CuS molecules. One can assume that the initial growth layers will be obtained with a deficiency in sulfur and with substantial violation of their stoichiometry and the structure of the initial compound.     

a-Si:H/CuInS2 heterojunctions for photovoltaic conversion

Heterojunctions of hydrogenated a-Si films prepared by r.f. sputtering with spraypyrolyzed CuInS₂ films have been studied. Capacitance-voltage measurements establish the formation of abrupt heterojunction. The barrier height varies from 0·26 to 0·55 V as the resistivity of CuInS₂ film decrease from 1·5 × 10³ to 65 Θm. These junctions exhibit photovoltaic behaviour withV _oc = 220 mV andI _sc = 0·20 mA/cm².     

Effects of Preparation and Heat-Treatment Conditions on the Optical Properties of Glasses Activated with CuInS2 and CuInS1.2Se0.8

CuInS₂- and CuInS_1.2Se_0.8-activated silicate glasses were prepared from starting charges containing various combinations of carbon (reductant), sulfur, and selenium, and their absorption spectra were measured before and after additional heat treatment. The introduction of carbon was shown to improve the optical properties of the glasses (optimal content, 2.0 wt %). Heat treatment has an insignificant effect on the absorption spectra of the glasses, because color centers are formed only during melt cooling.     

Structural and optical properties of Zn doped CuInS2 thin films

Copper indium sulphide (CIS) films were deposited by spray pyrolysis onto glass substrates from aqueous solutions of copper (II) sulphate, indium chloride and thiourea using compressed air as the carrier gas. The copper/indium molar ratio (Cu/In) in the solution 1(1:1) and the sulphur/copper ratio (S/Cu) was fixed at 4. Structural properties of these films were characterized. The effects of Zn (0–5%) molecular weight compared with CuInS₂ Source and different substrate temperatures on films properties were investigated using X-ray diffraction (XRD) and optical transmission spectra. Optical characteristics of the CuInS₂ films have been analysed using spectrophotometer in the wavelength range 300–1100 nm. The absorption spectra of the films showed that this compound is a direct bandgap material and gap values varied between 1·55 and 1·57 eV, depending on the substrate temperatures. Zn-doped samples have a bandgap energy of 1·55–1·95 eV. It was observed that there is an increase in optical bandgap with increasing Zn % molecular weight. The optical constants of the deposited films were obtained from the analysis of the experimentally recorded transmission and absorption spectral data. The refractive index, n and dielectric constants, ε ₁ and ε ₂, were also discussed and calculated as a function of investigated wavelength range and found it dependent on Zn incorporation. We found that the Zn-doped CuInS₂ thin films exhibit P-type conductivity and we predict that Zn species can be considered as suitable candidates for use as doped acceptors to fabricate CuInS₂-based solar cells. The paper presents a study concerning the influence of deposition parameters (temperature of the substrate and concentration of Zn (1–5)% from 0·16 M ZnCl₂) on the quality of CuInS₂ thin films achieved by spray pyrolysis on glass substrate from solutions containing 0·02 M CuCl₂·2H₂O, 0·16 M thiourea and 0·08 M In₂Cl₃·5H₂O.