Properties of CuIn(SxSe1−x)2 polycrystalline thin films prepared by chemical spray pyrolysis

CuIn(S_xSe_1−x)₂ thin polycrystalline films were grown by the chemical spray pyrolysis method on the glass substrate at 280-400°C. The alloy composition in the film was studied with relation to that in the splay solution. Films were characterized by X-ray diffraction, optical absorption, Raman spectroscopy, resistivity and surface morphology. The CuInSe₂-rich alloy films grown at high substrate temperature had chalcopyrite structure, while, the CuInS₂-rich films grown at low substrate temperature exhibited sphalerite structure. Optical-gap energies were smaller than that of the bulk crystal by 0.1-0.2 eV for CuInS₂-rich films. Raman spectra exhibited both CuInSe₂-like and CuInS₂-like A₁ modes, and their relative changed systematically with alloy composition.     

Characterization of interface between CuInSe2 and In2O3

CuInSe₂/In₂O₃ structures were formed by depositing CuInSe₂ films by stepwise flash evaporation onto In₂O₃ films, which were grown by DC reactive sputtering of In target in presence of (Ar+O₂) gas mixture. Phase purity of the CuInSe₂ and In₂O₃ films was confirmed by Transmission Electron Microscopy (TEM) studies. X-ray diffraction (XRD) results on CuInSe₂/In₂O₃/glass structures showed sharp peaks corresponding to (112) plane of CuInSe₂ and (222) plane of In₂O_3. Rutherford Backscattering Spectrometry (RBS) investigations were carried out on CuInSe₂/In₂O₃/Si structures in order to characterize the interface between In₂O₃ and CuInSe₂. The results show that the CuInSe₂ films were near stoichoimetric and In₂O₃ films had oxygen deficient composition. CuInSe₂/In₂O₃ interface was found to include a ∼20 nm thick region consisting of copper, indium and oxygen. Also, the In₂O₃/Si interface showed the formation of ∼20 nm thick region consisting of silicon, indium and oxygen. The results are explained on the basis of diffusion/reaction taking place at the respective interfaces.     

Structural analysis of Cu(In,Ga)Se2 films fabricated by using sputtering and post-selenization

We made Cu(In,Ga)Se₂ (CIGS) films by using sputtering and post-selenization. First, we deposited stacked metallic films by using the sputtering method and then carried out post-selenization for the precursor stacked metals with different amounts of Se powder, 0.160 g, 0.321 g, 0.642 g, and 0.964 g. We found that with a small amount of Se, separated CuInSe₂ and CuGaSe₂ layers were formed, which was confirmed by X-ray diffraction (XRD), Raman spectroscopy, and energy-dispersive X-ray analysis. For larger Se amounts, the CIGS phase was observed in the results of XRD and Raman spectroscopy. These results indicate that the amount or the partial pressure of Se plays an important role in the reaction kinetics for stacked precursor metals to form the CIGS phase.     

Hydrothermal synthesis of chalcopyrite CuInS2, CuInSe2 and CuInTe2 nanocubes and their characterization

CuInS₂, CuInSe₂ and CuInTe₂ nanocubes of chalcopyrite structure have been successfully synthesized by hydrothermal process using deionized water as solvent at 180 °C for 20 h. The crystallinity, compositional, morphological and optical properties of the synthesized samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), Raman and photoluminescence (PL) spectra analyses. The Raman spectra of the synthesized CuInS₂, CuInSe₂ and CuInTe₂ samples show the dominant A₁ modes at 293, 172 and 121 cm⁻¹ respectively. The possible chemical reaction and mechanism of nanocubes formation were discussed. The emission wavelength of as synthesized CuInS₂, CuInSe₂ and CuInTe₂ samples were blue shifted at 746 nm (1.66 eV), 863 nm (1.43 eV) and 859 nm (1.44 eV) respectively.     

Annealing study of electrodeposited CuInSe<Subscript>2</Subscript> and CuInS<Subscript>2</Subscript> thin films

In this study CuInSe₂ and CuInS₂ thin films were prepared onto ITO glass substrate using the electrodeposition technique in aqueous solution. The electrodeposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis. The annealing effects on electrodeposited precursors were investigated. The chalcopyrite structure of CuInSe₂/CuInS₂ showed an enhancement of crystallinity after subsequent selenization/sulfurization treatment in Se/S atmosphere, respectively. XRD and SEM studies revealed a dramatic improvement of the crystalline quality of CIS films after annealing treatments. Mott–Schottky measurements were used to assess the conductivity type of the films and their carrier concentration. The prepared samples underwent an etching process to remove the binary accumulated Cu_2?x(Se,S) phases shown in FESEM pictures. This etching process has shown a noticeable decrease in both, the flat band potential, V_fb (V), and the number of acceptors, N_A (cm^?3) in selenized CuInSe₂ and sulfurized CuInS₂ samples.     

Preparation of CuInS2 thin films by metal-organic decomposition

Metal-organic decomposition (MOD) technique has been developed as a low cost thin film CuInS₂ preparation method for solar cell application. XRD and Raman spectra measurement revealed that deposited films contain CuInS₂. Stoichiometric films with a bandgap of 1.53 eV and an FWHM of 0.45° were obtained from a solution with Cu/In=1.5.     

Zn incorporation and (CuIn)1−xZn2xSe2 thin film formation during the selenization of evaporated Cu and In precursors on Al:ZnO coated glass substrates

CuInSe₂ thin films with typical 1.0 eV gap energy and tetragonal chalcopyrite structure have been obtained on soda–lime glass substrates by the reaction of sequentially evaporated Cu and In layers with elemental selenium vapor, at 500 °C in flowing Ar. When analogous deposition and reaction processes were performed on Al:ZnO coated glasses, some increment in the band gap energy and diminution in the crystalline interplanar spacings have been detected for the resulting films with an extent that depends on the Cu/In atomic ratio of the evaporated precursor layers. This fact has been related to Zn incorporation into the selenized film, with quaternary (CuIn)_1−xZn_2xSe₂ compound formation that is influenced by the presence of copper selenide phases during the reaction process. Such deductions are supported by the optical, structural and compositional characterizations that have been performed comparatively on samples prepared by selenization of evaporated metallic precursors with two different Cu/In ratios (0.9 and 1.1) on bare and Al:ZnO coated glass substrates.     

Composition and morphology of partially selenized CuIn1−XGaXSe2 thin films prepared using diethylselenide (DESe) as selenium source

CuIn_1−xGa_xSe₂ (CIGS) thin films are being prepared by selenization of Cu-In-Ga precursors using diethylselenide, (C₂H₅)₂Se, (DESe) as selenium source in place of H₂Se gas because of lower toxicity and ease of handling. Rough estimates indicate that selenization process using DESe would cost approximately same or slightly less compared to that using H₂Se. Price of DESe per mole is approximately five times that of H₂Se. However, partial pressure of DESe, which reflects source material consumption, is approximately three to four times less than that of H₂Se, due to higher decomposition rate of DESe compared to that of H₂Se. The actual DESe consumption would be four to ten times less compared to that of H₂Se. A selenization set-up using DESe as selenium source has been designed, fabricated and installed at FSEC Photovoltaic Materials Lab. Initial characterization of CIGS thin films have been carried out using electron probe microanalysis (EPMA), X-ray diffraction (XRD), scanning electron microscopy, secondary ion mass spectroscopy and Auger electron spectroscopy. EPMA showed elemental ratios of film to be near stoichiometric composition CuInSe₂ with very low gallium content mainly because of tendency of gallium to diffuse towards back contact. XRD data shows formation of high crystalline CuInSe₂ phase consistent with the EPMA data.     

Fabrication of nanostructured CuInS2 thin films by ion layer gas reaction method

CuInS₂ thin films were prepared by a two-stage ion layer gas reaction (ILGAR) process in which the Cu and In precursors were deposited on glass substrate by using a simple and low-cost dip coating technique and annealed in H₂S atmosphere at different temperatures. The influence of the annealing temperature (250-450 °C) on the particle size, crystal structure and optical properties of the CuInS₂ thin films was studied. Transmission electron microscopy revealed that the particle radii varied in the range 6-21 nm with annealing. XRD and SAED patterns indicated polycrystalline nature of the nanoparticles. The optical band gap (E_g) varied from 1.48 to 1.56 eV with variation of particle size. The variation of Urbach tail with temperature indicated higher density of the defects for the films annealed at lower temperature. From the Raman study, it was observed that the FWHM of the A₁ mode at ∼292 cm⁻¹ corresponding to the chalcopyrite phase of CuInS₂ decreased with increasing annealing temperature.     

In situ investigation of the formation of Cu(In,Ga)Se2 from selenised metallic precursors by X-ray diffraction—The impact of Gallium, Sodium and Selenium excess

The chemical reactions during rapid thermal processing of stacked elemental layers were investigated by angle-dispersive in situ X-ray diffraction. With a time resolution of 5 diffractograms per minute four different solid state reactions resulting in ternary chalcopyrites were identified: (A) CuSe+InSe→CuInSe₂, (B) Cu₂Se+2InSe+Se→2CuInSe₂, (C) Cu₂Se+In2Se₃→2CuInSe₂, (D) Cu₂Se+Ga2Se₃→2CuGaSe₂. All these reactions form pure tenary chalcopyrites. The reaction resulting in the mixed crystal Cu(In,Ga)Se₂ starts not before (B) has begun. The reaction speed of (A) and the fraction of CuInSe₂ formed by (B) depend on Na-doping and Se-pressure, (C) takes place only, if the reaction paths (A) and (B) are suppressed. Reaction (D) is observed only, if 25% In is replaced by Ga in the precursor. The diffractograms were evaluated by Rietveld refinement to give the phase contents of the samples as a function of reaction time.     

Structural properties of CuInSe2 films prepared by selenization of metallic precursors on MoNx film substrates

The aim of this work was to study the effect of MoN_x film substrates on the structural properties of CuInSe₂ films prepared by selenization of metallic Cu-In alloy precursors. MoN_x films were prepared by reactive dc-magnetron sputtering. All the CuInSe₂ films exhibit single phase chalcopyrite structure with (1 1 2) preferred orientation, which can be explained by the reduction of lattice mismatch between CuInSe₂ and MoN_x. The bulk composition of selenized CuInSe₂ films are near stoichiometric, but the surface composition analysis suggests Cu deficiency on surface area. Furthermore, ordered defect compound, CuIn₂Se_3.5 is found on the surface of CuInSe₂ films. The results will be helpful for fabricating Cd-free ZnO buffer layer CuInSe₂ and Cu(In_1−xGa_x)Se₂ based thin film solar cells.     

Preparation of Cu（In,Ga）Se2 Thin Film Solar Cells by Selenization of Metallic Precursors in an Ar Atmosphere

Cu（In, Ga）Se2 thin films are deposited on Mo-coated glass substrates by Se vapour selenization of sputtered metallic precursors in the atmosphere of Ar gas flow under a pressure of about 10 Pa. The in situ heat treatment of as-grown precursor leads to the formation of a better alloy. During selenization, the growth of CuInSe2 phase preferably proceeds through Se-poor phases as CuSe and InSe at relatively low substrate temperature of 250℃, due to the absence of In2Se3 at intermediate stage at low reactor pressure. Subsequently, the Cu（In,Ga）Se2 phase is produced by the reactive diffusion of CuInSe2 with a Se-poor GaSe phase at high temperature of up to 560℃. The final film exhibits smooth surface and large grain size. The absorber is used to fabricate a glass/Mo/Cu（In, Ga）Se2/CdS/ZnO cell with the total-area efficiency of about 7%. The low open-circuit voltage value of the cell fabricated should result from the nonuniform distribution of In and Ga in the absorber, due to the diffusion-controlled reaction during the phase formation. The films, as well as devices, are characterized.     

使用硫化物纳米前驱物墨水法制备铜铟硫薄膜

提出了一种通过反应烧结来制备CuInS₂多晶薄膜的低成本旋涂工艺路线．通过将前驱物粉末在氢气中预还原的方法来优化旋涂时使用的墨水成分,氢气还原会使前驱物纳米粉末从硫化物混合粉末转变成CuInS₂和Cu-In合金的混合物．扫描电子显微镜、电子能谱、X射线衍射以及拉曼图谱的结果表明,这种优化能极大的提高CuInS₂多晶薄膜的性能,其中包括薄膜的排列密度更高,杂质相减少,薄膜质量变得更好等．吸收光谱测得优化后的铜铟硫薄膜的带隙约为1.45 eV．     

Effect of [Cu]/[In] ratio on properties of CuInS2 thin films prepared by successive ionic layer absorption and reaction method

CuInS₂ ternary films were prepared by a soft solution processing, i.e. successive ionic layer absorption and reaction (SILAR) method. The films were deposited on glass substrates at room temperature and heat-treated under Ar atmosphere at 500 °C for 1 h. CuCl₂ and InCl₃ mixed solutions with different ionic ratios ([Cu]/[In]) were used as cation precursor and Na₂S as the anion precursor. The effect of the [Cu]/[In] ratio in precursor solution on the structural, chemical stoichiometry, topographical, optical and electrical properties of CuInS₂ thin films was investigated. XPS results demonstrated that stoichiometric CuInS₂ film can be obtained by adjusting [Cu]/[In] ratios in solution. Chalcopyrite structure of the film was confirmed by XRD analysis. The near stoichiometric CuInS₂ film has the optical band gap E_g of 1.45 and resistivity decreased with increase of [Cu]/[In] ratios.     

Characterization of Cu(In,Ga)Se2 thin films prepared by evaporationfrom ternary compounds

Thin films of Cu(In,Ga)Se₂ were fabricated by evaporation from ternary CuGaSe₂ and CuInSe₂ compounds for photovoltaic device applications and their properties were investigated. From XRF analysis, the Cu:(In+Ga):Se atomic ratio in all thin films was approximately 1:1:2. The Ga/(In+Ga) atomic ratio in the thin films changed linearly from 0 to 1.0 with increasing the [CGS]/([CGS]+[CIS]) mole ratio in the evaporating materials. However, for thin films prepared at the [CGS]/([CGS]+[CIS]) mole ratio above 0.4, the composition by EPMA analysis was not consistent with that by XRF analysis. The result of EPMA analysis showed that the surface of a thin film was Cu-rich. XRD studies demonstrated that the thin films prepared at the [CGS]/([CGS]+[CIS]) mole ratio under 0.2 had a chalcopyrite Cu(In,Ga)Se₂ structure and the preferred orientation to the 112 plane. On the other hand, XRD patterns of the thin films produced at the [CGS]/([CGS]+[CIS]) mole ratio above 0.6 showed the diffraction lines from a chalcopyrite Cu(In,Ga)Se₂ and a foreign phase. The separation of a peak was observed near 2θ=27°, indicative the graded Ga concentration in Cu(In,Ga)Se₂ thin film.     

直流三极溅射法制备CuInS2 薄膜

采用直流三极溅射装置制备获得了CuInS₂薄膜, 其中溅射靶采用一定面积比的[Cu]/[In]混合靶,反应气体采用CS₂气体. 本文中主要研究了0.02 Pa分压反应气体条件下不同面积比的[Cu]/[In]混合靶和沉积基板温度对CuInS₂薄膜结构和成分的影响, 其中CuInS₂薄膜制备所用时间为2 h生长的厚度为1—2 μm. 通过对CuInS₂薄膜的EPMA, X射线衍射测试分析表明, 最佳的CuInS₂薄膜可在面积比[Cu]/[In]混合靶为1.4:1和可控温度(150, 250和350 ℃)的条件下制备获得, 并且其结构被确认为黄铜矿结构. 通过实验结果计算出CuInS₂薄膜层有约为8.9%的C杂质含量.     

Effects of Cu/In ratio of electrodeposited precursor on post-sulfurization process in fabricating quaternary CuIn(S,Se)2 thin films

This paper reports the analysis of S diffusion into electrodeposited CuInSe₂ (CISe) precursors during post-sulfurization treatment at 500 °C in an Ar/H₂S ambient. The characterizations of the sulfurized films by X-ray diffraction, grazing-incidence X-ray diffraction, Auger electron spectroscopy and micro-Raman spectroscopy allow the observation of the strong dependence of S incorporation into these films on the Cu/In ratio of the precursor. AES profiles reveal higher S content along the depth of Cu-rich film than Cu-poor film after sulfurization. Raman Scattering shows that copper sulfoselenides Cu-(Se,S) are only detected in Cu-rich samples. The re-crystallization of films during sulfurization was analyzed and it is presumed that quasi-liquid Cu-Se phases, which are related to Cu/In ratio of precursor, promote continuous incorporation of S into these films.     

Investigation of the solid solution series 2(MnX)-CuInX2 (X=S, Se)

(2MnX)_x(CuInX₂)_1−x with X=S and Se were prepared by solid state reaction from the end members α-MnS, β-MnS and CuInS₂ in the range 0<x≤0.2 (≤0.6 for β-MnS) as well as MnSe and CuInSe₂ in the range 0<x≤0.1. Mixed crystals with 0≤x≤0.1 crystallize in the tetragonal chalcopyrite type structure, (2α-MnS)_x(CuInS₂)_1−x samples with 0.1<x≤0.2 and (2β-MnS)_x(CuInS₂)_1−x samples up to x=0.6 consist of two phases, occuring as tetragonal domains (x∼0.1 for X=S) within a cubic matrix with zinc-blende type structure (x∼0.4 for X=S), indicating a miscibility gap. For tetragonal single phase samples the band gap energy, the lattice constants and the anion parameter have been determined. The first and the latter ones show a different composition dependent behaviour caused by the modification of the MnS (α-MnS with NaCl type structure, β-MnS with zinc-blende type structure) used during the synthesis. Additionally a CuMn_xIn_1−xS₂ powder sample, in which Mn substitutes the M^III site, was investigated. The SQUID measurements revealed a well-distinct magnetic transition between 15 and 16 K as well as ferromagnetic-like hysteresis loops pronounced for temperatures below the transition temperature. Below this temperature a clear splitting between the zero field cooling (ZFC) and the field cooling (FC) curves indicate to the existence of a long-range magnetic ordering phenomenon. This behaviour was not found in the other samples were Mn substitutes both sites M^I as well as M^III.     

Properties of In2S3 thin films deposited onto ITO/glass substrates by chemical bath deposition

In₂S₃ films have been chemically deposited on ITO coated glass substrates by chemical bath deposition, using different deposition times and precursor concentrations. The bilayers are intended for photovoltaic applications. Different characterization methods have been employed: optical properties of the films were investigated from transmittance measurements, structural properties by XRD and micro-Raman, and surface morphology by SEM microscopy analysis. Also, the direct and indirect band-gaps and the surface gap states were studied with surface photovoltage spectroscopy (SPS). We proposed that electronic properties of the In₂S₃ samples are controlled by two features: shallow tail states and a broad band centred at 1.5 eV approximately. Their relation with the structure is discussed, suggesting that their origin is related to defects created on the S sub-lattice, and then both defects are intrinsic to the material.     

Preparation and characterization of electrodeposited Sb2Se3 thin films from non-aqueous media

Semiconducting Sb₂Se₃ thin films have been prepared onto the stainless steel and fluorine doped tin oxide coated glass substrates from non-aqueous media using an electrodeposition technique. The electrodeposition potentials for different bath compositions and concentrations of solution have been estimated from the polarization curves. SbCl₃ and SeO₂ in the volumetric proportion as 1:1 with their equimolar solution concentration of 0.05 M form good quality films. The films are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and optical absorption techniques. The SEM studies show that the film covers the total substrate surface with uneven surface morphology. The XRD patterns of the films obtained by varying compositions and concentrations show that the as-deposited films are polycrystalline with relatively higher grain size for 1:1 composition and 0.05 M concentration. The optical band gap energy for indirect transition in Sb₂Se₃ thin films is found to be 1.195 eV.