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CuIn 1− x Ga x S 2 wide gap absorber thin films were grown by means of a low cost method using the close-spaced vapor transport principle. No high-cost vacuum apparatus is needed. From X-ray analyses, the chalcopyrite superstructure was found to be present on all the samples, except when the substrate temperatures were below 300 °C. Energy dispersive spectroscopy studies showed a large quasi-stoichiometry range, corresponding to substrate temperatures between 300 and 600 °C (glass substrate use limit). For initial pressures in the reactor close or equal to the atmospheric value, quasi-columnar structures were grown, with crystallite sizes of about 1 μm and thicknesses of the order of 2 μm. The deposition rates were about 0.05 μm/min. For low pressures (

This article is a study of copper, indium, and gallium interdiffusions in In2Se3/CuGaSe2/SnO2/glass thin film heterostructures annealed at different temperatures. The use of CuGaSe2 material in place of Cu(In,Ga)Se2 is only required by the indium diffusion studies. The CuGaSe2 layers were grown by close-spaced vapor transport for two types of sources having different grain sizes. The In2Se3 films were deposited by thermal evaporation. The heterostructures were annealed in vacuum at different temperatures and analyzed by secondary ion mass spectroscopy (SIMS). The copper, indium, and gallium SIMS concentration profiles show that the copper diffuses up to the In2Se3 film surface and that the indium can diffuse far away from the In2Se3/CuGaSe2 interface towards SnO2. The copper, indium, and gallium diffusions were studied and the interdiffusion parameters were computed. The simultaneous interdiffusions of copper and indium induces the formation of a p–n junction responsible for the photovoltaic effect of the...

The effects of source material grain size distribution on film structure and morphology were investigated in the growth of Cu(In,Ga)Se 2 thin films by close-spaced vapor transport. These films are designed to be used as absorbers in solar cells. The deposit morphology was simply changed by varying the grain mean size of the powder constituting the source. Film thicknesses on the order of 2 μm and 1–2 μm sized crystallites arranged in a quasi-columnar structure could be obtained. The results are explained in terms of vapor supersaturation and interaction between the gaseous phase and the source, considered as a porous object.

In this article we study (In,Se)–Cu(In,Ga)Se2/SnO2 thin film heterostructures for solar cells, the light coming through SnO2. The Cu(In,Ga)Se2 layers were grown by close-spaced vapor transport and the (In,Se) layers by close-spaced sublimation. We first clear up the main results obtained in the fabrication and characterization of the samples. Then, the diffusion mechanisms appearing in these structures are studied, from secondary ion mass spectroscopy studies. Copper diffusion is probably the key of the creation of a p–n junction lying near SnO2 and responsible for the photovoltaic effect that is observed.

The present work is an improvement of a close-spaced vapor transport method to deposit CuInSe2 thin films in a closed vertical reactor. The study concerns two points: (i) the determination of the actual source (Ts) and substrate (Td) temperatures from experimental values measured in accessible points. For that, the equivalent thermal circuit of the reactor was established, and the equations were written to deduce Ts and Td. (ii) The determination of the process governing the mass transfer, from experimental values of the deposition rate measured as a function of Ts and Td. In our experimental conditions, the transport is limited by the reaction kinetics, not by the diffusion.

Possible photovoltaic effects in CuInSe2(and related materials)/SnO2 thin film structures are discussed with the CuInSe2 layer grown by close-spaced vapor transport while the growth temperature increases. This procedure can particularly induce a photovoltaic effect having the positive polarity on SnO2, making this type of structure interesting in CuInSe2-type solar cells. The discussion is supported by electron-beam induced current studies and x-ray photoelectron spectroscopy. The band offsets of SnO2–CuInSe2 and CuInSe2–(In,Se) heterojunctions were determined, and energy-band diagrams drawn. (In,Se) involves InSe or In2Se3 phases, and possibly Cu-poor phases, which form in the layer when increasing the growth temperature. Finally, the photovoltaic effect, having the positive polarity on SnO2, is ascribed to either a shallow (from SnO2) p-n CuInSe2 homojunction or a shallow p CuInSe2-n (In,Se) heterojunction. The n-type doping of CuInSe2 could be due either to diffusions during the growth or stoichiometry...

p- and n-type CulnSe2 thin films were grown from close-spaced vapour transport in a vertical closed tube. The electrical conductivity variation of the films from p- to n-type was obtained by a simple adjustment of the source and substrate temperatures during the growth. The depositions were carried out in the temperature range where the filmy arc nearly stoichiometric (= 400 to 580°C). The films were characterized by X-rays, scanning cleclron microscopy, energy dispersive spectroscopy, optical absorption and Hall effect studies.

CuInSe 2 , Cu(In,Ga)Se 2 and CuIn(Se,S) 2 films were grown on glass and on SnO 2 thin films by using a close-spaced vapor transport in closed tube with iodine. The SnO 2 thin films were grown from a pyrosol method. The samples were studied by X-ray and scanning electron microscope analysis. We show that the CuInSe 2 films grown on SnO 2 thin films can have a very strong (100) (or (001)) preferred orientation, probably induced by the substrate, and not by the experimental conditions.

A simple method has been developed for growing low cost and large area CuInSe2 thin films, by close-spaced vapour transport in a vertical closed tube. A thermodynamical study of the system was carried out: the transport rate was measured as a function of the source and substrate temperatures, and compared to a model governed by either the diffusion or the reaction kinetics. With our experimental conditions, the growth rate is limited by the reaction kinetics, not by the diffusion. Nearly stoichiometric films were grown at temperatures as low as 350°C, with deposition rates of 0.5 μm min−1 and grain sizes of the order of 1 μm. Above 600 °C, the films are composed of (In,Se) compounds, mainly In2Se3.

CuGa x In 1 − x Se 2 polycrystalline thin films were grown by a simple technique using close-spaced vapour transport in closed tubes with iodine as a reagent. The depositions were carried out at temperatures below 600°C. Glass or molybdenum substrates could be used. The samples were characterized by X-ray, electron microprobe and scanning electron microscopy measurements. The optimal conditions for depositing good quality thin films were determined. The thin film resistivities, carrier densities and mobilities were deduced from Hall effect measurements. The energy gaps were calculated from optical absorption experiments at 77 and 300 K. The experimental conditions for depositing Cu(Ga, In)Se 2 −(Cd, Zn)S heterojunctions are discussed.

We have grown and studied CuGa(Se,Te)2 photovoltaic bulk materials and thin films. This compound can readily be grown with p‐type conductivity and can have a very good lattice match with CdS for a Se:Te ratio giving an energy gap close to 1.5 eV. The lattice parameters were determined by x‐ray diffraction, and the energy gap calculated for temperatures between 77 and 300 K from luminescence studies. Thin films were grown using a close‐spaced vapor transport technique, with iodine as reagent. The chemical equations governing the transport were determined. Good‐quality CuGaSe2 thin films were easily grown, but we could not get CuGa(SexTe1−x)2 thin films when x

We have grown CuInSe 2 , CuGaSe 2 and Cu(Ga, In)Se 2 thin films by a simple method using the close-spaced vapour transport technique. The deposits were made at temperatures lower than 620 °C, in glass tubes sealed under vacuum after the introduction of solid iodine. Glass or molybdenum substrates may be used. The thin films obtained at temperatures above 550 °C have a composition close to the stoichiometric composition. A thermodynamic study of the transport is carried out, and the chemical reactions are established. We show that the transport is mainly governed by diffusion, except for low iodine concentrations (less than 0.1 mg cm -3 ), for which limitations due to reaction and surface kinetics appear, and high iodine concentrations (above 0.5 mg cm -3 ), for which surface mechanisms at the substrate limit the deposition.

Close-spaced vapor transport in a vertical closed tube has been used and successfully developed for growing large area CuInSe/sub 2/ thin films. This method has been applied also to different Cu(In,Ga)(Se,Te)/sub 2/ ternary compounds. In this paper we present results concerning CuInS/sub x/Se/sub 2-x/ with composition x varying from 0 to 2.00. The parameters of quasi-stoichiometric deposition are determined. We can obtain columnar grains of nearly 10 /spl mu/m diameter, well oriented in the (112) direction. Deviations from these parameters induce the presence of copper iodide in the samples (source temperature below the optimal one) or the formation of (In,Se) compounds (source temperature above the optimal one).

Cet article concerne l'étude de couches minces de matériaux photovoltaïques CuXY2 (X = Ga, In ; Y = Se, Te) obtenues par une méthode de transport chimique à courte distance (CSVT) en tube fermé, en présence d'iode. Après un rappel de la méthode, et une synthèse des résultats déjà publiés sur l'aspect thermodynamique, nous donnons des résultats de caractérisation des couches minces obtenues. Les conditions de dépôt quasi-stœchiométriques ont été déterminées. Des transitions de phase ont été trouvées : par exemple, pour CuInSe2 et pour des températures de source $>580~^\circ$C, les couches sont formées de composés (In, Se), en particulier In2Se3 et InSe. Ces couches sont de type n, alors que les couches de CuInSe2, obtenues pour $T < 580~^\circ$C, sont de type p. On peut donc déposer successivement des couches p et n simplement en variant la température. Ces résultats ont été complétés par une étude des couches obtenues par sublimation à courte distance (CSS) à température modérée, en utilisant le même appareillage. On retrouve des couches formées de composés (In, Se).

A photovoltaic effect whose positive polarity is on SnO2 was found on CuInSe2 (or related materials)/SnO2 thin film structures. The CuInSe2 films were deposited by means of a simple and low cost method using the close-spaced vapour transport by iodine in a closed tube. The source temperature was increased during the depositions from 400–450 °C to 550–650 °C. depending on the material. By lighting through SnO2, open circuit voltages of the order of 350 mV or more and short circuit current densities of the order of 30 mA cm−2 were obtained. The interpretation proposed is the formation of a doping gradient in the CuInSe2 films, due to the deposition conditions. The films are p+ type next to SnO2 and p− or n type at the surface, where an n-type phase appears, formed from III-VI compounds. Moreover, there is probably an interaction between SnO2, iodine and CuInSe2, resulting in an n-doped layer in the film (perhaps due to Sn diffusion), adding to the first doping profile.