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Journal ArticleDOI

Photoconductivity in CuInSe2 films

TL;DR: CulnSe2 films with different Cu/In ratios (0.4-1.2) were deposited on glass substrates by three source evaporation techniques in this paper.
About: This article is published in Solar Energy Materials and Solar Cells.The article was published on 1994-06-01. It has received 34 citations till now. The article focuses on the topics: Photoconductivity & Evaporation (deposition).
Citations
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Journal ArticleDOI
TL;DR: In this article, the copper indium di selenide (CuInSe) compound was prepared by direct reaction of high-purity elemental copper, indium and selenium.
Abstract: The copper indium di selenide $(CuInSe_{2})$ Compound was prepared by direct reaction of high-purity elemental copper, indium and selenium. $CuInSe_{2}$ thin films were prepared on to well-cleaned glass substrates by hot wall deposition technique. The X-ray diffraction studies revealed that all the deposited films are polycrystalline in nature, single phase and exhibiting chalcopyrite structure. The crystallites were found to have a preferred orientation along the (1 12) direction. The SEM analysis indicated that the films are polycrystalline in nature. The composition of the chemical constituents present in the deposited $CuInSe_{2}$, thin films has been determined using energy dispersive X-ray analysis (EDX).Structural parameters of $CuInSe_{2}$, thin films coated with higher substrate temperatures were also studied. As the substrate temperature increases the grain size increases. Simultaneous TG-DTA analysis has been done for $CuInSe_{2}$ bulk and an endothermic, reaction is observed near the melting point of the compound. Optical transmittance spectrum of the hot wall-deposited CuInSe2 thin films of different thicknesses deposited at three different substrate temperatures were obtained. As the thickness of the film and the substrate temperature increases, the optical band gap decreases. The refractive index of the $CuInSe_{2}$ thin films are found decreasing with the incident photon wavelength.

45 citations

Journal ArticleDOI
TL;DR: In this article, the authors used X-Ray diffraction and Raman spectroscopy to find out the dominant conduction mechanisms in pure kesterite CZTS films, temperature variation of dark and photoconductivity has been investigated in the temperature range of 77 to 300 K.

44 citations

Journal ArticleDOI
TL;DR: In this paper, a modified close-spaced vapor transport hot-wall technique was used to study semiconducting films of CdS grown by photoluminescence (PL) in the range of 10-300 K.
Abstract: Semiconducting films of CdS grown by a modified close-spaced vapor transport hot-wall technique were studied by photoluminescence (PL) in the range of 10–300 K. The films were grown with an Ar pressure of 100 mTorr, the substrate temperature (Tsu) varied between 500 and 700 °C, while the source temperature (Tso) was kept at 750 °C. With these parameters it was possible to obtain different mean grain sizes. Several luminescence bands were observed, one located near the band-gap energy around 2.5 eV at 10 K. This band shows a strong temperature dependence and has an excitonic origin. Two other bands were detected around 2.4 and 2.1 eV at 10 K, and are denoted in the literature as green and yellow emission bands, respectively. The lower energy band with a mean width of 150 meV is accompanied by the corresponding optical phonon replica separated by exactly the LO-phonon energy of 38 meV at low temperatures. The nature of these bands and the photoluminescence process as a function of the temperature as well as of the grain size will be analyzed and discussed in this work.

38 citations

Journal ArticleDOI
28 Feb 2007-Vacuum
TL;DR: In this article, a hot wall deposition of copper indium diselenide (CuInSe2) compound was performed on glass substrates using quartz tubes of different lengths.

38 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that the stoichiometric CIS phase (CuInSe2) may be formed by selenization of the precursors at temperatures higher than 500°C.
Abstract: CuInSe2 (CIS) thin films were grown by selenization of electro-deposited or electroless-deposited Cu–In precursors. Cu–In precursors were formed by layer-by-layer electro-deposition of Cu and In as well as by electroless co-deposition of Cu and In. The major phases in the precursors were found to be Cu11In9 and elemental In. It was found that the stoichiometric CIS phase (CuInSe2) may be formed by selenization of the precursors at temperatures higher than 500°C. The Cu–In precursors as well as CIS films were characterized by X-ray diffraction and scanning electron microscopy. The cubic CIS phase was formed when electroless-deposited Cu–In precursor was selenized, whereas the chalcopyrite CIS or the In-rich phase (CuIn2Se3.5) was formed when the layered precursors were selenized at a high temperature.

37 citations

References
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Journal ArticleDOI
TL;DR: In this article, Boron doses of 1×1012-5×1015/cm2 were implanted at 60 keV into 1-μm-thick polysilicon films and Hall and resistivity measurements were made over a temperature range −50-250 °C.
Abstract: Boron doses of 1×1012–5×1015/cm2 were implanted at 60 keV into 1‐μm‐thick polysilicon films. After annealing at 1100 °C for 30 min, Hall and resistivity measurements were made over a temperature range −50–250 °C. It was found that as a function of doping concentration, the Hall mobility showed a minimum at about 2×1018/cm3 doping. The electrical activation energy was found to be about half the energy gap value of single‐crystalline silicon for lightly doped samples and decreased to less than 0.025 eV at a doping of 1×1019/cm3. The carrier concentration was very small at doping levels below 5×1017/cm3 and increased rapidly as the doping concentration was increased. At 1×1019/cm3 doping, the carrier concentration was about 90% of the doping concentration. A grain‐boundary model including the trapping states was proposed. Carrier concentration and mobility as a function of doping concentration and the mobility and resistivity as a function of temperature were calculated from the model. The theoretical and ex...

2,657 citations

Journal ArticleDOI
TL;DR: In this article, the transport properties of polycrystalline silicon films are examined and interpreted in terms of a modified grain-boundary trapping model, based on the assumption of both a δ-shaped and a uniform energy distribution of interface states.
Abstract: The transport properties of polycrystalline silicon films are examined and interpreted in terms of a modified grain‐boundary trapping model. The theory has been developed on the assumption of both a δ‐shaped and a uniform energy distribution of interface states. A comparison with experiments indicates that the interface states are nearly monovalent and peaked at midgap. Their density is 3.8×1012 cm−2, in accordance with carrier‐lifetime measurements performed on CVD films.

673 citations

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed a model which incorporates the above characteristics of a photoconductive film, except for the space charge effects, and derived numerical values for responsivity, noise, and sensitivity.
Abstract: Photoconductive films of the lead salt family are composed of a system of crystallites separated by intercrystalline barriers. The crystallites are lead salts while the intercrystalline barriers are an oxide of lead or of the lead salt. Space charge regions are present at the surface of the crystallites. The lifetime of hole-electron pairs is determined in part by surface states while the resistivity is strongly affected by intercrystalline barriers.We analyze a model which incorporates the above characteristics of a photoconductive film, except for the space charge effects. It is assumed that the primary photoeffect is absorption of light and production of hole-electron pairs in the crystallites. The change in conductivity results from a change in majority carrier density in the crystallites, and from reduction of intercrystalline barrier potentials.Equations are developed for the response to radiation, for the noise, and for the limit of sensitivity of the detector. These expressions contain familiar semiconductor parameters, and a new parameter which characterizes the relative importance of the change in carrier density as compared to the change in barrier potential. No attempt is made to calculate the parameters, but measurements necessary for their evaluation are briefly discussed. This permits a prediction of numerical values for responsivity, noise, and sensitivity which can be compared with experiment.

629 citations

Journal ArticleDOI
TL;DR: In this paper, a unified theory of exponetial absorption edges must rely on electric microfields as the cause, including exciton effects and the final-state interaction between the electron and the hole, and ascribe Urbach's rule to the relative, internal motion of the exciton.
Abstract: Exponential absorption edges $\ensuremath{\alpha}=A{e}^{g(\ensuremath{\hbar}\ensuremath{\omega}\ensuremath{-}\ensuremath{\hbar}{\ensuremath{\omega}}_{0})}$ have been observed in both ionic (Urbach's rule: $g=\frac{\ensuremath{\sigma}}{{k}_{B}{T}^{*}}$ and covalent materials. Arguments are given to show that a unified theory of exponetial absorption edges must (i) rely on electric microfields as the cause, (ii) include exciton effects and the final-state interaction between the electron and the hole, and (iii) ascribe Urbach's rule to the relative, internal motion of the exciton. An approximate calculation has been made in which the nonuniform microfields are replaced by a statistical distribution of uniform microfields; this calculation is a generalization to physically relevant intermediate-strength fields of previous strong- and weak-field theories of Redfield and Dexter. In contrast with the other microfield models, which obtain the exponential spectral shape by averaging over microfield distributions, the present theory obtains a quantitatively exponential edge as an inherent feature. The temperature dependences of the edges in various materials follow qualitatively from the nature of the microfield sources. The specific temperature dependence of Urbach's rule in ionic crystals is obtained from this model, with supplementary arguments to account for nonuniformity of the fields.

619 citations

Journal ArticleDOI
TL;DR: In this paper, the optical absorption coefficient for direct, excitonic transitions in a uniform applied electric field is calculated and the electron-hole scattering is treated within the effective mass approximation and leads to an absorption coefficient which differs markedly in size and shape from the Franz-Keldysh absorption spectrum.
Abstract: Numerical calculations of the optical-absorption coefficient for direct, excitonic transitions in a uniform applied electric field are presented. The electron-hole scattering is treated within the effective-mass approximation and leads to an absorption coefficient which differs markedly in size and shape from the Franz-Keldysh absorption spectrum. A detailed numerical study of the shape of the absorption-edge spectrum at photon energies somewhat below the zero-field absorption threshold suggests that for small field strengths the dominant asymptotic form of the absorption coefficient is $\mathrm{exp}(\ensuremath{-}\frac{{C}_{0}|E\ensuremath{-}{{E}_{0}}^{\ensuremath{'}}|}{f})$, where $f=\frac{|e|\mathrm{Fa}}{R}$ is the electric field strength in units of exciton Rydbergs per electron-exciton Bohr radius. This result contradicts the existing belief that the electron-hole interaction does not alter the asymptotic form of the Franz-Keldysh shape: $\mathrm{exp}(\ensuremath{-}\frac{{{C}_{0}}^{\ensuremath{'}}{|E\ensuremath{-}{{E}_{0}}^{\ensuremath{'}}|}^{\frac{3}{2}}}{f})$. Physical arguments are presented to show why the exciton effects should be important. A discussion is presented of the interrelationships among the present treatment of electro-absorption and various one-electron, exciton, and many-body formalisms.

366 citations