Impact of the Cd2+ treatment on the electrical properties of Cu2ZnSnSe4 and Cu(In,Ga)Se2 solar cells

The present contribution aims at determining the impact of modifying the properties of the absorber/buffer layer interface on the electrical performance of Cu₂ZnSnSe₄ (CZTSe) thin‐film solar cells, by using a Cd²⁺ partial electrolyte (Cd PE) treatment of the absorber before the buffer layer deposition. In this work, CZTSe/CdS solar cells with and without Cd PE treatment were compared with their respective Cu(In,Ga)Se₂ (CIGSe)/CdS references. The Cd PE treatment was performed in a chemical bath for 7 min at 70 °C using a basic solution of cadmium acetate. X‐ray photoemission spectroscopy measurements have revealed the presence of Cd at the absorber surface after the treatment. The solar cells were characterized using current density–voltage (J–V), external quantum efficiency, and drive‐level capacitance profiling measurements. For the CZTSe‐based devices, the fill factor increased from 57.7% to 64.0% when using the Cd PE treatment, leading to the improvement of the efficiency (η) from 8.3% to 9.0% for the best solar cells. Similar observations were made on the CIGSe solar cell reference. This effect comes from a considerable reduction of the series resistance (R_S) of the dark and light J–V, as determined using the one‐diode model. The crossover effect between dark and light J–V curves is also significantly reduced by Cd PE treatment. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of Cu/Sn Concentration Ratio on the Phase Equilibrium-Related Properties of Cu-Sn-S Sprayed Materials

Copper tin sulfide Cu-Sn-S compounds have been grown by the spray pyrolysis technique at 360 °C using SnCl₂·2H₂O, CuCl₂ and thiourea (SC(NH₂)₂ as precursors. Structural, morphological, and optical properties were studied showing that the obtained films crystallized in tetragonal and orthorhombic structures in terms of the Cu/Sn concentration ratio in the starting solution. Moreover, the deposited films showed a relatively high optical absorption coefficient of around 10⁴ cm⁻¹ and exhibited indirect transition gaps which lie within 1.17-1.38 eV domain.     

Growth of Cu2SnS3 thin films by solid reaction under sulphur atmosphere

Cu₂SnS₃ thin film have been synthesized by solid state reaction under vapour sulphur pressure at 530 °C, during 6 h, via a sequentially deposited copper and tin layers Cu/Sn/Cu…Sn/Cu/Sn. The structure and the composition were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Electron Probe Micro Analysis (EPMA). X-ray diffraction revealed that as the deposited film crystallizes in the cubic structure and the crystallites exhibit preferential 111 orientation of the grains. Moreover, EPMA analysis confirmed that the obtained film is stoichiometric. The SEM study shows the presence of spherical particles of ≈100-120 nm diameters. The optical absorption coefficient and band gap of the film were estimated by means of transmission and reflection optical measurements at room temperature. A relatively high absorption coefficient in the range of 10⁴ cm⁻¹ was indeed obtained and the band gap value is of the order of 1.1 eV. On the other hand, the electrical conductivity of Cu₂SnS₃ film prepared in the present experiment is suitable for fabricating a thin film solar cell based on not cheaper and environmental friendly material.     

Physical investigations on Ni doping ZnO thin films along with ethanol response

Journal of Materials Science: Materials in Electronics - Undoped and Ni-doped ZnO thin films were grown on glass substrates at 460 °C using the spray pyrolysis method. All samples...     

Luminescence of composites based on oxide aerogels incorporated in silica glass host matrix

This paper deals with the elaboration and photoluminescence (PL) examination of oxide powder (OP = ZnO, Al₂O₃, SnO₂, TiO₂) incorporated in silica host matrix. OP, in the first step, was prepared by a sol–gel method using supercritical drying of ethyl alcohol. The obtained powder, in a second step, was incorporated in silica aerogel monolith using tetraethylorthosilicate as SiO₂ precursor and ethyl alcohol supercritical conditions for drying. In the third step, silica aerogel containing oxide powders were heated under natural atmosphere at 1200 °C for 2 h to form the composites that exhibited a strong PL bands at Vis–IR range. Photoluminescence excitation (PLE) measurements show different origins of the emission. It was suggested that OH-related radiative centres and non-bridging oxygen hole centres (NBOHCs) defects resulting from thermal treatment and crystallization at the interfaces between OP and silica host matrix, were responsible for the bands at 400–600 and 700–900 nm respectively.     

SnxSy compounds growth by controlled sulfurisation of SnO2

In this work, thin layers of semiconducting tin sulfide Sn_xS_y compounds have been prepared by sulfrisation of tin oxide SnO₂ on glass substrate. Structural studies showed that, depending on sulfur supply concentration, a mixture of SnS₂ and Sn₂S₃ is obtained at an annealing temperature of 550 °C for 2 h. From the transmission and reflectance spectra, the extinction coefficient and refractive index were calculated as guides to understanding crystal growth kinetics. On the other hand, the exploitation of these optical measurements along with optothermal investigations showed that the electronic transitions in these layers were of allowed direct type and exhibit two gaps indicating the presence of two competent sulfide phases: SnS₂ and Sn₂S₃.     

Effect of tin content on the electrical and optical properties of sprayed silver sulfide semiconductor thin films

Silver sulfide (Ag₂S) thin films have been deposited on glass substrates by t spray pyrolysis using an aqueous solution which contains silver acetate and thiourea as precursors. The depositions were carried out at a substrate temperature of 250 °C. Structural studies by means of X-ray diffraction show that all tin (Sn)-doped Ag₂S thin films crystallized in a monoclinic space group with noticeable changes in the crystallites' orientation. The discussion of some structural calculated constants has been made with Sn doping in terms of microhardness measurements. Moreover, the optical analysis via the transmittance, reflectance as well as the photocurrent reveals that the direct band gap energy (E_gd) decreases (E_gd varies from 2.34 to 2.16 eV) and the indirect band gap energy (E_gi) increases (E_gi varies from 0.98 to 1.09 eV) slightly as a function of Sn content. Electrical study shows that Sn doping changes the electrical conductivity and proves the thermal activation of electrical conduction.     

Some physical investigations on AgInS2 sprayed thin films

AgInS₂ thin films have been prepared on glass substrates by the spray pyrolysis process using an aqueous solution which contains silver acetate (AgCH₃CO₂), thiourea (SC(NH₂)₂) and indium chloride (InCl₃) as precursors. The depositions were carried out in the range of the substrate temperature from 260 to 420 °C. The value of the concentration ratio in the spray solution of indium and silver elements x=[Ag⁺]/[In³⁺] was varied from 1 to 1.5 with [In³⁺]=10⁻² M and [S²⁻]/[In³⁺] was taken constant, equal to 4. The structural study shows that AgInS₂ thin film, prepared at 420 °C using optimal concentration ratio x=1.3 crystallizes in the chalcopyrite phase with a strong (1 1 2) X-ray diffraction line. Moreover, microprobe analysis (EPMA) shows that a nearly stoichiometric composition is obtained for these experimental conditions. Indeed, the atomic percentage of elements were. 24.5, 25.0, 49.5 for Ag, In and S, respectively. On the other hand from transmission and reflectance spectra, the obtained band gap energy is 1.83 eV for such film.     

Structural properties of FeTe2 thin films synthesized by tellurization of amorphous iron oxide thin films

This paper deals with the structural properties of FeTe₂ thin films obtained using a simple and non-toxic experimental procedure. First, iron oxide thin films have been prepared by the spray pyrolysis technique from an aqueous solution containing FeCl₃6H₂O (0.03 M) as a precursor onto glass substrates heated at 623 K. Second, these films were subjected to a heat treatment under tellurium atmosphere at various temperatures (723–803 K) for 24 h. XRD analysis revealed that FeTe₂-ortorombic phase films were obtained at a heat treatment of the order of 773 K. This film has a good crystalline state with a preferential orientation of the crystallites along (111) direction. Moreover, AFM as well as SEM morphological observations show a relatively perturbed surface state.To date, this simple and low cost route process to obtained FeTe₂ thin films has not yet been used.     

Vanadium doping patterns in ZnO lattices in the lattice compatibility theory framework

We investigate vanadium doping patterns in ZnO thin films prepared by spray pyrolysis for different controlled concentrations (1–5%). Lattice-scale analyses are carried out in the lattice compatibility theory (LCT) framework. Differences in vanadium doping behaviors for different concentrations are discussed in terms of Urbach tailing and the Faraday effect, as well as the intrinsic lattice patterns of the doping agent.