Application In Solar Cell Devices Research Articles

Characteristics of CuIn1−xGaxS2 thin films synthesized by chemical spray pyrolysis

CuIn1−xGaxS2 multi-component semiconductors thin films were prepared by chemical spray pyrolysis on glass substrates using different concentrations of gallium in the spray solutions (y=([Ga3+]/[In3+]) varying from 0 to 20at% by a step of 5at%). Samples were characterized using X-ray diffraction, Raman spectroscopy, Atomic Force Microscopy, photoluminescence spectroscopy, spectrophotometric and Hall effect measurements. The X-ray spectra reveal that the CuIn1−xGaxS2 thin films are of chalcopyrite crystalline phase with a highly (112) preferential orientation. The best crystallinity is obtained for 10at% Ga incorporation since the maximum (112) peak intensity and grain size are obtained at this Ga incorporation rate. The level of the residual microstrain and dislocation network seems to be reduced respectively to the values 0.09% and 4×108linesmm−2 for an optimum y=10at% for which the crystallinity of CuIn1−xGaxS2 thin layers is the best one. Raman spectra indicate that the sprayed thin films are grown only with CH-ordering. Optical analysis by means of transmission T(λ) and reflection R(λ) measurements allow us to determine the direct band gap energy value which increases by increasing the Ga content and it is in the range 1.39–1.53eV, indicating that CuIn1−xGaxS2 compound has an absorbing property favorable for applications in solar cell devices. Photoluminescence measurements are performed on CuIn1−xGaxS2 crystals and the analysis reveals that the emission is mainly due to donor–acceptor pair transitions. The film resistivity (ρ) and Hall mobility (μ) are strongly affected by Ga incorporation rate. The lowest resistivity (ρ=0.1Ωcm) and maximum value of Hall mobility (μ=0.5cm2V−1s−1) are also obtained for the thin layers prepared with y=10at%. Finally, we reported two new structures for CuInS2/β-In2−xAlxS2/ZnO:Al and CuIn1−xGaxS2 (y=10at%)/β-In2-xAlxS2/ZnO:Al solar cells to investigate the effect of gallium incorporation on the photovoltaic parameters. We found that the Ga-containing cell shows conversion efficiency (η=1.6%) higher than the Ga-free reference cell due to higher open-circuit voltage (Voc=540mV) and short-circuit current density (Jsc=10mAcm−2).

Synthesis of ZnO nanorods on ZnO/ITO seed layer by electrochemical method and its application in solar cell device

In this paper, we study on the effects of ZnO nanorods /seed ZnO on properties of hybrid solar cells. ZnO nanorods fabricated by electrochemical method of two-step stable flow of liquid Zn(NO3)2. 6H2O (0.005 M) and C6H12N4 (0.005 M). Morphology and optoelectronic properties of ZnO nanorods were studied by SEM images, UV-VIS transmission spectra, X-ray diffraction and photoluminescence spectrum. Elaboration of hybrid solar cells by inserting ZnO nanorods on organic photoactive layer of P3HT:PCBM and ITO, as result the solar cell conductivity performance is significantly improved. Experimental results show that ~ 1,392 mA/cm2 Jsc, Voc ~ 0.49 V, FF = 0.32, and PCE = 0.23%.

Quantum Cutting down Conversion by Cooperative Energy Transfer from Tb<sup>3+</sup> to Yb<sup>3+ </sup>in CeF<sub>3</sub> Nanophosphors

In the present work, Cerium Fluoride (CeF3) was selected as the host material because of its High density, fast response and high radiation resistance, efficient absorption and energy transfer by host (to activator). Rare earths have been used to show the process of Quantum Cutting (QC) via energy transfer process between Tb3+ and Yb3+ incorporated in CeF3. For the synthesis of CeF3 nanoparticles codoped with Tb3+ and Yb3+ ion, co-precipitation route was employed. Different doping concentrations were prepared to study the changes that take place in the luminescence spectra of the composition. Thus, concentration dependent study of the fluorescence of CeF3: Tb3+, Yb3+ was carried out. These materials have great applications in solar cell devices as quantum efficiencies up to 200 % can be achieved.

Effect of spray solution flow rate on the physical properties of CuInS2

CuInS 2 thin films have been successfully prepared on Pyrex substrates using spray pyrolysis technique. In this work, we study the effect of the flow rate on the physical properties of CuInS 2 thin films. X-ray diffraction pattern reveals the presence of tetragonal structure with (1 1 2) preferential orientation for CIS thin layers. Optical analysis by means of transmission T ( λ ) and reflection R ( λ ) measurements allows to determine the direct band gap energy value in the order of 1.44 eV, indicating that CuInS 2 compound has absorbing properties favorable for applications in solar cell devices. Photoluminescence measurements are performed on CuInS 2 crystals and the analysis reveals that the emission is mainly due to donor-acceptor pair transitions.

Physical properties of Cu2ZnSnS4 thin films deposited by spray pyrolysis technique

Thin films of Cu2ZnSnS4 (CZTS) were deposited on Pyrex substrates at various temperatures by spray pyrolysis technique from aqueous solution containing an economic stannous chloride (SnCl2) precursor for the tin and the effect of substrate temperature on the structural and opto-electronic properties was investigated. X-ray diffraction patterns and Raman spectroscopy reveal that all the CZTS films exhibited kesterite structure with preferential orientation along the (1 1 2) direction and some secondary phases. Also, they possessed different band gaps, which were found to lie between 1.52 and 1.81 eV, indicating that CZTS compound has absorbing properties favorable for applications in solar cell devices. Van der Pauw technique and Hall effect measurements were used to determine the electrical properties of CZTS films and the resistivity was of about 0.12 Ω cm for film grown at 280 °C.

Synthesis of rod and lath-shaped CuSe and tremella-shaped Cu2−x Se nanostructures at room temperature, and their optical properties

The research for tunable synthesis and characterization techniques is important for the investigation of nanomaterials. Herein we developed old precipitation reaction for the morphology- and phase-tunable synthesis of copper selenides nanostructures at room temperature, avoiding tedious preparation of selenium precursors, such as selenite or selenosulfate. The molar ratio of Cu2+ and Se sources served the function of a switch for selectively synthesis of stoichiometric CuSe and non-stoichiometric Cu2−xSe. Nanorod and lath-like CuSe formed with excess of selenium source, while tremella-shaped Cu2−xSe responded to the 1:1 of Cu2+/Se or excess of copper source. The structures of nanocrystals, especially the lifelike surface, were characterized in detail by electron microscopy techniques, such as STEM. Novel nanostructures put up the excellent absorption properties in the visible light region, respectively, and could bear potential applications in solar cell devices in the future. This strategy offered a convenient, mild and energy-efficient route for the preparation of other mental chalcogenides nanocrystals with different morphologies or tunable phases.

Polymer brushes assisted loading of high density CdS/CdSe quantum dots onto TiO2 nanotubes and the resulting photoelectric performance

Cadmium sulfide (CdS) and cadmium selenide (CdSe) quantum dots (QDs) are sequentially loaded onto anodized TiO2 nanotubes to fabricate a CdS/CdSe co-sensitized photoelectrode for visible light response. These QDs are loaded on TiO2 nanotubes by polymer brushes assisted in situ formation, and they are distributed uniformly around both inner and outer walls of TiO2 nanotubes. The interpenetrating polymer can provide a superior nano-confined environment and will prevent the nanoparticles from growing further during nucleation. More importantly, the potential advantage of using polymer brushes is the capability of tuning the loading amount of QDs via multiple cation exchange. The photoresponse of CdS/CdSe-TiO2 nanotubes has been efficiently extended into the visible-light region, indicating potential applications in solar cell devices.

Effect of indium doping on physical properties of nanocrystallized SnS zinc blend thin films grown by chemical bath deposition

SnS:In thin films have been successfully prepared on Pyrex substrates using low cost chemical bath deposition technique with different indium concentrations (y=[In][Sn]=4%,6%,8%,and10%). The structure, the surface morphology, and the optical properties of the SnS:In films were studied by x-ray diffraction, scanning electron microscope, atomic force microscopy, and spectrophotometer measurements. In order to obtain a thickness of the order of 308 ± 10 nm for potential applications in solar cell devices, a multilayer deposition has been prepared. It is found that the physical properties of tin sulphide are affected by indium concentration. In fact, x-ray diffraction study showed that better crystallinity in zinc blend structure with preferential orientations (111)ZB and (200)ZB was obtained for y equal to 6%. According to the AFM analysis, we remark that low average surface roughness value of SnS(ZB) thin film is obtained with In concentrations equal to y = 6%. Energy dispersive spectroscopy showed the existence of In, Sn, and S in the films. Optical analyses by means of transmission T(λ) and reflection R(λ) measurements show 1.57 eV as an optical band gap value of SnS:In(6%), which is lower than the previously obtained value (1.76 eV) for undoped tin sulphide. In doped tin sulphide exhibits a high absorption coefficient 2.5 × 106 cm−1, indicating that SnS:In can be used as absorber thin layer in photovoltaic structure such as SnS:In/ZnS/SnO2:F and SnS:In/In2S3/SnO2:F, where ZnS and In2S3 are chemically deposited as described in a previous work. In this study, the hetero-junctions SnS/In2S3:Al and SnS/ZnS:In are also investigated.

Effect of Deposition Time on Physical Properties of Nanocrystallized SnS Zinc Blend Thin Films Grown by Chemical Bath Deposition

Abstract. Zinc blend tin sulphide thin films have been successfully prepared on Pyrex substrates using low cost chemical bath depositiontechnique. In this work, we study the effect of time deposition on the physical properties of SnS thin film. A 200 nm thick layer is obtained as an optimum value for deposition time td equal to four hours. X-Ray diffraction study shows that SnS exhibits a zinc blend structure with preferential orientations (111)ZBand (200)ZB. Optical analyses by means of transmission T(λ) and reflection R(λ) measurements allow to determine the direct band gap energy value ≈1.7 eV. Thin layers of tin sulphide exhibit a high absorption coefficient up to 1.5×106cm-1in the visible domain, indicating that SnS compound has absorbing properties favorable for applications in solar cell devices.

Effects of reduced dimensionality on the electronic structure and defect chemistry of semiconducting hybrid organic–inorganic PbS solids

The combination of inorganic and organic frameworks to produce crystalline hybrid semiconductors offers a pathway for obtaining novel photovoltaic and optoelectronic materials. Taking an archetypal binary semiconductor, PbS (galena), we investigate the electronic effects of the reduced dimensionality in the PbS framework on transition from bulk PbS to three-dimensional and one-dimensional hybrid inorganic–organic networks. Analysis of density functional theory calculations reveals the substantial contribution of the organic (benzenehexathiol derivates) to the band-edge states. Implications for intrinsic defect formation and potential application in solar cell devices are discussed, as well as future design pathways for engineering the electronic properties of this new class of hybrid metal–organic framework.

Enhancing The Optical And Electrical Properties of Si-based Nanostructured Materials

Multilayer structures of Si rich silicon oxide (SiOx) alternated with two types of dielectric sublayers viz. SiO2 or SiNx have been studied. An enhancement in the density of nanoclusters within the SiOx sublayer is achieved by using the reactive magnetron co-sputtering method. The effect of SiNx sublayer thickness on the photoluminescence properties is investigated. We succeed in enhancing the absorption and the pholuminescence properties of the multilayers by replacing SiO2 by SiNx sublayers. We also achieve a higher conductivity in SiOx/SiNx with an improved thermal budget. This preliminary study gives a deep insight to optimize materials for future solar cell device applications with enhanced properties at reduced thermal budget.

Deposition and characterization of CuInSe 2 films for solar cells using an optimized chemical route

CuInSe 2 (CISe) thin films have been deposited on glass using successive ionic layer adsorption and reaction (SILAR). The as-deposited films are treated at 400 °C in argon atmosphere and etched in KCN solution to remove detrimental secondary phases. The preparation and temperature of the precursor solutions, the duration of the reaction cycles and the duration of the annealing stage have been optimized. The films have been characterized employing grazing incident X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive scanning spectroscopy. Relevant semiconductor parameters have been calculated. Photoelectrochemical tests confirm p-type conduction. The films are crystalline and the stoichiometry can be improved by renewing the precursor solution after completing half of the cycles, annealing for 90 min and later etching in KCN. The quality of the material seems to be promising for application in solar cell devices.

Comparison of Hybrid Blends for Solar Cell Application

In blended hybrid systems distinct micro- or nanostructured materials can be formed by phase separation. Network structures of particles or rods in a polymer matrix can be developed via self-assembly. We use this blending approach to compare active materials for application in solar cell devices. Blends were fabricated from either poly(hexylthiophene) P3HT or poly(triphenylamine) PTPA mixed with nanocrystalline TiO2 rods. In this manner, we compare two different hole conducting polymers in their performance in photovoltaic devices, while experimental conditions are kept identical. We find that the choice of solvent and photovoltaic characterization conducted in inert atmosphere is of importance for blends prepared from P3HT/TiO2 blends, but not for PTPA/TiO2 blends. Even though prepared with the same TiO2 rods, solar cells prepared from PTPA blends showed an enhanced efficiency when measured under ambient conditions. Furthermore, the PTPA/TiO2 showed higher long-term stability.

Design and growth of dendritic Cu2−xSe and bunchy CuSe hierarchical crystalline aggregations

Dendritic nanocrystals of copper selenide were fabricated in situ for the first time by using alcohol as the solvent. Cu2−xSe films composed of hierarchically ordered dendritic nanostructures were prepared on Cu substrates at a rather moderate temperature of 190–200 °C for just 1–3 h, while bunchy CuSe nanostructures could be further constructed above the Cu2−xSe dendrites by prolonging the reaction time of solvothermal growth with ethanol as the solvent. The resulting Cu2−xSe nanodendrites display highly symmetric corolitic morphology while the bunchy CuSe aggregations show particular nanostructures with a pronounced trunk and actinomorphic multi-branches. It is also found that the dendritic structures of crystalline Cu2−xSe could never be obtained when the reaction temperature is less than 190 °C, while the temperature needed is 160 °C for Ag2Se nanodendrites and higher than 220 °C for CdSe nanodendrites. These copper selenide nanostructures with hierarchically ordered 3-dimensional (3D) framework exhibited good absorbance and photoluminescence (PL) property and could bear potential applications in solar cell devices in the future.

Bilayer ZnO nanostructure fabricated by chemical bath and its application in quantum dot sensitized solar cell

Chemical bath method was used to synthesize bilayer ZnO nanostructure on ITO glass in the alkaline solution. As revealed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), the product consists of a layered structure of ZnO nanorods at the bottom and nanoflower atop. The as-prepared sample was assembled in quantum dot sensitized solar cell (QDSSC), which obtained the incident photon to current conversion efficiency (IPCE) of 15% at 400 nm and power conversion efficiency (PCE) of 0.45%. Therefore, this novel bilayer ZnO nanostructure has the potential for application in solar cell device as the photoelectrode.

Thermally evaporated thin films of SnS for application in solar cell devices

SnS (tin sulphide) is of interest for use as an absorber layer and the wider energy bandgap phases e.g. SnS 2, Sn 2S 3 and Sn/S/O alloys of interest as Cd-free buffer layers for use in thin film solar cells. In this work thin films of tin sulphide have been thermally evaporated onto glass and SnO 2:coated glass substrates with the aim of optimising the properties of the material for use in photovoltaic solar cell device structures. In particular the effects of source temperature, substrate temperature, deposition rate and film thickness on the chemical and physical properties of the layers were investigated. Energy dispersive X-ray analysis was used to determine the film composition, X-ray diffraction to determine the phases present and structure of each phase, transmittance and reflectance versus wavelength measurements to determine the energy bandgap and scanning electron microscopy to observe the surface topology and topography and the properties correlated to the deposition parameters. Using the optimised conditions it is possible to produce thin films of tin sulphide that are pinhole free, conformal to the substrate and that consist of densely packed columnar grains. The composition, phases present and the optical properties of the layers deposited were found to be highly sensitive to the deposition conditions. Energy bandgaps in the range 1.55 eV–1.7 eV were obtained for a film thickness of 0.8 μm, and increasing the film thickness to > 1 μm resulted in a reduction of the energy bandgap to less than 1.55 eV. The applicability of using these films in photovoltaic solar cell device structures is also discussed.

Photoactive ionic assemblies between n dopable perylene and p dopable carbazole derivatives

The study of molecular assemblies obtained by ionic interactions between two π-conjugated organic molecules one possessing electron donor properties and the other possessing electron acceptor properties is discussed here. The electron acceptor molecules chosen are two tetra-chlorinated 3,4,9,10-perylene tetracarboxylic diimides bearing pyridine or amine functions (( 1) or ( 2)) and the electron donor is 4-carbazol-9-yl-butane-1-sulfonic acid ( 3). The electrochemical characterizations and UV–vis/photoluminescence spectroscopy studies of each compound were realized. Moreover, photoluminescence quenching of ( 1) and ( 2) solutions is observed when they are protonated with the acid function of ( 3). Interestingly, with a simple mixture of ( 1) or ( 2) with 9-ethyl-carbazole, ( 1) and ( 2) solutions fluorescence quenching is very low. Finally, the relative energy levels values of the HOMO and LUMO of ( 1)–( 3) were estimated and the results are compatible with a possible electron transfer from carbazole to perylene unit making these ionic assemblies attractive candidate for an active layer application in solar cell devices.

Mapping of gradient composition CuxGaySe2 film properties using Raman and PL-spectroscopy

Detailed Raman studies were conducted for the structural characterization of CuxGaySe2 films grown using physical vapour deposition. CuxGaySe2 gradient composition samples were mapped using Raman spectroscopy in combination with photoluminescence (PL) and energy dispersive x-ray spectroscopy. The Raman spectra recorded under excitation with near band gap laser light have a high signal-to-noise ratio and can be used to study the film structure. In particular, composition dependent changes result in significant changes in the A1-mode frequency at 187 cm−1, the line width of the E1-mode at 277 cm−1, and the normalized intensities of the E1-mode at 277 cm−1 and the B2-mode at 199 cm−1. It is shown that the intensity increase in Raman modes, with the [Ga]-content increasing in the range 0.9 < [Cu]/[Ga] < 1, is correlated to an increase in defect concentration and lowering of film crystallinity. Moreover, it is shown that the [Cu]/[Ga] fraction of Ga-rich films, used in solar cell device applications, can be calibrated with respect to the band width of the E1-mode.

Mixtures of organic macrocycles for applications in solar cell devices

AbstractIn this paper we present spectroscopic and photoelectric studies of two families of macrocycles and their mixtures: phthalocyanines and naphthalocyanines complexed with various ions. The dyes are characterized by significant light absorption and each dye absorbs in a different spectral region and covers only a part of the solar light spectrum. The use of the dyes mixture extends the light absorption region and can lead to the enhancement of photovoltaic effects. The spectroscopic properties are studied to establish the radiative and non–radiative deactivation pathways of the dye excited states as processes competitive to charge separation. As it is shown, the excitation energy transfer improve the efficiency of light energy to electric energy conversion. The dynamics of the electromagnetic field in the phthalocyanine–naphthalocyanine–solvent system as a multicomponent body in the sense of extended phenomenological electrodynamics is also presented. Lagrange–Hamilton formalism can be used in the investigation of the local electromagnetic field in the dyes–solvent mixture. The presented results seem to be essential in the determination of the conditions required for the enhancement of the photoeffects in the photoelectrochemical cell based on the organic materials.

Novel ‘Photochemical deposition’ and conventional ‘Electrochemical deposition’ of CdS and HgxCd1−xTe thin films and their characterization for solar cell device applications

ABSTRACTSolar cell devices of the structures CdS/CdTe and CdS/HgCdTe, based on II-VI semiconductor thin films have been fabricated and analyzed. CdS thin films were deposited by the recently established novel deposition technique, namely, 'Photochemical deposition' and the Cd rich HgxCd1−xTe films used for the device fabrication were deposited by the conventional ‘electrochemical deposition’ technique. First solar cell devices of the structures CdS/CdTe and CdS/HgCdTe using photochemically deposited CdS films, were fabricated and analyzed for the conversion efficiency.