Ternary Chalcopyrite Compounds Research Articles

Design and Simulation of a High‐Efficiency CuInS2 Thin‐Film Solar Cell with a Thin CIS Current Augmenter

Ternary chalcopyrite compound cupper indium disulfide (CuInS2)‐based photovoltaic cells are designed and numerically computed. In this design, n‐CdS and p++‐MoS2 have been used as window and back surface field (BSF) layers, respectively. The modeled n‐CdS/p‐CuInS2/p++‐MoS2 device provides power conversion efficiency (PCE) of 24.6% with JSC of 26.98 mA cm−2, VOC of 1.05 V, and fill factor (FF) of 86.93%. This efficiency is ≈60% higher the than n‐CdS/p‐CuInS2 single heterostructure. Furthermore, the use of a second CuInSe2 (CIS) absorber layer between CuInS2 absorber and MoS2 BSF layer significantly enhances the short‐circuit current. As a result, the current expressively improves to 38.48 mA cm−2, yielding an efficiency of 32.4%. The greater built‐in potential in absorber/BSF interface is attributed to the high JSC and VOC, causing the increment of efficiency. Besides, the photon management by Bragg reflector with 90% back and front reflectance recycling effect further increases the PCE to 36.1%. This work indicates the prospects of CuInS2 solar cells with a CuInSe2 current augmenter and MoS2 BSF layers for the fabrication of efficient CuInS2 solar cells.

First Principle Study of Electronic, Optical and Thermoelectric Properties of CuInS2 and CuInSe2

We report the bandgap, thermoelectric and optical properties of CuInS2 and CuInSe2 ternary chalcopyrite compounds based on DFT calculations. Our calculations shows that both CuInS2 and CuInse2 have a direct bandgap which were at the Γ-points. The computed bandgap were 1.35 and 0.85 eV for CuInS2 and CuInSe2. The optical properties analysis shows that the fundamental edge of absorption arise at 0.82 eV and 0.35 eV along the perpendicular and parallel polarization for CuIns2, while it arise at 0.13 eV and 0.16 eV along the perpendicular and parallel polarization for CuInSe2. The static dielectric constant, static refractive index and birefringence were then calculated. The calculated birefringence was negative, which meets the non-critical phase matching (NCPM) requirement, which is beneficial for high-performing laser systems. The optical absorption threshold lies at 1.4, and 0.83 eV for CuInS2 and CuInSe2. These compounds shows low reflectivity and high absorption in the visible region. Both compounds have high electrical conductivity and Seebeck coefficient, making them promising candidates for thermoelectric devices.

Investigation of the electronic, structural, optical and thermoelectric properties of ternary chalcopyrite ACuS2(A=Al, Ga and In): Ab initio study

In the present work, the structural, electronic, optical and thermoelectric properties of the ternary chalcopyrite compounds defined by ACuS2(A=Al, Ga, In) has been performed by density functional theory (DFT) combined with Boltzmann transport theory. Based on the generalized gradient (GGA) approach, the stability accompanied with the structural parameters of the studied structure compounds was evaluated. Furthermore, modified Becke-Johnson exchange potential (TB-mBJ) was adopted for the exchange correlation potential in order to prove the electronic and optical features of ACuS2(A=Al, Ga and In). The plotted density of state, band structure, distribution charge density of the ACuS2(A=Al, Ga and In) component, with dielectric function, reflectivity, Seebeck coefficients, electrical and thermal conductivity are obtained and discussed. Our result reveal, for electronic properties, that all components exhibit p-type semiconductor with direct band gap, with 1.51 eV for GaCuS2. The chemical bonding analysis shows the presence of ionic bonding between Al/In/Ga and S. The calculated dielectric function and the absorption coefficient indicate that InCuS2 followed by GaCuS2 display an excellent absorption in the visible range with low reflectivity. The evaluated results are in excellent agreement with available experimental and theoretical data. The physical properties of the novel ACuS2 (A=Al, Ga and In) compound show promising candidate toward photovoltaic, optoelectronic and thermoelectric device.

DFT Investigations of BeSnN2 Chalcopyrite Compound for Optoelectronic Applications

The ternary chalcopyrite compounds are a very renowned category to perform the theoretical investigation in order to find out a proper and apt compound for optoelectronic application. Solar cell is a very interesting field to compensate the energy supplying needs in place of other electricity generating sources. Several semiconductor compounds have been investigated and amongst them we have done a theoretical investigation of pure BeSnN2 using DFT based computational tool i.e. Wien2k. The exchange correlation used for our study is Perdew Burke Ernzerhoff: Generalized Gradient Approximation (PBE-GGA). We have done electronic and optical investigation of the compound using the basic lattice parameters and other essential input parameters. The investigation has offered a bandgap of 1.005 eV which is suitable to quote for the optoelectronic applications. Optical properties like absorption, dielectric tensor (both real and imaginary), refraction and reflection have been investigated.

Predicting the stable rhodium based chalcopyrites with remarkable optical properties

The ternary chalcopyrite compounds and related structures are well known for their noteworthy electronic and optical properties. The interaction between monovalent and trivalent atoms has a significant influence on their electronic as well as optical behavior. In the present work, a density functional theory based first-principles calculation is performed to investigate the structural, electronic, lattice dynamical, and optical properties of rhombohedral CuRhX2 (X = S, Se, Te) compounds. The electronic band structure of these compounds depicts semiconducting nature with an indirect bandgap of 1.8, 1.17, and 0.75 eV for CuRhS2, CuRhSe2, and CuRhTe2, respectively. There is a greater hole mobility and p-type conductivity in these compounds due to strong p-d hybridization. The phonon dispersion curves of these compounds confirm their dynamical stability as there is no imaginary frequency for any of the phonon modes in the entire Brillouin zone (BZ). Furthermore, we discuss mode compatibility at the zone center of the BZ and other high symmetry points of the BZ. The Raman spectra of CuRhX2 demonstrate two Raman active modes, namely, the Eg and A1g. The frequency of Raman active modes Eg and A1g decreases due to the increase in Rh–X bond length. The static dielectric constants fall in the range of 8.7–10.4. The absorption coefficient of these compounds is in the range of 1.5–2.0 eV depending upon the ionic radii of chalcogen atoms. Thus, it can be deduced that these systems can be efficiently used in solar energy converters in the UV as well as in the visible region.

Electron short-wave phonon scattering in crystals with chalcopyrite lattice

Electron short-wavelength phonon scattering is an effective channel for energy relaxation in crystals with a pseudo-direct optical gap. The equilibrium parameters of crystal structures and spectra of electrons and phonons in the ternary chalcopyrite compounds ZnSiP2 and ZnGeP2 are calculated self-consistently in good agreement with available experimental and theoretical calculations. The ab initio probabilities of phonon-assisted intervalley scattering of electrons in the conduction bands of the pseudo-direct-gap compounds ZnSiP2 and ZnGeP2 between the central Γ minima and the lowest lateral minima (valleys) at the T and N points have been calculated using the density functional perturbation theory. Electron–phonon scattering rates associated with intervalley phonons are calculated. Coupling constants for intervalley phonons in the chalcopyrite phosphides are close to their values in Si, Ge, and in the binary analog GaP.

Zone-center phonons and elastic properties of ternary chalcopyrite ABSe2 (A = Cu and Ag; B = al, Ga and In)

Abstract The zone-center phonon frequencies and the elastic properties of six ternary chalcopyrite compounds represented by ABSe2 (A = Cu and Ag; B = Al, Ga and In) are systematically calculated by using the rigid ion model. In the present paper, we calculate four bond-stretching and three bond-bending interactions, along with three effective dynamical charges. The calculated results are compared and found to be in fairly good agreement with the available experimental and theoretical results. The elastic anisotropy of the studied compounds is analyzed and visualized by plotting three-dimensional surfaces representing the directional dependences of Young's modulus.

A density functional study of chalcopyrite MgGeSb2

The structural, electronic, elastic, dynamic and optical properties of the ternary chalcopyrite compound MgGeSb2 were studied by using the density functional theory (DFT) framework for different exchange–correlation functionals. The obtained equilibrium structural parameters are in good agreement with the available theoretical result. After considering the electronic band structure and electronic density of states (DOS) calculation; this compound is a semiconductor as suggested in the previous work. However; all considered functionals underestimate considerably the electronic band gap energies compared with the experimental results. We have predicted single-crystal elastic constants and related properties such as Young’s modulus, Poisson ratio, shear modulus and bulk modulus. Optical properties such as the dielectric function, refractive index, extinction index have been calculated in the range of 0–20 eV. The obtained results can facilitate an assessment of possible applications of MgGeSb2.

Fabrication of solar cells made with CuInTe2−xSex quantum dots sensitized hierarchical TiO2 sphere having a CuS counter electrode: Dependence on the Te/Se ratio

In this study, we have succeeded in fabricating quantum dot sensitized solar cells (QDSSC’s) which utilize the semiconductor CuInTe2−xSex (of different Te/Se ratios) quantum dots sensitized hierarchical TiO2 sphere (HTS) having CuS as the photoanode. The solar to electric energy conversion performance of the resulting QDSSC depends strongly on the Te/Se ratios in the ternary chalcopyrite compound. In this study, the assembled device exhibiting the highest energy conversion efficiency η of 3.751% (Voc=0.683V, Jsc=11.707mAcm−2, FF=0.516) is the one having CuInTe1.2Se0.8 quantum dots. This value is quite an improvement over those of the CuInTe2 (η=1.970%) and CuInSe2 (η=2.286%). The efficiency of the devices decreases as the Se increases.

Lattice Dynamical Properties and Elastic Constants of the Ternary Chalcopyrite Compounds CuAlS2, CuGaS2, CuInS2, and AgGaS2

Lattice dynamics calculations have been performed for ternary chalcopyrite compounds CuAlS2, CuGaS2, CuInS2, and AgGaS2 using the proposed theoretical model. This model is applied to study the zone-centre (GAMMA = 0) phonon frequencies of CuAlS2, CuGaS2, CuInS2, and AgGaS2. The interatomic interactions up to third nearest neighbours were calculated. The calculated zone-centre phonon frequencies are found to be in very good agreement with observed and previous calculated data available in the literature. Single crystal elastic constants and related properties for these materials were also calculated and compared with the available data in the scientific literature.

Electronic and optical properties of CuInTe2

The electronic and optical properties of a ternary chalcopyrite compound CuInTe2 with diamond like structure have been studied. The calculations are carried out using the density functional theory (DFT) based full potential-linearized augmented plane wave (FP- LAPW) method within the framework of GGA and modified Becke Johnson (mBJ) potential approach. The presence of direct energy band gap of 0.8 eV suggests the sample material can be a good material for solar cell application. The study of the optical response of the material against the incident photon energy radiation indicates the material can be an effective candidate for the optoelectronic devices.

The Copper Indium Selenium (CuInSe2) thin Films Solar Cells for Hybrid Photovoltaic Thermal Collectors (PVT)

Ternary chalcopyrite compounds which may act as an absorber in thin films solar cells are mainly CuGaSe2, the CuInS2, CuInSe2 and the CuAlSe2. Because of their large optical absorption coefficient, a thickness of 1.5-2 microns is sufficient to absorb the useful portion of the solar spectrum. The most promising appears to be the CuInSe2 material, a 18.8% efficiency is obtained by the solar cells based on this material. However, its low band gap (1,04ev) limits the open circuit voltage and thus the efficiency of the solar cell.In this work we present the application of this material in hybrid photovoltaic thermal collectors (PVT). For the determination of its electrical and thermal performance through the development of a heat balance that involves heat exchange between the different components of the collector. The results obtained show that we can have a thermal efficiency equal to (85.68%) and an electrical efficiency of the order of (19.22%) for our PVT collector based on CIS are better than the values obtained by PVT collector based on monocristallin silicon.

Brush Plated Copper Indium Selenide Films and Their Characteristics

In recent years, there has been a growing attention to ternary chalcopyrite compound CuInSe2 (CIS) and its alloys with gallium CuIn x Ga1−x Se2 (CIGS) owing to their promising performance for thin film solar cell applications. The conversion efficiencies have already exceeded 19% using these materials at the laboratory scale. Over the past decades, CIS thin films have been successfully electrodeposited using direct current (d.c.) under the potentialstatic or galvanostatic condition, and periodic pulse electrodeposition technique. In this work, the brush plating technique has been employed for the first time to deposit CIS films.CIS films were deposited by the brush plating technique for the first time. Analar grade Copper sulphate (0.03M), Indium sulphate (0.05 M) and 0.005 M Selenium oxide was used for the deposition of films. The deposition current density was 1.0 mA cm-2. The films were deposited at different electrolyte temperatures in the range of 30 - 80°C. Thickness of the films estimated by Mitutoyo surface profilometer increased from 400 nm to 800 nm.The typical XRD patterns of CIS films deposited at different electrolyte temperatures exhibit the chalcopyrite structure which is easily identified for the films (JCPDS card no. 00-040-1487). The films deposited at lower electrolyte temperatures, show a poor crystallinity with weak and broadened diffraction peaks. As the electrolyte temperature increases, the diffraction peaks become sharp and the peak intensity also increases. Three well defined characteristic peaks at 26.6°, 44.1° and 52.4°are observed. The crystallite size of the films calculated using Scherrer’s equation varied from 15 – 40 nm with duty cycle. Dislocation density and strain were calculated.Composition of the films determined from EDAX measurement indicated that as the electrolyte temperature increased the films became more stoichiometric. At lower electrolyte temperature slight excess of copper is deposited compared to indium since, the deposition potential for copper is more positive compared to indium and a lower concentration of indium ions are available for deposition. At higher electrolyte temperatures, the concentration of the indium ion increases, hence the Cu/In ratio approaches unity at 80°C.The band gap of the films increased from 1.05 eV to 1.17 eV as the electrolyte temperature decreased. The increase in band gap at lower temperatures is due to the small crystallites. The values of the band gap agree well with the earlier report.The room temperature transport parameters were measured by Hall Van der Pauw technique by providing gold ohmic contact. The magnitude of the resistivity increased from 0.1 ohm cm to 20.0 ohm cm as the electrolyte temperature is increased. The resistivity values are comparable to earlier report on three source evaporated films.Solar cell structure of the configuration, Mo/CuInSe2/CuInS2/Ag was studied. For solar cell studies, CuInSe2 films were brush electrodeposited at different bath temperatures on Molybdenum substrate, over this layer, n-CuInS2 films ( 400 nm) were brush electrodeposited at 80°C. The resistivity of the CuInS2 layer was 2.0 ohm cm. On top of the CuInS2, a silver grid was vacuum evaporated. The solar cell parameters, open circuit voltage (Voc), short circuit current density (Jsc), series resistance (Rs),shunt resistance (Rsh), and fill factor (FF) were studied under 100 mW cm-2. The cell area was 0.65 cm2. The results show that the cells exhibit higher efficiency compared to an earlier report on pulse reverse deposited CuInSe2 films.The results of this work clearly point to the possibility of successfully employing the brush electrodeposition technique for the growth of CIS films with grain size in the range of 15 – 40 nm and for the preparation of films with resistivity in the range of 0.1 – 20.0 ohm cm.

Investigation on New CuInS2/Carbon Composite Counter Electrodes for CdS/CdSe Cosensitized Solar Cells

The search for semiconductor-sensitized solar cell (SSC) counter electrode alternatives has been a continuous effort and long ongoing work, while the studies in counter electrode kinetic performance and stability are important to improve the overall efficiency. Here, a ternary chalcopyrite compound CuInS2 is first employed as counter electrode (CE) material for CdS/CdSe cosensitized solar cells. Besides, in order to increase the electron transfer activity at the counter electrode/electrolyte interface and stability, an appropriate amount of active carbon/carbon black mixture is introduced to afford CuInS2/carbon composite electrodes. Electron transfer processes in CuInS2-based electrodes are investigated in detail with the aid of electrochemical impedance spectroscopy and I-E measurement. Up to 4.32% of the light-to-electricity conversion efficiency has been achieved for the CdS/CdSe SSCs with the CuInS2/carbon composite electrode. Besides, a preliminary long-term stability test reveals that the new CuInS2/carbon composite counter electrode exhibits good stability after being kept in the dark at room temperature and without current flow for 1000 h.

Structural and optical properties of thermally evaporated cadmium thiogallate CdGa2S4nanostructure films

Nano structure films of cadmium thiogallate CdGa 2 S 4 have been prepared by a conventional thermal evaporation technique (at substrate temperature = 303 K). These films were deposited on both glass and quartz substrates. X-ray diffraction measurements showed that CdGa 2 S 4 compound in the powder form has a polycrystalline nature with a tetragonal structure. The as-deposited film was annealed at 673 K for 2 h under vacuum 10 -3 Pa and was irradiated by 10 kGy γ co rays. This resulted in a transformation to nanostructure grains of CdGa 2 S 4 thin films. Transmission electron microscopy was carried out for all of the investigated films, which also confirmed that those films could be transformed to nanostructure grains. Optical properties of the CdGa 2 S 4 films under investigation were examined using spectrophotometric measurements of transmittance and reflectance at normal incidence in the wavelength range 400–2500 nm. It was found that both refractive index n and absorption index k changed with the heat and irradiation treatments. The dispersion of refractive index in CdGa 2 S 4 was analyzed according to the single oscillator model. Some dispersion parameters were determined for all investigated films. The calculated values of β (which is defined as the parameter used to determine the type of crystal) indicate that CdGa 2 S 4 belongs to the covalent class for all films investigated. The ratio of the free carrier concentration to the effective mass N / m * was also determined. The analysis of the absorption coefficient indicated that this ternary defect chalcopyrite compound has both direct and indirect transitions in relevance to the energy gaps E g 1 dir , E g 2 dir and E g ind , respectively. These energy values decreased by irradiation, while they increased by annealing.

Structural and optical properties of flash evaporated AgInTe2thin films

Thin films of AgInTe2 were prepared on quartz substrates by a flash evaporation technique at substrate temperature ~303 K. The compositions of both the bulk and thin films, with thickness (~208–350 nm), were checked using energy dispersive X-ray spectroscopy (EDX). X-ray diffraction (XRD) measurements showed that AgInTe2 compound is characterized by a tetragonal structure while the as deposited films have amorphous nature. On annealing at 423 and 573 K (for two hours and under vacuum ~10−3 Pa), the films were identified to be single-phase, polycrystalline with a preferred (112) orientation. The optical properties of the films were investigated using spectrophotometric measurements of transmittance and reflectance at normal incidence in the wavelength range (~500–2500 nm). The refractive index (n) and the absorption index (k) of AgInTe2 were determined from the absolute values of the measured transmittance and reflectance. It was found that both (n) and (k) depend markedly on the temperature of heat treatment. The dispersion of refractive index in AgInTe2 was analyzed using the concept of the single oscillator model. Within this concept some dispersion parameters were determined for as deposited and annealed flash evaporated AgInTe2 films at 423 K for 2 h. The calculated values of β indicated that AgInTe2 films belong to ionic class. The ratio of the free carrier concentration to the effective mass (N/m*) were, also determined. The analysis of the absorption coefficient indicated that, this ternary chalcopyrite compound has three allowed direct transitions corresponding to three energies gaps Eg 1, Eg 2 and Eg 3. The crystal field (Δcf), the spin orbit (Δso) and the deformation potential (b) were calculated for both as deposited and annealed flash InAgTe2 films at ~423 K for 2 h.

Lattice dynamics and related properties of AIBIII and AIIBIV compounds, I. Elastic constants

AbstractThe present state of knowledge of the elastic properties of the ternary chalcopyrite compounds and some related materials is reviewed. Results of experimental elastic constant determinations are critically evaluated by comparing with other experimentally available material parameters that directly depend on the elastic constants. Possible reasons for existing discrepancies and obvious inconsistencies in the experimental data are discussed. The results of theoretical calculations of the elastic constants of these compounds based on different theoretical models and approaches are compared with experimental data and are assessed concerning achievable accuracy and reliability. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Investigation of structural anomaly and metal ordering in the solid solution 2ZnS–CuInS 2 by neutron diffraction

Powder samples of Zn 2 x (CuIn) 1 −x S 2 were synthesized by solid state reaction ( T=950°C) in sealed evacuated silica tubes. Based on neutron- and X-ray diffraction data structural parameters were determined using the Rietveld method. Samples with 0.4⩽ x⩽1 crystallize in the cubic sphalerite-type structure, samples with 0.1⩾ x⩾0 crystallize in the tetragonal chalcopyrite-type structure. A miscibility gap was found in the region 0.1< x<0.4, indicated by the coexistence of two phases, occuring as tetragonal domains in a cubic matrix. The anion displacement specifying the structural anomaly of ternary A IB IIIC 2 VI chalcopyrites relative to the binary AC zinc-blende analogon was considered in dependence on the chemical composition of the mixed crystals. This work extends the ‘conservation of tetrahedral bonds’ model to quarternary mixed crystals by modifying the equations for the ternary chalcopyrite compounds to incorporate the 2Zn↔(Cu,In) substitution as well as different types of cation ordering. A non-statistic Zn distribution on the cation sites of the chalcopyrite structure accompanied by Cu–In anti site occupation was deduced from the experimental determined anion parameter and metal site occupancies from the Rietfeld refinement of the neutron-diffraction data.

Influence of radiation on the optical parameters of AgInSe2 films

The analysis of optical constants of AgInSe2 thin films has been discussed. That ternary chalcopyrite compound shows an allowed direct transition near the fundamental absorption edge Eg1 in addition to a transition originating from crystal-field split levels Eg2. The optical band gaps of as-deposited films and γ-irradiated films at 0.5, 1.25, 2.75 and 3.5 Mrad were calculated. For the high γ doses (2.75 and 3.5 Mrad) the chalcopyrite film shows a three-fold optical structure near the fundamental edge due to crystal field and spin orbit splitting of the uppermost valence band. The extinction coefficient (k), refractive index (n) and dielectric constants (ε1, ε2) were also calculated for irradiated films.

Structural studies of CuAlSe 2 and CuAlS 2 chalcopyrites at high pressures

The ternary chalcopyrite compounds CuAlSe 2 and CuAlS 2 were studied up to 14.8 GPa in a diamond anvil cell by energy dispersive X-ray diffraction (EDXRD). The powder X-ray diffraction data at high pressure show that CuAlSe 2 undergoes a pressure-induced structural phase transition around 12.5 GPa from the chalcopyrite structure to NaCl type structure. CuAlS 2 exhibits structural stability up to 14.8 GPa. The pressure-induced structural phase transition observed in the EDXRD experiments is consistent with the theoretical total energy calculations. The results are consistent with the conclusions of a recent high-pressure Raman study reported for these compounds.