Layers For Solar Cell Applications Research Articles

Strain engineering of electronic, mechanical, and optical properties of orthorhombic III–V group monolayers by first principles calculations

Using first principles calculations, we systematically investigated the effects of strain engineering on the electronic, mechanical, and optical properties of two-dimensional (2D) orthorhombic III–V group materials, including BN, BP, BAs, AlN, AlP, and GaN. It is shown that all the III–V orthorhombic monolayers exhibit excellent mechanical anisotropy for Young’s modulus, Shear modulus, and Poisson’s ratio, especially for the AlN and GaN monolayers. AlN, AlP, and GaN are predicted to be indirect bandgap semiconductors, with their bandgap of 0.70, 0.15, and 0.53 eV, respectively. And BN is demonstrated to be a direct bandgap semiconductor (0.63 eV). Under uniaxial tensile strains, their electronic structures have non-monotonic anisotropic variations and these monolayers can be effectively modulated from metal to semiconductor, experiencing indirect–direct bandgap transitions. In addition, all the orthorhombic III–V materials exhibit highly anisotropic light-harvesting performances and the optical absorbance can be efficiently tailored with tensile strains applied along a- and b-directions. The strong optical absorptions in the visible light regions suggested that AlN, BN, and GaN may be optically tunable 2D materials for component absorbance layers for solar cell applications. The excellent anisotropic and tunable electronic, mechanical, and optical performances indicate that the orthorhombic III–V monolayers are promising candidates for potential applications of optoelectronics and photovoltaics.

Influence of annealing temperature on nano crystalline description for CuZnS thin films

Copper Zinc Sulphide (Cu0.5Zn0.5S) alloy and thin films were fabricated in a vacuum. Nano crystallized (CZS) film with thick 450±20 nm was deposit at substrates glasses using thermal evaporation technique below ~ 2 × 10− 5 mbar vacuum to investigated the films structural, morphological and optical properties depended on annealing temperatures ( as-deposited, 423, 523 and 623) K for one hour. The influences annealed temperature on structurally besides morphologically characteristics on these films were investigated using XRD and AFM respectively. XRD confirms the formation a mixed hexagonal phase of CuS-ZnS in (102) direction with polycrystalline in nature having very fine crystallites size varying from (5.5-13.09) nm. AFM analysis shows the uniform distribution of closely packed grains, grain size for that film diverge on ranges as of (52.37 to 89.25) nm after annealed. The optical properties of all films prepared had been examined for the wavelength range 400 - 1000 nm using UV-Vis-NIR spectrometer. The band gaps of (Cu0.5Zn0.5S) films are obtained in the range of 2.4 to 1.9 eV, which makes it a suitable absorber as well as buffer/window layer for solar cell applications.

Binary ZnS–ZnO films as an alternative buffer layer for solar cell applications

In this research, binary ZnS–ZnO films were fabricated by a two-step process, offering an alternative buffer layer solution for photovoltaic solar cell applications. ZnS films were attained through thermal evaporation, after which they were annealed in air at separate temperatures resulting in films containing both ZnS and ZnO phases. Structural, electrical, ellipsometric, optical, and surface properties were examined in detail to elucidate their applicability as a buffer layer in photovoltaic applications. X-ray diffraction patterns revealed that the films exhibit cubic ZnS and hexagonal ZnO crystal structures, wherein crystallite size is augmented with higher annealing temperatures. ZnS films exhibited a needle-shaped surface morphology, as confirmed through atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) images. Annealing caused noteworthy modifications on the surfaces of the films. Additionally, absorption spectra denote two distinct absorption regions forming as a result of the annealing process, possibly indicating the emergence of ZnS and ZnO phases. Photoluminescence analyses demonstrate that binary ZnS–ZnO films exhibit greater emission intensities than single-phase ZnS films. Additionally, the annealing process caused the electrical resistivity of films to reduce from 1.28 × 105 to 3.84 × 101 Ω cm. These results suggest that binary ZnS–ZnO films produced via annealing can be considered as promising buffer layers in potential photovoltaic solar cell applications.

High-energy sputtering for the deposition of a conductive and adherent single molybdenum layer for solar cell applications

Molybdenum (Mo) thin films are thought to be an excellent back contact for CuIn1-xGaxSe2 (CIGS) solar cells. Mo films require high conductivity and good adhesion to glass substrates; however, these characteristics cannot be combined in sputtered Mo under the same deposition conditions. Direct current Magnetron Sputtering (DcMS) and High-Power Impulse Magnetron Sputtering (HiPIMS) were used to deposit Mo films on glass substrates, and the effects of working pressure and substrate bias on their characteristics were investigated. To begin, single layers of Mo were produced at pressures ranging from 0.2 to 1.4 Pa. The Mo films deposited at the lowest working pressure of 0.2 Pa were then subjected to a negative substrate bias varying from -50 to -200 V. All of the HiPIMS films adhered well to the glass substrate, whereas the DcMS films deposited at various pressures showed poor adhesion. Furthermore, our findings demonstrated that applying a negative substrate bias reduced the resistivity of Mo films to the lowest values of 2.56 × 10−5 Ω.cm and 2.771 × 10−5 Ω.cm, respectively, for the HiPIMS and DcMS-deposited films, while improving the adhesion of the DcMS-samples due to the development of films with homogenous stress distribution.

Fabrication of Europium-Doped CaF2 Films via Sol-Gel Synthesis as Down-Shifting Layers for Solar Cell Applications.

In the present work, an in-depth study on the sol-gel process for the fabrication of Eu-doped CaF2 materials in the form of thin films has been addressed for the production of down-shifting layers. Fine-tuning of the operative parameters, such as the annealing temperature, substrate nature and doping ion percentage, has been finalized in order to obtain Eu(III)-doped CaF2 thin films via a reproducible and selective solution process for down-shifting applications. An accurate balance of such parameters allows for obtaining films with high uniformity in terms of both their structural and compositional features. The starting point of the synthesis is the use of a mixture of Ca(hfa)2•diglyme•H2O and Eu(hfa)3•diglyme adducts, with a suited ratio to produce 5%, 10% and 15% Eu-doped CaF2 films, in a water/ethanol solution. A full investigation of the structural, morphological and compositional features of the films, inspected using X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX), respectively, has stated a correlation between the annealing temperature and the structural characteristics and morphology of the CaF2 thin films. Interestingly, crystalline CaF2 films are obtained at quite low temperatures of 350-400 °C. The down-shifting properties, validated by taking luminescence measurements under UV excitation, have allowed us to correlate the local environment in terms of the degree of symmetry around the europium ions with the relative doping ion percentages.

Halogenated graphene derivatives as an absorber layer for solar cell applications : A DFT study with vdw correction

Due to the flexible nature and high transparency of Graphene (G) in the ultraviolet to infrared spectrum, it is ideal for thin-film solar cell applications. To use graphene for such a purpose, there is a need to tune its band gap at Fermi level, and the most convenient method is chemical functionalization. So, in this study, we will investigate electronic and mechanical properties, along with the structure and stability analysis of halogenated (X) bilayer and trilayer graphene B(T)LG using density functional theory with van der Waals correction (vdw-GGA). These halogenated B(T)LGs are designed by adsorbing the top and bottom surfaces with fluorine (F) and chlorine (Cl) at the maximum possible separation. BLGs are designed as X/graphene/graphene/X with bernal (AB) and non-bernal (AA) stacking. TLGs are designed as X/graphene/graphene/graphene/X as AAA, ABA, and ABC stacking with 50% X termination at the top and 50% on the bottom side. Chlorination results in weak physisorption while fluorination results in chemisorption. Binding energies Eb found quite higher for fluorinated bilayer graphene derivatives. Halogenation of TLG disturbs Dirac cones at Fermi level in case of fluorine adsorption while remaining unaffected under chlorination. Due to repositioning of some states above EF, provide an additional path for intraband transition, made systems more conductive except for fluorinated bilayer graphenes F-BLGs. A small band gap of 0.2 meV and 0.04 eV appeared at Fermi level of fluorinated non-bernal and bernal configuration, respectively. An E-field applied normal to the plane of F-BLGs can further tune the band gap. Due to underestimation of Band gap using GGA, hybrid functionals HSE06 were used for better estimation.

Optimizing the performance of Cs2AgBiBr6 based solar cell through modification of electron and hole transport layers

This work investigates the potential of Cs2AgBiBr6 as an absorber layer for solar cell applications and explores ways to advance the PV performance of cells by studying different electron transport layers (ETLs) and hole transport layers (HTLs). The energy band diagrams of the Cs2AgBiBr6 based cell are analyzed with different ETLs and HTLs to illustrate how electrons and holes flow within the cell. Specifically, one of the proposed cells substitutes TiO2 with chlorine passivated tin oxide (Cl@SnO2), while the other uses phenyl-C60 -butyric acid methyl ester on tin oxide (C60 -SnO2) as the ETL. The PV characteristics of the Cs2AgBiBr6-based solar cell is evaluated using SCAPS 1D. The PV performance parameters of Cs2AgBiBr6-based solar cells has been analyzed in search of optimum thickness of Cs2AgBiBr6 layer. Subsequently, the impact of bulk defect density in Cs2AgBiBr6 layer at the obtained optimum thickness i.e., 611 nm has also been explored. C60-SnO2 is found to have higher electron mobility, work function, and stability than Cl@SnO2, making it a better choice for the ETL. The resulting PV parameters for the cell Cl@SnO2/CS2AgBiBr6/Me4PACz are: VOC - 1.527 V, JSC - 10.42 mA/cm2, FF − 75.66%, and PCE - 12.08%. While the cell SnO2-C60/Cs2AgBiBr6/Me4PACz delivers PV parameters VOC- 1.53 V, JSC- 12.81 mA/cm2, FF - 79.15%, and PCE - 13.43%.

Effect of annealing temperatures on the structural, optical, and electrical properties of Cu2Sb thin films

The Cu2Sb thin films were successfully synthesized by the chemical bath deposition method to form an as-prepared thin film and annealed at 300, 400, and 500 °C. The X-ray diffraction results of the Cu2Sb thin films were found with the CuSb2O6 phase for the as-prepared, 300 °C, and 400 °C films and exhibited crystallinity. Then, the thin film became amorphous after annealing at 500 °C. Field-emission scanning electron microscopy (FESEM) was used to examine surface morphologies. Linear optical, dispersion, optoelectrical, and nonlinear optical properties were evaluated. Furthermore, the energy bandgap (Eg), Urbach energy (Eu), and electrical properties were determined. It can be suggested that the optimum annealing temperature for our synthesized mixed-phase thin films should not exceed 400 °C. Finally, the majority of the carriers in the Cu2Sb thin film exhibited p-type conductivity. Thus, the distinctive parameters investigated for our thin-film materials show a further promising optical system in optoelectronic and nonlinear optical devices and a new absorber layer for solar cell applications.

1,8‐Octanedithiol as an Effective Intermediate Layer for Deposition of Cu Electrodes via Inkjet Printing and Laser Sintering on III–V Triple‐Junction Solar Cells

This research study combines surface modification techniques with back‐end‐of‐line (BEOL) methods for cost‐effective, scalable front contact electrode deposition on III–V solar cells. Copper nanoparticle grids are deposited by inkjet printing on surface‐modified III–V solar cells. The deposition of a self‐assembled monolayer (such as 1,8‐octanedithiol) as an intermediate layer is a proven method for surface modification to improve the wettability of the substrate surface and the adhesion of the printed copper nanoparticle structures on the substrate to perform inkjet printing of coherent and narrow electrode structures. Then, the printed copper ink is converted to a conductive copper grid by a picosecond pulsed laser with optimized settings and an additional galvanic plating step is required for the thickening of inkjet‐printed and laser‐sintered seeding layer for solar cell applications. As a result, an ohmic copper contact on III–V layer with low contact resistivity (5 mΩ cm2) is realized successfully. The processed solar cell shows a functioning behavior with 20% conversion efficiency.

The Effect of SiGe/PTAA Thin Film Thickness as An Active Layer for Solar Cell Application

This paper presents the results of electrical simulations at different active thickness layers of hybrid photovoltaic devices using GPVDM software. A combination of inorganic n-type semiconductor SiGe and organic p-type semiconductor PTAA has been chosen to be simulated in this research work. The thickness of SiGe and PTAA varies from 100 nm – 500 nm and 1000 rpm – 5000 rpm. The results show that the thickness of both semiconductor affects the electrical properties. Higher current density, Jsc, can be obtained as the thickness of SiGe increases. PTAA as an active layer had affected the value of open-circuit voltage, Voc. The SiGe combination with lower rpm depicted a higher value of Voc than the other combinations. The FF and efficiency rate of the solar panel is also presented in this work. This research focuses on the thickness combination of both semiconductors layer on the performance of its electrical characteristics.

Optimization of electrodeposition time on the properties of Cu2ZnSnS4 thin films for thin film solar cell applications

The Electrochemical deposition was used to create a quaternary CZTS (Cu2ZnSnS4) kesterite thin layer. An aqueous solution of CZTS was used to deposit a thin layer over Indium Tin Oxide. The effects of deposition time (variation) on CZTS thin films under ambient conditions were investigated in this study. Several available characterization systems were used to study the samples as they were produced. The polycrystalline description of the layer is investigated by X-ray diffraction. The SEM as well as AFM study show that the deposition time improved surface morphology and topography of CZTS thin films which increase several nm in grain size. Furthermore, depending upon the deposition duration that affect the thickness and crystallinity of the films prepared, the optical study reveals an acceptable band gap in a range of 1.71–1.42 eV. Characteristics of high-quality CZTS absorber layers for solar cell applications are determined by deposition time variation. To check the effect of this band gap variation (1.71–1.42 eV, depending upon the deposition time) on the performance of a CZTS based thin film solar cell, a simulation software SCAPS-1D is being used.

Investigation of Defects in Cs2SnI6‐Based Double Perovskite Solar Cells Via SCAPS‐1D

AbstractEffective conversion of solar photons into electrical power through the development of smart and eco‐friendly materials is one of the most extensively researched methods for generating renewable energy. In this work, an inorganic lead‐free double perovskite Cs2SnI6 material is employed as an active layer for solar cell applications, together with GO (graphene oxide) as electron transport layer (ETL) and Cu2O as hole transport layer (HTL). In order to find the most efficient photovoltaic device, a detailed theoretical study using the SCAPS‐1D simulation program is conducted. The device performance is monitored and analyzed by considering various HTLs, doping density in active layer, light intensity, ETL thickness, operating temperature, parasitic resistances, and the role of defects on device performance. The optimized device displays a power conversion efficiency of 23.64% with excellent photovoltaic characteristics. This theoretical study reveals that Cs2SnI6 can be a promising choice for solar cell applications as a lead‐free double perovskite material.

Interface engineering at electron transport/perovskite layers using wetting mesoporous titanium dioxide to fabricate efficient and stable perovskite solar cells

The unique photovoltaic features of perovskites have encouraged researchers to use them as an active layer for solar cell applications. Recombination issue at electron transport layer (ETL)/perovskite interface is one of the reasons for performance reduction in perovskite solar cells (PSCs) and need to address. Hereof, we developed a simple and cheap method to modify this interface by wetting the mesoporous TiO2 ETL using mixed solvents of γ-butyrolactone (GBL) and dimethyl sulfoxide (DMSO). With optimization of the ratio of GBL and DMSO, our results showed a smoother perovskite layer with fewer pinholes on it. In addition, ETL wetting affected perovskite grain sizes and passivated grain boundaries in it. The mentioned reasons reduced carriers' trap centers in the perovskite film and suppressed charge recombination processes within PSCs. The improved crystalline properties of the modified perovskite layer facilitate electron extraction at ETL/perovskite interface and reduce charge accumulation, which brings a champion efficiency of 18.72% for the treated devices higher than that of 15.21% for the untreated devices. Moreover, due to the boosted hydrophobic property of the modified perovskite film, the stability behavior of the related PSCs was improved remarkably.

NiO and MWCNT based hole transporting layers for solar cell applications

NiO and MWCNT based hole transporting layers for solar cell applications

Opto-electronic properties and solar cell efficiency modelling of Cu2ZnXS4 (X = Sn, Ge, Si) kesterites

In this work, first-principles calculations of Cu2ZnSnS4, Cu2ZnGeS4 and Cu2ZnSiS4 are performed to highlight the impact of the cationic substitution on the structural, electronic and optical properties of kesterite compounds. Direct bandgaps are reported with values of 1.32, 1.89 and 3.06 eV respectively for Cu2ZnSnS4, Cu2ZnGeS4 and Cu2ZnSiS4 and absorption coefficients of the order of 104 cm−1 are obtained, indicating the applicability of these materials as absorber layer for solar cell applications. In the second part of this study, ab initio results are used as input data to model the electrical power conversion efficiency of kesterite-based solar cells. In that perspective, we used an improved version of the Shockley–Queisser model including non-radiative recombination via an external parameter defined as the internal quantum efficiency. Based on predicted optimal absorber layer thicknesses, the variation of the solar cell maximal efficiency is studied as a function of the non-radiative recombination rate. Maximal efficiencies of 25.71%, 19.85% and 3.10% are reported respectively for Cu2ZnSnS4, Cu2ZnGeS4 and Cu2ZnSiS4 for vanishing non-radiative recombination rate. Using an internal quantum efficiency value providing experimentally comparable values, cell efficiencies of 15.88%, 14.98% and 2.66% are reported respectively for Cu2ZnSnS4, Cu2ZnGeS4 and Cu2ZnSiS4. We confirm the suitability of Cu2ZnSnS4 in single junction solar cells, with a possible efficiency improvement of nearly 10% enabled through the reduction of the non-radiative recombination rate. In addition, Cu2ZnGeS4 appears to be an interesting candidate as top cell absorber layer for tandem approaches whereas Cu2ZnSiS4 might be interesting for transparent photovoltaic windows.

Structural, surface and luminescent properties of SrF2:Eu annealed thin films

The effect of calcined temperature on the structural, surface and luminescent properties of a SrF2:Eu thin film were investigated for possible application as a downshifting layer for solar cell application. The film was deposited on sodium lime glass by a spin coating method and obtained after heat-treatment under Ar/H2 atmosphere. The thin film's structure as well as the morphology were investigated with X-ray diffraction and scanning electron microscopy, respectively. The elemental composition of the film was obtained with X-ray photoelectron spectroscopy (XPS). The XPS depth profile showed that oxygen and silicon segregated into the 600 °C calcined film and formed an intermediate layer. The XPS results for the SrF2 thin films confirmed that the elements of thin film existed in their stable form on the surface. The electric dipole allowed transitions of Eu2+ ions dominated the film's photoluminescent (PL) spectra at low calcination temperatures. The 5D0-7F0 PL transition of Eu3+ was, however, observed at elevated temperatures. The results suggested that Eu might be a good sensitizer for other lanthanide ions, such as Tb3+ and Er3+, at low temperature treatments.

A comparative study of CdS thin films grown on ultra-thin glass substrates by RF magnetron sputtering and chemical bath deposition

The structural, morphological and optoelectrical characteristics of cadmium sulfide (CdS) thin films grown on ultra-thin glass substrates via Radio Frequency (RF) magnetron sputtering and chemical bath deposition (CBD) have been explored in this study. CdS thin films were characterized using the X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), UV–Vis spectrophotometer and Hall effect measurement system. As obvious from XRD investigation, the stable hexagonal wurtzite crystalline structure with (002) preferential orientation was resulted from both deposition methods. FESEM study demonstrated uniform grain structure for the sputtered films. Compositional analysis confirmed that S/Cd ratio is 0.28 for the sputtered films and 0.20 for the CBD films. AFM study exhibited spherical crystal surface formation, hills and valleys for CBD films. The optical analysis showed a band gap of 2.40 eV and 2.32 eV for the sputtering and the CBD methods, respectively. Hall effect analysis recorded carrier concentration and resistivity in the order of 1013 cm−3 and 104 Ω cm, respectively. The experimental results recommend that the CdS thin films grown by the sputtering might be favourable as the window layer for solar cell application.

Artificial bee colony algorithm: a novel strategy for optical constants and thin film thickness extraction using only optical transmittance spectra for photovoltaic applications

An effective approach to determine thin film thickness (d) and optical constants (n,k,α) from transmittance spectrum with interference fringes is proposed. The developed strategy is based on applying the artificial bee colony (ABC) algorithm and Cauchy dispersion model. The accuracy test of this method has been assessed by using simulated and real tests. Simulated test is used to check the ability of ABC algorithm to determine the parameters of simulated transmittance spectra. Real test deals with the investigation of the determination approach on experimental measured transmittance spectra. Those spectra were measured from six elaborated samples of amorphous hydrogenated silicon (a-Si:H) thin films with different thicknesses, which will be used as an eco-friendly layer for solar cell applications. The obtained results noticeably show the high effectiveness of the developed strategy to accurately determine the thin film thickness and optical constants.

A comprehensive comparative study of CdTe thin films grown on ultra-thin glass substrates by close-spaced sublimation and RF magnetron sputtering

This study elucidates a comprehensive comparative study on the structural, morphological and electrical characteristics of cadmium telluride (CdTe) thin films grown on ultra-thin glass (UTG) substrates via close-spaced sublimation (CSS) and RF magnetron sputtering. Deposited CdTe films were characterized utilizing the X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and Hall effect measurement system. CdTe thin films were in cubic and hexagonal-cubic orientations based on the deposition methods. Micro-strain and dislocation density for sputtered films were very high compared to CSS films. Crystallite sizes were in the range of 30–40 nm for CSS films and 7–25 nm for sputtering films. Grain size was estimated to be around 2 µm and thickness was approximately 1.5 µm for both CSS and sputtering system. Resistivity was almost same as 6.98 × 104 Ω-cm and 6.57 × 104 Ω-cm for CSS and sputtered films, respectively. The experimental results suggest that the CdTe films grown by CSS might be favorable as the optimum absorber layer for solar cell application.

Theoretical modeling of a “giant” colloidal core–shell quantum dot with an alloyed interfacial layer for solar cell applications

We proposed a theoretical modeling of a “giant” colloidal core–shell quantum dot with a strain-adapting alloyed interfacial layer between the core and shell materials for solar cell applications. The recently modified detailed balance model [J. Appl. Phys. 125, 174302 (2019)JAPIAU0021-897910.1063/1.5086015] is further modified in this paper to obtain a more realistic conversion efficiency (CE) of the C d S e / C d S e x S 1 − x / C d S quantum dot solar cell. This proposed model computes the CE, considering the significant impact of the energy gap and oscillator strength simultaneously. The CE is investigated for different alloying factors “ x ” by considering the strain effect between the heterostructure. The results obtained in terms of CE and photoluminescence peak wavelength nearly approximate the experimental studies of similar dot structure and dimensions.