Improvement Of Cell Efficiency Research Articles

Heavy Alkali Treatment of Cu(In,Ga)Se2Solar Cells: Surface versus Bulk Effects

AbstractChalcopyrite solar cells achieve efficiencies above 23%. The latest improvements are due to post‐deposition treatments (PDT) with heavy alkalis. This study provides a comprehensive description of the effect of PDT on the chemical and electronic structure of surface and bulk of Cu(In,Ga)Se2. Chemical changes at the surface appear similar, independent of absorber or alkali. However, the effect on the surface electronic structure differs with absorber or type of treatment, although the improvement of the solar cell efficiency is the same. Thus, changes at the surface cannot be the only effect of the PDT treatment. The main effect of PDT with heavy alkalis concerns bulk recombination. The reduction in bulk recombination goes along with a reduced density of electronic tail states. Improvements in open‐circuit voltage appear together with reduced band bending at grain boundaries. Heavy alkalis accumulate at grain boundaries and are not detected in the grains. This behavior is understood by the energetics of the formation of single‐phase Cu‐alkali compounds. Thus, the efficiency improvement with heavy alkali PDT can be attributed to reduced band bending at grain boundaries, which reduces tail states and nonradiative recombination and is caused by accumulation of heavy alkalis at grain boundaries.

Plasmon-Assisted Crystalline Silicon Solar Cell with TiO2 as Anti-Reflective Coating

The present study focuses on the employment of TiO2 (titanium dioxide) film as an anti-reflective coating (ARC) on thin crystalline silicon (Si)-based solar cells along with the incorporation of plasmonic silver nanoparticles (Ag NPs) on its front surface having ITO (Indium Tin Oxide) as top metal contact. The response of solar cell has been studied in context of the external quantum efficiency (EQE) and the photovoltaic current-voltage characteristics. The EQE is enhanced appreciably in the entire wavelength range of 300 to 1100 nm (from 13.26% for bare Si solar cell to 61.93% for solar cell having both TiO2 and Ag nanoparticles at a wavelength of 600 nm), on incorporating anti-reflective TiO2 coating and Ag nanoparticles on the thin Si solar cell. A significant increment in the power conversion efficiency from 9.53% (bare cell) to 16.04% (cell with anti-reflective coating of TiO2 thin film and silver nanoparticles) has also been observed. The presence of TiO2 film reduces the reflection of incident light from the top Si surface and hence appreciably improves solar cell efficiency. Besides this, Ag NPs help in trapping more light due to the plasmonic effect and hence result in further improvement in solar cell efficiency. The achieved results are encouraging for the commercial development of thin Si-based solar cells with TiO2 ARC and Ag NPs.

Numerical Analysis of Single Negative Broadband Metamaterial Absorber Based on Tri Thin Layer Material in Visible Spectrum for Solar Cell Energy Harvesting

A broadband nanostructure metamaterial absorber (MA) based on tri-layer metallic-optical-thin film molded shape is proposed for visible spectrum solar energy scavenging. This MA is investigated for photon mobility to achieve significant photon conversion and absorption to integrate into solar cell technology, IoT components, or energy harvesting. Design and analysis of the proposed MA were performed using the “Yee’s Finite-Difference Time-Domain (FDTD)” method based on commercially available CST microwave studio simulation software. Numerical computational tools depict an absorptivity of higher than 80%, which covered nearly the visible region 430~627 THz. This significant absorptivity can be maintained with both transverse electric and transverse magnetic polarizations. Furthermore, molded shape with two-dimensional split and nano-square window expedites the unit cell to exhibit single negative (SNG) metamaterial characteristics and photon conversion acceleration. Compared with related previously reported broadband absorbers, the proposed MA has promising application, in conventional solar cell efficiency improvement and emitter.

Inhibited aggregation of lithium salt in spiro-OMeTAD toward highly efficient perovskite solar cells

Organic small molecule material, spiro-OMeTAD, is widely used in perovskite solar cells as the hole transport material due to its desirable properties, such as suitable highest occupied molecular orbital energy levels, high solubility and good film forming ability. However, the aggregation and hydrolysis of the common additive, Li-TFSI, in the spiro-OMeTAD, lead to the existence of voids/pinholes in the hole transport layer, which limits further improvement of perovskite solar cell efficiency. Here, we develop a low-cost and easy-fabrication technique to substantially reduce the undesired voids in hole transport layer by modifying it with commercially available PbI2. The strong interaction between the PbI2 and the TBP retards the evaporation of TBP, which hinders the agglomeration of Li-TFSI and generation of voids in the HTL. Consequently, the HTL shows a dramatically improved mobility and efficiency of charge carrier extraction, leading to a better response to steady-state condition with less than 1s for the corresponding photovoltaic device (where the control device shows more than 26s). A champion power conversion efficiency of over 20% is obtained from PbI2 added devices by optimizing its adding amount. This work provides a facile and effective strategy to improve the performance of the hole transport materials and perovskite solar cells.

Quantitative trade-off analysis of infrared light absorber effects contributed to photovoltaic cells performance

It is widely known that organic and inorganic coatings absorb more of the solar spectrum, and due to a considerable share of 45% infrared radiation, the energy efficiency drop by the increasing of temperature should be considered. The purpose of this study is to implement a system to characterize silicon solar cell performance and increasing energy efficiency by imposing such coatings as infrared wave absorber to overcome the Shockley–Queisser limit. In other words, this research efforts to improve cell efficiency (coating effects) in addition to imposing the efficiency decreasing effects (temperature increasing). The core of the study is laboratory and experimental set-up measurements to find an organic absorber with the highest absorbance. Ruthenium-based dye, N719, has shown the best performance in experimental conditions and heat extraction to enhance cell energy efficiency. Due to increased absorption in a solar cell (SC), to control the temperature rise of the system, the fan is used as a cooling system. The imposing of N719 results in increasing energy efficiency by up to 1.38%. It is worth noting that a 1.60% increase in energy efficiency is observed due to temperature reduction by 2 degrees.

Re-evaluating the role of phosphinic acid (DINHOP) adsorption at the photoanode surface in the performance of dye-sensitized solar cells.

Dineohexyl phosphinic acid (DINHOP) is a popular amphiphilic molecular insulator considered as the most efficient co-adsorbent (co-grafter) for the improvement of the photovoltaic performance of TiO2 based hybrid solar cells. Although the effect of its incorporation on the improvement of cell performance has been well demonstrated, the mechanisms through which it affects the photovoltaic and electrodynamic parameters of the cells are not yet clear. Here we re-examine the mechanism through which the DINHOP co-adsorbent affects the photovoltaic and electrodynamic parameters of dye-sensitized solar cells. Although DINHOP is widely believed to inhibit (passivate) recombination across the TiO2/electrolyte interface, we demonstrate that this is sublte, noticeable only for a very high concentration (e.g. 750 μM) of DINHOP, co-sensitized with a dye. For the most frequently used DINHOP concentrations (e.g. 75 μM and 375 μM), an observed increase of the diffusion coefficient and recombination rate could be directly associated with a decrease of total intra-gap states in TiO2. For a DINHOP concentration as low as 75 μM, the conduction band edge of TiO2 moves upward due to the combined effect of charge accumulation and a decrease in the total number of intra-gap states leading to an effective enhancement of the DCCS VOC, where the decrease in total intra-gap states does not contribute positively. The decrease of total intra-gap states enhances both the transport and recombination rates of charge carriers by the same fraction due to a transport-limited recombination process. On the other hand, adsorption of DINHOP molecules at higher concentrations such as 375 μM and 750 μM additionally modifies the distribution of intra-gap states, affecting the nonlinear recombination parameter of charge carriers at the anode-electrolyte interface, leading to an overall enhancement of the DSSC VOC. In all cases, incorporation of DINHOP results in an overall improvement of the solar cell efficiency (∼14% compared with the reference one), with a maximum for a concentration of 375 μM, where no inhibition of recombination was observed. Interestingly, for this DINHOP concentration, we estimate that 1 DINHOP molecule per every 12 molecules of dye occupies the intra-gap states of the TiO2 surface. The results presented in this work elucidate the physical phenomena involved in the interaction of co-adsorbents, pre-treatments or additives with the electrolyte at the surface of the TiO2 photoanode of dye-sensitized solar cells and can be easily adapted to study other electrochemical systems.

Performance improvement of ultrasonic spray deposited polymer solar cell through droplet boundary reduction assisted by acoustic substrate vibration

This study demonstrates the performance improvement of ultrasonic spray deposited bulk heterojunction type polymer solar cells through droplet boundary reduction assisted by acoustic substrate vibration of varying frequencies between 0–20 kHz. The optimum performance was achieved at 15 kHz of applied frequency, where ∼68% improvement in short-circuit current density and ∼85% improvement in overall cell efficiency were observed compared to the reference devices fabricated on stationary substrates. The performance enhancement is mainly attributed to the improved film morphology due to uniform and homogenous droplet spreading and coalescence under the influence of acoustic vibration. Systematic improvement was observed until 15 kHz when smooth films with significantly reduced droplet boundaries were observed with surface roughness around 10 nm only. However, beyond this point, higher frequencies were found to have detrimental effect on film formation. Significant improvement was observed for every cell parameter for 15 kHz samples. Almost ∼16% enhancement in carrier generation rate and ∼46% enhancement in exciton dissociation probability were observed, as estimated from the photo-current analysis. Urbach energy estimation reveals that the films, prepared at 15 kHz substrate vibration, forms less amount of band edge localized defect states (Eu (no vibration) = 161 meV and Eu (15 kHz) = 120 meV), resulting into reduced non-radiative recombination and better performances. The presented approach opens up new pathways for uniform and scalable thin film growth through acoustic substrate vibration assisted ultrasonic spray deposition technique, which would be beneficial for large scale industrial organic photovoltaic production.

Efficient electrocatalytic conversion of carbon dioxide in a low-resistance pressurized alkaline electrolyzer

Electrochemical carbon dioxide conversion offers a means to utilize carbon dioxide and simultaneously store excess renewable energy. To be economical, industrial carbon dioxide electroreduction systems require high energy efficiencies to minimize electrical input. To this end, these systems need high product selectivity at low cell voltages and industrially viable current densities. Here, a liquid phase flow cell electrolyzer using a silver catalyst for carbon dioxide conversion to carbon monoxide is reported. Significant improvements in cell efficiency are demonstrated through the synergistic combination of three factors: minimal electrode spacing (0.25 mm flow field), pressurization (50 bar), and alkalinity (5 M KOH). Diminished electrode spacings reduce ohmic losses, pressurization increases carbon monoxide selectivities, and alkaline conditions improve reaction kinetics. The combination of these three factors enables an uncorrected full cell energy efficiency of 67% at 202 mA/cm2, the highest reported above 150 mA/cm2. This system maintains a competitive energy efficiency of 47% at a high current density of 941 mA/cm2.

Passivating Detrimental DX Centers in CH3 NH3 PbI3 for Reducing Nonradiative Recombination and Elongating Carrier Lifetime.

After a period of rapid, unprecedented development, the growth in the efficiency of perovskite solar cells has recently slowed. Further improvement of cell efficiency will rely on the in-depth understanding and delicate control of defect passivation. Here, the formation mechanism of iodine vacancies (VI ), a typical deep defect in CH3 NH3 PbI3 (MAPbI3 ), is elucidated. The structural and electronic behaviors of VI are like those of a DX center, a kind of detrimental defect formed by large atomic displacement. Aided by the passivation mechanism of DX centers in tetrahedral semiconductors, it is found that the introduction of Br strengthens chemical bonds and prevents large atomic displacements during defect charging. It therefore reduces the defect states and diminishes electron-phonon coupling. Using time-domain density functional theory (DFT) combined with nonadiabatic molecular dynamics, it is found that the carrier lifetime can be enhanced from 3.2 ns in defective MAPbI3 to 19 ns in CH3 NH3 Pb(I0.96 Br0.04 )3 . This work advances our understanding of how a small amount of Br doping improves the carrier dynamics and cell performance of MAPbI3 . It may also provide a route to enhance the carrier lifetimes and efficiencies of perovskite solar cells by defect passivation.

Enhancement Open Circuit Voltage of Calcium Titanate AR Coated Magnesium Solar Cell

The present research aims to enhance the open circuit voltage of fabricated solar cell through Anti–Reflection (AR) coating on the cell substrate. Solar cell is fabricate using ITO Glass, titanium dioxide, magnesium and redox. Calcium Titanium Oxide (CaTiO3) is chosen as the AR coating material for constructing thin film layer on fabricated solar cell. Selected AR coating material have unique features such as orthorhombic, biaxial, non-radioactive and non-magnetic with electron bulk density of 3.91 g/cm3 respectively. Commonly, voltage generation of the multi crystalline solar cell is low (12% to 14%) due to much reflection of inward sun radiation. Deposition of AR coating on the substrate (fabricated solar cell) can minimize the reflection loss of sun radiation. The maximum improvement in solar cell efficiency after AR coating has been reported as 19.3%. Sputter coating technique is more favorable for thin film coating due to its salient features like uniform coating thickness controlled by time. This uniform coating thickness absorbs more sun radiation. Radio Frequency (RF) magnetron sputter coating technique is utilized in the current research to deposit CaTiO3 on solar cells. Prior to coating, the AR material is pelletized using Universal Testing Machine (UTM). The substrate are coated under varying time duration of 15-minutes, 30-minutes and 45-minutes in order to analyze the variation in open circuit voltage. The deposition of coating on the substrate are confirmed using SEM and FESEM. Open circuit voltage of controlled atmosphere studies for pure and AR coated solar cells (fabricated) are examined. Controlled atmosphere tests of AR coated thin films are conducted by placing the substrate inside a solar simulator and the solar simulator consist of IR thermometer (To measure Temperature), solar power meter (To measure Radiation) and multimeter (To measure Open circuit voltage). Neodym daylight lamp is used to control the radiation in solar simulator. The improvement in cell voltage proves that thin film AR coating considerably minimizes the reflective loss.

Shape-controlled growth of three-dimensional flower-like ZnO@Ag composite and its outstanding electrochemical performance for Ni-Zn secondary batteries

A novel three-dimensional (3D) flower-like ZnO@Ag composite is successfully synthesized through a simple and facile process, which is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).When evaluated as an anodic material for nickel-zinc alkaline secondary batteries, the 3D flower-like ZnO@Ag composite exhibits the high discharge capacity (627 mAh g−1) and long cycle life (830 cycles). The outstanding electrochemical performance is ascribed to the Ag nanoparticles enhancing electron conductivity and the uniform flower-like structure providing enough electrochemical reaction sites, so as to reduce electrode polarization and improve cell efficiency. Furthermore, the possible growth mechanism of 3D flower-like ZnO@Ag composite has been proposed. The effect of silver content on formation of ZnO@Ag composites was also investigated in detail, indicating the appropriate silver content plays a key role in forming a defined 3 D flower-like structure for the ZnO@Ag composite.

Tunable optoelectronic properties of radio frequency sputter-deposited Sb2Se3 thin films: Role of growth angle and thickness

In thin film photovoltaics, antimony selenide (Sb2Se3) is making a mark as an important absorber layer for its attractive structural, optical, and electrical properties. Several deposition techniques are used to grow Sb2Se3 films, albeit growth angle-dependent physical properties of Sb2Se3 films are yet to be explored in a systematic manner. In this work, we investigate the roles of growth angle (in the range of 0°-87°) and thickness (250 and 1000 nm) in governing optoelectronic properties of Sb2Se3 films grown by radio frequency sputter deposition technique. It is interesting to note that upon increasing the growth angle, a systematic enhancement in the optical band-gap takes place. This is accompanied by a systematic reduction in the work function of these amorphous films with increasing growth angle. Subsequently, after postgrowth annealing at 573 K for 180 s (in vacuum) all Sb2Se3 films undergo a structural phase transition from amorphous to crystalline one. Following this, the band-gap and work function of these films also get modified. This study paves the way to fabricate Sb2Se3 films having tunable optoelectronic properties like absorption coefficient, band-gap, and work function. Thus, it should be extremely useful to select Sb2Se3 films having optimal thickness and optoelectronic properties to fabricate Sb2Se3 absorber layer-based multi-junction hole-blocking solar cells having improved cell efficiencies.

Influences of Structural Modification of Naphthalenediimides with Benzothiazole on Organic Field-Effect Transistor and Non-Fullerene Perovskite Solar Cell Characteristics.

Developing air-stable high-performance small organic molecule-based n-type and ambipolar organic field-effect transistors (OFETs) is very important and highly desirable. In this investigation, we designed and synthesized two naphthalenediimide (NDI) derivatives (NDI-BTH1 and NDI-BTH2) and found that introduction of 2-(benzo[d]thiazol-2-yl) acetonitrile groups at the NDI core position gave the lowest unoccupied molecular orbital (LUMO; -4.326 eV) and displayed strong electron affinities, suggesting that NDI-BTH1 might be a promising electron-transporting material (i.e., n-type semiconductor), whereas NDI-BTH2 bearing bis(benzo[d]thiazol-2-yl)methane at the NDI core with a LUMO of -4.243 eV was demonstrated to be an ambipolar material. OFETs based on NDI-BTH1 and NDI-BTH2 have been fabricated, and the electron mobilities of NDI-BTH1 and NDI-BTH2 are 14.00 × 10-5 and 8.64 × 10-4 cm2/V·s, respectively, and the hole mobility of NDI-BTH2 is 1.68 × 10-4 cm2/V·s. Moreover, a difference in NDI-core substituent moieties significantly alters the UV-vis absorption and cyclic voltammetry properties. Thus, we further successfully employed NDI-BTH1 and NDI-BTH2 as electron transport layer (ETL) materials in inverted perovskite solar cells (PSCs). The PSC performance exhibits that NDI-BTH2 as the ETL material gave higher power conversion efficiency as compared to NDI-BTH1, that is, NDI-BTH2 produces 15.4%, while NDI-BTH1 gives 13.7%. The PSC performance is comparable with the results obtained from OFETs. We presume that improvement in solar cell efficiency of NDI-BTH2-based PSCs is due to the well-matched LUMO of NDI-BTH2 toward the conduction band of the perovskite layer, which in turn increase electron extraction and transportation.

Incorporation of CdCl2 surface treatment into the CdS/ZnTe hetero-junction solar cell device structures for efficiency improvement

p-ZnTe thin film semiconductors have been successfully used as an absorber material to n-CdS window layer by effectively optimising the ZnTe absorber layer thickness. In order to create a two terminal hetero-junction diode from the n- and p- type materials, two ohmic electrical contacts are required. This was achieved by depositing n-CdS layers on glass/fluorine-doped tin oxide (FTO) conducting substrate and evaporating Au on p-ZnTe layer. The ZnTe layer was successfully electroplated on CdS thin film grown on glass/fluorine-doped tin oxide (FTO) conducting substrates. The device structures were subjected to heat treatment in air with and without CdCl2 surface treatment using temperature of 400oC and duration of 10 minutes. The incorporation of the CdCl2 treatment led to enhancement in the solar cell efficiency. Solar cells developed from glass/FTO/n-CdS/p-ZnTe/Au device structure gave an open circuit voltage (Voc) of 450 mV, short circuit current density (Jsc) of 7.26 mAcm-2 and fill-factor (FF) of 0.31 resulting in 1.0% efficiency (η) for n-CdS/p-ZnTe heterostructure annealed ordinarily in air. After treating the top surface of n-CdS/p-ZnTe heterostructure with CdCl2 solution, all the solar cell parameters improved with Voc of 480 mV, Jsc of 24.0 mAcm-2 and FF of 0.46 giving a total efficiency of 5.3%. For the CdS/ZnTe heterostructures treated without and with CdCl2 solution, the rectification factors (RF) observed from the I-V characteristics under dark condition for these devices are 101.0 and 102.2 respectively. Both devices show ideality factors (n) in excess of 2.0 and the reverse saturation currents are 79.4 and 0.16 nA for hetero-junction structures without and with CdCl2 treatment respectively. The improvement in the solar cell efficiency can be accredited to the integration of the CdCl2 treatment in the p-n junction cells. Keywords: Solar Cells, p-n Junction Diodes, n-CdS, Heterostructure, p-ZnTe, CdCl2 surface treatment.

Morphology luminescence and photovoltaic performance of lanthanide-doped CaWO4 nanocrystals

Multifunctional materials have attracted recent attention due to their various applications in many fields. In this work, CaWO4 nanocrystals were prepared by a hydrothermal method. Nanoparticles, nanowires, and micro-sized structures were obtained by controlling the reaction temperature, Ca2+-to-WO42− ratio and type of dopant. The influence of rare earth ions on the morphology and luminescence properties was investigated. Upconversion and downconversion luminescence behaviors showed CaWO4 to be an excellent host for rare earth doping. CaWO4:Er3+ nanowires were also used in dye-sensitized solar cells (DSSCs) to improve device performance. Increased light harvesting caused by improved dye loading capacity and enhanced light scattering led to improved cell efficiency. Moreover, reduced charge recombination due to the additional energy levels of CaWO4:Er3+ was another reason for the improved cell efficiency. Therefore, in this work, we demonstrated the synthesis of CaWO4 nanocrystals and the control of their morphology and luminescence by rare earth doping, which has significant future applications in lighting and display. The applications in DSSCs provide a new strategy to achieve high-performance solar cells by using nanocrystals via increased light harvesting and reduced charge recombination.

Application of Core-Shell Metallic Nanoparticles in Hybridized Perovskite Solar Cell-Various Channels of Plasmon Photovoltaic Effect.

We analyze the microscopic mechanism of the improvement of solar cell efficiency by plasmons in metallic components embedded in active optical medium of a cell. We focus on the explanation of the observed new channel of plasmon photovoltaic effect related to the influence of plasmons onto the internal cell electricity beyond the previously known plasmon mediated absorption of photons. The model situation we analyze is the hybrid chemical perovskite solar cell CHNHPbICl with inclusion of core–shell Au/Si0 nanoparticles filling pores in the AlO or TiO porous bases at the bottom of perovskite layer, application of which improved the cell efficiency from 10.7 to 11.4% and from 8.4 to 9.5%, respectively, as demonstrated experimentally, mostly due to the reduction by plasmons of the exciton binding energy.

Ternary Metal Chalcogenides: Into the Exciton and Biexciton Dynamics.

Intra-band-gap state-induced low-toxicity colloidal I-III-VI ternary metal chalcogenide nanocrystals (NCs) have emerged as promising alternatives to the toxic Cd- and Pb-chalcogenides for different optoelectronic and bioimaging applications. In this Perspective, we provide the primary understanding of the intra-band-gap state-induced photoluminescence (PL) of I-III-VI NCs, specifically CuInS2 and AgInS2, as a function of particle size and composition and correlated with time-resolved PL measurements. The intra-band-gap state-induced ultrafast exciton and biexciton dynamics are discussed in detail to unravel the subpicosecond carrier relaxation dynamics through transient absorption measurement. Furthermore, ultrafast dissociation of the biexciton on Au@CuInS2 hybrid NCs has been revealed to be due to the presence of Au, which has direct relevance to the improvement of the solar cell efficiency. The proper fundamental insight of the ultrafast exciton and biexciton dynamics of these materials will enable utilization of ternary metal chalcogenides in photovoltaic as well as light-emitting devices.

Effect on the reduction of the barrier height in rear-emitter silicon heterojunction solar cells using Ar plasma-treated ITO film

In this study, we investigated the effect of plasma treatment on an indium tin oxide (ITO) film under an ambient Ar atmosphere. The sheet resistance of the plasma-treated ITO film at 250 W (37.6 Ω/sq) was higher than that of the as-deposited ITO film (34 Ω/sq). Plasma treatment was found to decrease the ITO grain size to 21.81 nm, in comparison with the as-deposited ITO (25.49 nm), which resulted in a decrease in the Hall mobility. The work function of the Ar-plasma-treated ITO (WFITO=4.17 eV) was lower than that of the as-deposited ITO film (WFITO = 5.13 eV). This lower work function was attributed to vacancies that formed in the indium and oxygen vacancies in the bonding structure. Rear-emitter silicon heterojunction (SHJ) solar cells fabricated using the plasma-treated ITO film exhibited an open circuit voltage (VOC) of 734 mV, compared to SHJ cells fabricated using the as-deposited ITO film, which showed a VOC of 704 mV. The increase in VOC could be explained by the decrease in the work function, which is related to the reduction in the barrier height between the ITO and a-Si:H (n) of the rear-emitter SHJ solar cells. Furthermore, the performance of the plasma-treated ITO film was verified, with the front surface field layers, using an AFORS-HET simulation. The current density (JSC) and VOC increased to 39.44 mA/cm2 and 736.8 mV, respectively, while maintaining a WFITO of 3.8 eV. Meanwhile, the efficiency was 22.9% at VOC = 721.5 mV and JSC = 38.55 mA/cm2 for WFITO = 4.4 eV. However, an overall enhancement of 23.75% in the cell efficiency was achieved owing to the low work function value of the ITO film. Ar plasma treatment can be used in transparent conducting oxide applications to improve cell efficiency by controlling the barrier height.

Enhanced Light Harvesting in Photovoltaic Devices Using an Edge-Located One-Dimensional Grating Polydimethylsiloxane Membrane.

In streamlined multipurpose applications for light management and protection, encapsulants are merged with photonic crystal structures into solar modules. We present an edge-located 1D grating, attachable polymer on the top of a photovoltaic module to provide a strategy for capturing solar light and improving cell efficiency. Large-area solar arrays suffer from space utilization problems due to nonactive area. The introduction of periodically patterned gratings with specific geometric range is highly preferred to redirect the light toward photovoltaic active areas. To realize optimized broadband light diffraction for solar devices, the theoretical analysis of one-dimensional line patterned diffraction gratings was performed through wave-optic-based simulation. Based on the experimental results, the replica molding-based patterning method was adopted to fabricate the grating polymer for low-cost thin-film production. Also, we demonstrated enhanced light collection by grating patterned encapsulants with improved current density in comparison to the performance of a flat surface.

Effect of combination of natural dyes and post-TiCl4 treatment in improving the photovoltaic performance of dye-sensitized solar cells

Herein, dye-sensitized solar cells (DSSCs) have been sensitized with natural red dye (extracted from red spinach) and yellow dye (extracted from turmeric) and five different combinations of red and yellow dyes (at different volume ratios) to determine the optimum combination of red and yellow dyes for the maximum cell efficiency. In addition, the effect of post-TiCl 4 treatment in improving cell efficiency has been studied. From UV-vis absorption spectrum, higher absorbance and cumulative absorption properties over the entire visible region show that the combination of red and yellow dyes absorbs light better than the individual red or yellow dyes. DSSCs sensitized with red and yellow dyes have a photoconversion efficiency of 0.416% and 0.921%, respectively. DSSCs sensitized with the combination of red and yellow dyes showed higher cell parameters than the DSSCs sensitized with the individual yellow or red dye. The photoelectrical parameters of DSSCs cosensitized with the optimum combination of dyes (40% red + 60% yellow) were as follows: short-circuit current ( I sc ) = 5.343 mA, open-circuit voltage ( V oc ) = 0.493 V, fill factor (FF) = 0.481, and overall photoconversion efficiency = 1.267%. However, after the treatment of FTO (fluorine doped tin oxide) / TiO 2 with TiCl 4 , a significant amount of improvement in the I sc , V oc , and FF was observed. DSSCs fabricated with TiCl 4 -treated FTO/TiO 2 and sensitized with the optimum combination of red and yellow dyes showed the following cell parameters: I sc = 5.829 mA, V oc = 0.498 V, and F·F = 0.541. Hence, the efficiency obtained was 1.572%, which is almost 1.24 times higher than that of the DSSCs fabricated without TiCl 4 treatment. Finally, the possible effect of water content in the combination of dyes has been observed with a fixed amount of red dye in the combination.