Efficiency Enhancement Of Solar Cells Research Articles

Efficiency and stability enhancement of perovskite solar cells using reduced graphene oxide derived from earth-abundant natural graphite.

Graphene – two-dimensional (2D) sheets of carbon atoms linked in a honeycomb pattern – has unique properties that exhibit great promise for various applications including solar cells. Herein we prepared two-dimensional (2D) reduced graphene oxide (rGO) nanosheets from naturally abundant graphite flakes (obtained from Tuv aimag in Mongolia) using solution processed chemical oxidation and thermal reduction methods. As a proof of concept, we used our rGO as a hole transporting material (HTM) in perovskite solar cells (PSCs). Promisingly, the use of rGO in the hole transporting layer (HTL) not only enhanced the photovoltaic efficiency of PSCs, but also improved the device stability. In particular, the best performing PSC employing rGO nanosheets exhibited a power conversion efficiency (PCE) of up to 18.13%, while the control device without rGO delivered a maximum efficiency of 17.26%. The present work demonstrates the possibilities for solving PSC issues (stability) using nanomaterials derived from naturally abundant graphite sources.

Efficiency enhancement of small molecule organic solar cells using hexapropyltruxene as an interface layer

The effect of a thin layer of hexapropyltruxene inserted at the interface between the electron donor boron subphthalocyanine chloride (SubPc) and its underlying hole contact in planar heterojunction solar cells was investigated.

Quantum dot-modified titanium dioxide nanoparticles as an energy-band tunable electron-transporting layer for open air-fabricated planar perovskite solar cells

Perovskite solar cells have been attracted as new representatives for the third-generation photovoltaic devices. Simple strategies for high efficiency with the long-term stability of solar cells are the challenges for commercial solar cell technology. Another challenge of the development toward industrial scale in perovskite solar cells is the production under the ambient and high humidity. In this sense, we successfully fabricated perovskite solar cells via solution depositions of all layers under ambient air with a relative humidity above 50%. Titanium dioxide (TiO2) nanoparticles with the roles for efficient charge extraction and electron transportation properties were used as an electron-transporting layer in the cell fabrication. The modification of TiO2 nanoparticles for energy band adjustment was done by doping with nontoxic cadmium sulfide (CdS) quantum dots. With the variation of CdS concentrations, energy band is not only changeable, but the enhancement of the perovskite solar cells efficiency could be achieved compared with the conventional cells made of pristine-TiO2 film and TiO2 nanoparticles.

Facile Fabrication of Plasmonic Enhanced Noble-Metal-Decorated ZnO Nanowire Arrays for Dye-Sensitized Solar Cells

Novel decoration of high aspect ratio zinc oxide nanowires (ZnO NWs) with noble metals such as Ag and Au nanoparticles (NPs) was demonstrated in this work. A facile method of chemical deposition with good controllability, as well as good homogeneity would be a huge advantage towards large scale fabrication. The highlight of this work is the feasibility of multiple component decoration such as a hybrid (co-exist) Ag-Au NPs decorated ZnO NWs formation that could be beneficial towards the development of nanoarchitectured materials with the most desired properties. The local surface plasmon effect (LSPR) of Ag and Au NPs were confirmed using extinction spectra and significant photoelectrochemical conversion efficiency (PCE) enhancement of dye-sensitized solar cells (DSSCs) was achieved. The Ag-NPs and hybrid Ag-Au NPs decorated ZnO NWs marked an impressive 125 and 240% efficiency improvement against pure ZnO NWs. The improved dye light extinction resulted from the LSPR effect that had enabled greater electron generation leading to improved PCE. As the complex design of oxides' nanoarchitectures have reached a point of saturation, this novel method would enable further enhancement in their photoelectrochemical properties through decoration with noble metals via a simple chemical deposition route.

45% efficiency enhancement of ZnO nanorod bulk-heterojunction solar cells by PbS QDs

Absorption of near-infrared (NIR) photons of solar energy which includes the ~40% of the sunlight energy is an effective approach to improve the photovoltaic performance of solar cells. In the present study, we have investigated PbS quantum dots (QDs) with different numbers of synthesis cycles (n) were introduced to ZnO nanorods (ZNRs) bulk-heterojunction (BHJ) solar cells. Our analysis revealed improving the power conversion efficiency (PCE) by absorbing the light in the visible and near-infrared regions. The Light absorption of solar cells was enhanced by PbS QDs which led to an increase in the photocurrent. With increasing (n), the PCE increases at first, then it decreases because of the attenuation of possible facilitation of exciton dissociation. For this reason, the number of cycles was optimized. As a result,byoptimizing the numbers of synthesis cycles (n), the PCE of PbS QD sensitized ZNR bulk heterojunction solar cells were improved from 2.76% to 4.01% by 1.45 times.

Absorption Efficiency Enhancement of Organic Solar Cells by Double Grating Structure

A novel surface-plasmon-enhanced structure is proposed to improve the absorption efficiency of organic solar cells in this paper. The PEDOT:PSS-Ag light-trapping structure introduced allows light to be reflected multiple times between the multilayer films, increasing the optical path length of light in the device and the light absorption by the absorption layer. The Ag film in P3HT:PCBM absorption layer can induce surface plasmons, which can enhance the electromagnetic energy around Ag film, improving the light absorption ability of organic solar cells. Based on the finite element method, the COMSOL-RF module is used to simulate the designed structure, and the absorption efficiency, electric field mode distribution and total power loss density distribution at different structural parameters were obtained. The results reveal that the absorption efficiency is more than 80% in the wavelength range of 485 nm to 520 nm in TE mode and more than 85% in the wavelength range of 495 nm to 595 nm in TM mode, providing a reliable basis for the development of high-performance organic solar cells.

Efficiency enhancement of pyridinium ylide dye-sensitized solar cells by introduction of benzothiadiazolyl chromophore: A computational study

Organic pyridinium ylide sensitizers NO108-NO111 with different anchoring groups show attractive applications in dye-sensitized solar cells. To elucidate the intrinsic sensitization mechanism of this series of dyes, theoretical calculations of electrochemical and spectroscopic properties for free and adsorbed ylides have been performed. Moreover, to prescreen and optimize suitable candidates for pyridinium ylide cells, the benzothiadiazole (BTD) group is introduced in the best-performing ylide NO111, and the afforded dye is coded as NO111-1. Comparing pyiridine-N-oxide in NO108, diethylmalonate in NO111 shows superior properties in terms of interfacial charge transfer, anti-aggregation, and long-term stability. It also demonstrates that the novel designed NO111-1-sensitized film possesses higher average theoretical maximum limit of short-circuit photocurrent density (JSCmax≈ 23 mA/cm2), and slower parasitic recombination than NO111 one. This result is expected to further reveal the effects of anchoring groups on properties of dyes, and is helpful for the design of more efficient pyridinium ylide dyes.

Luminescent europium-doped titania for efficiency and UV-stability enhancement of planar perovskite solar cells

Perovskite solar cells (PSCs) have demonstrated high power conversion efficiencies (PCEs) but poor stability against ultraviolet (UV) irradiation. Here, we report a one-pot synthesized luminescent europium-doped titania (Eu-TiO2) via chemical-bath deposition at low-temperature (70 °C) for planar PSCs, which enables simultaneous efficiency and UV-stability enhancement. We show that the Eu-TiO2 could effectively convert damaging UV photons into useful visible luminescence for additional light harvesting. A more optimal energy band alignment at the Eu-TiO2/perovskite interface leads to facilitated charge extraction and suppressed non-radiative recombination. The use of Eu-TiO2 in PSCs results in increased photocurrent and open-circuit voltage, yielding an enhanced PCE of 21.40% with relative to pristine TiO2 device (19.22%). More importantly, the Eu-TiO2 devices exhibit remarkably improved UV stability, retaining 75% of the initial PCE after exposing to UV illumination for 500 h, while the devices with pristine TiO2 lost the majority of their original PCEs in 150 h. As a proof-of-concept, we further demonstrate the scalability of our method by fabricating a large-area Eu-TiO2 film of 64 cm2 showing excellent uniformity.

Enhancing the efficiency of dye-sensitized solar cell by increasing the light trapping and decreasing the electron-hole recombination rate due to Ag@TiO2 core-shell photoanode structure

In this research, efficiency enhancement of dye-sensitized solar cell (DSSC) with Ag doped TiO2 core-shell (C–S) as plasmonic photoanode structure, abbreviated as Ag@TiO2, was investigated using Sol-Gel- Dr Blade method. Different amount of Ag in two different thick of photoanode were applied to enhance the light absorption for high-performance DSSCs. The localized surface plasmonic resonance (LSPR) effect of Ag@TiO2 showed an improvement in light trapping and power conversion efficiency (PCE) of developed DSSCs. Conforming to the conclusions under AM 1.5 spectrum, the prepared plasmonic solar cells exhibited 21.9% and 41.46% increase in PCE for 13 μm and 8.4 μm thick of photoanode, respectively.

Performance Enhancement of Betanin Solar Cells Co-Sensitized with Indigo and Lawsone: A Comparative Study.

Co-sensitization is an important strategy toward efficiency enhancement of solar cells by enabling better light harvesting across the solar spectrum. Betanin is a natural dye which absorbs light in the major portion of the incident solar spectrum (green region) and is the most efficient natural pigment used in dye-sensitized solar cells. This study investigates the performance enhancement of a betanin solar cell by co-sensitizing it with two natural pigments which show complementary light absorption, i.e., indigo and lawsone, absorbing in the red and blue regions of the solar spectrum, respectively. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital energies of the pigment molecules, derived from density functional theory (DFT) simulations, confirmed their optimal alignment with respect to the conduction band energy of the TiO2 semiconductor and reduction potential energy level of the I–/I3– electrolyte, a necessary requirement for optimal device performance. Lawsone solar cells displayed better performance, showing average efficiencies of 0.311 ± 0.034%, compared to indigo solar cells showing efficiencies of 0.060 ± 0.004%. Betanin was co-sensitized with indigo and lawsone, and the performances of the co-sensitized solar cells were compared. The betanin/lawsone co-sensitized solar cell showed a higher average efficiency of 0.793 ± 0.021% compared to 0.655 ± 0.019% obtained for the betanin/indigo co-sensitized solar cell. An 11.7% enhancement in efficiency (with respect to betanin) was observed for the betanin/indigo solar cell, whereas a higher enhancement of 25.5% was observed for the betanin/lawsone solar cell. Electrochemical impedance spectroscopy studies confirmed that the higher efficiency can be attributed to the higher electron lifetime of 313.8 ms in the betanin/lawsone co-sensitized solar cell compared to 291.4 ms in the betanin/indigo solar cell. This is due to the energy levels being more optimally aligned in lawsone compared to that of indigo, as observed in the DFT studies, and the lack of dipole moment in indigo, resulting in more efficient charge separation and charge transfer in lawsone.

Enhancing the performance of photovoltaic operating under harsh conditions using carbon-nanotube thermoelectric harvesters

This paper proposes a novel configuration for enhancing the efficiency of photovoltaics (PV) operating in high-temperature environment using a nano-thermoelectric carbon nanotube-based harvester attached to the backside of the solar cell (SC). The attached harvester will not only extract heat energy from the cell but will also convert this wasted heat energy into electrical energy. The proposed configuration has been fabricated and tested experimentally, where I–V measurements have been conducted. An overall enhancement in SC efficiency of 50%, with respect to reference cell, has been achieved using the proposed harvester. In addition, the harvester itself provided a power in the range of hundreds of microwatts that can be utilized in various low-power applications.

Efficiency enhancement of perovskite solar cells based on opal-like photonic crystals.

Perovskite solar cells have shown a tremendous interest for photovoltaics since the past decade. However, little is known on the influence of light management using photonic crystals inside such structures. We present here numerical simulations showing the effect of photonic crystal structuring on the integrated quantum efficiency of perovskite solar cells. The photo-active layer is made of an opal-like perovskite structure (monolayer, bilayer or trilayer of perovskite spheres) built in a T i O 2 matrix. Fano resonances are exploited in order to enhance the absorption, especially near the bandgap of perovskite material. The excitation of quasi-guided modes inside the absorbing spheres enhances the integrated quantum efficiency and the photonic enhancement factor. More specifically, a photonic enhancement factor as high as 6.4% is predicted in the case of spheres monolayer compared to an unstructured perovskite layer. The influences of sphere's radius and incident angle on the absorbing properties are also estimated. Those numerical results can be applied to the nascent field of photonic structuring inside perovskite solar cells.

Efficiency enhancement of organic solar cells enabled by interface engineering of sol-gel zinc oxide with an oxadiazole-based material

Abstract Organic solar cells (OSCs) have acquired much attentions owing to their advantages in terms of solution-processability, low-cost, lightweight and compatibility for large-scale roll-to-roll processing. Aside from materials design, studies on interface engineering are also crucial to enhance photovoltaic performance for the realization of high-performing OSCs. In this study, interface engineering on sol-gel zinc oxide (ZnO) electron-transporting layer (ETL) was conducted by introducing additional oxadiazole-based electron-transporting materials, PBD between ZnO ETL and photoactive layer. The significance of incorporating PBD on ZnO was demonstrated by investigating the change in optical, electrical and morphological properties of pristine ZnO ETL. Herein, the utilization of PBD could enhance ZnO film's conductivity, which was favorable for better charge transport ability. As compared to ZnO ETL, ZnO/PBD ETL had lower work function to facilitate more efficient electron extraction from the photoactive layer. Moreover, PBD could smoothen the ZnO film's morphology and improve hydrophobicity of the surface to provide uniform and intimate interfacial contact between ETL and the photoactive layer. As a result, through this hybrid bilayer strategy, inverted OSCs based on PBDB-T:IT-M photoactive layer system exhibited ~7% enhancement in the power conversion efficiency from 10.8% (ZnO-based device) to 11.6% (optimized ZnO/PBD-based device).

Enhancement of solar cell efficiency via luminescent downshifting by an optimized coverglass

A novel approach to enhance the solar cell efficiency via employing a luminescent downshifting mechanism is presented in this work. Gold metal ions were diffused into a commercially available sodalime silicate glass using a versatile field-assisted solid-state ion diffusion technique under different experimental conditions. Some of these samples were irradiated with ns-laser to segregate the diffused ions into dimers and trimers to enhance their luminescence characteristics. The consequent structural modifications in the glass matrix were examined using Fourier transform infrared spectroscopy. Optical absorption and luminescence measurements were performed to check the presence of resonant plasmonic absorption of nanoclusters and suitability of the samples as luminescent downshifters, respectively. At UV excitation wavelengths (260 and 340 nm), the doped samples downshifted the solar spectrum compared to their undoped counterparts. Furthermore, ns-laser irradiation of the doped samples significantly enhanced the luminescence intensity in comparison to the unirradiated samples. Real-time performance of these samples was tested by measuring the output power of a Si solar cell covered with the treated coverglass when illuminated with a solar simulator. Finally, the Vicker's micro-indentation was applied to conclude that ionic diffusion increased the glass hardness as well.

Understanding of Imine Substitution in Wide-Bandgap Polymer Donor-Induced Efficiency Enhancement in All-Polymer Solar Cells

The authors thank Dawei Wang (Sun Yat-Sen University),Yuexing Zhang (Hubei University), Xin Song (King Abdullah University of Science & Technology (KAUST)), Lingling Shui (SCNU), Jinwei Gao (SCNU), and Wei Wei (SCNU) for help in XRD, DFT calculation, PESA, contact angle, thin film thickness, and PL measurements, respectively. The authors thank SCNU Analysis & Testing Center for technical support.

Enhancement of Solar Cell Efficiency by Using TiO2 Nanostructure Doped Fe2O3 Dye and Effect Concentration of Solvent on Optical Properties

Solar energy has the greatest potential of all the sources of renewable energy, as only a small amount of this form of energy could be used, especially when other sources (coal, oil or gas) in the country have depleted. A solar cell is a solid electrical device that converts solar energy directly to electricity. Hybrid solar cells based on inorganic and organic compounds are a promising renewable energy source.
 Aims: The aim of this study was to prepare a nanostructured thin film of titanium oxide: doped iron oxide for enhancement of solar cell efficiency. In addition to studying the effect doped on optical properties of titanium oxide nanostructure thin film.
 Study Design: The spray pyrolysis deposition method used for preparation the nanostructure material.
 Place and Duration of Study: This study was conducted in the department of physics and department of materials sciences, Al-neelain university, between January 2016 and January 2019.
 Methodology: Thin films of Titanium Oxide (TiO2) doped Iron Oxide (Fe2O3) have been prepared by chemical spray pyrolysis deposition technique. A laboratory designed glass atomizer was used for spraying the aqueous solution. Which has an output nozzle about 1mm then the film was deposited on preheated cleaned glass substrates at the temperature of 400ºC. we used different concentration to study optical parameters. A 1.5 g TiO2 powder of anatase structure doped with 1.5 g of Fe2O3 was mixed with 2 ml of ethanol and stirred using a magnetic stirrer for 30 minutes to form TiO2 paste to obtain the starting solution for deposition and spray time was 10 s and spray interval 2 min was kept constant. The carrier gas (filtered compressed air) was maintained at a pressure of 105 Nm-2, and distance between nozzle and substrate was about 30 cm ± 1 cm. The thickness of the sample was measured using the weighting method and was found to be around 400 nm. Optical transmittance and absorbance were records in the wavelength range of (200-1100) nm using UV-Visible spectrophotometer (Shimadzu Company Japan).
 Results: The results obtained showed that the optical band gap decreased from 5.58 eV before doping to (3.9, 3.81, 3.81 and 3.81 eV) after doped for TiO2:Fe2O3 thin films, this result refers to the broadening of secondary levels that product by TiO2: doping to the Fe2O2 thin films. Also, the results showed the variation of refractive index with wavelength for different concentration after doped of TiO2:Fe2O3 films from this figure, it is clear that n decrease with low concentration and increase with high concentration after doped that mean the density is decreased of this films. In addition the extinction coefficient of TiO2:Fe2O3 thin films recorded before doped and with different concentration (1.1, 1.2, 1.5 and 1.6 mol/L) and in the range of (300 – 1200) nm and after doped it observed from that the extinction coefficient, decrease sharply with the increase of wavelength for all prepared films and all the sample after doped is interference between them accept the sample before annealing is far from the other sample.
 Conclusion: Based on the results obtained doping of titanium oxide increases the efficiency of TiO2 thin film in DSSC. It also proves that the fabrication of TiO2 thin films by spray pyrolysis deposition method is successful.

Efficiency enhancement of perovskite solar cell by modifying the TiO 2 with Ag/TiO 2 core–shell nanowires

Different ratio incorporation of Ag/TiO 2 core–shell nanowires (ATCSN) into TiO 2 as an electron transport layer of perovskite solar cells (PSCs) is studied. This structure can prevent the formation of silver halides between perovskite and silver nanowire. It is found that because of the effective improvement of light absorption and separation of photo-generated electron–hole pairs, the introduction of ATCSN leads to increase of short current density and photoelectric conversion efficiency (PCE) of PSCs. 20 mg incorporation of ATCSN PSCs exhibits the best performance of PCE and a 17.7% increase is achieved compared to the control sample.

Efficiency enhancement of Cu2BaSnS4 experimental thin-film solar cell by device modeling

Copper barium tin sulfide (CBTS) is a direct band gap earth abundant, non-toxic and quaternary semiconductor compound. It is used as absorber because of its direct band gap of 1.9 eV. A numerical guide is proposed for CBTS-based photovoltaic cell to enhance the efficiency of experimentally designed device with introducing Cu2O as back surface field (BSF) layer by means of numerical modeling. Device optimization was performed in SCAPS–1D software under 1.5 AM illumination spectrum. After introducing BSF layer and optimized physical parameters, promising result was achieved with PCE of 9.72%, Voc of 0.81 V, Jsc of 15.73 mA/cm2 and FF of 78.23%. The promising outcomes of this work will give a guideline for the feasible production of high-efficiency inorganic CBTS-based photovoltaic cells.

Cold Crystallization Temperature Correlated Phase Separation, Performance, and Stability of Polymer Solar Cells

Summary Fabrication of non-fullerene (NF)-based polymer solar cells (PSCs) has been an arduous task involving various approaches to optimize the morphology of blend film for superior performance. In this work, unique exothermic peaks can be observed in differential scanning calorimetry first heating scan of the blend films, which are assigned to the cold crystallization temperature (TCC) of NF acceptors when blended with different degree of crystallinity polymers, and TCC contains the phase information at quenched stage of the film development. A linear correlation between the phase separation parameters and TCC was established, which helps to select the appropriate donor for a specific acceptor. Utilizing multiple polymer-NF blend systems, we report an expectation TCC value between 210°C and 230°C, which would promise balanced domain size, purity, and consequentially superior performance. Further investigation revealed that TCC can also be used to evaluate the thermal stability.

Wave optics light-trapping theory: mathematical justification and ultimate limit on enhancement

This paper addresses a number of important and underlying theoretical and practical questions regarding the recently developed wave optics light-trapping theory for solar cells. We provide a rigorous and complete justification of its mathematical validity, using the second law of thermodynamics as well as fundamental properties of resonant scattering as described by the temporal coupled-mode theory. For maximal absorption, all optical modes supported by a solar cell structure must couple and only couple to the incident channel of sunlight radiation. For the first time to the best of our knowledge, we derive the ultimate limit of light trapping, which depends positively on the number of optical modes and hence on the periodicity of the structure. The ultimate limit is reached when every mode in the structure can couple only to the incident channel. Furthermore, we predict the theoretical optimal operating regimes of nanophotonic solar cells under practical scenarios. Our work reveals significant gaps between state-of-the-art nanophotonic solar cell designs and the ultimate limit, pointing to important future opportunities for nanophotonic light management for efficiency enhancement and cost reduction of solar cells.