Nanostructured Solar Cells Research Articles

Simulation of the functionality of ZnO, TiO2 and Ta2O5, and MoO2 carrier selective contacts of GaAs0.99Bi0.01 nanowire-based solar cells

Abstract Photovoltaic performance of perpendicularly aligned GaAs0.99Bi0.01/CSC/ITO core-shell nanowire solar cell is thoroughly investigated in this simulation based theoretical study for both electron selective contact (ESC) and hole selective contact (HSC) as carrier selective contact (CSC) shell around GaAs0.99Bi0.01 core nanowire. The overall performance has been compared with radial PiN doped GaAs0.99Bi0.01 NWSC to mark the improvement caused by carrier selectivity. ZnO, TiO2, and Ta2O5 materials have been chosen as ESC material and MoO2 is chosen as HSC material in order to carry out this comparative study. We have thoroughly performed geometry optimization test over a wide range of periods in order to select the optimized ITO (Indium Tin Oxide) thickness for obtaining maximum photo current generation. The maximum short circuit photo current density (Jsc) of 38.76 mA/cm2 is obtained with ZnO coated nanowire solar cell (NWSC) for a pitch (P) of 400 nm and ITO shell thickness of 90 nm. For this optimized geometry, TiO2, Ta2O5 and MoO2 coated structures offered Jsc of 35.82 mA/cm2, 35.69 mA/cm2, and 35.27 mA/cm2 respectively and the uncoated NW generated Jsc of 31.15 mA/cm2. The planar structure without coating exhibits a Jsc of 24.86 mA/cm2, which is significantly lower than the nanostructured solar cells. Finally Lumerical 3D charge transport simulator is used to perform the electrical stimulation of ZnO coated structure, which offers maximum ideal Jsc. A detailed electrical performance analysis of GaAs0.99Bi0.01/CSC/ITO unit nanowire solar cell for ZnO, TiO2, Ta2O5 as ESC and MoO2 as HSC have also been covered in this article which reveals that ZnO as ESC possesses promising potential for designing highly efficient solar cells as it offers a photo conversion efficiency(PCE) of the order of 25% and open circuit voltage (Voc) even for very less minority carrier lifetime (Ʈn) 0.1 ns of GaAs0.99Bi0.01 and 1ps Ʈn of ZnO.

Management of Light Absorption Based on Sidewall Reflection for Fabricating High-Performance Flexible Nano-Coned Sb2Se3 Thin Film Photovoltaics.

High performance and robustness are the key factors to boosting wearable and portable applications. Although the 1D crystal structure makes the Sb2Se3 thin film more tolerant to physical deformation upon bending, the conventional planar structures still cannot undergo repeated mechanical bending due to the induced stress/strain inside devices, which can be well addressed by constructing three-dimensional nanostructures. Besides, the electron diffusion length has two values, 0.3 μm in the [221] direction and 1.7 μm in the [001] direction, in the Sb2Se3 thin film, which limits the absorber thickness, for getting an effective carrier collection; thus, a strong light trapping effect enabling sufficient light harvesting is needed to allow the use of a very thin light absorption layer. Herein, the nanoconed Sb2Se3 solar cells have been designed, and their light absorption behaviors were investigated within a finite-element simulation under the substrate back-reflection, indicating that the reflection of the bottom part always works positively, while the effect of the nanocone sidewall on absorption enhancement largely depends on its geometry, arising from resonant or scattering modes. These results provide a practical guide in designing/establishing an easier/simpler way to fabricate high-performance and mechanically stable flexible nanostructured Sb2Se3 thin film solar cells.

Chemical Bath Deposition of ZnO/ZnGa2O4 Core-Shell Nanowire Heterostructures Using Partial Chemical Conversion.

The development of innovative heterostructures made of ZnO nanowires is of great interest for enhancing the performances of many devices in the fields of optoelectronics, photovoltaics, and energy harvesting. We report an original fabrication process to form ZnO/ZnGa2O4 core-shell nanowire heterostructures in the framework of the wet chemistry techniques. The process involves the partial chemical conversion of ZnO nanowires grown via chemical bath deposition into ZnO/ZnGa2O4 core-shell nanowire heterostructures with a high interface quality following their immersion in an aqueous solution containing gallium nitrate heated at a low temperature. The double-step process describing the partial chemical conversion relies on successive dissolution and reaction mechanisms. The present finding offers the possibility to fabricate ZnO/ZnGa2O4 core-shell nanowire heterostructures at low temperatures and over a wide variety of substrates with a large surface area, which is attractive for nanostructured solar cells, deep-UV photodetectors, and piezoelectric devices.

Influence of Annealing Process on Cu2O Nanofilm and the Efficiency of Annealed p-Cu2O/n Si Nanostructure Solar Cell Prepared by Thermal Evaporation Technique

Influence of Annealing Process on Cu2O Nanofilm and the Efficiency of Annealed p-Cu2O/n Si Nanostructure Solar Cell Prepared by Thermal Evaporation Technique

Perovskite half tandem v-shaped grating nanostructure solar cells: Improvement by light trapping and carrier transfer towards efficiency enhancement

In this paper, the enhancement of the perovskite solar cells (PSCs) efficiency through the implementation of a half-tandem structure featuring two absorbent layers of MAPbI3 and MoTe2 with a V-shaped nanostructured grating was investigated. MoTe2 was utilized as the second lower absorbent with a smaller bandgap than the first and upper absorbent, MAPbI3, to cover the incident light absorption in the infrared wavelength range. Additionally, the structure was also optimized by introducing a nanostructured V-shaped grating to increase the light propagation path and improve the absorption in the active layers. Also, the critical role of the electron transfer layer (ETL) and hole transfer layer (HTL) in carrier transfer and prevention of charge leakage was examined for materials including TiO2, TiO2-Gr (5%) nanocomposite, and Al-doped ZnO (AZO) as ETLs, and Cu2FeSnS4 (CFTS) and reduced Graphene Oxide (rGO) as HTLs in four distinct cell configurations. In this study, the optical and electrical models were solved to determine the optimal solar cell structure and materials through a comparative analysis of structures. Our findings revealed substantial improvements in short-circuit current density (Jsc), open-circuit voltage (Voc), and power conversion efficiency (PCE), where they increased from 15.27 to 31.55 mA/cm2, 0.91 to 1.30 V, and 11.78 to 27.63%, respectively. This resulted in a 2.35 times efficiency enhancement for the nanostructured V-shaped half-tandem solar cell with MAPbI3 (250 nm) and MoTe2 (150 nm) as absorbent layers, AZO (40 nm) as ETL and rGo (40 nm) as HTL compared to the planar non-tandem solar cell with MAPbI3 (250 nm) as absorbent layer, TiO2 (40 nm) as ETL and CFTS (40 nm) as HTL.

Optimized absorption of light in perovskite nanowire solar cells

Metal halide perovskite nanowires (PrvNWs) have recently emerged as an interesting path for nanostructured solar cells. Here, we model the absorption of light in PrvNW arrays for varying diameter and length of the PrvNWs and period for the array by solving the Maxwell equations. For long enough bare PrvNW arrays, we find that the optimum diameter is fixed to that which places the absorption peak from the HE11 waveguide mode in the PrvNWs to the vicinity of the bandgap wavelength. In contrast, when we include a transparent conductive oxide (TCO) top contact layer, the optimum diameter shifts to a larger value by 100 nm. The origin of this shift is traced to a reduced reflection at the interface between the TCO layer and the PrvNW array when the PrvNW’s diameter is larger. Overall, we find that 1500 nm long PrvNWs can reach 90% of the broadband absorption potential, making this system of high interest for photovoltaics.

All layers patterned conical nanostructured thin-film silicon solar cells for light-trapping efficiency improvement

Thin-film silicon solar cells (TSSC) has received great attention due to its advantages of low cost and eco-friendly. However, traditional single-layer patterned solar cells (SPSC) still fall short in light-trapping efficiency. This article presents an all layers patterned (ALP) conical nanostructured TSSC to enhance the low absorption caused by the thin absorption layers. The Finite-Difference Time-Domain result shows that a photocurrent density up to 41.27 mA/cm2 can be obtained for the structure, which is 31.39% higher than that of the SPSC. An electrical optimization simulation of doping concentration was carried out on the parameters of the optically optimal structure of the model. The power conversion efficiency is 17.15%, which is 1.72 times higher than that of the planar structure. These results demonstrate a success for the potential and prospect of the fully patterned nanostructures in thin-film photovoltaic devices.

The fingerprint of charge transport mechanisms on the incident photon-to-current conversion efficiency spectra of perovskite solar cells

Perovskite solar cells (PSCs), the most promising nanostructured solar cells for large-scale production, have been fabricated with different types of electron and hole collectors to improve efficiency and stability. Incident photon-to-current conversion efficiency (IPCE) is an important measurement to evaluate the optical/electrical behavior of the structure to modify the device structure. In this research, we have investigated how different mechanisms affect the IPCE spectra and the difference between short-circuit current density (Jsc) recorded from the current density-voltage (J-V) and the IPCE curves of n-i-p PSCs. Results show that by removing the electron-transport layer (ETL) in a device with a compact PSK layer, the IPCE spectrum does not change and only a slight shift of interference peak position is observable. By removing the hole-transport layer (HTL), not only IPCE value drops substantially for all wavelengths, its shape (including interference peaks) deforms significantly in the 500–800 nm wavelength range. In the case of cells with imperfect HTLs, only a slight change in this range (not the blue range) is observable. Utilizing different charge-transport and PSK materials, we have shown how significant the nonlinearity of the device's characteristics (such as charge-transfer resistance) with light intensity increases in the difference between Jsc value from J-V and integrated Jsc from IPCE curves. Selecting charge-collecting layers also directly affect interference peaks in IPCE spectra, for instance using TiO2 nanograss as ETL or CuIn0.75Ga0.25S2/carbon hole-collector instead of Spiro OMeTAD/Au hole-collector results in disappearing interference peaks.

Effective index model as a reliable tool for the design of nanostructured thin-film solar cells

Nanostructured anti-reflection coatings (ARC) are used to reduce the reflectivity of the front surface of solar cells. Computational electromagnetism helps to evaluate the spectral reflectivity of of this type of ARC using several approaches. They typically require large computational resources both in time and hardware elements (memory allocation, speed of processors, etc.). Long computational times may jeopardize optimization processes based on the iterative evaluation of a given merit function that depends on several parameters. Then, simplified analytic methods can speed up this evaluation with moderate computational resources. In this contribution we adapt an Effective Index Model (EIM) to the case of the design of an ARC made with nanoparticles (NP) embedded in a medium at the front surface of a thin-film silicon solar cell. Our approach modifies the discrete dipole approximation method to adapt it to the geometric and material properties of the NPs. The results obtained from the analytic method are compared with those evaluated through a Finite Element Method (FEM) for several cases involving variations in the size and geometry of the NP arrangement, obtaining reflectances that differ less than 10% for the worst case analyzed but bieng about 100 times faster than the FEM.

Block copolymer interfaces investigated by means of NMR, atomic force microscopy and dielectric spectroscopy

Self-assembly of block copolymers (BC) is a key feature for bottom-up patterning that is applied in the fabrication of templates for nanostructured membranes, photonic nanodevices, or solar cells. The wide range of possible BC applications is because the dissimilar blocks can be appropriately selected to form distinct domains with controllable dimensions and functionalities. An important representative of these materials is polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblock copolymer. This copolymer is of considerable academic interest and therefore it is examined by a plethora of experimental techniques to elucidate its structure and molecular dynamics. Particularly worth investigating is the interphase, consisting of polymer chains located at the interface of crystallite-amorphous and inter-domain regions, which codetermines the properties of such a system. It is shown that below the melting point of the PEO, the majority of the amorphous PEO are occupying interfacial sites and are represented by the rigid amorphous fraction (RAF) which can be monitored by dielectric and nuclear magnetic resonance spectroscopies. Moreover, two independent NMR spin-diffusion experiments reveal the asymmetrical nature of PS-PEO interface indicating a significant fraction of the PEO phase under the influence of stiff, adjacent polystyrene. An analysis of complementary thermal calorimetry and X-ray scattering data confirms the presence of microphase-separated morphology as well as the semicrystalline nature of PEO component. Lamelar domain architecture was confirmed by atomic force microscopy data acquired in the case of thin copolymer film.

Lead-free MAGeI3 as a suitable alternative for MAPbI3 in nanostructured perovskite solar cells: a simulation study

The lead is a heavy metal with hazardous impacts on environment and human life. Lead-free perovskite solar cells have attracted much attention in recent years, due to eco-friendly characteristics. Meanwhile, Pb-containing cells showed the highest efficiencies among the various types of cells. Hence, designing novel Pb-free solar cells with comparable or better performance than the Pb-containing ones is highly required. In this work, a lead-free methyl-ammonium-germanium-iodide (MAGeI3)-based perovskite solar cell with ITO/TiO2/MAGeI3/Spiro-OMeTAD/Ag multilayer nanostructure has been proposed and its main characteristics including open-circuit voltage (VOC) and power conversion efficiency (η) have been evaluated and compared with those of MAPbI3-based cell, in simulation study. The VOC and η of the MAGeI3-based cell (1.18V and 11.9%) have been found comparable with those of the MAPbI3 one (1.10V and 14.6%). These results can excite more attention to Ge as a more environment-friendly element than Pb, in highly efficient upcoming perovskite solar cells.

The Shading Influence on the Economic Viability of a Real Photovoltaic System Project

Renewable resources for producing energy for self-consumption are growing, namely solar energy. This work focuses on the comparison of photovoltaic systems for energy production for self-consumption on a property in three different regions of Portugal using traditional and emerging technologies, without batteries’ implementation. According to Portuguese law, there is no stipulated value for selling surplus energy produced by a self consumption unit, to the public grid. In order to analyse the economic viability of the project, two scenarios are studied: the delivery, at zero cost of the surplus energy produced to the grid, and its sale. Furthermore, the same analysis is carried out considering partial shading on the photovoltaic generator. The results show that if there is no surplus production sale to the grid, the project becomes economically unviable for the four PV technologies. Otherwise, for the traditional technologies, the project is economically viable, presenting a payback time lower than 10 years. Using emerging technologies, the project becomes economically unviable. When applying partial shading on the generator, the project becomes, in all the scenarios under study, economically unviable. It can be concluded that introducing nanostructures in solar cells to power an infrastructure is not, for now, the best solution from an economic point of view, considering the current legislation. In addition, the shading makes the projects under study unviable, as it is a factor that cannot be controlled in its entirety.

Comparative analysis between traditional and emerging technologies: economic and viability evaluation in a real case scenario

This research work aims to study photovoltaic systems that generate energy for self-consumption using different traditional technologies, such as silicon, and emerging technologies, like nanowires and quantum. The photovoltaic system without batteries was implemented in a residential property in three different places, in Portugal. According to Portuguese Law, the sale of surplus energy to the grid is possible but the respective value for its selling is not defined. To evaluate the project viability, two different analyses are considered: with and without the sale of surplus energy to the grid. Results show that if there is no sale of excess energy produced to the grid, the project is not economically viable considering the four different technologies. Otherwise, using traditional technologies, the project is economically viable, presenting a payback time lower than 10 years. This shows that the introduction of nanostructures in solar cells is not yet a good solution in the application of solar systems namely with the current law. Furthermore, independently of the used technology, the current Portuguese law seems to difficult the investment return, which should not be the way to encourage the use of renewable sources.

Investigation of bacterial pigment from Serratia nematodiphila as a sensitizer for a nanostructured solar cell

Investigation of bacterial pigment from Serratia nematodiphila as a sensitizer for a nanostructured solar cell

Theoretical Insights into the Coupled Optoelectronic Analysis of InP truncated nanopyramid/Germanium Ttandem Solar Cells

The rapid progress in photovoltaic sector is motivating researchers to carry out exhaustive investigation of highly efficient, cost-effective solar cells by lowering active material requirements or employing nanostructured Solar Cells (SCs). The detailed-balancing Shockley-Queisser limit of efficiency for thin-film or nanostructure single-junction p–n junction SC imposes a restriction on the Power Conversion Efficiency (PCE) corresponding to a particular material. However, by stacking multiple layers of variable bandgap energy materials, the efficiency of the SC can be enhanced to exceed the Shockley-Queisser limit in a multijunction (tandem) SC. In this article, we have stacked two semiconducting layers of different bandgap energies in series in the form of InP truncated nanopyramid (TNP) as a top subcell (Eg = 1.35 eV) grown over Ge substrate as a bottom subcell (Eg = 0.78 eV) and explored the optoelectronic study of this InP TNP on Ge multijunction (tandem) SC using the Ansys Lumerical software. The height of InP TNP nanostructure and thickness of Ge substrate are optimized to achieve equal current density (Jsc) in order to fulfill the current matching condition for a tandem SC. Jsc of 23.1 mA/cm2 and 22.9 mA/cm2 are obtained for InP TNP with height h1 = 1 μm and Ge substrate with height h2 = 700 nm, respectively. For the electrical analysis of the InP TNP and Ge subcells, we have optimized the doping profile of the p-n region of each subcell in order to obtain a similar electrical Jsc. Finally, we have obtained the J-V plot of the proposed tandem SC using the mathematical equations for two series connected photovoltaic cells.

Properties of High Efficiency Nanostructured Copper Indium Gallium Selenide Thin Film Solar Cells

Nowadays it is widely acknowledged that solar photovoltaic energy is one of the preferred options for sustainable management of the future energy needs of the world. For this, new technological processes, known as second and third generations, based on the use of thin films and nanomaterials, have recently been developed in order to reduce the cost of solar cells. Over the past few years, the yield of second-generation Cu(In, Ga)Se2 thin-film cells has exceeded 22 %. It was found that as nanostructured materials such as nanowire arrays often have a higher light absorption rate than thin films, they can therefore be used. This article aims to design and model nanostructured CIGS thin film solar cells based on indium tin oxide (ITO) nanowires. Modelling provides information on the operation of CIGS solar cells, as well as on the mechanisms of absorption and electric charge transport. The purpose of this work is to evaluate the electrical and optical characteristics (ISC, VOC, FF, η) of a ZnO/CdS/CIGS heterojunction thin film structure. Thus, an optimum efficiency of 17.57 % and a form factor of 76.56 % were achieved. Afterwards, the Mo film rear contact was replaced with ITO nanowires which were introduced into the CIGS-based solar cell. The results indicated that the solar cells under study exhibited very good photovoltaic performance, with an efficiency of 21.26 %. It is worth noting that this performance is higher than that of the corresponding CIGS thin film cells. In addition, the large active surface area of the ITO nanowire electrode and the short distance that the charge must travel helped to improve charge collection in the nanostructure. This would certainly increase the short circuit current ISC, and consequently the electrical efficiency. The simulation was based on the low-field mobility model, and on Shockley-Read-Hall (SRH) and Auger carrier transport and recombination models which may be activated in ATLAS-SILVACO (2D).

Geometrical Optimization of Gallium Arsenide (GaAs) nanostructure based Solar Cells

In order to meet the demand of rising global power, the research on nanostructured solar cell is gaining momentum at a massive rate. Planar solar cells are less efficient compared to nanostructured solar cells, since nanostructured solar cells have large surface to volume ratio. We have considered GaAs based nanostructures like nanowire (NW), nanocone (NC), and truncated nanocone (TNC), which are designed with a substrate height of 200 nm, nanostructure height of 2000 nm, and diameter ranging from 60 nm to 220 nm with four different filling ratios (FR) of 0.3, 0.5, 0.7, and 0.9. We have investigated the absorption spectra, electric field profiles, and photogeneration profile of the proposed nanostructures for the wavelength range of 300–860 nm considering the Finite Element Method (FEM) as implemented in COMSOL Multiphysics. Considering the optical absorption spectra, we have calculated the optical short circuit density (Jsc) analytically. We have observed that the optical current density for the geometrically optimized nanowire, nanocone, and truncated nanocone are 27.85 mA/cm2, 30.78 mA/cm2 and 27.27 mA/cm2 respectively. This variation in optical current is due to the different light reflection, and absorption capability of the nanostructures, which is confirmed from the absorption, transmittance, and reflectance profile of the nanostructures.

A small-molecule-templated nanostructure back electrode for enhanced light absorption and photocurrent in perovskite quantum dot photovoltaics

A nanostructured spiro-OMeTAD can be fabricated via nanoimprint soft lithography and realizes back-side nanostructured perovskite quantum dot solar cells showing improved photovoltaic performance due to the enhanced light absorption and photocurrent.

Plasmonic Photocurrent Improvement in P3HT:PCBM Organic Solar Cells

The need to develop and deploy large-scale, cost-effective, renewable energy is becoming tremendously important in the last few decades. Nanostructured organic solar cells have the long-term potential to provide low cost, and high-efficiency renewable energy. In recent years, photovoltaic cells based on nanoparticles blended with semiconducting polymers have achieved good performance and distinguished power conversion efficiencies, greater than 17%. These structures include various sizes and shapes of metal nanoparticles. Intensive research is being done towards achieving organic solar cell efficiency of 20%. In this work, a detailed numerical simulation is done for a proposed nanostructured organic solar cell design. Different nanoparticle shapes and sizes are considered in the active layer (P3HT:PCBM) to obtain a highly efficient organic solar cell.

Optimization and Comparison of Photovoltaic Parameters of Zinc Oxide (ZnO)/Graphene Oxide (GO) and Zinc Oxide (ZnO)/Carbon Quantum Dots (CQDs) Hybrid solar cell using Firefly Algorithm for application in Solar Trigeneration System in Commercial Buildings

Solar cells formed by the combination of organic and inorganic nanoparticle semiconductors are gaining interest in today’s era because of their major features, such as being suitable for scalable solar power conversion and being of low cost to produce desirable photovoltaic devices. This work is an attempt to develop two forms of hybrid solar cells, one by the amalgamation of zinc oxide and carbon quantum dots and second, by incorporating graphene oxide into zinc oxide. In this study, optimization, validation, and comparison of the photovoltaic parameters of the two nanostructured solar cells were attempted using the Artificial Neural Network technique. The ANN was instructed using the Firefly Algorithm. The input parameters are the spectral power density and temperature. The output parameters are the short circuit current (ISC), open-circuit voltage (VOC), fill factor of the cell (FF), and maximum voltage point prediction (VMPP). The results obtained for both the hybrid solar cells were compared and it was noted that the addition of CQDs to ZnO resulted in a considerable increase in the values of ISC, VOC and FF. The output obtained by the ANN trained model was compared with the results obtained from the experimental tests. It is observed that there is considerable agreement between the results obtained from the ANN and experimental values. The optimized values of VOC, ISC, FF, VMPP, Incident Photon to Current Efficiency (IPCE), Power Conversion Efficiency (PCE) for ZnO/GO are 0.623 V, 0.546 mA, 62%, 0.509 V, 36.95%, 9.12% respectively. Similarly values of VOC, ISC, FF, VMPP, IPCE, PCE for ZnO/CQDs are 0.636 V, 0.597 mA, 68%, 0.531 V, 40.72%, 10.35% respectively. Therefore, the precise values of all the stated parameters were obtained for both the cells after optimization and hybrid cells made of CQDs proves to be a better candidate. Also, the desirable value of the coefficient of correlation (R) is obtained, approximately close to 1, which means that the fabricated samples are efficient for useful applications. Proper execution of this algorithm on any model of the hybrid solar cell can lead to an evolution in the field of solar cells, resulting in the improvement of efficiency. These optimized cells have been utilized to propose two models of solar trigeneration system used in a commercial building North Service Centre (Olefin building) of Haldia Petrochemicals Limited, Haldia, West Bengal, India. The trigeneration systems were based on photovoltaic modules, heat pump and photovoltaic-thermal collectors. The objective is to provide enough electricity, domestic hot water, heating and cooling power to meet the typical demand of a single office building. System performance has been predicted and evaluated in the work. Considerations should be made regarding the physical constraints imposed by the environment where the installation has to be performed. The location should be carefully selected to achieve maximum efficiency.