Conversion Efficiency Of Photovoltaic Cells Research Articles

Strain-Prompted Giant Flexo-Photovoltaic Effect in Two-Dimensional Violet Phosphorene Nanosheets.

As a second-order nonlinear optical phenomenon, the bulk photovoltaic (BPV) effect is expected to break through the Shockley-Queisser limit of thermodynamic photoelectron conversion and improve the energy conversion efficiency of photovoltaic cells. Here, we have successfully induced a strong flexo-photovoltaic (FPV) effect, a form of BPV effect, in strained violet phosphorene nanosheets (VPNS) by utilizing strain engineering at the h-BN nanoedge, which was first observed in nontransition metal dichalcogenide (TMD) systems. This BPV effect was found to originate from the disruption of inversion symmetry induced by uniaxial strain applied to VPNS at the h-BN nanoedge. We have revealed the intricate relationship between the bulk photovoltaic effect and strain gradients in VPNS through thickness-dependent photovoltaic response experiments. A bulk photovoltaic coefficient of up to 1.3 × 10-3 V-1 and a polarization extinction ratio of 21.6 have been achieved by systematically optimizing the height of the h-BN nanoedge and the thickness of VPNS, surpassing those of reported TMD materials (typically less than 3). Our results have revealed the fundamental relationship between the FPV effect and the strain gradients in low-dimensional materials and inspired further exploration of optoelectronic phenomena in strain-gradient engineered materials.

Performance prediction of a novel solar power tower system based on spectral beam splitting

Photovoltaic technology is currently the most widely used solar generation technology in engineering. The particular spectral response band of PV cells cannot convert all solar radiation into electricity. Meanwhile, some radiation will become heat, leading to an increase in cell temperature and a decrease in the conversion efficiency of photovoltaic cells. Spectral splitting technology is an effective technology to improve electrical generation efficiency and can achieve full spectrum utilization of solar energy. The current work involved (1) proposing a novel solar power tower comprehensive utilization system based on spectral splitting; (2) developing a spectral splitting thin film configuration by using the Needle method whose transmittance is higher than 90% against the band range of 510 nm-1, 020 nm; (3) setting up a spectral splitting PV panel whose cover glass is coated the developed film, and replacing the heliostat of SPT system by using such spectral splitting PV panels; (4) predicting the electrical power generation of the spectral splitting-based tower type concentrating solar power system. The results demonstrate that the power generation efficiency of the proposed system is 5.5% and 3.46% higher than PV power generation and SPT systems respectively.

Topotactic, Vapor-Phase, In Situ Monitored Formation of Ultrathin, Phase-Pure 2D-on-3D Halide Perovskite Surfaces.

Two-dimensional (2D) halide perovskites, HaPs, can provide chemical stability to three-dimensional (3D) HaP surfaces, protecting them from exposure to ambient species and from reacting with contacting layers. Both actions occur with 2D HaPs, with the general stoichiometry R2PbI4 (R: long or bulky organic amine) covering the 3D ones. Adding such covering films can also boost power conversion efficiencies of photovoltaic cells by passivating surface/interface trap states. For maximum benefit, we need conformal ultrathin and phase-pure (n = 1) 2D layers to enable efficient tunneling of photogenerated charge carriers through the 2D film barrier. Conformal coverage of ultrathin (<10 nm) R2PbI4 layers on 3D perovskites is challenging with spin coating; even more so is its upscaling for larger-area devices. We report on vapor-phase cation exchange of the 3D surface with the R2PbI4 molecules and real-time in situ growth monitoring by photoluminescence (PL) to determine limits for forming ultrathin 2D layers. We characterize the 2D growth stages, following the changing PL intensity-time profiles, by combining structural, optical, morphological, and compositional characterizations. Moreover, from quantitative X-ray photoelectron spectroscopy (XPS) analysis on 2D/3D bilayer films, we estimate the smallest width of a 2D cover that we can grow to be <5 nm, roughly the limit for efficient tunneling through a (semi)conjugated organic barrier. We also find that, besides protecting the 3D against ambient humidity-induced degradation, the ultrathin 2D-on-3D film also aids self-repair following photodamage.

THEORETICAL STUDY OF NEW CANDIDATE ORGANIC MATERIALS FOR PHOTOVOLTAIC APPLICATIONS

Our work consists of a theoretical prediction, through DFT and TD-DFT methods, of the electronic and optical properties of six conjugated organic compounds used as electron donor materials in BHJ solar cells, of which PCBM is the acceptor material. This study is necessary to discuss the effect of substituents (donor units) on the different properties of these compounds, and to predict promising materials in organic solar cells using the AMPS-1D simulation software. The results obtained show that all the molecules have good geometric, electronic and optical properties, thus showing an increase in the power conversion efficiency of photovoltaic cells based on these materials, which reaches a value of 17% for the molecule P-Eth-TEdotT-A.

Application of Photovoltaic (PV) Cell and Limited Factor

With the concept of carbon neutrality and carbon emissions peak, the Chinese government emphasize the importance of the application of renewable energy like photovoltaic energy. Internationally, some countries and regions already have ability to replace fossil energy with renewable resources such as wind, solar, wind, and hydrogen energy. This thesis focuses on photovoltaic energy and its applications. Photovoltaic energy usually uses monocrystalline silicon and polysilicon as raw materials, and this paper compares the advantages and disadvantages of both raw materials. The technology of building PV integration, which combines PV cells with buildings, and the technology that increases the conversion efficiency of PV cells by passivating the back contact of the emitting area are described in detail. In addition, this study illustrates the reasons that limit the development of photovoltaic cells under the current technology in terms of both self-factors and environmental factors. The self-factors are mainly the conversion rate of its own materials and energy consumption of meta-components, and the environmental factors are mainly the geographical location leading to the solar altitude angle and the amount of solar radiation. In the future, the global PV market will continue to maintain a rapid growth trend, driven by favorable factors such as the continued decline in the cost of photovoltaic power generation and the positive market orientation.

Global sensitivity analysis of photovoltaic cell parameters based on credibility variance

Photovoltaic cells can directly convert solar energy into electrical energy, which is environmentally friendly and has a wide range of applications. In practical engineering, the uncertainty of photovoltaic cell parameters has an important impact on cell performance. In order to study the influence of parameter uncertainty on the output performance of photovoltaic cells, a photovoltaic cell model is established and five parameters are selected: irradiation intensity, photovoltaic cell surface temperature, temperature coefficient, equivalent series resistance and equivalent parallel resistance. The influence of these parameters on the output power and conversion efficiency of photovoltaic cells is studied by using the global sensitivity analysis method based on fuzzy theory. The principal and total global sensitivity indexes describing the influence of each parameter on the output performance were therefore calculated and ranked. The key parameters influencing the performance of photovoltaic cells were determined to be related to cell surface temperature and equivalent parallel resistance. In actual production and life, the output performance of photovoltaic cells can be improved by controlling these two factors. The results of this study can help to guide the performance analysis and parameter optimization of photovoltaic cells, accelerating the development and improving the adoption of photovoltaic systems.

Spectral Dependence of Photovoltaic Cell Conversion Efficiency for Monochromatic Radiation

Theoretical limit of solar cell conversion efficiency given by Shockley and Queisser is calculated for the case that the cell is illuminated by solar radiation. If the input radiation is monochromatic, the efficiency can exceed the limit. The aim of our study is to experimentally demonstrate this theoretical prediction and to obtain the experimental results of spectral dependence of photovoltaic cell conversion efficiency. Conversion efficiencies of two types of Si photodiodes (equivalent to solar cells) are determined through the measurements of current–voltage characteristics as a function of the wavelength and the incident radiant power. As the theory predicts, it has been confirmed that the conversion efficiency is almost proportional to the wavelength and also to the logarithm of the incident radiant power. Also, it has been experimentally confirmed that the power conversion efficiency for long wavelength monochromatic radiation is higher than that for white radiation.

Design of double axis solar automatic light tracing device based on cloud platform

Solar energy is a widely distributed and inexhaustible "green" renewable new energy, which is one of the best solutions to the energy crisis in the world. However, the conversion efficiency of photovoltaic cells in large-scale solar applications is not high, and the cost is very high. Therefore, in order to increase the power generation capacity and efficiency of solar power generation, automatic tracking power generation devices should be used to replace fixed solar photovoltaic panels and other solar equipment. This design proposes a two axis solar tracking system based on the Internet of Things cloud platform. This system uses the sun viewing motion tracking method to drive photovoltaic panels in horizontal and vertical directions to track the sun. The preset tracking angle of the system is based on the sun azimuth angle and altitude angle operation rules calculated and collected by the sun angle calculation software, and combined with weather data to find the best angle for real-time tracking. This design will elaborate the design process from the aspects of system overall scheme design, hardware circuit design and host computer software development.

Photovoltaic System Efficiency Enhancement with Thermal Management: Phase Changing Materials (PCM) with High Conductivity Inserts

- The electrical conversion efficiency of photovoltaic cells from solar radiation heavily depends on the cell temperature. Here we propose a novel thermal management strategy to keep the cell temperature in the same order to attain maximum efficiency. The comparative study presented is based on four solar module configurations: a conventional photovoltaic module (PVT module), a conventional module with PCM layer underneath (PVT/PCM-I), a configuration where fins embedded into PCM (PVT/PCM-II), and configuration where the bottom of the PCM layer in PVT/PCM-II was cooled via convection (PVT/PCM-III). The developed 3D numerical model is solved via ANSYS software involving the solar ray tracing radiation model for incident solar radiations and a transient melting-solidification thermo-fluid model to cater for PCM phase transition. Results from the numerical model were validated via a comparison of experimentally studied results presented in the literature. After 120 minutes, results show that the conversion efficiency of PV cells becomes 16.84%, 18.65%, 18.83%, and 18.98% after 120 minutes for PVT module, PVT/PCM-I, PVT/PCM-II, and PVT/PCM-III with an inlet velocity of 3m/s, respectively. For the respective configurations, the specific electrical power per unit area produced reaches 75.30W/m2, 83.39W/m2, 84.19W/m2, and 89.42W/m2 for solar radiation of 540W/m2 and 26°C ambient temperature. Results reveal that a 5 mm increase in the fin height for PVT/PCM-II results in a 0.22% increase in efficiency while a 0.5m/s increase in the inlet velocity of the cooling air for PVT/PCM-III results in about 0.06% increase in efficiency.

Comparison analyses of three photovoltaic solar-assisted heat pumps based on different concentrators

The main problem of concentrated photovoltaics is the high temperature caused by high radiance, which deteriorates the electrical efficiency and service life of photovoltaic cells. Most concentrated photovoltaics are assembled into the photovoltaic/thermal systems and cooled by water. However, if concentrating photovoltaics is combined with an evaporator in a direct-expansion solar-assisted heat pump, the photovoltaic damages (reduced life span and conversion efficiency of photovoltaic cells) caused by the high temperature in concentrators will be much better alleviated. But at present, there is little research on the combination of concentrating photovoltaic and direct-expansion solar-assisted heat pump. To enrich the relevant content and explore the optimal concentrating method combined with heat pumps, three hybrid heat pumps with different concentrating evaporators are proposed and investigated. Results indicate that in the photovoltaic heat pump system based on Fresnel concentrator, photovoltaic heat pump system based on compound parabolic concentrator, and the photovoltaic heat pump system based on 3-D crossed compound parabolic concentrator, the electrical efficiency could achieve 30.31%, 15.37%, and 11.66% under 300 W/m2. The coefficient of performance (considering both electricity and heat) could reach 7.65, 5.67, and 5.45 under 800 W/m2, meanwhile, the 29.87%, 16.25%, and 13.66% exergy efficiency can be obtained under the same irradiation. Therefore, the photovoltaic heat pump system based on Fresnel concentrator has the best capacity, followed by the system based on compound parabolic concentrator and 3-D crossed compound parabolic concentrator. Besides, in the FPV-SAHP system, two concentration ratios are designed and discussed. And the effect of ambient temperature, water temperature, as well as solar irradiance on the systems is also explored.

Improving performance of solar roof tiles by incorporating phase change material

There is an increasing interest in integrating photovoltaic cells in building components, such as roof tiles. However, conversion efficiency of photovoltaic cells is temperature-dependant and high temperature will reduce the conversion efficiency. This paper studies the performance of mortar roof tiles with integrated solar cells and protective glass. To control the temperature of the solar cells, a phase change material (PCM) at a concentration of 3 wt% was mixed into the mortar roof tiles. The influence of the PCM on the solar-to-electrical power generation is evaluated for the solar roof tiles, and life cycle cost analysis is performed to assess the economic feasibility. It is found that the electrical energy output from the solar roof tiles with PCM is about 4.1% higher than that of the counterpart without PCM in winter days, whereas the corresponding improvement is in the range of 2.2 – 4.3% in six summer days. The economical payback time of the solar roof tiles with PCM is found to be 5.7 years including the inverter cost. The use of PCM increases the initial cost of roof tiles by 1.2%; however, considering an overall improvement of 4.1% in the energy output, the payback time is estimated to be three months shorter than that of the counterpart without PCM. The study also confirms that the ambient conditions influence the overall power generation substantially because of the impact on the working temperature of the solar roof tiles.

Analysis of attitude planning and energy balance of stratospheric airship

Solar energy is an essential energy source collected by photovoltaic (PV) cells for long-endurance stratospheric airships. Attitude control is crucial for the energy production of the PV array attached to the airship hull. This study was conducted to analyze the energy balance of stratospheric airships with attitude planning. A solar radiation and PV array model is proposed, then a steerable attitude strategy is established considering the roll, pitch, and yaw control of the PV array. The energy balance of the model is analyzed under an attitude planning scheme based on an actual airship design. The daily net energy of the airship is calculated according to monthly wind data of various latitudes. The influence on the net energy considering the conversion efficiency of PV cells and specific density of the energy stored system (ESS) is also analyzed. The results shows that attitude planning has a significant effect on both the energy production and wind resistance of the airship. The energy balance of the airship is markedly improved when PV conversion efficiency is high and ESS energy capacity is large. The results presented here may prove valuable for future stratospheric airship applications.

Novel MPPT method based on large variance GA‐RBF

The photoelectric conversion efficiency of photovoltaic cells is mainly affected by temperature and irradiance. In order to promote the development of photovoltaic power generation, it is necessary to improve the photoelectric conversion efficiency of photovoltaic cells. This paper combines two major factors that affect photovoltaic cells, a maximum power point tracking scheme based on large variation GA-RBF network is proposed. The system used in this scheme is simulated through Matlab. The simulation results show that the new maximum power point tracking scheme has higher accuracy and rapidity, the photoelectric conversion efficiency of the photovoltaic cell is greatly improved.

Application of an extension method on optimal site selection for PV power systems: A case study in Taiwan

Photovoltaic (PV) power investors mainly consider the investment cost and payback period when settling on a new PV power site. This study applies the analytical hierarchy process (AHP) to decompose complex decision‐making problems into several subproblems, which are then organized into a tree‐like structure. The relative importance of each subproblem is weighted to prevent subjective cognitive differences when setting the weight for each factor. Subsequently, this study adopts the extension theory to solve the contradictory problems generated during quality assessments, to analyze the principal factors influencing the installation sites for PV power systems, and to evaluate optimal installation sites. This study further integrates AHP with a quality assessment method based on the extension theory to select the optimal site for installing PV power systems. Factors affecting installation sites comprise sunshine, temperature, PV cell conversion efficiency, feed‐in tariffs, investment payback period, interest rate on bank loans, land rental, and installation costs. Sites located in Northern, Central, and Southern Taiwan and the outlying islands of Taiwan were analyzed. Finally, results from the analysis verify that the method proposed herein generates results quickly and is easy to use. Therefore, the proposed method can help select the optimal installation site for PV power systems. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Analytical study of pulsed laser irradiation on some materials used for photovoltaic cells on satellites

The present research concerns on the study of laser-powered solar panels used for space applications. A mathematical model representing the laser effects on semiconductors has been developed. The temperature behavior and heat flow on the surface and through a slab has been studied after exposed to nano-second pulsed laser. The model is applied on two different types of common active semiconductor materials that used for photovoltaic cells fabrication as silicon (Si), and gallium arsenide (GaAs). These materials are used for receivers’ manufacture for laser beamed power in space. Various values of time are estimated to clarify the heat flow through the material sample and generated under the effects of pulsed laser irradiation. These effects are theoretically studied in order to determine the performance limits of the solar cells when they are powered by laser radiation during the satellite eclipse. Moreover, the obtained results are carried out to optimize conversion efficiency of photovoltaic cells and may be helpful to give more explanation for layout of the light-electricity space systems.

Self-Sustained, Independent Trifold Solar Energy Conversion System for Isolated Locations in Hot Climate Areas

This paper proposes two configurations for a hybrid solar energy conversion device that can be used as a self-sustained, independent power generation system in isolated locations in hot climate areas. Given the strong dependence of photovoltaic cell conversion efficiency on operation temperature, the cooling of the backside becomes imperative, increasing not only electrical, but also the overall solar energy conversion efficiency. The hybrid system provides now electricity and hot hater for domestic applications. To further improve electrical efficiency, a thermoelectric generator module is added to the system, harvesting the thermal energy that otherwise would be regarded as waste heat and rejected to environment. The optimization of the parameters that influence the total efficiency demonstrate the strong connection between the three parts of the system, PV-TE-DHW.

Novel Na(+) doped Alq3 hybrid materials for organic light-emitting diode (OLED) devices and flat panel displays.

Pure and Na(+) -doped Alq3 complexes were synthesized by a simple precipitation method at room temperature, maintaining a stoichiometric ratio. These complexes were characterized by X-ray diffraction, Fourier transform infrared (FTIR), UV/Vis absorption and photoluminescence (PL) spectra. The X-ray diffractogram exhibits well-resolved peaks, revealing the crystalline nature of the synthesized complexes, FTIR confirms the molecular structure and the completion of quinoline ring formation in the metal complex. UV/Vis absorption and PL spectra of sodium-doped Alq3 complexes exhibit high emission intensity in comparison with Alq3 phosphor, proving that when doped in Alq3 , Na(+) enhances PL emission intensity. The excitation spectra of the synthesized complexes lie in the range 242-457 nm when weak shoulders are also considered. Because the sharp excitation peak falls in the blue region of visible radiation, the complexes can be employed for blue chip excitation. The emission wavelength of all the synthesized complexes lies in the bluish green/green region ranging between 485 and 531 nm. The intensity of the emission wavelength was found to be elevated when Na(+) is doped into Alq3 . Because both the excitation and emission wavelengths fall in the visible region of electromagnetic radiation, these phosphors can also be employed to improve the power conversion efficiency of photovoltaic cells by using the solar spectral conversion principle. Thus, the synthesized phosphors can be used as bluish green/green light-emitting phosphors for organic light-emitting diodes, flat panel displays, solid-state lighting technology - a step towards the desire to reduce energy consumption and generate pollution free light.

Scenario analysis of a bioethanol fueled hybrid power generation system

BackgroundRegarding most of FC/PV/Battery based hybrid power generation systems, the photovoltaic (PV) power usually dominates the main power supply and the water electrolyzer is used to produce hydrogen. The energy efficiencies of these hybrid power generation (HPG) systems are usually low due to the low conversion efficiency of PV cell and the extra power consumption to hydrogen production. To reduce the electricity demand by the PV system and improve the energy efficiency of hydrogen production unit, a scenario-based design of the HPG system is necessary.ResultThis paper proposes an EFC/PV/Battery based hybrid power generation system to meet 24-hour power demand. An ethanol-fueled fuel cell (EFC) power generator not only dominates the main power supply, but also a combination of the stand-alone EtOH-to-H2 processor and PEMFC can ensure higher energy efficiency. A PV system is treated as an auxiliary power generator which can reduce the (bio)ethanol consumption. A backup battery not only stores excess power from PV or EFC, but also it can precisely satisfy the power demand gap. Finally, scenario analysis of the hybrid power generation (HPG) system in regard to the hybrid power dispatch and energy efficiency is addressed.ConclusionAn optimized fuel processing unit using ethanol fuel can produce high-purity hydrogen. The simulation shows that the stand-alone EtOH-to-H2 processor not only guarantee the high energy efficiency, but also it can continuously produce hydrogen if the fuel is enough. According to scenarios for the daily operation of the HPG system, the EFC power dominates the power supply during the night, the PV system dominates the power supply during the day and the backup battery aims to instantly compensate the power gap and store the excess power from PV or EFC. According to the hybrid power dispatch, the distribution of the HPG system efficiency is specified.

Plasmon‐Enhanced Polymer Photovoltaic Device Performance Using Different Patterned Ag/PVP Electrospun Nanofibers

Significant enhancement of P3HT (poly(3‐hexylthiophene)):PC61BM ([6,6]‐phenyl C61‐butyric acid methyl ester) photovoltaic devices using different patterns of electrospun Ag/PVP composite nanofibers, including nonwoven, aligned, and crossed patterns, is reported. The composite electrospun nanofibers are prepared using in situ reduction of silver (Ag) nanoparticles in Ag/poly(vinyl pyrrolidone) (PVP) via a two‐fluid coaxial electrospinning technique. The composition, crystalline orientation, and particle size of Ag are manipulated by controlling the core/shell solution concentration. The smallest diameter of the composite nanofibers leads to the highest orientation of the Ag nanoparticles and results in the largest conductivity due to geometric confinement. Such composite nanofibers exhibit the surface plasmon resonance (SPR) effect, which provides near field enhancement of electromagnetic field around active layer. Additionally, composite nanofibers with the crossed or nonwoven patterns further enhance high carrier mobility, compared to that of the aligned pattern. It leads to the 18.7% enhancement of the power conversion efficiency of photovoltaic cell compared to the parent device. The results indicate that the high conductivity and SPR effect of the Ag/PVP electrospun nanofibers can significantly improve the photocurrent and PCE, leading to promising organic solar cell applications.

Double superexchange in quantum dot mesomaterials

A new optoelectronic mesomaterial is proposed in which a network of quantum dots is covalently connected via organic molecules. Optically generated excitons are rapidly dissociated with electrons subsequently hopping from dot to dot while holes transit via the connecting moieties. The molecules serve as efficient mediators for electron superexchange between the dots, while the dots themselves play the complementary role for hole transport between molecules. The network thus exhibits a double superexchange. In addition to enhancing carrier hopping rates, double superexchange plays a central role in mediating efficient polaron dissociation. Photoluminescence, dissociation, and transport dynamics are quantified from first-principles for a model system composed of small silicon quantum dots connected by organic moieties. The results demonstrate that double superexchange can be practically employed to significantly improve charge generation and transport. These are currently viewed as the critical obstacles to dramatic enhancements in the energy conversion efficiency of photovoltaic cells based on quantum dots.