Efficiency Of GaAs Solar Cell Research Articles

Achieving high photovoltaic performance in graphene/AlGaAs/GaAs Schottky junction solar cells by incorporating an InAlGaP hole reflector layer

The purpose of this study is to enhance the efficiency of Graphene/AlGaAs/GaAs Schottky junction solar cells by introducing various Ga-based thin-film materials as a hole reflector (HR) layer. These HR layers are designed to minimize the recombination rate at the back contact and increase the photogeneration rate. In order to investigate the effect of various HR layers on the efficiency of GaAs solar cells, a reference cell was simulated with an efficiency of 14%. The simulation was conducted using the Silvaco ATLAS simulator, under AM1.5G light with a power density of 100 mW/cm2. Subsequently, InAlGaP (InAl0.65Ga0.35P), AlGaAs (Al0.2Ga0.8As), and InGaP (In0.5Ga0.5P) thin films were individually introduced as HR layers to the Graphene/AlGaAs/GaAs single junction solar cell (SJSC). The addition of HR layers to the conventional Graphene/AlGaAs/GaAs Schottky junction solar cell was found to improve the short-circuit current density (Jsc) by enhancing carrier collection and reducing back interface recombination. This approach has also led to a significant increase in external quantum efficiency (EQE) at long wavelengths of around 500–900 nm. The results of this study demonstrate that incorporating an InAlGaP HR layer in the proposed structure due to its wide bandgap, higher photogeneration rate, and higher absorption rate significantly improves the EQE by absorbing longer wavelength photons and increases the efficiency of the solar cell by more than 1.6%.

Sharp angular and unidirectional filter based on accidental degeneracy between two twisted Weyl semimetal-based defect modes in a one-dimensional photonic crystal.

To address the challenges associated with the realization of optical non-reciprocity and enhance the efficiency of GaAs solar cells, among other systems, in this study, we investigated defect-mode interactions in a one-dimensional photonic crystal containing two Weyl semimetal-based defect layers. Moreover, two non-reciprocal defect modes were observed, namely, when defects are identical and nearby. Increasing the defect distance weakened the defect-mode interactions, thus causing the modes to gradually move closer and then degenerate into one mode. It should be noted that by changing the optical thickness of one of the defect layers, the mode was found to degrade to two non-reciprocal dots with different frequencies and angles. This phenomenon can be attributed to an accidental degeneracy of two defect modes with dispersion curves that intersect in the forward and backward directions, respectively. Moreover, by twisting Weyl semimetal layers, the accidental degeneracy occurred only in the backward direction, thus resulting in a sharp angular and unidirectional filter.

Potential high efficiency of GaAs solar cell with heterojunction carrier selective contact layers

Advanced configurations of gallium arsenide (GaAs) solar cells are proposed, using hydrogenated amorphous silicon (a-Si: H) and zinc oxide (ZnO) layers as passivation and carrier selective contacts (CSC), as alternatives to the conventional epitaxial GaInP CSC layers. The cell operation is simulated based on the AFORS-HET simulation program. The results show that with a wide-gap ZnO window layer, single-junction GaAs solar cells can reach a higher short-circuit current density (Jsc) and open-circuit voltage (Voc) than that obtained with conventional GaInP CSC layers without affecting the fill factor (FF). Notably, wide-gap and n-type doping ZnO layers show great potential as electron selective contacts in GaAs solar cells with high barriers at the valence band for blocking hole-transport. An efficiency of 30% is reached for a single-junction GaAs cell with a front ZnO electron selective contact. A 4-terminal GaAs/c-Si tandem solar cell configuration with an estimated conversion performance of 35.16% is proposed. These results indicate enormous potential for the development of low-cost and high-efficiency GaAs-based solar cells in the future.

Preparation of non-stoichiometric Al2O3 film with broadband antireflective by magnetron sputtering

Al2O3/MgF2 bilayer antireflection film was deposited on the glass with magnetron sputtering. The results indicate that the O:Al ratio of Al2O3 films varied between 1.92:1 and 2.31:1, was higher than the normal stoichiometric ratio of 1.5:1. Al2O3 films were amorphous, and particles with different sizes and quantities were distributed on the surface. The lowest refractive index of Al2O3 film was 1.421, and the average transmittance of coated glass reached 94.10%. The average transmittance within 300–1100 nm of the bilayer film coated glass reached 95.13%. Moreover, Al2O3/MgF2 coated glass enhanced photoelectric conversion efficiency of GaAs solar cell by 4.07%.

Effect of SF6 flow ratio on microstructure and properties of MgF2 thin films prepared by magnetron sputtering

In order to suppress F- deficiency of MgF2 film prepared with magnetron sputtering, the effects of SF6: Ar gas flow ratio on the structure and properties of the film were investigated. F: Mg ratio increased rapidly first then decreased with the increase of SF6 flow ratio, got 2.13 at 7%, closest to the stoichiometric ratio 2:1; while the film's refractive index first decreased and then increased, got a minimum at 550 nm 1.409 at 7%. MgF2 film increased the glass substrate transmittance within 300–1100 nm to 94.24% from 93.2%, and improved photoelectric conversion efficiency of GaAs solar cell by 2.1%.

Light Reflection Loss Reduction by Nano-Structured Gratings for Highly Efficient Next-Generation GaAs Solar Cells

This paper mainly focuses on increasing the conversion efficiency of GaAs solar cells by reducing the light reflection losses. The design of nano-structured gratings and their light trapping performance are modelled and optimised by using the finite-difference time-domain (FDTD) method. The sunlight directly impinges on the solar panel or cells, then a portion of the incident sunlight reflects back to the air from the surface of the panel, thus leading to a reduction in the light absorption capacity of the solar cells. In order to proliferate the light absorption capacity of solar cells nano-grating structures are employed, as they are highly capable of capturing the incident sunlight compared to a conventional (or flat type) solar cell, which results in generating more electrical energy. In this study, we design three different types of nano-grating structures, optimise their parameters and their performance in light capturing capacity. From the simulation results, we confirm that that it is possible to reduce light reflection losses up to 27%, by using the nano-grating structures, compared to conventional type solar cells. This reduction of reflection losses helps to improve the conversion efficiency of next-generation GaAs solar cells significantly for a sustainable green Earth.

Study of the Role of Window Layer Al0.8Ga0.2As on GaAs-based Solar Cells Performance

Numerical simulation of various structures of a solar cell plays a crucial role in the design, performance prediction and the comprehension of the physics involved in their operation. It also allows of better understanding the different ways to improve the solar cells efficiency before the manufacture of the practical cell. Objectives: In this study, numerical results were obtained using SCAPS-1D program in order to improve GaAs solar cells performance. Methods: The analysis deals with the role of Alx Ga1-x As-type window layer on overall electrical performance of solar cells. The variations of thickness and doping levels in this window layer were also investigated. Findings: By growing this layer at the GaAs surface, the efficiency increased from 17.23% to 27.37%. The simulation results showed that this window layer should be very thin and slightly doped to achieve good performances of the entire solar cells. Improvements/Applications: These results are interesting because they show how much the window layer is important in improving the efficiency of GaAs solar cells. Keywords: Efficiency Improvement, GaAs, Numerical Simulation, SCAPS-1D, Solar Cell, Window Layer

Enhancement in Power Conversion Efficiency of GaAs Solar Cells by Utilizing Gold Nanostar Film for Light-Trapping.

Light trapping, caused by the introduction of metallic nanoparticles, has been demonstrated to enhance photo-absorption in GaAs solar cells. In this study, we successfully synthesized gold nanostar thin film with hot spots and obtained a notable improvement of power conversion efficiency (PCE) in single-junction and three-junction high-performance GaAs solar cells by incorporating the poly (3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) layer, which enables a much stronger light trapping capability and scattering enhancement than conventional metal nanostructures. Increases of 5.2% and 3.94% in short circuit current density (Isc) were achieved for single-junction cells and three-junction cells while the enhancement in cell PCE was 3.85 and 2.50%, respectively. The relationship between the optical characteristics, the distribution density of the gold NSs and the performance of GaAs solar cells was systemically investigated.

Theoretical and experimental study on the uniformity of reflective high concentration photovoltaic system with light funnel

Abstract The efficiency of GaAs solar cell was significantly reduced resulting from non-uniformity of energy flux-density on receiver surface, and damage of solar cells was made by “hot spots”. In this paper, a light funnel is added between the concentrator and the receiver to improve the uniformity of energy flux-density on receiver surface, which is designed according to the ray tracing method. The simulation result shows that the uniformity of the energy flux-density on the receiver surface is 92.26%, which agrees with the experimental result (94.64%). According to the maximum output efficiency of GaAs solar cell, the layout range of the cell is determined. The simulation results shown that the cell is arranged in the radius of 58 mm, which is similar to the experimental value (60 mm), and the effective area rate of the photoelectric conversion is 69.4%. At normal operation temperature (20 °C), the photoelectric conversion efficiency is 29.64%, and the total efficiency is about 83%.

Black GaAs by Metal-Assisted Chemical Etching.

Large area surface microstructuring is commonly employed to suppress light reflection and enhance light absorption in silicon photovoltaic devices, photodetectors, and image sensors. To date, however, there are no simple means to control the surface roughness of III-V semiconductors by chemical processes similar to the metal-assisted chemical etching of black Si. Here, we demonstrate the anisotropic metal-assisted chemical etching of GaAs wafers exploiting the lower etching rate of the monoatomic Ga<111> and <311> planes. By studying the dependence of this process on different crystal orientations, we propose a qualitative reaction mechanism responsible for the self-limiting anisotropic etching and show that the reflectance of the roughened surface of black GaAs reduces up to ∼50 times compared to polished wafers, nearly doubling its absorption. This method provides a new, simple, and scalable way to enhance light absorption and power conversion efficiency of GaAs solar cells and photodetectors.

Increasing the quantum efficiency of GaAs solar cells by embedding InAs quantum dots

Development of Metalorganic Vapor Phase Epitaxy (MOVPE) technology of InAs quantum dots (QDs) in GaAs for photovoltaic applications is presented. The growth peculiarities in InAs-GaAs lattice-mismatched system were considered. The photoluminescence (PL) intensity dependences on different growth parameters were obtained. The multimodal distribution of QDs by sizes was found using AFM and PL methods. GaAs solar cell nanoheterostructures with imbedded QD arrays were designed and obtained. Ones have been demonstrated a significant increase of quantum efficiency and photogenerated current of QD solar cells due to photo effect in InAs QD array (0.59 mA/cm2 for AM1.5D and 82 mA/cm2 for AM0).

Modeling the Effect of ARC and other Parameters on the Efficiency of GaAs Solar Cell Using Silvaco

Gallium Arsenide (GaAs) based solar cell which have nearly ideal direct bandgap of 1.43eV hold the highest single junction solar cell efficiency. GaAs solar cell without Anti-Reflective Coating (ARC) layer was studied and shows the efficiency ranges between 8% to 15%, followed by GaAs solar cell with efficiency ranges between 20% to 25% with ARC layer. The substrate thickness for both GaAs solar cell was varied from 0.1μm to 1.0μm. Increased of P-type substrate thickness shows a small variation in efficiency with parabolic shape, while increased of N-type substrate thicknesss increased the efficiency between 21% to 25% for single layer GaAs with ARC thickness. Besides that, increased of P-type doping concentration from 1×1018cm-3 to 1×1019cm-3 and fixed N-type doping will decreased the efficiency. However increased the N-type doping concentration from 1×1017cm-3 to 1×1018cm-3 and fixed the P-type doping will increased the efficiency. The thickness of ARC layer on GaAs solar cell was studied and shows that highest efficiency achieved at narrow thickness of ARC.

Optimization of Anti-reflection Coating for Improving the Performance of GaAs Solar Cell

The objective of this work is to reduce the front surface reflectivity of the GaAs solar cell by depositing AR-coating of appropriate thickness and refractive index material. We use MgO and ZnO film and optimize their thickness for minimum reflectivity. Results indicate that the reflectivity is reduced up to 4% for MgO film and 2% for ZnO film at solar spectrum wavelength range from 550 nm to 650 nm. The external efficiency of GaAs solar cell with AR-coating is increased by 31.53% and 33.09% for MgO and ZnO film respectively.

Influence of quantum wells on the quantum efficiency of GaAs solar cells

Influences of InGaAs/GaAsP quantum wells on the quantum efficiency of GaAs solar cells are investigated. In addion of extending the absorption spectrum from 890 nm to 1000 nm, introduction of quantum wells has important effects on the quantum efficiency below 890 nm. In the range of shorter wavelengths(&lt;680 nm), the GaAs control cells have higher quantum efficiencies, while in the longer wavelengths (680-890 nm), the quantum well solar cells have higher quantum efficiencies. This phenomenon can be explained by the difference in the absorption coefficients of quantum well structure and GaAs materials.

Reuse of GaAs substrates for epitaxial lift-off by employing protection layers

We demonstrate repeated use of GaAs wafers for multiple growths by employing lattice-matched epitaxial protection layers to preserve the wafer surface in its original condition following their etch removal after growth. The protection layers provide a regrowth surface that eliminates the need for repolishing prior to subsequent growth. Between growths, the protection layers are removed by wet chemical etching. The resulting surface quality is examined using atomic force microscope and energy dispersive spectrometry. We show that the surface roughness, chemical composition, morphology, and electronic properties of the GaAs surface after protection-layer removal are comparable to that of the original substrate surface. We show that p-n junction GaAs solar cells grown on original and reused wafers have nearly identical performance with power conversion efficiencies of ∼23%, under simulated 1 sun illumination, AM1.5 G. The high power conversion efficiency of GaAs solar cells combined with reduced costs associated with multiple parent wafer reuses promise cost competitiveness with incumbent solar cell technologies.

Efficiency Enhancement of GaAs Photovoltaics Due to Sol-Gel Derived Anti-Reflective AZO Films

Aluminum (Al)-doped ZnO (AZO) thin films are prepared via the sol-gel method and utilized as an anti-reflective coating (ARC) to enhance the light gathering capability and short-circuit current density (Jsc) of GaAs solar cells. The AZO films are prepared chemically by spin coating the sol with an aqueous solution of zinc acetate dihydrate and aluminum nitrate. The current–voltage measurements of the solar cells confirm that the AZO film increases short-circuit current. 4 atom% Al-doped ZnO film exhibits the best anti-reflective characteristics. The conversion efficiency of cells is significantly enhanced by the ARC (8.3% versus 11.2%). The AZO film, which has a suitable refractive index and excellent transmittance, reduces reflectance and significantly enhances the external quantum efficiency of GaAs solar cells compared to those obtained for an undoped ZnO coating. In degradation tests of the solar cells after irradiation treatment, the ZnO and AZO coatings both exhibit lowered J-V characteristics and external quantum efficiency decay of the solar cell after proton irradiation, making them suitable for use as the radiation-resistant and anti-reflective layer in GaAs solar cells.

Improved efficiency in GaAs solar cells by 1D and 2D nanopatterns fabricated by laser interference lithography

We demonstrate an improvement in efficiency of GaAs solar cells using front surface texturing with dielectric 1D and 2D nanopatterns obtained by a low cost laser interference lithography technique. The strong light scattering by the surface dielectric nanopatterns effectively increases the optical path of the incident light in the absorber layers resulting in an efficiency increase up to 23.5% compared to that of the reference solar cell. The observed efficiency improvement in the studied solar cells shows the potential use of low cost photoresist as an antireflection coating material and further application of other robust dielectric materials as texturing layer.

Efficiency enhancement in GaAs solar cells using self-assembled microspheres

In this study we develop an efficient light harvesting scheme that can enhance the efficiency of GaAs solar cells using self-assembled microspheres. Based on the scattering of the microspheres and the theory of photonic crystals, the path length can be increased. In addition, the self-assembly of microspheres is one of the simplest and the fastest methods with which to build a 2D periodic structure. The experimental results are confirmed by the use of a simulation in which a finite-difference time-domain (FDTD) method is used to analyze the absorption and electric field of the 2D periodic structure. Both the results of the numerical simulations and the experimental results show an increase in the conversion power efficiency of GaAs solar cell of about 25% when 1 microm microspheres were assembled on the surface of GaAs solar cells.

Epitaxial lift-off process for GaAs solar cell on Si substrate

This research has established the process to transplant GaAs solar cells from GaAs substrate to Si substrate without degrading the conversion efficiency. The conversion efficiency of GaAs solar cell bonded to Si substrate using epitaxial lift-off process is almost the same as that grown on GaAs substrate and is superior to that grown on Si substrate by heteroepitaxy.

Simulation of solar cells utilization on the surface of Mars

Results concerning the simulation of solar cells operation on Mars surface are reported in this article. PV arrays based on silicon and gallium arsenide solar cells are analyzed under the assumption of both ideal and present state-of-the-art technology. Measurements performed by the Viking Landers are used as inputs. They refer to ambient temperature, wind speed and the optical depth of the Martian atmosphere. The incoming global solar radiation flux (direct, diffuse and ground reflected) is computed by using a model previously proposed by the author. A thermodynamic model of solar cell is developed. Simulations were performed for both Viking Landers 1 and 2 sites during all the four Martian seasons. Information about the optimum voltage and cell temperature is provided as well as details about the electric power supply and cell efficiency. Different sorts of stationary and tracking solar cells arrays are studied. The PV efficiency is obviously higher than that obtained under terrestrial conditions due to the lower ambient temperature on Mars. One confirms that the low operating temperatures will reduce the advantage in efficiency of GaAs solar cells over silicon. The strategy to be chosen for maximum power supply mainly depends on the atmospheric optical depth.