Numerical Modeling and Simulation of CIGS-Based Solar Cells with ZnS Buffer Layer

Usually a buffer layer of cadmium sulphide is used in high efficiency solar cells based on Cu(In,Ga)Se2(CIGS). Because of cadmium toxicity, many in-vestigations have been conducted to use Cd-free buffer layers. Our work focuses on this type of CIGS-based solar cells where CdS is replaced by a ZnS buffer layer. In this contribution, AFORS-HET software is used to simulate n-ZnO: Al/i-ZnO/n-ZnS/p-CIGS/Mo polycrystalline thin-film solar cell where the key parts are p-CIGS absorber layer and n-ZnS buffer layer. The characteristics of these key parts: thickness and Ga-content of the absorber layer, thickness of the buffer layer and doping concentrations of absorber and buffer layers have been investigated to optimize the conversion efficiency. We find a maximum conversion efficiency of 26% with a short-circuit current of 36.9 mA/cm2, an open circuit voltage of 824 mV, and a fill factor of 85.5%.

Thermal modeling optimization and experimental validation for a single concentrator solar cell system with a heat sink

A single concentrator solar cell model with a heat sink is established to simulate the thermal performance of the system by varying the number, height, and thickness of fins, the base thickness and thermal resistance of the thermal conductive adhesive. Influence disciplines of those parameters on temperatures of the solar cell and heat sink are obtained. With optimized number, height and thickness of fins, and the thickness values of base of 8, 1.4 cm, 1.5 mm, and 2 mm, the lowest temperatures of the solar cell and heat sink are 41.7 ~C and 36.3 ~C respectively. A concentrator solar cell prototype with a heat sink fabricated based on the simulation optimized structure is built. Outdoor temperatures of the prototype are tested. Temperatures of the solar cell and heat sink are stabilized with time continuing at about 37 ℃-38 ℃ and 35 ℃-36 ℃respectively, slightly lower than the simulation results because of effects of the wind and cloud. Thus the simulation model enables to predict the thermal performance of the system, and the simulation results can be a reference for designing heat sinks in the field of single concentrator solar cells.

Thermal modeling and the optimized design of metal plate cooling systems for single concentrator solar cells

A metal plate cooling model for 400~ single concentrator solar cells was established. The effects of the thickness and the radius of the metal plate, and the air environment on the temperature of the solar cells were analyzed in detail. It is shown that the temperature of the solar cells decreased sharply at the beginning, with the increase in the thickness of the metal plate, and then changed more smoothly. When the radius of the metal plate was 4 cm and the thickness increased to 2 mm or thicker, the temperature of the solar cell basically stabilized at about 53℃. Increasing the radius of the metal plate and the convective transfer coefficient made the temperature of the solar cell decrease remarkably. The effects of A1 and Cu as the metal plate material on cooling were analyzed contrastively, and demonstrated the superiority of A1 material for the cooling system. Furthermore, considering cost reduction, space holding and the stress of the system, we optimized the structural design of the metal plate. The simulated results can be referred to the design of the structure for the metal plate. Finally, a method to devise the structure of the metal plate for single concentrator solar cells was given.

Modeling Multiple Quantum Well and Superlattice Solar Cells

The inability of a single-gap solar cell to absorb energies less than the band-gap energy is one of the intrinsic loss mechanisms which limit the conversion efficiency in photovoltaic devices. New approaches to “ultra-high” efficiency solar cells include devices such as multiple quantum wells (QW) and superlattices (SL) systems in the intrinsic region of a p-i-n cell of wider band-gap energy (barrier or host) semiconductor. These configurations are intended to extend the absorption band beyond the single gap host cell semiconductor. A theoretical model has been developed to study the performance of the strain-balanced GaAsP/InGaAs/GaAs MQWSC, and GaAs/GaInNAs MQWSC or SLSC. Our results show that conversion efficiencies can be reached which have never been obtained before for a single-junction solar cell.

Optimizing a Single-Absorption-Layer Thin-Film Solar Cell1 Model to Achieve 31% Efficiency

This research builds upon the authors’ previous work that introduced and modeled a novel Gallium-Arsenide, Emitterless, Back-surface Alternating Contact (GaAs-EBAC) thin-film solar cell to achieve >30% power conversion efficiency. Key design parameters are optimized under an Air-Mass (AM) 1.5 spectrum to improve performance and approach the 33.5% theoretical efficiency limit. A second optimization is performed under an AM0 spectrum to examine the cell’s potential for space applications. This research demonstrates the feasibility and potential of a new thin-film solar cell design for terrestrial and space applications. Results suggest that the straight-forward design may be an inexpensive alternative to multi-junction solar cells.

Effect of the Dynamic Resistance on the Maximum Output Power in Dynamic Modelling of Photovoltaic Solar Cells

Several studies on PV solar cells are found in the literature which use static models. Those models are mainly one-diode, two-diode or three-diode models. In the dynamic modelling, a variable parallel capacitance is incorporated. Unlike the previous studies which do not clearly establish a relationship between the capacitance and the voltage, in the present paper, the link between the capacitance and the voltage is investigated and established. In dynamic modelling investigated in this paper, the dynamic resistance is introduced in the modelling of the solar cell. It is introduced in the current-voltage characteristic. The value of the dynamic resistance is evaluated at the maximum power point and its effect on the maximum power is investigated. The study shows for the first time, that the dynamic resistance must be introduced in the current-voltage characteristic, because it has an influence on the PV cell output.

The Solar Cell Parameters as a Function of Its Temperature in Relation to Its Diurnal Efficiency

The variation of the temperature of the solar cell subjected to the incident global solar radiation along the local daytime in relation to its efficiency is studied. The heat balance equation is solved. The solution revealed that the cell temperature is a function of the maximum value of the daily incident global solar radiation qmax, the convection heat transfer coefficient (h), the optical, physical and the geometrical parameters of the cell. The temperature dependence of the short circuit current Isc, the dark saturation current Io, the open circuit voltage Voc, and the energy band gap Eg characterizing a Silicon solar cell is considered in evaluating the cell efficiency. Computations of the efficiency concerning operating conditions and astronomical locations (Egypt) as illustrative examples are given.

Guidelines for Optimization of the Absorber Layer Energy Gap for High Efficiency Cu(In,Ga)Se₂Solar Cells

This work investigates in-depth the effects of variation of the compositional ratio of the absorber layer in Cu(In,Ga)Se2 (CIGS) thin-film solar cells. Electrical simulations were carried out in order to propose the most suitable gallium double-grading profile for the high efficiency devices. To keep the model as close as possible to the real behavior of the thin film solar cell a trap model was implemented to describe the bulk defects in the absorber layer. The performance of a solar cell with a standard CIGS layer thickness (2 μm) exhibits a strong dependence on the front grading height (decreasing band gap toward the middle of the CIGS layer). An absolute gain in the efficiency (higher than 1%) is observed by a front grading height of 0.22. Moreover, simulation results show that the position of the plateau (the region characterized by the minimum band gap) should be accurately positioned at a compositional ratio of 20% Ga and 80% In, which corresponds to the region where a lower bulk defect density is expected. The developed model demonstrates that the length of the plateau is not playing a relevant role, causing just a slight change in the solar cell performances. Devices with different absorber layer thicknesses were simulated. The highest efficiency is obtained for a CIGS thin film with thicknesses between 0.8 and 1.1 μm.

Light scattering of nanocrystalline TiO_2 film used in dye-sensitized solar cells

This paper studies the light scattering and adsorption of nanocrystalline TiO2 porous films used in dye-sensitized solar cells composed of anatase and/or rutile particles by using an optical four-flux radiative transfer model. These light properties are difficult to measure directly on the functioning solar cells and they can not be calculated easily from the first-principle computational or quantitative theoretical evaluations. These simulation results indicate that the light scattering of 1 25 nm TiO2 particles is negligible, but it is effective in the range of 80 and 180 nm. A suitable mixture of small particles （10 nm radius）, which are resulted in a large effective surface, and of larger particles （150 nm radius）, which are effective light scatterers, have the potential to enhance solar absorption significantly. The futile crystals have a larger refractive index and thus the light harvest of the mixtures of such larger rutile and relatively small anatase particles is improved in comparison with that of pure anatase films. The light absorption of the 10μm double-layered films is also examined. A maximal light absorption of double-layered film is gotten when the thickness of the first layer of 10 urn-sized anatase particles is comparable to that of the second larger rutile layer.

Optical Absorption Enhancement Effects of Silver Nanodisk Arrays in the Application of Silicon Solar Cell

Surface plasmon resonance of noble metal nanoparticles leads to the optical absorption enhancement effects,which have great potential applications in solar cell.By using the general numerical method of discrete dipole approximation （DDA）,we study the absorption and scattering properties of two-dimensional square silver nanodisks （2D SSN） arrays on the single crystal silicon solar cell.Based on the effective reflective index model of the single crystal silicon solar cell,we investigate the optical enhancement absorption of light energy by varying the light incident direction,particle size,aspect ratio,and interparticle spacing of the silver nanodisks.The peak values and position of the optical extinction spectra of the 2D square arrays of noble metal nanodisks are obtained with the different array structures.

二氧化锡基染料敏化太阳能电池电子传输模型优化及器件性能研究

针对染料敏化太阳能电池(DSSC)而言,其光阳极的材料特性与设计参数对DSSC性能具有显著影响。为了深入研究这一影响,本文采用数值模拟的方式,以探究光阳极结构变化对DSSC性能的详细影响。但目前的数学模型不够完善且预测精度较低,因而本文在光电子传输理论和朗伯比尔定律的基础上,采用常数堆叠法和可变堆叠法将孔隙率对电子扩散系数的影响引入到DSSC的数学模型中,建立了更加完善且精确的电子传输模型,该模型能够更深入剖析光阳极结构参数变化对DSSC性能的影响。通过数值模拟了在不同孔隙体积、电子寿命、SnO_(2)涂层厚度及比表面积下DSSC的性能。结果发现:随着SnO_(2)薄膜孔隙体积的增加,太阳能电池的短路电流密度逐渐减小,而开路电压则呈增大趋势,这导致光电转换效率逐渐降低。当孔隙体积达到0.10 cm^(3)/g时,DSSC光电转换效率达5.16%,因此在保证电池刚性的前提下,尽量降低SnO_(2)的孔隙体积,有利于吸收系数和扩散系数的提升,这两个参数的提升有利于DSSC整体性能的提升,同时电子寿命的延长会带来太阳能电池短路电流密度和开路电压的增大,进而提升光电转换效率,当电子寿命达到200 ms时,光电转换效率达到5.82%。本研究通过详细的数值模拟分析,为优化光阳极结构从而提升DSSC的光电性能提供了有力的理论指导,有助于进一步推动DSSC的研究与应用。

一种确定太阳电池特征参数的实验方法

确定太阳电池的特征参数不仅是建立其电流-电压方程的基础,也是理解太阳电池这一非线性器件的关键。本文提出了一种简单的实验方法,基于太阳电池在非标准测试条件与暗条件下的电流和电压测量结果,通过修正得到了其在标准测试条件下的电流和电压,根据建立的模型得到了太阳电池在标准测试条件下的光电流、反向饱和电流、品质因子、串联电阻与并联电阻五个特征参数,据此得到了太阳电池的电流-电压方程。最后通过比较电流-电压方程的曲线与修正后的测量结果,发现本方法的电流均方根误差小于0.12A,能满足实验的要求。该方法有助于增强学生对太阳电池非线性输出性能的理解。

离子迁移相关的钙钛矿太阳电池J-V模型建立及其光电过程研究

重点研究离子迁移对钙钛矿薄膜太阳能电池Jsc和Voc的影响.通过理论建模和计算,发现离子迁移对电池的Voc产生了明显的影响,并证实其是J V迟滞效应的主要原因.此外,还研究多种动力学参数对电池性能的影响,如扩散系数、载流子寿命、注入速率,以及这些参数与钙钛矿薄膜厚度的关系.这一模型揭示了电池光电性能的影响因素,为钙钛矿太阳能电池性能和器件优化提供了重要的科学依据.

基于非线性互补算法的太阳能电池储能系统设计与网络建模

太阳能是一种环保型能源,利用储能系统,将太阳能转化为电能并用于驱动其他设备元件,有助于实现能源的高效利用。针对上述背景,研究基于非线性互补算法的太阳能电池储能系统设计与网络建模方法。分析太阳能储能系统的研究现状及发展趋势,结合等价非线性互补原则,确定储能部件的能量转化收敛性,实现基于非线性互补算法的电池储能收敛性研究。选用合适的电池储能元件,并在此基础上,完善动态储能模型,完成太阳能电池储能系统的网络建模与设计。

管式PECVD设备腔内大容量石墨舟力学性能的数值分析

提高等离子体增强化学气相沉积(PECVD)法制备的氮化硅薄膜品质在太阳电池光电转换效率领域有举足轻重的作用。承载大量硅片的石墨舟是管式PECVD设备中的关键核心部件,随着生产效率的不断提升,热力耦合环境下腔内大容量石墨舟力学性能的稳定性引人关注。通过CAD软件建立石墨舟有限元模型并使用ANSYS仿真软件进行热力学仿真研究,综合分析其在高温条件下受力、受热后的变形情况。研究结果显示:结构自重是石墨舟形变及应力集中产生的主要因素,温度产生的影响并不明显;采用结构增强设计可有效提升石墨舟整体的力学性能。

一个新的太阳电池显式模型以预测在任何太阳辐照度和温度时的I-V

采用求解满足实验结果的微分方程,建立一个三参数的显函数模型。经过22条实验数据的验证肯定该模型的正确性。更好的结果是该工作成功地发展出次级模型即模型参数同太阳辐照度及温度的定量关系,从而实现用太阳辐照度和温度预测太阳电池的I-V。

考虑阴影变化的太阳电池模型及动态参数分析

针对太阳电池静态模型与实际运行偏差较大,尤其是局部遮挡下均匀光照下的太阳电池模型难以适应新场景的问题,研究阴影变化下的太阳电池建模。首先,分析太阳电池的正向、反向、动态特性和小面积阴影时的内部情况,建立局部阴影下包含正、反向特性的动态模型。然后,研究阴影变化下光伏组件模型,比较模型仿真结果与实验结果,验证所建模型的准确性。最后,利用电池仿真模型,分析环境变化时电池动态参数和输出电流的变化规律。结果表明,所建模型可用于阴影变化下太阳电池动态特性仿真与动态参数分析。

Transmission line model and field analysis of metamaterial absorber：ideal concentrator of electromagnetic waves

Arising from the proposed Transmission Line(TL) model for ERR and wire structure, a TL model for a metamaterial absorber is proposed. The S-parameters obtained by this TL model demonstrate the same shapes as the simulation. An investigation of the TL model and average absorption power densities shows that the metamaterial absorber does not simply convert the electromagnetic wave into thermal energy, but concentrate the electromagnetic wave into a small space where it is finally absorbed. This suggests that the metamaterial absorber can be applied to solar cells for the purpose of light trapping.

太阳电池工程简化模型参数确定及模型应用

针对现有文献中太阳电池工程简化模型的模型系数值不适用于当今光伏组件的问题,提出简单的仅需利用光伏组件出厂数据的模型系数确定方法.系数b通过拟合25℃下不同辐照度对应的开路电压数据得到,系数a和c分别取短路电流和开路电压的温度系数.不同厂家生产的光伏组件系数b不同,同一厂家生产的不同型号的光伏组件系数b可以取相同值.综合改进后的太阳电池工程简化模型、分段函数形式的太阳电池温度模型和考虑安装条件的入射光强度模型,开展光伏组件电气输出特性的动态仿真.当组件倾角小于最佳倾角时,角度变化对最大输出功率的影响很小;当倾角大于最佳倾角时,角度变化对最大输出功率的影响较大,影响程度随着角度的增大而增大.

双面光伏组件建模及发电性能研究

针对双面光伏组件建立一种耦合模型,可用于模拟双面光伏组件在实际运行过程中的输出特性。采用视角系数法建立便于模拟背面辐照度的二维辐照度模型,提出一种简化计算方法来求解七参数电学模型,并根据能量守恒的非稳态热学模型来估计电池温度。之后通过输入参数的传递,对耦合模型进行求解,并通过实验数据验证模型的准确性。结果表明:辐照度模型可对不同天气条件下双面光伏组件辐照度进行模拟,晴天时更准确,均方根误差仅为6.9%;采用简化方法求解的七参数电学模型,求解结果与实测值较吻合,在最大功率处的功率偏差仅为0.4 W;所建立的耦合模型可对双面光伏组件单日输出功率及年度发电性能进行评估,模拟结果与实测数据吻合较好。