Ag纳米粒子等离子体共振增强太阳能电池吸收

针对薄膜太阳能电池硅薄膜层吸收效率较低的问题,提出了运用金属纳米粒子局域表面等离子体共振(LSPR)增强太阳能电池的吸收效率,采用时域有限差分(FDTD)法,模拟计算了太阳能电池中不同厚度的硅薄膜层吸收特性,分析了不同几何参数的矩形Ag纳米粒子与Ag背反射膜对增强太阳能电池吸收效率的影响作用。计算结果表明,硅薄膜层厚度为500nm的太阳能电池具有较高的吸收效率,通过调整Ag纳米粒子的相关参数,有效地降低了太阳电池硅薄膜表面的反射损耗,取得最大吸收增强因子为1.35。Ag背反射膜有效地降低了Ag纳米粒子硅薄膜结构的透射损耗,其最大的吸收增强因子达到1.42。     

Absorption enhancement of silicon solar cell with Ag nanoparticles by surface plasmons resonance

The absorption enhancements of silicon layer in silicon solar cells with three kinds of Ag nanoparticles including sphere, cylinder and cuboid are studied by the finite difference time domain （FDTD） method, respectively. The results show that the light absorption of silicon is significantly improved due to the localized surface plasmon （LSP） reso- nance. The relations of the absorption enhancement with the parameters of nanoparticles are thoroughly analyzed. The optimal absorption enhancement can be achieved by adjusting the relevant parameters. Among the three types of Ag nanoparticles, i.e., sphere, cylinder and cuboid, the silicon with the cubical Ag nanopaticles shows the most efficient absorption enhancement at optimal conditions, its maximum absorption enhancement factor is 1.35, and that with the spherical Ag nanopaticles gets the lowest absorption enhancement. The work is useful for the further theoretical study and design for the plasmonic thin-film solar cell.     

Enhanced absorption of Ag diamond-type nanoantenna arrays

The optical metal nanoantenna on thin film solar cell is effective to enhance light absorption. In this paper, the diamond-type Ag nanoantenna arrays are proposed for increasing the efficiency of solar cells by localized surface plasmons resonance(LSPR). The effect of metal nanoantenna on the absorption enhancement is theoretically investigated by the finite difference time domain(FDTD) method. Broadband absorption enhancements in both visible and near-infrared regions are demonstrated in case of solar cell with diamond-type Ag nanoantennas. The spectral response is manipulated by geometrical parameters of the nanoantennas. The maximum enhancement factor of 1.51 for solar cell is obtained. For comparison, the other three nanoantennas are also analyzed. The results show that the solar cell with optimized diamond-type nanoantenna arrays is more efficient in optical absorption.     

Design of Ag nanograting for broadband absorption enhancement in amorphous silicon thin film solar cells

Light trapping is one of the key issues to improve the light absorption and increase the efficiency of thin film solar cells. The effects of the triangular Ag nanograting on the absorption of amorphous silicon solar cells were investigated by a numerical simulation based on the finite element method. The light absorption under different angle and area of the grating has been calculated. Furthermore, the light absorption with different incident angle has been calculated. The optimization results show that the absorption of the solar cell with triangular Ag nanograting structure and anti-reflection film is enhanced up to 96% under AM1.5 illumination in the 300–800 nm wavelength range compared with the reference cell. The physical mechanisms of absorption enhancement in different wavelength range have been discussed. Furthermore, the solar cell with the Ag nanograting is much less sensitive to the angle of incident light. These results are promising for the design of amorphous silicon thin film solar cells with enhanced performance.     

Improved Conversion Efficiency of GaN/InGaN Thin-Film Solar Cells

In this letter, we report on the fabrication and photovoltaic characteristics of p-i-n GaN/InGaN thin-film solar cells. The thin-film solar cells were fabricated by removing sapphire using a laser lift-off technique and, then, transferring the remaining p-i-n structure onto a Ti/Ag mirror-coated Si substrate via wafer bonding. The mirror structure is helpful to enhance light absorption for a solar cell with a thin absorption layer. After the thin-film process for a conventional sapphire-based p-i-n solar cell, the device exhibits an enhancement factor of 57.6% in current density and an increment in conversion efficiency from 0.55% to 0.80%. The physical origin for the photocurrent enhancement in the thin-film solar cell is related to multireflection of light by the mirror structure.      

High efficiency all‐GaAs solar cell

The reduction of surface recombination in GaAs solar cells is known to be a major concern for photovoltaic cells designers. A common technique used to reduce this effect is to cover the GaAs surface with a wide band gap window layer, therefore the creation of a heterojunction. To avoid a heterojunction with its inconveniences; interface surface states, poor photon absorption in addition to the technological exigencies, one can use an all‐GaAs solar cell. In this type of structure, a thin highly doped layer is created at the surface known as a front surface field (FSF). The main role of an FSF layer is to reduce the effect of front surface recombination and the enhancement of light‐generated free carriers' collection. This is achieved by the drastic reduction of the effective recombination at the emitter upper boundary. In this work, a simple analytical model is used to simulate the influence of the FSF layer on GaAs solar cell parameters; photocurrent, open circuit voltage and energy conversion efficiency. The effects of the FSF layer doping density and its thickness on the cell performance are discussed by using computed results. Copyright © 2010 John Wiley & Sons, Ltd.     

100‐period, 1.23‐eV bandgap InGaAs/GaAsP quantum wells for high‐efficiency GaAs solar cells: toward current‐matched Ge‐based tandem cells

Major challenges for InGaAs/GaAsP multiple quantum well (MQW) solar cells include both the difficulty in designing suitable structures and, because of the strain‐balancing requirement, growing high‐quality crystals. The present paper proposes a comprehensive design principle for MQWs that overcomes the trade‐off between light absorption and carrier transport that is based, in particular, on a systematical investigation of GaAsP barrier effects on carrier dynamics that occur for various barrier widths and heights. The fundamental strategies related to structure optimization are as follows: (i) acknowledging that InGaAs wells should be thinner and deeper for a given bandgap to achieve both a higher absorption coefficient for 1e‐1hh transitions and a lower compressive strain accumulation; (ii) understanding that GaAs interlayers with thicknesses of just a few nanometers effectively extend the absorption edge without additional compressive strain and suppress lattice relaxation during growth; and (iii) understanding that GaAsP barriers should be thinner than 3 nm to facilitate tunneling transport and that their phosphorus content should be minimized while avoiding detrimental lattice relaxation. After structural optimization of 1.23‐eV bandgap quantum wells, a cell with 100‐period In_0.30GaAs(3.5 nm)/GaAs(2.7 nm)/GaAsP_0.40(3.0 nm) MQWs exhibited significantly improved performance, showing 16.2% AM 1.5 efficiency without an anti‐reflection coating, and a 70% internal quantum efficiency beyond the GaAs band edge. When compared with the GaAs control cell, the optimized cell showed an absolute enhancement in AM 1.5 efficiency, and 1.22 times higher efficiency with 38% current enhancement with an AM 1.5 cut‐off using a 665‐nm long‐pass filter, thus indicating the strong potential of MQW cells in Ge‐based 3‐J tandem devices. Copyright © 2013 John Wiley & Sons, Ltd.     

Broadband Finite‐Difference Time‐Domain Modeling of Plasmonic Organic Photovoltaics

We develop accurate finite‐difference time‐domain (FDTD) modeling of polymer bulk heterojunction solar cells containing Ag nanoparticles between the hole‐transporting layer and the transparent conducting oxide‐coated glass substrate in the wavelength range of 300 nm to 800 nm. The Drude dispersion modeling technique is used to model the frequency dispersion behavior of Ag nanoparticles, the hole‐transporting layer, and indium tin oxide. The perfectly matched layer boundary condition is used for the top and bottom regions of the computational domain, and the periodic boundary condition is used for the lateral regions of the same domain. The developed FDTD modeling is employed to investigate the effect of geometrical parameters of Ag nanospheres on electromagnetic fields in devices. Although negative plasmonic effects are observed in the considered device, absorption enhancement can be achieved when favorable geometrical parameters are obtained.     

Efficiency Enhancement of Organic Solar Cells by Using Shape‐Dependent Broadband Plasmonic Absorption in Metallic Nanoparticles

It is been widely reported that plasmonic effects in metallic nanomaterials can enhance light trapping in organix solar cells (OSCs). However, typical nanoparticles (NP) of high quality (i.e., mono‐dispersive) only possess a single resonant absorption peak, which inevitably limits the power conversion efficiency (PCE) enhancement to a narrow spectral range. Broadband plasmonic absorption is obviously highly desirable. In this paper, a combination of Ag nanomaterials of different shapes, including nanoparticles and nanoprisms, is proposed for this purpose. The nanomaterials are synthesized using a simple wet chemical method. Theoretical and experimental studies show that the origin of the observed PCE enhancement is the simultaneous excitation of many plasmonic low‐ and high‐order resonances modes, which are material‐, shape‐, size‐, and polarization‐dependent. Particularly for the Ag nanoprisms studied here, the high‐order resonances result in higher contribution than low‐order resonances to the absorption enhancement of OSCs through an improved overlap with the active material absorption spectrum. With the incorporation of the mixed nanomaterials into the active layer, a wide‐band absorption improvement is demonstrated and the short‐circuit photocurrent density (J_sc) improves by 17.91%. Finally, PCE is enhanced by 19.44% as compared to pre‐optimized control OSCs. These results suggest a new approach to achieve higher overall enhancement through improving broadband absorption.     

Organic solar cells using plasmonics of Ag nanoprisms

We demonstrate plasmonic effects in bulk heterojunction organic solar cells (OSCs) consisting of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) by incorporating silver (Ag) triangular shaped nanoparticles (nanoprisms; NPSs) into a poly(3,4-ethylenedioxythiophene) buffer layer. The optical absorption and geometric characteristics of the Ag NPSs were investigated in terms of their tunable in-plane dipole local surface plasmon resonance (LSPR) bands. The photovoltaic characteristics showed that the power conversion efficiency (PCE) of the plasmonic OSCs was enhanced by an increase of short circuit current (J_sc) compared to that of the reference cells without any variation in electrical properties. The enhanced J_sc is directly related to the enhancement of optical absorption efficiency by the LSPR of the Ag NPSs. We measured the photovoltaic characteristics of the plasmonic OSCs with various distances between the Ag NPSs and the P3HT:PCBM active layer, in which the PCEs of the plasmonic OSCs decreased with increasing distance. This suggests that the increase of photocurrent and optical absorption was due to near field enhancement (i.e., intensified incident light on the active layer) by the LSPR of the Ag NPSs.     

Broadband scattering of the solar spectrum by spherical metal nanoparticles

Metal nanoparticles offer the possibility of improved light trapping in solar cells, but careful design is required to maximise scattering and minimise parasitic absorption across the wavelength range of interest. We present an analysis of the broadband scattering and absorption characteristics of spherical metal nanoparticles, optimized for either crystalline silicon (c‐Si) or amorphous silicon (a‐Si:H) solar cells. A random two‐dimensional array of optimally sized Ag spheres can scatter over 97% of the AM1.5 spectrum from 400 to 1100 nm. Larger particles are required for c‐Si devices than a‐Si:H due to the increased spectral range, with optimum particle sizes ranging from 60 nm for a‐Si:H to 116 nm for c‐Si. Positioning the particles at the rear of the solar cell decreases absorption losses because these principally occur at short wavelengths. Increasing the refractive index of the surrounding medium beyond the optimum value, which is 1.0 for a‐Si:H and 1.6 for c‐Si, shifts absorption to longer wavelengths and decreases scattering at short wavelengths. Ag nanoparticles scatter more of the solar spectrum than Au, Cu or Al nanoparticles. Of these other metals, Al can only be considered for a‐Si:H applications due to high absorption in the near‐infrared, whereas Au and Cu can only be considered for the rear of c‐Si devices due to high absorption in the ultraviolet (UV) and visible. In general, we demonstrate the importance of considering the broadband optical properties of metal nanoparticles for photovoltaic applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Open‐circuit voltage recovery in type II GaSb/GaAs quantum ring solar cells under high concentration

We report on the open‐circuit voltage recovery in GaSb quantum ring (QR) solar cells under high solar concentration up to 2500 suns. The detailed behaviour of type II GaSb/GaAs QR solar cells under solar concentration, using different temperatures and light illumination conditions, is analysed through optical and electrical measurements. Although enhancement of the short‐circuit current was observed because of sub‐bandgap photon absorption in the QR, the thermionic emission rate of holes was found to be insufficient for ideal operation. The direct excitation of electron–hole pairs into QRs has revealed that the accumulation of holes is one of the causes of the open‐circuit voltage (V_OC) degradation. However, using concentrated light up to 2500 suns, the GaSb QR cell showed much quicker V_OC recovery rate than a GaAs control cell. Copyright © 2015 John Wiley & Sons, Ltd.     

金属表面等离激元增强聚合物太阳电池

研究了Au纳米颗粒表面等离激元增强聚噻吩(P3HT)与富勒烯衍生物(PCBM)共混体系聚合物太阳电池的光电转换效率。Au纳米颗粒表面由双十烷基二甲基溴化铵(DDAB)修饰,能够均匀分散在活性层中。研究了Au纳米颗粒的质量分数对电池性能的影响,发现质量分数为1.2%时,电池性能最佳,转换效率高达3.76%,较未掺杂的参比电池相对提高约20%。掺入Au纳米颗粒后P3HT和PCBM共混膜光吸收显著增强,从而使电池外量子效率大大增加。电池效率的提升主要归结于Au纳米颗粒表面等离激元激发所引起的近场增强。     

基于纳米锥结构的钙钛矿材料吸收特性研究

本文对ZnO结构太阳能电池钙钛矿(CaTiO₃)薄 膜层中嵌入的Ag粒子的等离子体增强进行了理论分析。由于引入了Ag颗粒,归因于Ag颗粒的 强表面等离子体吸收和Ag与CaTiO₃之间的协同作用,太阳能电池的吸收得以增强。在计算 分析中,Ag粒子的最佳半径为80 nm。优化的纳米结构的平均吸收效 率可以达到80％,比纯CaTiO₃薄膜层结构的平均吸收效率高24％。因此认为,本文设计研究的 Ag/CaTiO₃太阳能电池结构可能以低成本和简单的制造工艺成为未来工业制造领域的焦点 。     

Nanoparticle‐enhanced light trapping in thin‐film silicon solar cells

A systematic investigation of the nanoparticle‐enhanced light trapping in thin‐film silicon solar cells is reported. The nanoparticles are fabricated by annealing a thin Ag film on the cell surface. An optimisation roadmap for the plasmon‐enhanced light‐trapping scheme for self‐assembled Ag metal nanoparticles is presented, including a comparison of rear‐located and front‐located nanoparticles, an optimisation of the precursor Ag film thickness, an investigation on different conditions of the nanoparticle dielectric environment and a combination of nanoparticles with other supplementary back‐surface reflectors. Significant photocurrent enhancements have been achieved because of high scattering and coupling efficiency of the Ag nanoparticles into the silicon device. For the optimum light‐trapping scheme, a short‐circuit current enhancement of 27% due to Ag nanoparticles is achieved, increasing to 44% for a “nanoparticle/magnesium fluoride/diffuse paint” back‐surface reflector structure. This is 6% higher compared with our previously reported plasmonic short‐circuit current enhancement of 38%. Copyright © 2011 John Wiley & Sons, Ltd.     

Broadband absorption enhancement in ultra‐thin crystalline Si solar cells by incorporating metallic and dielectric nanostructures in the back reflector

We propose a back reflecting scheme in order to enhance the maximum achievable current in one micron thick crystalline silicon solar cells. We perform 3D numerical investigations of the scattering properties of metallic nanostructures located at the back side and optimize them for enhancing absorption in the silicon layer. We validate our numerical results experimentally and also compare the absorption enhancement in the solar cell structure, both with quasi‐periodic and random metallic nanostructures. We have looked at the interplay between the metallic nanostructures and an integrated back reflector. We show that the combination of metallic nanoparticles and a metallic reflector results in significant parasitic absorption. We compared this to another implementation based on titanium dioxide nanoparticles, which act as a Lambertian reflector of light. Our simulation and experimental results show that this proposed configuration results in reduced absorption losses and in broadband enhancement of absorption for ultra‐thin solar cells, paving the way to an optimal back reflector for thin film photovoltaics. Copyright © 2014 John Wiley & Sons, Ltd.     

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 ceil.Based on the effective reflective index model of the single crystal silicon solar ceil,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.     

Incorporation of silver and gold nanostructures for performance improvement in P3HT: PCBM inverted solar cell with rGO/ZnO nanocomposite as an electron transport layer

Inefficient light absorption and inefficient charge separation are considered as two major impediments for the efficiency improvement in bulk heterojunction organic solar cells (BHJ OSCs). In this work, we report the simultaneous role of modified electron transport layer (ETL) and photoactive layers on the performance of poly (3-hexylthiophene), [6, 6]-phenyl C61-butyric acid methyl ester (P3HT: PCBM) BHJ OSCs. To modify the ETL, composite of reduced graphene oxide (rGO) (0.4 wt %) and ZnO nanoparticles (NPs) was used, which resulted in efficiency enhancement from 3.13 to 3.81%, as compared to a value of 3.13% when only ZnO was used. Thereafter, to improve upon the optical absorption properties, the photoactive layer is modified by embedding nanoparticles and nanorods of Ag and Au into it. The size of Ag and Au nanoparticles were chosen to be 50 nm while the dimensions of Ag and Au nanorods were so controlled to obtain length of approx. 50 nm and width of ∼10 nm. All the devices were fabricated in inverted geometry and 20 wt% nanostructures embedded devices showed the best results. For Ag and Au NPs embedded devices, the maximum power conversion efficiency was found to be 4.21% and 4.44%, respectively. On the other hand, for Ag and Au NRs embedded devices, the maximum efficiency was 4.37% and 4.85%, respectively. For comparison, the control devices where no nanostructures were embedded, which shows efficiency of 3.81%. Therefore, an overall enhancement in efficiency was nearly 1.21 and 1.1, 1.16, 1.14, 1.27 fold after modifying ETL as well as the active layer. The reasons for performance improvement were ascribed to better charge extraction properties of ETL, enhanced light absorption due to localized surface plasmon resonance (LSPR) and efficient light scattering by the nanostructures and improved global mobilities.     

The application of porous Si photonic crystals for metal-resonance enhanced fluorescence

This paper has demonstrated the resonance fluorescence enhancement of R6G when gold nanoparticles (Au NPs) deposited in the porous Si photonic crystal device. Both of microcavity (MC) and distributed Bragg reflector (DBR) with different parameters are investigated for making the photon transmission of photonic crystal device play an optimal role in enhancing fluorescence resonance. While minor changes were observed on the DBR substrates, a significant change in the intensity of enhanced fluorescence varies with the defect modes of MC substrates. Particularly, the strongest enhancement has been presented as the MC defect mode wavelength located at the maximum absorption wavelength of Au NPs. In this case, the fluorescence intensity of R6G on MC device is 2.5 times of that of R6G based on DBR device.     

Enhanced Structural Stability and Performance Durability of Bulk Heterojunction Photovoltaic Devices Incorporating Metallic Nanoparticles

Despite the progress on organic photovoltaic (OPV) performance, the photoactive layer degradation during prolonged solar illumination is still a major obstacle. In this work, an approach to mitigate the degradation pathway related to structural/morphological changes of the photoactive layer occurring upon continuous illumination in air is presented. It is shown, for the first time, that the incorporation of Ag nanoparticles in poly(3‐hexylthiophene) (P3HT) and [6‐6]‐phenyl‐C61‐butyric acid methyl ester bulk heterojunction (BHJ) leads to improved structural and morphological properties of the composite BHJ solar cells and to better photovoltaic (PV) stability after long periods of continuous illumination. This is evidenced by an original approach based on joint in‐situ time‐resolved X‐ray and atomic force microscopy monitoring. Besides the structural stability improvement and reduced photodegradation rate, it is shown that the composite blends exhibit superior PV performance compared to the pristine BHJs. It can be postulated that the incorporation of metallic nanoparticles in the BHJ leads to a dual enhancement, a plasmon absorption mediated effect, causing improved initial cell efficiency, and a structural stability effect giving rise to reduced degradation rate upon prolonged illumination. The results are in favor of the exploitation of polymer–nanoparticle composites as a promising approach to mitigate the aging effects in OPVs.