微晶硅/晶体硅/微晶硅异质结太阳能电池窗口层的模拟计算与优化

采用Afors-het太阳能电池异质结模拟软件,模拟了不同工作温度下,微晶硅窗口层对μc-si(p)/c-si(n)/μc-si(p+)异质结太阳能电池性能的影响,结果表明:随着微晶硅窗口层帯隙的增加,转化效率先增加后下降、开路电压不断增加;掺杂浓度的增加,电池性能整体呈现先上升后小幅下降的趋势;厚度的增加,电池的性能整体上呈现下降的趋势。随着工作温度的增加,微晶硅窗口层对应的最佳厚度和掺杂浓度值都有明显的减小趋势;但其对应的最佳帯隙有明显的增加的趋势。该实验结果为在不同温度下工作的电池提供了商业化生产的实验参数。     

P型硅衬底异质结太阳电池的优化设计

采用Afors-het软件模拟分析了结构为TCO/a-Si:H(n)/a-Si:H(i)/c-Si(p)/a-Si:H(p+)/Ag的p型硅衬底异质结太阳电池的性能,研究了各层厚度、带隙、掺杂浓度以及界面态密度等结构参数和物理参数对电池性能的影响。通过模拟优化,结合理论分析和实际工艺,得到合适的各结构参数取值。采用厚度薄且掺杂高的窗口层,嵌入本征层以钝化异质结界面缺陷,合理利用背场对于少子的背反作用,获得了较佳的太阳电池综合性能:开路电压Voc为678.9mV、短路电流密度Jsc为38.33mA/cm2、填充因子FF为84.05%、转换效率η为21.87%。     

非晶硅/微晶硅叠层电池的模拟研究

电流匹配和隧穿复合结是影响氢化非晶硅/氢化微晶硅叠层电池性能的两个关键因素.文章采用wxAMPS模拟软件研究了氢化非晶硅/氢化微晶硅叠层电池中顶电池与底电池的厚度匹配对电池短路电流的影响,以及隧穿复合结的中间缺陷态密度和掺杂浓度对叠层电池性能的影响.研究发现当顶电池和底电池的本征层厚度分别为200和2 000 nm、中间缺陷态提高到1017 cm-3·eV-1以上,且掺杂浓度提高到5×1019 cm-3时,叠层电池获得最佳性能:换效率为15.60％,短路电流密度为11.68 mA/cm2,开路电压为1.71V.     

N 型背接触晶硅太阳电池前表面场研究

利用 Silvaco 公司的 Athena 工艺仿真软件和 Atlas 器件仿真软件,对 N 型插指背结背接触(InterdigitatedBack Contact,IBC)晶硅太阳电池普遍采用的前表面场（FSF）结构进行研究,详细分析了 IBC 晶硅电池 FSF 表面掺杂浓度及扩散深度对电池性能的影响。结果表明：具有不同表面掺杂浓度和扩散深度的 FSF 对 IBC 晶硅太阳电池短路电流密度(Jsc)、开路电压(Voc)和填充因子(FF)产生显著影响,从而影响电池的转换效率(Eff)。具有较低表面浓度、深扩散 FSF 结构的 IBC 晶硅太阳电池可获得较高转换效率,当表面掺杂浓度为 5×1017cm–3时,电池转换效率Eff最高,且随 FSF 扩散深度增加略有增加,最高转换效率可达 22.3%。     

n型异质结背接触太阳电池前表面的场钝化

利用Silvaco-TCAD仿真软件建立二维模型,对n型异质结背接触(HBC)单晶硅太阳电池前表面场进行模拟研究。通过在n型单晶硅衬底正面分别引入一层较薄的本征非晶硅层和一层n+非晶硅层对电池前表面进行高质量的场钝化,分析了n+非晶硅层的厚度和掺杂浓度以及本征非晶硅层的厚度和带隙宽度对电池电学性能的影响。模拟结果表明:当n+非晶硅层厚度小于6 nm,掺杂浓度为1×1019 cm-3,本征非晶硅层的厚度为3 nm,带隙宽度大于1.5 eV时,电池前表面实现了良好的场钝化效果,HBC太阳电池获得了24.5%的转换效率。     

纳米硅/晶体硅异质结太阳电池的优化设计

采用AFORS-HET软件对TCO/nc-SiC∶H（p）/nc-Si∶H（i）/c-Si（n）/nc-Si∶H（n＋）/Al异质结太阳电池进行了模拟,分别讨论了窗口层、本征层、界面态和背场对太阳电池性能参数的影响。模拟结果表明,厚度尽可能薄的p层能减少入射光及光生载流子在窗口层的损失,对应最佳的窗口层禁带宽度为1.95eV。本征层的引入主要是钝化异质结界面,降低界面态的影响,提高电池转换效率。合理的背场设计可提高电池的转换效率1.7个百分点左右,此时最佳的异质结太阳电池的性能参数为：开路电压Voc=696.1mV,短路电流密度Jsc=38.49mA/cm^2,填充因子FF=83.52%,转换效率η=22.38%。     

中间层掺杂对具有隧穿结构的非晶硅/微晶硅叠层电池的影响

为了提高非晶硅/微晶硅叠层电池的转换效率和稳定性,在隧穿结构中引入ZnO∶B中间层,研究了中间层掺杂情况对叠层电池短路电流密度、开路电压、填充因子、转换效率等性能的影响。实验结果表明:最佳的非晶硅/微晶硅叠层电池中间层为厚度较薄、掺杂浓度较高的ZnO∶B,有利于叠层电池整体性能的提高。最终,采用厚度为40 nm,B2H6流量为5 ml/min的ZnO∶B中间层,制备出了初始效率为12.2%、衰退率在8%以内的叠层电池。     

梯度掺杂对β-FeSi2(n)/c-Si(p)太阳能电池转化效率的影响

用AFORS-HET软件对β-FeSi2(n)/c-Si(p)太阳能电池的发射层进行了梯度掺杂模拟,并研究了发射区掺杂总量相同时梯度掺杂和均匀掺杂对电池转化效率的影响。分别讨论了梯度掺杂时发射区的能带、发射区的浓度差、发射区的层数对电池转化效率的影响。实验结果表明,发射区梯度掺杂可以明显提高电池转化的效率。随着发射区各层浓度比的增大,电池转化效率先增大后保持不变;随着发射区层数的增加,电池转化效率先增大后保持不变;随着发射区厚度的增加,电池转化效率逐渐降低。梯度掺杂电池转化效率的提高总量远大于因梯度发射区过厚造成的电池转化效率的降低总量。     

β-FeSi_2(n)/c-Si(p)HIT型太阳能电池的模拟与优化

运用afors-het软件对β-FeSi2(n)/a-Si(i)/c-Si(p)结构的太阳能电池进行模拟,依次讨论了本征层、发射层、界面态对电池性能的影响。结果表明:添加本征层电池性能提高,但随着本征层厚度的增加载流子收集率下降、串联电阻增大,造成电池光电转化效率下降;发射层厚度的增加使得载流子的收集率下降造成光电转化效率下降,同时发射层掺杂浓度增大虽然使得内建电场强度增大,但载流子的复合也会加大,最终使得电池性能保持稳定;界面态使得电池性能下降,为使电池获得较好性能,界面态密度应尽可能小于1011 cm–2·e V–1。通过优化,最终使得该结构的太阳能电池光电转化效率达到17.00%。     

β-FeSi2(n)/a-Si(i)/c-Si(p)/μc-Si(p+)异质结太阳能电池模拟与优化

运用AFORS-HET软件对β-FeSi2(n)/a-Si(i)/c-Si(p)/μc-Si(p+) HIT型异质结太阳能电池的性能进行了模拟,并对各层参数进行了优化。模拟结果表明,在FeSi2(n) /c-Si(p)结构上加上本征层和背场,能显著地提高电池的性能。加入缺陷并优化各项参数后,电池的最后参数为VOC=647.7 mV, JSC=42.29 mA·cm-2, FF=75.32%, EFF=20.63%, β-FeSi2(n) /c-Si(p)太阳能电池的效率提高了2.3%。     

非晶硅薄膜光伏电池结构参数分析

考虑到nip型[ITO/a-Si(n)/a-Si(i)/a-Si(p)/Al]非晶硅光伏电池的各膜层厚度、掺杂浓度等因素,对非晶硅光伏电池的转换效率、填充因子、开路电压等性能参数进行了数值分析与讨论。结果表明,随p型层厚度的增加,光伏电池的短路电流密度、转换效率、开路电压值都有所增加。当本征层的厚度增加时,短波段内的光谱响应变差、内量子效率下降。当n型层厚度为5 nm,本征层厚度为5 nm,p型层厚度为10μm,受主掺杂浓度为2.5×1019cm-3,施主掺杂浓度为1.5×1016cm-3时,转换效率可达9.728%。     

Copolymers of Cyclopentadithiophene and Electron‐Deficient Aromatic Units Designed for Photovoltaic Applications

Alternating copolymers based on cyclopentadithiophene (CPDT) and five different electron‐deficient aromatic units with reduced optical band gaps are synthesized via Suzuki coupling. All polymers show a significant photovoltaic response when mixed with a fullerene acceptor. The frontier orbital levels of the new polymers are designed to minimize energy losses by increasing the open‐circuit voltage with respect to the optical band gap, while maintaining a high coverage of the absorption with the solar spectrum. The best cells are obtained for a copolymer of CPDT and benzooxadiazole (BO) with a band gap of 1.47 eV. This cell gives a short‐circuit current of 5.4 mA cm^?2, an open‐circuit voltage of 0.78 V, and a fill factor of 0.6, resulting in a power conversion efficiency of about 2.5%.     

Design,fabrication, and analysis of transparent silicon solar cells for multi‐junction assemblies

Transparent silicon solar cells can lead to an increased efficiency of silicon‐based multi‐junction assemblies by transmitting near and below band gap energy light for conversion in a low band gap solar cell. This analysis shows that the maximum efficiency gain for a low band gap solar cell beneath silicon at a concentration of 50 suns is 5.8%, based on ideal absorption and conversion of the photons. This work analyzes the trade‐offs between increased near band edge absorption in the silicon and silicon solar cell transparency. Application of these results to real cases including a germanium bottom solar cell is analyzed, leading to a range of cases with increased system efficiency. Non‐ideal surfaces and real silicon and germanium solar cell device performance are presented. The range of practical system gains may be as low as 2.2 – 1% absolute when compared with the efficiency of a light‐trapped silicon solar cell for 1‐sun operation, based on this work. Copyright © 2012 John Wiley & Sons, Ltd.     

Optimization and characterization of amorphous/crystalline silicon heterojunction solar cells

Amorphous hydrogenated silicon/crystalline silicon (a‐Si:H/c‐Si) heterojunction solar cells are investigated and optimized with regard to efficiency and simplicity of processing. Starting with a survey of a‐Si:H/c‐Si heterojunction solar cell results from the literature, we describe the fabrication steps of our a‐Si:H/c‐Si technology and analyze the electronic device properties by quantum efficiency, current–voltage, admittance, and capacitance–voltage measurements. The open‐circuit voltage and the fill factor of the a‐Si:H/c‐Si heterojunction solar cells under investigation are limited by recombination in the neutral zone of the crystalline Si absorber. Recombination at the a‐Si:H/c‐Si‐interface is subsidiary in respect of the limitation of the open‐circuit voltage. Our best n‐type a‐Si:H/p‐type c‐Si solar cell prepared without high‐efficiency features such as back‐surface field or surface texturing has an independently confirmed efficiency of 14.1% and an open‐circuit voltage of 655 mV. Copyright © 2001 John Wiley & Sons, Ltd.     

Silicon germanium active layer with graded band gap and µc-Si:H buffer layer for high efficiency thin film solar cells

We investigated solar cells with graded band gap hydrogenated amorphous silicon germanium active layer and hydrogenated microcrystalline silicon buffer layer at the interface of intrinsic and n-type doped layer. A significantly improved, 10.4% device efficiency was observed in this type of single junction solar cell. The intrinsic type microcrystalline silicon buffer layer is thought to play dual roles in the device; as a crystalline seed-layer for growth of n-type hydrogenated microcrystalline silicon layer and helping efficient electron collection across the i/n interface. Based on these, an enhancement in cell parameters such as the open-circuit voltage (V_oc), and fill factor (FF) was observed, where the FF and V_oc reaches up to 69% and 0.85 V respectively. Our investigation shows a simple way to improve device performance with narrow-gap silicon germanium active layer in solar cells in comparison to the conventionally constant band gap device structure.     

高效率n型硅离子注入双面太阳电池

为进一步提升n型硅双面太阳电池的转化效率,采用了磷离子注入技术制备n型硅双面太阳电池的背场.基于离子注入技术准直性和均匀性好的特点,掺杂后硅片的表面复合电流密度降低到了1.4×10-13 A/cm2,隐性开路电压可达670 mV,且分布区间更紧凑.在电阻率为1～3 Ω·cm的n型硅片基底上,采用磷离子注入技术工业化生产的n型硅双面太阳电池的正面平均转化效率达到了20.64％,背面平均转化效率达到了19.52％.内量子效率的分析结果显示,离子注入太阳电池效率的增益主要来自长波段光谱响应的提升.     

Record 1.0 V open‐circuit voltage in wide band gap chalcopyrite solar cells

Tandem solar cell structures require a high‐performance wide band gap absorber as top cell. A possible candidate is CuGaSe₂, with a fundamental band gap of 1.7 eV. However, a significant open‐circuit voltage deficit is often reported for wide band gap chalcopyrite solar cells like CuGaSe₂. In this paper, we show that the open‐circuit voltage can be drastically improved in wide band gap p‐Cu(In,Ga)Se₂ and p‐CuGaSe₂ devices by improving the conduction band alignment to the n‐type buffer layer. This is accomplished by using Zn_1−x Sn_x O_y , grown by atomic layer deposition, as a buffer layer. In this case, the conduction band level can be adapted to an almost perfect fit to the wide band gap Cu(In,Ga)Se₂ and CuGaSe₂ materials. With an improved buffer band alignment for CuGaSe₂ absorbers, evaporated in a 3‐stage type process, we show devices exhibiting open‐circuit voltages up to 1017 mV, and efficiencies up to 11.9%. This is to the best of our knowledge the highest reported open‐circuit voltage and efficiency for a CuGaSe₂ device. Temperature‐dependent current‐voltage measurements show that the high open‐circuit voltage is explained by reduced interface recombination, which makes it possible to separate the influence of absorber quality from interface recombination in future studies.     

Analysis of the EWT‐DGB solar cell at low and medium concentration and comparison with a PESC architecture

Silicon represents an interesting material to fabricate low‐cost and relatively simple and high‐efficient solar cells in the low and medium concentration range. In this paper, we discuss a novel cell scheme conceived for concentrating photovoltaic, named emitter wrap through with deep grooved base (EWT‐DGB), and compare it with the simpler passivated emitter solar cell. Both cells have been fabricated by means of a complementary metal–oxide–semiconductor‐compatible process in our laboratory. The experimental characterization of both cells is reported in the range 1–200 suns in terms of conversion efficiency, open circuit voltage, short circuit current density and fill factor. In particular, for the EWT‐DGB solar cells, we obtain an encouraging 21.4% maximum conversion efficiency at 44 suns. By using a calibrated finite‐element numerical electro‐optical simulation tool, validated by a comparison with experimental data, we study the potentials of the two architectures for concentrated light conditions considering possible realistic improvements with respect to the fabricated devices. We compare the solar cell figures of merit with those of the state‐of‐the‐art silicon back‐contact back‐junction solar cell holding the conversion efficiency record for concentrator photovoltaic silicon. Simulation results predict a 24.8% efficiency at 50 suns for the EWT‐DGB cell and up to 23.9% at 100 suns for the passivated emitter solar cell, thus confirming the good potential of the proposed architectures for low to medium light concentration. Finally, simulations are exploited to provide additional analysis of the EWT‐DGB scheme under concentrated light. Copyright © 2017 John Wiley & Sons, Ltd.     

Photonic crystal microcrystalline silicon solar cells

Enhancing the absorption of thin‐film microcrystalline silicon solar cells over a broadband range in order to improve the energy conversion efficiency is a very important challenge in the development of low cost and stable solar energy harvesting. Here, we demonstrate that a broadband enhancement of the absorption can be achieved by creating a large number of resonant modes associated with two‐dimensional photonic crystal band edges. We utilize higher‐order optical modes perpendicular to the silicon layer, as well as the band‐folding effect by employing photonic crystal superlattice structures. We establish a method to incorporate photonic crystal structures into thin‐film (~500 nm) microcrystalline silicon photovoltaic layers while suppressing undesired defects formed in the microcrystalline silicon. The fabricated solar cells exhibit 1.3 times increase of a short circuit current density (from 15.0 mA/cm² to 19.6 mA/cm²) by introducing the photonic crystal structure, and consequently the conversion efficiency increases from 5.6% to 6.8%. Moreover, we theoretically analyze the absorption characteristics in the fabricated cell structure, and reveal that the energy conversion efficiency can be increased beyond 9.5% in a structure less than 1/400 as thick as conventional crystalline silicon solar cells with an efficiency of 24%. © 2015 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.     

a-Si:H/a-SiGe:H/a-SiGe:H叠层结构太阳能电池性能的数值模拟

本文采用AMPS-1D(Analysis of Microelectronic and Photonic Structures)模拟软件在AM1.5G (100 mW/cm2) 的辐射及室温条件下模拟了a-Si:H/a-SiGe:H/a-SiGe:H三叠层太阳能电池的各项性能。本文首先对三个子电池进行模拟,设定构成叠层电池的三个子电池的带隙分别为1.8、1.6和1.4 eV。计算结果表明：缺陷态是影响电池开路电压及填充因子的重要因素。在对三叠层太阳能电池的数值模拟过程中采用两步匹配法进行电流匹配,并对隧穿结进行优化设计。模拟结果表明：叠层电池的开路电压、填充因子和转换效率在优化隧穿结后都得到提高,且S型的J-V曲线消失。同时本文还对叠层太阳能电池的能带图和载流子复合图进行分析,并将本模拟结果与实验数据相比较,可以得出模拟结果与实验数据符合的较好。