石墨烯/硅肖特基结太阳能电池的研究进展

太阳能电池利用光伏效应直接将光能转变成电能,能有效地解决未来能源危机和环境污染,符合可持续发展的理念.传统的硅基太阳能电池存在需要高温过程,工艺复杂,发电成本无法与火电和水电相抗衡等问题.针对上述问题,近年来研究人员开发了诸多新型太阳能电池以降低制造成本,其中采用石墨烯作为透明电极的石墨烯/硅肖特基结太阳能电池被认为是新一代低成本、高效率的太阳能电池.然而,石墨烯功函数较低、方阻较高,载流子沿界面复合严重,并且平面硅反射率较高,导致石墨烯/硅肖特基结太阳能电池的效率远低于传统硅基太阳能电池.因此,近年来,主要研究重点在石墨烯掺杂改性、抑制界面处的载流子复合和降低器件的反射率等方面.目前,石墨烯/硅肖特基结太阳能电池的光电转换效率(PCE)已由1.65％提升到16.61％.目前,成功应用于提升器件性能的石墨烯掺杂剂主要有HNO3、金属纳米粒子和双(三氟甲磺酰基)酰胺(TFSA)等.其中,HNO3应用最为广泛,但其稳定性较差,采用金属纳米粒子等物理掺杂可以同时提升器件的PCE和稳定性.在石墨烯和硅之间引入Al2 O3、MoS2、量子点等界面层和表面钝化,可以有效地减少硅表面的悬空键,抑制载流子复合,从而提高器件的性能.此外,研究人员通过在石墨烯表面引入TiO2、PMMA、MgF2/ZnS等减反射膜,或在硅表面引入纳米线、多孔硅等微结构,来降低器件的反射率,提高其对光的利用率.本文总结了近年来石墨烯/硅太阳能电池的研究进展,简要介绍了器件的结构和原理,重点介绍了石墨烯掺杂、石墨烯层数选择、硅的纳米或微米结构、减反射膜和界面优化等手段,分析了目前石墨烯/硅肖特基结太阳能电池商业化所面临的问题并对其提出展望,以期为制备效率高和稳定性强的新型石墨烯/硅肖特基结太阳能电池提供一定参考.     

基于碳纳米管背电极的晶体硅太阳能电池

碳纳米管(CNTs)具有优异的电学与光电性能,可用作太阳能电池的空穴传输材料。本文将CNTs薄膜置于晶体硅(c-Si)太阳能电池的背面,以取代铝背电极,构成c-Si/CNTs太阳能电池。c-Si/CNTs太阳能电池的短路电流密度可达35.5 mA·cm~(-2),比刷涂铝背极c-Si电池的高8%。表明CNTs具有很强的空穴收集和输运能力,可用作c-Si太阳能电池的背电极。用稀氢氟酸(HF)处理c-Si/CNTs界面,放置100 h后,电池的填充因子由44.5%提高到62.6%,转换效率由7.1%提高到10.9%。     

Si/PEDOT:PSS异质结太阳能电池研究进展

以有机材料作为空穴传输层的Si/有机杂化太阳能电池由于其器件结构与制备工艺的不断优化,在短期内实现了理论探究与合成应用的快速增长。但有机材料具有的导电性低和复合界面间稳定性差等缺点,严重影响了复合器件的光电转化效率和使用寿命,阻碍了异质结太阳能电池的技术发展与市场应用。在Si/有机杂化太阳能电池领域,聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸盐(PEDOT∶PSS)是目前为止效果最佳的有机半导体。PEDOT∶PSS具有高导电性和高透过率等特点,使其成为一种理想的有机空穴传输层材料,并在异质结太阳能电池技术发展和工业应用中脱颖而出。利用PEDOT∶PSS的高导电性能可实现空穴的有效传输,其较高的透过性降低了P-N结生成过程中的寄生吸收,并且在制备中免去了传统硅基太阳能电池所需的高温环节,有效地降低了实际生产成本。近五年来,为降低PEDOT∶PSS中绝缘的PSS对电子传输和表面复合性的影响,大量学者进行了掺杂改性和界面设计的研究工作,有效降低了绝缘性PSS带来的影响,充分发挥了PEDOT高透性和高导电率的优势,优化表面陷光性和器件稳定性,实现了光电转化效率从5.09%至17.4%的大幅度跳跃。本文从Si/PEDOT∶PSS异质结太阳能电池的结构与工作原理出发,重点介绍了Si材料和PEDOT∶PSS有机物的表面修饰、PEDOT∶PSS的掺杂改性、界面氧化层改性和对嵌入式微电网电极改造手段及它们对整体器件性能提升的影响等工作,归纳并分析了Si/PEDOT∶PSS杂化太阳能电池的最新研究进展,展望了太阳能电池的技术研发和理论研究,对未来Si/PEDOT∶PSS异质结太阳能电池的实验室技术研发与工业化生产应用具有一定参考意义。     

P3HT及CTCHT修饰纳米TiO2的光电性能研究

用光电流作用谱、光电流-电势图等光电化学方法研究了聚3-己基噻吩(P3HT)及3-己基噻吩和2-噻吩甲酸共聚物(CTCHT)修饰纳米结构TiO2电极的光电转换性质。结果表明,经修饰后的纳米TiO2电极光电流明显增强,光电转换效率得到明显提高。在复合膜电极中存在p-n异质结,异质结的存在有利于光生电子-空穴对的分离,降低了电荷的反向复合几率,提高了光电转换效率。     

有机薄膜太阳能电池

有机太阳能电池作为一种新兴的有着巨大潜力的光电转换器件,吸引了越来越多的关注。综述了有机薄膜太阳能电池主要的两种器件结构的研究进展,即基于无机异质结发展出来的双异质结型有机太阳能电池和基于扩展双层异质结活性层受限的接触面积而提出的体异质结型太阳能电池;阐述了这两种器件结构的工作原理、影响有机太阳能电池光电转换效率的因素以及两种结构的不足之处,并展望了有机太阳能电池发展的广阔前景。     

多层减反射膜对PERC太阳电池性能的影响

优化晶体硅材料的光学特性,可有效提高晶体硅太阳能电池的光电转换效率.采用等离子体增强化学气相沉积(PECVD)法,在钝化发射极和背表面太阳电池(PERC)上成功制备出叠层结构的多层减反射薄膜提升硅材料的光学特性.研究结果表明,正面使用二氧化硅(SiO2)、氮化硅(SiNx)、氮氧化硅作为器件的叠层介质膜,将SiO2/Si优良的界面性质和SiNx、氮氧化硅稳定的化学性质结合起来,使器件具有稳定的钝化特性.在叠层结构器件中,Si O 2作为缓冲层有利于减少光学损失和钝化表面缺陷态,薄的SiO2几乎不会对多层减反结构产生干扰.SiNx可以有效降低光在器件表面的光学反射率,增加光的透射从而减少器件本身的光学损失.氨气有助于强化氢气在硅片表面的扩散,降低长波的光学损失和降低表面复合速率.PECVD制备的氮氧化硅在短波区域具有很好的吸收效果,表面复合速率明显下降,有效提高器件的短波响应.与此同时,经过热处理的减反射薄膜还可以钝化器件的缺陷,最终提升太阳能电池的减反射性能和钝化性能.     

碳纳米管和二甲基亚砜对钙钛矿太阳电池中PEDOT:PSS空穴传输层的协同影响

聚(3,4-亚乙二氧基噻吩)-聚(苯乙烯磺酸)(PEDOT:PSS)是平面结构钙钛矿太阳电池中空穴传输层的典型材料, 为了改善其导电性能以及促进后续钙钛矿层的生长, 本文将碳纳米管(CNTs)和二甲基亚砜(DMSO)同时引入PEDOT:PSS进行共修饰。结果表明: CNTs和DMSO在CNT-DMSO-PEDOT:PSS共修饰膜中展现了优异的协同效应。均匀贯穿于基体且几近网格状的CNTs具有促进后续钙钛矿层生长及降低共修饰膜方块电阻的功能; DMSO扮演着加强共修饰膜的导电能力及控制CNTs流失的角色。因此, 与单修饰膜相比, 共修饰膜不仅能更有效地传输电荷, 而且其表面生长的钙钛矿层晶粒尺寸更大, 覆盖率更高。此外, 共修饰膜在可见光范围内仍然保持优异的透光率, 550 nm波长处的透光率为88.8%。组装成器件后, 共修饰膜的光电转换效率(PCE)为5.75%, 远高于CNTs和DMSO单修饰膜及纯PEDOT:PSS膜, 后三者的PCE分别为3.01%、2.03%和1.30%。     

超声低温等离子体在太阳能电池表面的改性作用

传统硅基太阳能制备工艺生产出的多晶硅太阳能电池的光电转换效率在17%左右~([1]),难以突破。利用超声低温等离子体设备对电池表面进行处理,结果显示,经过处理后,多晶硅太阳能电池的峰值功率与光电转换效率提升了5%左右。由此推测,利用超声低温等离子体处理多晶硅电池表面的方法,具有使氮化硅表面钝化、去除磷硅玻璃、清洗电池片以及优化表面绒面等作用,因此,利用该技术可提升太阳能电池片的产品性能。     

高效热稳定碳基钙钛矿太阳能电池的制备技术探究

太阳能作为一种绿色环保的技术受到人们的广泛关注,但由于太阳能电池存在自身缺陷,难以实现更大规模的推广。因此,薄膜光伏半导体材料应运而生。其中,卤化物钙钛矿(HPV)材料的应用使太阳能电池的光电转换效率提升了20%以上,但仍与理论值存在一定的差距,所以该材料的效率还存在提升空间。基于此,该文主要研究了CsPbI2Br钙钛矿材料的集成器件的吸光性能、光电转换效率等,促进高效的热稳定碳基钙钛矿太阳能电池的制备技术的发展进步。     

铜铟硫纳米粒子对钙钛矿太阳能电池性能的影响

为克服钙钛矿太阳能电池滞后效应,本文通过热注射法制得CuInS_2纳米粒子,将其以0.01%(摩尔比例)掺入甲胺/甲脒(FAPbI_3)_x(MAPbCl_3)_(1-x)混合钙钛矿中制备吸光层,并组装正向平面异质结钙钛矿太阳能电池,掺杂CuInS_2器件的正向扫描光电转化效率达15.66%,反向扫描结果达15.36%,两者仅相差1.95%;而未经掺杂的器件正向扫描光电转化效率为15.14%,反向扫描结果为13.58%,两者相差11.49%。结果表明,在(FAPbI_3)_x(MAPbCl_3)_(1-x)混合钙钛矿吸光层中掺杂CuInS_2有利于相应器件磁滞效应等各项性能的提升。     

Solar cells with graphene and carbon nanotubes on silicon

Graphene and carbon nanotubes (CNTs) represent attractive materials for photovoltaic (PV) devices due to their unique electronic and optical properties. Graphene and single-wall carbon nanotubes (SWNTs) layers can be directly configured as energy conversion materials to fabricate thin-film solar cells, serving as both photogeneration sites and charge carrier collecting/transport layers. SWNTs can be modified into either p-type conductor through chemical doping (like acidic purification) or n-type conductor through polymer functionalisation. The solar cells can be simply made of a semitransparent thin film of graphene (or SWNTs) deposited on a proper type of silicon substrate to create high-density Schottky (or p–n) junctions at the interface. The high aspect ratios and large surface area of these carbon nano-structured materials can benefit exciton dissociation and charge carrier transport thus improving the power conversion efficiency.     

Influence of Cu2O surface treatment on the photovoltaic properties of Al-doped ZnO/Cu2O solar cells

Low cost Al-doped ZnO (AZO)/Cu₂O Schottky barrier solar cells with a high conversion efficiency of 2.19% were fabricated by depositing a transparent conducting AZO thin film on high quality Cu₂O sheets prepared by thermally oxidizing copper sheets. To achieve efficiencies higher than 2%, it is necessary to form the AZO thin film at a low deposition temperature using a low-damage deposition method, i.e., at room temperature by a pulsed laser deposition. In addition, the obtained efficiency could be enhanced with a surface treatment of the Cu₂O sheets, such as by applying a Pd-Sn catalyst layer as a coating or a rapid thermal annealing treatment at approximately 500 °C in air.     

Robust and Aligned Carbon Nanotube/Titania Core/Shell Films for Flexible TCO‐Free Photoelectrodes

Carbon nanotube (CNT)/semiconducting oxide hybrids are an ideal architecture for light‐harvesting devices, in which the CNTs are expected to not only act as a scaffold but also provide fast transport paths for photogenerated charges in the oxide. However, the current potential of CNTs for charge transport is largely suppressed due to the nanotubes not being interconnected but isolated by the low conductive oxide coatings. Herein, a flexible and conductive CNT/TiO₂ core/shell heterostructure film is reported, with aligned and interconnected CNTs wrapped in a continuous TiO₂ coating. Without using additional transparent conducting oxide (TCO) substrates, this unique feature of the film boosts the incident photon‐to‐electron conversion efficiency to 32%, outperforming TiO₂ nanoparticle electrodes fabricated on TCO substrates. Moreover, the film shows high structural stability and can generate a stable photocurrent even after being bent hundreds of times.     

Highly Efficient (>10%) Flexible Organic Solar Cells on PEDOT‐Free and ITO‐Free Transparent Electrodes

A novel approach to fabricate flexible organic solar cells is proposed without indium tin oxide (ITO) and poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) using junction‐free metal nanonetworks (NNs) as transparent electrodes. The metal NNs are monolithically etched using nanoscale shadow masks, and they exhibit excellent optoelectronic performance. Furthermore, the optoelectrical properties of the NNs can be controlled by both the initial metal layer thickness and NN density. Hence, with an extremely thin silver layer, the appropriate density control of the networks can lead to high transmittance and low sheet resistance. Such NNs can be utilized for thin‐film devices without planarization by conductive materials such as PEDOT:PSS. A highly efficient flexible organic solar cell with a power conversion efficiency (PCE) of 10.6% and high device yield (93.8%) is fabricated on PEDOT‐free and ITO‐free transparent electrodes. Furthermore, the flexible solar cell retains 94.3% of the initial PCE even after 3000 bending stress tests (strain: 3.13%).     

陷光结构在GaAs薄膜太阳电池中的应用

陷光结构由于其独特的光学特性,在光伏器件中发挥的作用越来越重要。目前硅基太阳电池中陷光结构的应用很常见,然而在GaAs薄膜太阳电池中陷光结构的报道并不多。详细介绍了陷光结构的原理及其在GaAs薄膜电池中的研究现状和应用情况。综述了GaAs薄膜太阳能电池中常用的三类陷光结构:正面陷光结构(包括纳米颗粒、纳米线、纳米锥等)、背面陷光结构(如镜面背反射层)以及混合陷光结构。大量研究表明,陷光结构的使用可以进一步提高GaAs薄膜电池的光电转换效率,一定程度上达到降低电池生产成本的目的。     

High-performance single CdS nanowire (nanobelt) Schottky junction solar cells with Au/graphene Schottky electrodes

High-performance single CdS nanowire (NW) as well as nanobelt (NB) Schottky junction solar cells were fabricated. Au (5 nm)/graphene combined layers were used as the Schottky contact electrodes to the NWs (NBs). Typical as-fabricated NW solar cell shows excellent photovoltaic behavior with an open circuit voltage of ～0.15 V, a short circuit current of ～275.0 pA, and an energy conversion efficiency of up to ～1.65%. The physical mechanism of the combined Schottky electrode was discussed. We attribute the prominent capability of the devices to the high-performance Schottky combined electrode, which has the merits of low series resistance, high transparency, and good Schottky contact to the CdS NW (NB). Besides, a promising site-controllable patterned graphene transfer method, which has the advantages of economizing graphene material and free from additional etching process, was demonstrated in this work. Our results suggest that semiconductor NWs (NBs) are promising materials for novel solar cells, which have potential application in integrated nano-optoelectronic systems.     

Flexible cadmium telluride/cadmium sulphide thin film solar cells on mica substrate

Polycrystalline thin film II–VI compound semiconductors of cadmium sulfide (CdS) and cadmium telluride (CdTe) are the leading materials for the development of cost effective and reliable photovoltaic systems. The two important properties of these materials are its nearness to the ideal band gap for photovoltaic conversion efficiency and they have high optical absorption coefficients. Usually thin film solar cells are made by hetero-junction of p-type CdTe with n-type CdS partner window layer. In this article, we have deposited CdTe films on mica substrates using thermal evaporation technique and CdTe/CdS junction were developed by depositing a thin layer of CdS on to the CdTe substrate from chemical bath deposition method. The device was characterized by current voltage and photocurrent spectroscopy technique prior to the deposition of the transparent conducting layer. The devices were annealed in air at different temperatures and found that the device annealed at 673?K had better photovoltaic parameters. The efficiency of a typical device under 50?mW?cm^?2 illumination was estimated as 4%.     

Hybrid silicon nanocone-polymer solar cells

Recently, hybrid Si/organic solar cells have been studied for low-cost Si photovoltaic devices because the Schottky junction between the Si and organic material can be formed by solution processes at a low temperature. In this study, we demonstrate a hybrid solar cell composed of Si nanocones and conductive polymer. The optimal nanocone structure with an aspect ratio (height/diameter of a nanocone) less than two allowed for conformal polymer surface coverage via spin-coating while also providing both excellent antireflection and light trapping properties. The uniform heterojunction over the nanocones with enhanced light absorption resulted in a power conversion efficiency above 11%. Based on our simulation study, the optimal nanocone structures for a 10 μm thick Si solar cell can achieve a short-circuit current density, up to 39.1 mA/cm(2), which is very close to the theoretical limit. With very thin material and inexpensive processing, hybrid Si nanocone/polymer solar cells are promising as an economically viable alternative energy solution.     

聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸复合LB膜在OLED器件上的应用

采用Langmuir-Blodgett(LB)膜静电诱导沉积法制备聚3,4-乙烯二氧噻吩(PEDOT)高度有序导电聚合物复合薄膜,研究了薄膜的导电性能并进一步研究薄膜在改善器件性能方面的作用.并将其应用于有机电致发光二极管(OLED)器件的空穴缓冲层,将聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸(PEDOT/PSS)复合LB沉积于纳米铟锡金属氧化物(ITO)电极上,制备了以复合LB膜为空穴缓冲层的OLED器件.发现复合LB膜改善了器件性能(启动电压降低,最大亮度增加),但进一步的研究表明LB膜器件在一定时间后出现性能劣化.I-V特性和X射线反射率(XRR)分析表明,薄膜的结构发生一定程度的改变是导致器件性能变差的可能原因.     

Scalable Bacterial Cellulose-Based Radiative Cooling Materials with Switchable Transparency for Thermal Management and Enhanced Solar Energy Harvesting

Radiative cooling materials that can dynamically control solar transmittance and emit thermal radiation into cold outer space are critical for smart thermal management and sustainable energy-efficient buildings. This work reports the judicious design and scalable fabrication of biosynthetic bacterial cellulose (BC)-based radiative cooling (Bio-RC) materials with switchable solar transmittance, which are developed by entangling silica microspheres with continuously secreted cellulose nanofibers during in situ cultivation. Theresulting film shows a high solar reflection (95.3%) that can be facilely switched between an opaque state and a transparent state upon wetting. Interestingly, the Bio-RC film exhibits a high mid-infrared emissivity (93.4%) and an average sub-ambient temperature drop of ≈3.7 °C at noon. When integrating with a commercially available semi-transparent solar cell, the switchable solar transmittance of Bio-RC film enables an enhancement of solar power conversion efficiency (opaque state: 0.92%, transparent state: 0.57%, bare solar cell: 0.33%). As a proof-of-concept illustration, an energy-efficient model house with its roof built with Bio-RC-integrated semi-transparent solar cell is demonstrated. This research can shine new light on the design and emerging applications of advanced radiative cooling materials.