高浓度石墨烯水系分散液及其气液界面自组装膜

通过测试石墨烯分散液的吸光度,比较了几种表面活性剂分散石墨烯的能力.结果表明:聚乙烯吡咯烷酮(PVP)这种"绿色"、低成本的表面活性剂,具有很好的分散能力.通过提高PVP溶液浓度,可以得到浓度高达～1.3mg/mL的石墨烯分散液,这种高浓度石墨烯分散液可以在气液界面自组装得到石墨烯膜,这种无支撑石墨烯膜具有平整的表面和规则的结构,在很多领域都有良好的潜在应用价值.     

石墨烯/锂金属复合材料的制备和电化学性能

对于高能量密度锂金属电池体系,安全、稳定的锂负极材料是关键。采用微波还原、热还原和机械剥离方法制备了3种具有不同形貌结构的石墨烯,并通过压制和叠层工艺,制备出石墨烯/锂金属复合材料。通过扫描电子显微镜(SEM)、拉曼(Raman)、X射线光电子能谱(XPS)和N₂吸脱附曲线分析了不同石墨烯材料的形貌、组成、结构以及石墨烯/锂金属复合材料的形貌。同时采用Li||Li对称电池和LiFeO₄全电池,评价了石墨烯/锂金属复合材料作为负极的电化学性能。结果表明,石墨烯/锂金属复合材料具有层状结构,在微波还原石墨烯(MRGO)、热还原石墨烯(RGO)和机械剥离石墨烯(EG)中,MRGO最适用于改性金属锂,叠层3次得到的4MRGO/3Li复合材料具有最优的电化学性能。基于4MRGO/3Li的Li||Li对称电池在9.9 mV左右的极化电压下稳定循环1200圈,相对于纯锂金属,极化电压降低10.6 mV,安全性和稳定性大大提升。以4MRGO/3Li复合材料为负极的LiFeO₄全电池稳定循环800圈后,放电容量保持为156 mAh/g。     

CuSCN作为石墨烯/硅异质结太阳能电池无机界面层的数值模拟

界面工程是改善石墨烯/硅异质结太阳能电池性能的有效方法之一,但目前常用的界面材料存在价格高、稳定性差等问题.本实验采用AFORS-HET软件对石墨烯/硅太阳能电池进行数值模拟,并引入无机界面材料CuSCN实现降低电池成本、优化器件性能和稳定性的目的,研究了CuSCN界面层的作用、CuSCN层的空穴迁移率和CuSCN/n-Si的价带补偿对太阳能电池性能的影响.结果表明,引入CuSCN界面层和增加CuSCN层的空穴迁移率均有利于提高器件的光伏性能.当CuSCN/n-Si界面的价带补偿大于-0.1 eV时,CuSCN层可作为电子阻挡-空穴传输层;并且当CuSCN/n-Si界面的价带补偿为0.2 eV时,所构建的石墨烯/CuSCN/硅异质结太阳能电池模型取得了25.8％的最佳光电转换效率.本研究有助于揭示影响石墨烯/CuSCN/硅异质结太阳能电池性能的各种因素,为制备低成本、高效率的石墨烯/硅太阳能电池提供了有效途径.     

三维碳纳米管阵列/石墨烯的制备及在电池和超级电容器中的应用

石墨烯是一种由碳原子以sp~2杂化轨道结合,呈六角型蜂巢晶格的二维平面材料,是构成碳质材料的基本单元。石墨烯是目前强度最大、导电导热性能最强的材料,在传感器、电池和超级电容器等领域有广泛的应用。但是在电池和超级电容器应用中,石墨烯与电解液的接触面积仍比较小,一维碳纳米管阵列垂直生长在石墨烯平台上,形成三维碳纳米管阵列/石墨烯,可进一步扩大石墨烯与电解液的接触面积同时产生协同效应,显著提高电池和超级电容器的性能。综述了三维碳纳米管阵列/石墨烯的制备方法及在电池和超级电容器中的应用。     

用于锂离子电池的石墨烯材料——储能特性及前景展望

石墨烯具有独特的二维结构、优异的性能和各种潜在的应用价值,是当前材料科学领域研究的热点.通过简要评述石墨烯作为锂离子电池负极材料的结构与性能的关系,讨论了作为电极材料的石墨烯结构与功能调控的重要性,指出石墨烯基纳米材料是一种很有吸引力的锂离子电池电极材料,尤其针对高能量密度与高功率密度电池.     

石墨烯及其复合材料在锂离子电池负极材料中的应用

石墨烯作为一种仅有单原子层厚度的新型碳材料,具有独特的结构和优异的电学、热学、力学等性能.石墨烯的产业化应用一直是国际上的研究热点.由于其高电导率、超大的比表面积、高化学稳定性等优异的物理和化学特性,石墨烯作为锂离子电池电极材料有着巨大的应用前景.综述了近5年来石墨烯及其复合材料在锂离子电池负极材料中应用的最新研究成果和进展,并对今后的研究工作进行了展望.     

锂离子电池中石墨烯导电剂分散方法的研究进展

石墨烯具有柔性、二维、超薄的结构特性,兼具电导率高、导热性好、力学性能强及化学稳定性良好等物理化学性质,是一种极具潜力的锂离子电池导电剂,石墨烯难以分散的问题是制约其在锂离子电池中广泛应用的重要原因。结合石墨烯的结构特征、衍生物种类及制备方法,从提升石墨烯的浸润性、协同分散以及防止二次团聚等方面,综述了石墨烯导电剂的分散方法,包括化学改性法、原位还原法、复合导电剂法、引入分散剂法以及其它方法,并对未来石墨烯导电剂的应用趋势及研究方向进行了展望。     

石墨烯及其复合材料作为锂离子电池负极材料的研究进展

石墨烯作为一种锂离子电池负极材料表现出优异的电化学性能。本文介绍了石墨烯负极材料、金属/石墨烯复合材料、金属氧化物/石墨烯复合材料和其他石墨烯复合材料的研究现状,阐述了石墨烯作为负极材料的优越性,展望了石墨烯及其复合复合材料在锂离子电池负极材料中的应用前景。     

石墨烯应用于锂硫电池的研究进展

锂硫电池具有很高的理论放电比容量(1 675 mAh/g)和能量密度(2 600 Wh/kg),被认为是最具前景的新型电池之一。石墨烯具有优良的导电性和电化学性能,具有开阔的负载硫的表面和空间,是导电性差的硫黄和硫化锂的良好载体,为锂硫电池正极材料提供了新的研发平台。本文介绍了近年来石墨烯及其复合材料应用于锂硫电池中的研究进展,包括石墨烯或氧化石墨烯负载硫、杂原子掺杂石墨烯负载硫、石墨烯三维网格负载硫和石墨烯-多孔炭复合炭材料负载硫等4种石墨烯基-硫正极材料,概述了其锂硫电池的比容量、倍率性能和循环寿命等性能指标。从石墨烯基锂硫电池正极材料的设计和合成的角度,总结了不同微结构特征的石墨烯及其复合材料组装成锂硫电池的性能特点,并分析了材料组成和微结构对电池性能的影响机制。在总结的基础上展望了石墨烯应用于锂硫电池的发展方向。     

石墨烯/硅肖特基结界面优化研究进展

在各种商业太阳能电池中,传统硅基太阳能电池由于其原材料丰富、制作工艺成熟等优势,在全球光伏市场中占据着主导地位。但是传统硅基太阳能电池在生产过程中需要高温扩散或者离子注入形成p-n结等原因使其成本高于常规能源,并且这个过程能耗高同时对环境造成污染,与清洁能源的目标相矛盾。因此,进一步降低光伏发电成本,一直是人们所追求的目标。近年来,石墨烯/硅(Gr/Si)肖特基结太阳能电池因其工艺简单且有望实现低成本器件制备而备受关注。石墨烯具有透光率高、导电性好等特点,可作为此类太阳能电池中光生载流子分离的活性层和透明电极。同时石墨烯的导电性可通过化学掺杂或增加石墨烯薄膜层数得以提高。当前,界面工程、化学掺杂、减反薄膜等技术的引入使石墨烯/硅(Gr/Si)肖特基结太阳能电池的光电转换效率在短短几年就从1.65%提高到16.61%(接近传统硅基太阳能电池的水平),说明石墨烯/硅(Gr/Si)肖特基结太阳能电池具有巨大的发展潜力。但是硅表面存在大量的悬挂键和缺陷,这些表面态可以充当电子的俘获和复合中心,极大地增加了硅表面载流子复合速率,造成费米能级钉扎、肖特基势垒降低,不利于器件性能的提升。通过Gr/S...     

A highly efficient polymer non-fullerene organic solar cell enhanced by introducing a small molecule as a crystallizing-agent

Non-fullerene organic solar cells (OSCs) have attracted tremendous interest because of their potential to replace traditional expensive fullerene-based OSCs. To further increase the power conversion efficiency (PCE), it is necessary to offset the narrow absorption of the non-fullerene materials, which is often achieved by adding an additive (>10?wt%) to form a ternary blend. However, a high ratio of the third component can often be detrimental to the active layer morphology and can increase the complexity in understanding the device physics toward rationally designed improvements. In this work, we introduce 2,4-bis-[(N,N-diisobutylamino)-2,6-dihydroxyphenyl]-4-(4-diphenyliminio) squaraine (ASSQ) in the poly [(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl) benzo [1,2-b:4,5-b′] dithiophene)-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl) benzo [1,2-c:4,5-c′] dithiophene-4,8-dione)] (PBDB-T): 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno [2,3-d:2′,3′-d′]-s-indaceno [1,2-b:5,6-b′] dithiophene (ITIC) as an active layer “crystallizing-agent”. Through detailed morphology characterization, we find that the addition of 4?wt% ASSQ assists ITIC organization order and promotes PDBD-T:ITIC aggregation in the preferential face-on orientation. In addition, we demonstrate that the ASSQ and PBDB-T show efficient exciton dissociation in the ternary blend over Förster resonance energy transfer (FRET). We reveal using surface potential and solubility measurements that a ASSQ-ITIC co-crystalline structure forms which facilitates a significant improvement in the device PCE, from 8.98% to 10.86%.     

Investigation of post-thermal annealing-induced enhancement in photovoltaic performance for squaraine-based organic solar cells

In this work, we have systematically investigated the post-thermal annealing-induced enhancement in photovoltaic performance of a 2,4-bis[4-(N, N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (DIBSQ)/C₆₀ planar heterojunction (PHJ) organic solar cells (OSCs). An increased power conversion efficiency (PCE) of 3.28% has been realized from a DIBSQ/C₆₀ device with thermal annealing at 100 °C for 4 min, which is about 33% enhancement compared with that of the as-cast device. The improvement of the device performance may be mainly ascribed to the crystallinity of the DIBSQ film with post-thermal annealing, which will change the DIBSQ donor and C₆₀ acceptor interface from PHJ to hybrid planar-mixed heterojunction. This new donor–acceptor heterojunction structure will significantly improve the charge separation and charge collection efficiency, as well as the open circuit voltage (V_oc) of the device, leading to an enhanced PCE. This work provides an effective strategy to improve the photovoltaic performance of SQ-based OSCs.     

Solution‐Processed Semitransparent Organic Photovoltaics: From Molecular Design to Device Performance

Recent research efforts on solution‐processed semitransparent organic solar cells (OSCs) are presented. Essential properties of organic donor:acceptor bulk heterojunction blends and electrode materials, required for the combination of simultaneous high power conversion efficiency (PCE) and average visible transmittance of photovoltaic devices, are presented from the materials science and device engineering points of view. Aspects of optical perception, charge generation–recombination, and extraction processes relevant for semitransparent OSCs are also discussed in detail. Furthermore, the theoretical limits of PCE for fully transparent OSCs, compared to the performance of the best reported semitransparent OSCs, and options for further optimization are discussed.     

一种可增强光陷阱效应的多孔ZnO/PEIE电子传输层在高效有机太阳能电池中的应用

在本工作中,我们制备了一种多孔的有机/无机复合电子传输层(P-ZnO),并将其成功用于反向有机太阳能电池中.P-ZnO不仅拥有适宜的功函,且可形成较大欧姆接触面积的独特表面,有利于器件中的电荷提取.与ZnO基器件相比,P-ZnO基器件的活性层具有增强的光陷阱效应.在PBDB-T/DTPPSe-2F,PM6/Y6和PTB...     

A 3-Fluoropyridine Manipulating the Aggregation and Fibril Network of Donor Polymers for Eco-Friendly Solution-Processed Versatile Organic Solar Cells

The development of eco-friendly solvent-processed organic solar cells (OSCs) suitable for industrial-scale production should be now considered the imperative research. Herein, asymmetric 3-fluoropyridine (FPy) unit is used to control the aggregation and fibril network of polymer blends. Notably, terpolymer PM6(FPy = 0.2) incorporating 20% FPy in a well-known donor polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b’]dithiophene))-alt-(5,5-(1’,3’-di-2-thienyl-5’,7’-bis(2-ethylhexyl)benzo[1’,2’-c:4’,5’-c’]dithiophene-4,8-dione)] (PM6) can reduce the regioregularity of the polymer backbone and endow them with much-enhanced solubility in eco-friendly solvents. Accordingly, the excellent adaptability for fabricating versatile devices based on PM6(FPy = 0.2) by toluene processing is demonstrated. The resulting OSCs exhibit a high power conversion efficiency (PCE) of 16.1% (17.0% by processed with chloroform) and low batch-to-batch variation. Moreover, by controlling the donor-to-acceptor weight ratio at 0.5:1.0 and 0.25:1.0, semi-transparent OSCs (ST-OSCs) yield significant light utilization efficiencies of 3.61% and 3.67%, respectively. For large-area (1.0 cm²) indoor OSC (I-OSC), a high PCE of 20.6% is achieved with an appropriate energy loss of 0.61 eV under a warm white light-emitting diode (3,000 K) with the illumination of 958 lux. Finally, the long-term stability of the devices is evaluated by investigating their structure–performance–stability relationship. This work provides an effective approach to realizing eco-friendly, efficient, and stable OSCs/ST-OSCs/I-OSCs.     

Over 14% Efficiency in Organic Solar Cells Enabled by Chlorinated Nonfullerene Small‐Molecule Acceptors

To make organic solar cells (OSCs) more competitive in the diverse photovoltaic cell technologies, it is very important to demonstrate that OSCs can achieve very good efficiencies and that their cost can be reduced. Here, a pair of nonfullerene small‐molecule acceptors, IT‐2Cl and IT‐4Cl, is designed and synthesized by introducing easy‐synthesis chlorine substituents onto the indacenodithieno[3,2‐b]thiophene units. The unique feature of the large dipole moment of the C? Cl bond enhances the intermolecular charge‐transfer effect between the donor–acceptor structures, and thus expands the absorption and down shifts the molecular energy levels. Meanwhile, the introduction of C? Cl also causes more pronounced molecular stacking, which also helps to expand the absorption spectrum. Both of the designed OSCs devices based on two acceptors can deliver a power conversion efficiency (PCE) greater than 13% when blended with a polymer donor with a low‐lying highest occupied molecular orbital level. In addition, since IT‐2Cl and IT‐4Cl have very good compatibility, a ternary OSC device integrating these two acceptors is also fabricated and obtains a PCE greater than 14%. Chlorination demonstrates effective ability in enhancing the device performance and facile synthesis route, which both deserve further exploitation in the modification of photovoltaic materials.     

16.67% Rigid and 14.06% Flexible Organic Solar Cells Enabled by Ternary Heterojunction Strategy

Ternary heterojunction strategies appear to be an efficient approach to improve the efficiency of organic solar cells (OSCs) through harvesting more sunlight. Ternary OSCs are fabricated by employing wide bandgap polymer donor (PM6), narrow bandgap nonfullerene acceptor (Y6), and PC₇₁BM as the third component to tune the light absorption and morphologies of the blend films. A record power conversion efficiency (PCE) of 16.67% (certified as 16.0%) on rigid substrate is achieved in an optimized PM6:Y6:PC₇₁BM blend ratio of 1:1:0.2. The introduction of PC₇₁BM endows the blend with enhanced absorption in the range of 300–500 nm and optimises interpenetrating morphologies to promote photogenerated charge dissociation and extraction. More importantly, a PCE of 14.06% for flexible ITO‐free ternary OSCs is obtained based on this ternary heterojunction system, which is the highest PCE reported for flexible state‐of‐the‐art OSCs. A very promising ternary heterojunction strategy to develop highly efficient rigid and flexible OSCs is presented.     

Over 12% Efficiency Nonfullerene All‐Small‐Molecule Organic Solar Cells with Sequentially Evolved Multilength Scale Morphologies

In this paper, two near‐infrared absorbing molecules are successfully incorporated into nonfullerene‐based small‐molecule organic solar cells (NFSM‐OSCs) to achieve a very high power conversion efficiency (PCE) of 12.08%. This is achieved by tuning the sequentially evolved crystalline morphology through combined solvent additive and solvent vapor annealing, which mainly work on ZnP‐TBO and 6TIC, respectively. It not only helps improve the crystallinity of the ZnP‐TBO and 6TIC blend, but also forms multilength scale morphology to enhance charge mobility and charge extraction. Moreover, it simultaneously reduces the nongeminate recombination by effective charge delocalization. The resultant device performance shows remarkably enhanced fill factor and J_sc. These result in a very respectable PCE, which is the highest among all NFSM‐OSCs and all small‐molecule binary solar cells reported so far.     

High‐Efficiency All‐Small‐Molecule Organic Solar Cells Based on an Organic Molecule Donor with Alkylsilyl‐Thienyl Conjugated Side Chains

Two medium‐bandgap p‐type organic small molecules H21 and H22 with an alkylsily‐thienyl conjugated side chain on benzo[1,2‐b:4,5‐b′]dithiophene central units are synthesized and used as donors in all‐small‐molecule organic solar cells (SM‐OSCs) with a narrow‐bandgap n‐type small molecule 2,2′‐((2Z,2′Z)‐((4,4,9,9‐tetrahexyl‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(methanylylidene))bis(3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (IDIC) as the acceptor. In comparison to H21 with 3‐ethyl rhodanine as the terminal group, H22 with cyanoacetic acid esters as the terminal group shows blueshifted absorption, higher charge‐carrier mobility and better 3D charge pathway in blend films. The power conversion efficiency (PCE) of the SM‐OSCs based on H22:IDIC reaches 10.29% with a higher open‐circuit voltage of 0.942 V and a higher fill factor of 71.15%. The PCE of 10.29% is among the top efficiencies of nonfullerene SM‐OSCs reported in the literature to date.     

Halogen-Free Donor Polymers Based on Dicyanobenzotriazole with Low Energy Loss and High Efficiency in Organic Solar Cells

Halogenation of organic semiconductors is an efficient strategy for improving the performance of organic solar cells (OSCs), while the introduction of halogens usually involves complex synthetic process and serious environment pollution problems. Herein, three halogen-free ternary copolymer donors (PCNx, x = 3, 4, 5) based on electron-withdrawing dicyanobenzotriazole are reported. When blended with the Y6, PCN3 with strong interchain interactions results in appropriate crystallinity and thermodynamic miscibility of the blend film. Grazing-incidence wide-angle X-ray scattering measurements indicate that PCN3 has more ordered arrangement and stronger π–π stacking than previous PCN2. Fourier-transform photocurrent spectroscopy and external quantum efficiency of electroluminescence measurements show that PCN3-based OSCs have lower energy loss than PCN2, which leads to their higher open-circuit voltage (0.873 V). The device based on PCN3 reaches power conversion efficiency (PCE) of 15.33% in binary OSCs, one of the highest values for OSCs with halogen-free donor polymers. The PCE of 17.80% and 18.10% are obtained in PM6:PCN3:Y6 and PM6:PCN3:BTP-eC9 ternary devices, much higher than those of PM6:Y6 (16.31%) and PM6:BTP-eC9 (17.33%) devices. Additionally, this ternary OSCs exhibit superior stability compared to binary host system. This work gives a promising path for halogen-free donor polymers to achieve low energy loss and high PCE.