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fluorination vs. chlorination： a case study on high performance organic photovoltaic materials

Science China Chemistry 2018年第10期61卷 1328-1337页

作者： Yun Zhang Huifeng Yao Shaoqing Zhang Yunpeng Qin Jianqi Zhang Liyan Yang Wanning Li Zhixiang Wei Feng Gao Jianhui Hou State Key Laboratory of Polymer Physics and Chemistry Beijing National Laboratory for Molecular Sciences CAS Research/Education Center for Excellence in Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China School of Chemistry and Biological Engineering University of Science and Technology Beijing Beijing 100083 China Key Laboratory of Nanosystem and Hierarchical Fabrication National Center for Nanoscience and Technology Beijing 100190 China Department of Physics Chemistry and Biology (IFM) Linkoping University Linkoping SE-581 83 Sweden

Halogenation is a very efficient chemical modification method to tune the molecular energy levels, absorption spectra and molecular packing of organic semiconductors. Recently, in the field of organic solar cells(OSCs), both fluorine-and chlorinesubstituted photovoltaic materials, including donors and acceptors, demonstrated their great potentials in achieving high power conversion efficiencies(PCEs), raising a question that how to make a decision between fluorination and chlorination when designing materials. Herein, we systemically studied the impact of fluorination and chlorination on the properties of resulting donors(PBDB-T-2 F and PBDB-T-2 Cl) and acceptors(IT-4 F and IT-4 Cl). The results suggest that all the OSCs based on different donor and acceptor combinations can deliver good PCEs around 13%–14%. Chlorination is more effective than fluorination in downshifting the molecular energy levels and broadening the absorption spectra. The influence of chlorination and fluorination on the crystallinity of the resulting materials is dependent on their introduction positions. As chlorination has the advantage of easy synthesis, it is more attractive in designing low-cost photovoltaic materials and therefore may have more potential in largescale applications.

关键词： organic solar cells bandgap engineering fluorination chlorination

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fluorination of suspended graphene

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Nano Research 2017年第9期10卷 3151-3163页

作者： Claudia Struzzi Mattia Scardamaglia Nicolas Reckinger Jean-Francois Colomer Hikmet Sezen Matteo Amati Luca Gregoratti Rony Snyders Carla Bittencourt Chimie des Interactions Plasma-Surface CIRMAP University of Mons 7000 Mons Belgium Research Group on Carbon Nanostructures (CARBONNAGe) University of Namur 5000 Namur Belgium Elettra - Sincrotrone Trieste S.C.p.A. di interesse nazionale Strada Statale 14 km 163.5 34149 Trieste Italy Materia Nova Research Center B-7000 Mons Belgium

Suspended graphene is exposed to different fluorine-containing species produced by a plasma source fed with CF4 precursor gas. We investigate the fluorination process by selecting two different kinetic energies for the ions striking the graphene surface. The chemical-bonding environment is discussed, and the control of the graphene-fluorination homogeneity is investigated at the individual graphene sheets. The modifications of the electronic and structural properties are examined by scanning photoelectron microscopy, micro-Raman analysis, and scanning electron microscopy. The results are compared with those obtained for supported graphene on copper. Suspended graphene provides a quasi-ideal model for investigating the intrinsic properties of irradiated carbon nano-systems while avoiding damage due to backscattered atoms and recoil due to a supporting substrate.

关键词： graphene fluorination spectromicroscopy X-ray photoelectron spectroscopy (XPS) Raman scanning electron microscopy (SEM)

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fluorination-substitution effect on all-small-molecule organic solar cells

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Science China Chemistry 2019年第7期62卷 837-844页

作者： Qiong Wu Dan Deng Jianqi Zhang Wenjun Zou Yang Yang Zhen Wang Huan Li Ruimin Zhou Kun Lu Zhixiang Wei CAS Key Laboratory of Nanosystem and Hierarchical Fabrication CAS Center for Excellence in Nanoscience National Center for Nanoscience and Technology Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China Sino-Danish College University of Chinese Academy of Sciences Beijing 100190 China

Due to the strong crystallinity and anisotropy of small molecules, matched molecular photoelectric properties and morphologies between small molecules and non-fullerene acceptors are especially important in all-small-molecule organic solar cells(OSCs).Introducing fluorine atoms has been proved as an effective strategy to achieve a high device performance through tuning molecular energy levels, absorption and assembly properties. Herein, we designed a novel benzodithiophene-based small molecule donor BDTF-CA with deep highest occupied molecular orbital(HOMO) energy level. All-small-molecule OSCs were fabricated by combing non-fullerene acceptor IDIC with different fluorine-atom numbers. Two or four fluorine atoms were introduced to the end-capped acceptor of IDIC, which are named as IDIC-2 F and IDIC-4 F, respectively. With the increase of fluorination from IDIC to IDIC-4 F, the open circuit voltage(Voc) of the devices decreased, while hole and electron mobilities of the active layers increased by one order of magnitude. Contributed to the most balanced Voc, short-circuit current(Jsc) and fill factor(FF), the device based on BDTF-CA/IDIC-2 F achieved the highest power conversion efficiency of 9.11%.

关键词： organic solar cells all-small-molecule fluorination blend morphology energy levels

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fluorination over Cr doped layered perovskite Sr_(2)TiO_(4) for efficient photocatalytic hydrogen production under visible light illumination

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Journal of Energy Chemistry 2020年第12期29卷 30-38页

作者： Jinxing Yu Xiaoxiang Xu Clinical and Central Lab Putuo People’s HospitalTongji University1291 Jiangning RoadShanghai 200060China Shanghai Key Lab of Chemical Assessment and Sustainability School of Chemical Science and EngineeringTongji University1239 Siping RoadShanghai 200092China

Cr doped Ruddlesden-Popper compound Sr2 TiO4 has been successfully modified by fluorine to form a new compound Sr2 Ti(0.95) Cr(0.05) O3 F2. Structure analysis suggests two types of fluorine in the structure of this new compound, i.e. intralayer and interlayer F, which induce strong built-in electric field within this layered compound. The electric field stems from uneven distribution of F atoms on the two sides of perovskite layers therefore leads to charge disproportionation. DFT calculations suggest that this unique structural feature is highly beneficial for charge dissociations as it breaks the coplanar settlement of conduction band minimum and valence band maximum whilst maintains the 2 D charge transportation properties. This is clearly demonstrated by the superior photocatalytic activities of Sr2 Ti(0.95) Cr(0.05) O3 F2 for hydrogen production from water. Apparent quantum efficiency(AQE) as high as 1.16% at 420 ± 20 nm has been achieved which stands as the highest AQE reported on Sr2 TiO4 to date. Photoelectrochemical(PEC)analysis confirms improved charge separation conditions and prolonged charge lifetime.

关键词： DFT fluorination Sr_(2)TiO_(4) Photocatalytic water splitting 2D charge transportation

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fluorination-mitigated high-current degradation of amorphous InGaZnO thin-film transistors

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Journal of Semiconductors 2023年第9期44卷 57-61页

作者： Yanxin Wang Jiye Li Fayang Liu Dongxiang Luo Yunping Wang Shengdong Zhang Lei Lu School of Electronic and Computer Engineering Peking University Shenzhen Graduate SchoolShenzhen 518055China Huangpu Hydrogen Innovation Center/Guangzhou Key Laboratory for Clean Energy and Materials School of Chemistry and Chemical EngineeringGuangzhou UniversityGuangzhou 510006China Institute of Microelectronics Peking UniversityBeijing 100871China

As growing applications demand higher driving currents of oxide semiconductor thin-film transistors(TFTs),severe instabilities and even hard breakdown under high-current stress(HCS)become critical *** this work,the triggering voltage of HCS-induced self-heating(SH)degradation is defined in the output characteristics of amorphous indium-galliumzinc oxide(a-IGZO)TFTs,and used to quantitatively evaluate the thermal generation process of channel donor *** fluorinated a-IGZO(a-IGZO:F)was adopted to effectively retard the triggering of the self-heating(SH)effect,and was supposed to originate from the less population of initial deep-state defects and a slower rate of thermal defect transition in a-IGZO:*** proposed scheme noticeably enhances the high-current applications of oxide TFTs.

关键词： amorphous indium-gallium-zinc oxide(a-IGZO) thin-film transistors(TFTs) current stress self-heating(SH) fluorination

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fluorination strategy enables greatly improved performance for organic solar cells based on polythiophene derivatives

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Chinese Chemical Letters 2021年第7期32卷 2274-2278页

作者： Chenyi Yang Shaoqing Zhang Junzhen Ren Pengqing Bi Xiaotao Yuan Jianhui Hou School of Chemistry and Biology Engineering University of Science and Technology BeijingBeijing 100083China State Key Laboratory of Polymer Physics and Chemistry Beijing National Laboratory for Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190China

The power conversion efficiencies(PCEs)of organic solar cells(OSCs)have reached 18%recently,which have already met the demand of practical ***,these outstanding results were generally achieved with donor-acceptor(D-A)type copolymer donors,which can hardly fulfill the low-cost largescale production due to their complicated synthesis ***,developing polymer donors with simple chemical structures is urgent for realizing low-cost ***(PT)derivatives are currently regarded as promising candidates for such kind of donor materials,which has been illustrated in many *** this work,two new alkylthio substituted PT derivatives,P301 and P302,were synthesized and tested as donors in the OSCs using Y5 as the accepto *** comparison,the introduction of fluorine atoms on the backbone of P302 can not only downshift the energy levels,but also greatly improve the phase separation morphologies of the active layers,which is ascribed to the enhanced aggregation effect and the reduced miscibility with the non-fullerene *** a result,the P302:Y5-based OSC exhibits a significantly improved PCE of 9.65%than that of P301:Y5-based one,indicating the important role of fluorination in the construction of efficient PT derivative donors.

关键词： Organic solar cells Polythiophene derivatives fluorination Aggregation effect Miscibility

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Understanding how charge-charge interaction affects the stereochemistry of enamine fluorination by chiral primary amine catalysis

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Science China Chemistry 2023年第10期66卷 2828-2835页

作者： Yanfang Han Kai Yang Long Zhang Sanzhong Luo Jin-Pei Cheng Center of Basic Molecular Science(CBMS) Department of ChemistryTsinghua UniversityBeijing 100084China Haihe Laboratory of Sustainable Chemical Transformations Tianjin 300192China

Electrostatic interaction, especially electrostatic attraction, usually plays critical roles in controlling the reactivity and selectivity in catalytic transformations;however, the like-charge repulsion, which is ubiquitous in physical systems, is rarely applied in reaction control. Herein we disclosed an unexpected like-charge repulsion induced enantio-control mode in primary aminecatalyzed fluorination reactions with 1-fluoro-2,4,6-trimethylpyridinium triflate. The ionic reaction works favorably in both highly polar(methanol) and non-polar(hexane) solvents, a seldom observed phenomenon in asymmetric catalysis. Erying plot analysis showed that an inversion temperature existed in Me OH, which was explained by the solvent-solute cluster model under different temperatures. Density functional theory(DFT) study and energy decomposition analysis(EDA) verified that the likecharge repulsion takes effect in polar solvent methanol, while in nonpolar solvents, the steric repulsion associated with ion-pair was found to be the major effect for the observed enantioselectivity.

关键词： aminocatalysis fluorination like-charge repulsion iso-inversion temperature ion-pair effect

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Optimal extent of fluorination enabling strong temperature-dependent aggregation, favorable blend morphology and high-efficiency polymer solar cells

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Science China Chemistry 2017年第4期60卷 545-551页

作者： Guofang Yang Zhengke Li Kui Jiang Jie Zhang Jianya Chen Guangye Zhang Fei Huang Wei Ma He Yan State Key Laboratory for Mechanical Behavior of Materials Xi 'an Jiaotong University Xi 'an 710049 China Institute of Polymer Optoelectronic Materials and Devices South China University of Technology Guangzhou 510640 China Department of Chemistry and Energy Institute The Hong Kong University of Science and Technology ClearWater Bay Kowloon Hong Kong China HKUST-Shenzhen Research Institute Shenzhen 518057 China

Temperature-dependent aggregation is a key property for some donor polymers to realize favorable bulk-heterojunction(BHJ)morphologies and high-efficiency(>10%) polymer solar *** studies find that an important structural feature that enables such temperature-dependent aggregation property is the 2nd position branched alkyl chains sitting between two thiophene *** this report,we demonstrate that an optimal extent of fluorination on the polymer backbone is a second essential structural feature that enables the strong temperature-dependent aggregation *** compare the properties of three structurally similar polymers with 0,2 or 4 fluorine substitutions in each repeating unit through an in-depth morphological *** show that the non-fluorinated polymer does not aggregate in solution(0.02 mg mL^(-1) in chlorobenzene) at room temperature,which results in poor polymer crystallinity and extremely large polymer *** the other hand,the polymer with four fluorine atoms in each repeating unit exhibits an excessively strong tendency to aggregate,which makes it difficult to process and causes a large *** the polymer with two fluorine atoms in each repeating unit exhibits a suitable extent of temperature-dependent aggregation *** a result,its blend film achieves a favorable morphology and high power conversion *** provides another key design rationale for developing donor polymers with suitable temperature-dependent aggregation properties and thus high performance.

关键词： temperature-dependent aggregation fluorination morphology polymer solar cells

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The impact of fluorination on both donor polymer and non-fullerene acceptor:The more fluorine,the merrier

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Nano Research 2019年第9期12卷 2400-2405页

作者： Nicole Bauer Qianqian Zhang Jeromy James Rech Shuixing Dai Zhengxing Peng Harald Ade Jiayu Wang Xiaowei Zhan Wei You Department of Chemistry University of North Carolina at Chapel HillNorth Carolina 27599USA Department of Materials Science and Engineering College of EngineeringKey Laboratory of Polymer Chemistry and Physics of Ministry EducationPeking UniversityBeijing 100871China Department of Physics and ORaCEL North Carolina State UniversityRaleighNorth Carolina 27695USA

fluorination of the donor polymer or non-fullerene acceptor (NFA) in an organic photovoltaic device is an effective method to improve device *** there have been many studies on donor polymer fluorination,blends containing both a fluorinated donor and fluorinated NFA have rarely been *** this study,we use two donor polymers (4'-FT-HTAZ and 4'-FT-FTAZ) and two NFAs (ITIC-Th and ITIC-Th1) with different amounts of fluorine (from 2F to 6F) to investigate how the degree of fluorination in a blend impacts device *** find that fluorinating the NFA leads to a higher short-circuit current density (Jsc) and fill factor (FF),however,the open-circuit voltage (Voc) is decreased due to a depressed lowest unoccupied molecular orbital (LUMO) *** additional fluorine to the donor polymer does not have a large effect on the Jsc or FF,but it does lead to an improved *** fluorinating the NFA and having more fluorine on the donor polymer,we obtain both a high Jsc and Voc simultaneously,leading to a power conversion efficiency over 10% in the case of 4'-FT-FTAZ:ITIC-Th1,which has the most amount of fluorine (6F).

关键词： organic solar cells non-fullerene acceptors fluorination bulk heterojunction

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Band Gap Adjustment of SiC Honeycomb Structure through Hydrogenation and fluorination

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Chinese Physics Letters 2017年第1期34卷 110-114页

作者：安玉凤戴振宏赵银昌廉超刘兆庆 Computational Physics Laboratory Institute of Opto-electronic Information Science and TechnologyYantai University Beijing National Laboratory for Condensed Matter Physics and Institute of PhysicsChinese Academy of Sciences National Natural Science Foundation of China

Previous calculations show that the two-dimensional (2D) silicon carbide (SiC) honeycomb structure is a structurally stable monolayer. Following this, we investigate the electronic properties of the hydrogen and fluorine functionalized SiC monolayer by first-principles calculations. Our results show that the functionalized monolayer becomes metallic after semi-hydrogenation or semi-fluorination, while the semiconducting properties are obtained by the full functionalization. Compared with the bare SiC monolayer, the band gap of the fully hydrogenated system is increased, in comparison with the decrease of the gap in the fully fluorinated case. As a result, the band gap can be tuned from 0.73 to 4.14 eV by the functionalization. In addition to the metal-semiconductor transition, hydrogenation and functionalization also realize a direct-indirect semiconducting transition in the 2D SiC monolayer. These results provide theoretical guidance for design of photoelectric devices based on the SiC monolayer.

关键词： HYDROGENATION ENERGY gaps (Physics) SILICON carbide HONEYCOMB structures fluorination

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