- Dialkoxynaphthalene as an electron-rich unit for high-performance polymer solar cells with large open circuit voltages
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Dialkoxynaphthalene is a simple aromatic building block, which can be synthesized easily in a large scale. In this work, two dialkoxynaphthalene derivatives were copolymerized with electron-withdrawing benzothiadiazole (BT) derivatives to afford three donor-acceptor copolymers, PNDTBT, PNT2FTBT and PN2FTBT. The three copolymers have diverse bandgaps ranged from 1.73 to 1.86 eV, and deep HOMO energy levels up to -5.61 eV. Thermogravimetric analysis and electrochemical measurements show that these copolymers have good thermal and environment stability. The hole mobilities of these copolymers were investigated using the space charge limited current (SCLC) method as well as the organic field effect transistor (OFET) method. Polymer solar cells based on PNDTBT exhibit the best photovoltaic performance with a power conversion efficiency of 6.24% and a Voc of 0.94 V, much better than those of previously reported copolymers based on dialkoxynaphthalene.
- Qin, Hao,Cai, Dongdong,Wang, Meng,Ma, Yunlong,Yin, Zhigang,Tang, Changquan,Chen, Shan-Ci,Zheng, Qingdong
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- Terthiophene-Based D-A Polymer with an Asymmetric Arrangement of Alkyl Chains That Enables Efficient Polymer Solar Cells
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We report a series of difluorobenzothiadizole (ffBT) and oligothiophene-based polymers with the oligothiophene unit being quaterthiophene (T4), terthiophene (T3), and bithiophene (T2). We demonstrate that a polymer based on ffBT and T3 with an asymmetric arrangement of alkyl chains enables the fabrication of 10.7% efficiency thick-film polymer solar cells (PSCs) without using any processing additives. By decreasing the number of thiophene rings per repeating unit and thus increasing the effective density of the ffBT unit in the polymer backbone, the HOMO and LUMO levels of the T3 polymers are significantly deeper than those of the T4 polymers, and the absorption onset of the T3 polymers is also slightly red-shifted. For the three T3 polymers obtained, the positions and size of the alkyl chains play a critical role in achieving the best PSC performances. The T3 polymer with a commonly known arrangement of alkyl chains (alkyl chains sitting on the first and third thiophenes in a mirror symmetric manner) yields poor morphology and PSC efficiencies. Surprisingly, a T3 polymer with an asymmetric arrangement of alkyl chains (which is later described as having an "asymmetric bi-repeating unit") enables the best-performing PSCs. Morphological studies show that the optimized ffBT-T3 polymer forms a polymer:fullerene morphology that differs significantly from that obtained with T4-based polymers. The morphological changes include a reduced domain size and a reduced extent of polymer crystallinity. The change from T4 to T3 comonomer units and the novel arrangement of alkyl chains in our study provide an important tool to tune the energy levels and morphological properties of donor polymers, which has an overall beneficial effect and leads to enhanced PSC performance.
- Hu, Huawei,Jiang, Kui,Yang, Guofang,Liu, Jing,Li, Zhengke,Lin, Haoran,Liu, Yuhang,Zhao, Jingbo,Zhang, Jie,Huang, Fei,Qu, Yongquan,Ma, Wei,Yan, He
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- Influences of the non-covalent interaction strength on reaching high solid-state order and device performance of a low bandgap polymer with axisymmetrical structural units
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A high organic field-effect transistor mobility (0.29 cm2V -1s-1) and bulk-heterojunction polymer solar cell performance (PCE of 6.82%) have been achieved in a low bandgap alternating copolymer consisting of axisymmetrical structural units, 5,6-difluorobenzo-2,1, 3-thiadiazole. Introducing the fluorine substituents enhanced intermolecular interaction and improved the solid-state order, which consequently resulted in the highest device performances among the 2,1,3-thiadiazole-quarterthiophene based alternating copolymers. Copyright
- Jheng, Jyun-Fong,Lai, Yu-Ying,Wu, Jhong-Sian,Chao, Yi-Hsiang,Wang, Chien-Lung,Hsu, Chain-Shu
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- n-Type core effect on perylene diimide based acceptors for panchromatic fullerene-free organic solar cells
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Perylene diimide (PDI) based high bandgap acceptors, DTBTP, DTF2BTP, and DTF2TZP, are synthesized for use in fullerene-free organic solar cells. The two PDI rings are connected to the end of the n-type core, forming a PDI-n-type core-PDI structure. Several n-type core materials, 4,7-dithieno-2,1,3-benzothiadiazole (DTBT), 5,6-difluoro-4,7-dithieno-2,1,3-benzothiadiazole (DTF2BT), and 4,6-difluoro-2H-benzo[d][1,2,3]triazole (DTF2TZ), are incorporated in the PDI acceptors and the n-type core effect on photovoltaic properties is studies. The introduction of alkyl side chains onto the core structure weakened the intermolecular interaction, whereas fluorination of the core structure improved the backbone planarity and intermolecular ordering. DTF2BTP having a planar core structure without bulky alkyl chains yielded the best power conversion efficiency, 4.41%, when mixed with PTB7-Th donor. The n-type core structure was beneficial in terms of increasing the electron accepting properties and the absorption in the high bandgap region of non-fullerene acceptors.
- Eom, Seung Hun,Kim, Hee Su,Do, Hee Jin,Lee, Un-Hak,Wibowo, Febrian Tri Adhi,Hwang, Do-Hoon,Yoon, Sung Cheol,Jung, In Hwan
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p. 318 - 325
(2018/04/23)
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- Novel organic semiconductor compounds containing benzothiadiazole group, its manufacturing method and organic semiconductor device using the same
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The present invention provides a novel organic semiconductor compound comprising a benzothiadiazole group having high charge mobility and solubility, and a manufacturing method thereof. In addition, the present invention provides an organic semiconductor device containing the novel organic semiconductor compound comprising the benzothiadiazole group. The organic semiconductor compound is represented by chemical formula 1.COPYRIGHT KIPO 2016
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- Effect of fluorination pattern and extent on the properties of PCDTBT derivatives
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Herein, we report the synthesis of a series of fluorinated dithienyl carbazole-alt-benzothiadiazoles (PCDTBT analogues) and the characterisation of their optical, electrochemical, thermal and molecular organisation in the solid state. The polymers were decorated with fluorine on either the benzothiadiazole unit, carbazole unit or both to yield PCDTffBT, PCffDTBT and PCffDTffBT, respectively. The copolymers displayed decomposition temperatures in excess of 350°C. PCDTffBT, PCffDTBT and PCffDTffBT displayed optical band gaps of 1.86, 1.82 and 1.88 eV, respectively. It was speculated this was a consequence of the higher molecular weight of PCffDTBT relative to the other polymers. PCffDTBT and PCffDTffBT displayed shallower HOMO levels relative to PCDTffBT; a consequence of fluorinating the carbazole-donor moiety. XRD studies confirmed that fluorinating the benzothiadiazole-acceptor moiety improves molecular ordering by promoting π-π stacking of polymer backbones in solid state. Interestingly, fluorinating the carbazole-donor unit does not improve π-π stacking of polymer backbones.
- Cartwright, Luke,Yi, Hunan,Iraqi, Ahmed
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p. 1655 - 1662
(2016/02/19)
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- Effects of fluorination on the electrochromic performance of benzothiadiazole-based donor - Acceptor copolymers
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A series of thiophene and benzothiadiazole-based copolymers (PDAT-DTBT) is synthesized through Stille coupling polymerization with two mono- and di-fluorinated benzothiadiazole analogues: PDAT-DTBT-F (1F) and PDAT-DTBT-2F (2F). The introduction of fluorine atoms onto the conjugated polymer backbone is found to have a pronounced effect on the optical, electrochemical and morphological properties, which in turn, influences the electrochromic performance of the fabricated absorption/transmission type devices greatly. All the polymers switch reversibly between the colored neutral states (green/blue) to transmissive oxidized states. Systematic enhancement in the reduction process to sub-second speeds (2 C-1) and substantially improved ambient stability are observed upon fluorination of electron acceptors. Long-term stability testing of the PDAT-DTBT-F electrochromic device is carried out for up to 10 000 repeated redox cycles between the applied potentials of +1.6 and -1.6 V, without the observation of significant degradation.
- Neo, Wei Teng,Ong, Kok Haw,Lin, Ting Ting,Chua, Soo-Jin,Xu, Jianwei
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p. 5589 - 5597
(2015/06/08)
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