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Shen T, Gao Y, Wang C, Xu Z, Liu X. Methine-Quinoidal Fragment Induces Significant Bathochromic Shifts in Organic Dyes. J Phys Chem B 2021; 125:1447-1452. [PMID: 33530685 DOI: 10.1021/acs.jpcb.0c10752] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bathochromical shifts in the UV-vis absorption (and emission) spectra and reduced molecular sizes are two desirable features of organic dyes in many applications, i.e., live-cell fluorescence imaging and solar cells. Yet, these two features are often viewed as contradictory requirements as expanding the π-conjugation is one of the most widely used methods for prompting this redshift. Interestingly, it has been reported that linking a methine-quinoidal unit can result in a significant redshift in the UV-vis absorption spectra in comparison with the methine-benzenoidal constitutional isomers (by 61 nm in dioxane). Herein, using comprehensive quantum chemical calculations with various functionals and solvent formalisms in 10 solvents with different polarities, we demonstrated that the formation of the quinoidal moiety plays a decisive role in this redshift. We further showed that the inclusion of a quinoidal unit without increasing the molecular size represents a general design strategy for the bathochromic shifts of many organic dyes.
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Affiliation(s)
- Tianruo Shen
- Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore
| | - Ying Gao
- Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore.,Jilin Engineering Normal University, 3050 Kaixuan Road, Changchun 130052, China
| | - Chao Wang
- Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore.,CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Zhaochao Xu
- CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Xiaogang Liu
- Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore
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Do TT, Pham HD, Manzhos S, Bell JM, Sonar P. Molecular Engineering Strategy for High Efficiency Fullerene-Free Organic Solar Cells Using Conjugated 1,8-Naphthalimide and Fluorenone Building Blocks. ACS APPLIED MATERIALS & INTERFACES 2017; 9:16967-16976. [PMID: 28467709 DOI: 10.1021/acsami.6b16395] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We designed, synthesized, and characterized a series of novel electron deficient small molecule nonfullerene acceptors based on 1,8-naphthalimide (NAI) and 9-fluorenone (FN) with different branched alkyl chains using various techniques. These molecules are based on an acceptor-donor-acceptor-donor-acceptor (A1-D-A2-D-A1) molecular design configuration with NAI as the end-capping acceptor (A1), FN as electron-withdrawing central (A2) group, and thiophene ring as a donor (D) unit. These materials are named as NAI-FN-NAI (BO) and NAI-FN-NAI (HD) where BO and HD represent butyloctyl and hexyldecyl alkyl groups, respectively. To further modify energy levels of these materials, we converted the weak electron withdrawing ketonic group (C═O) attached to the FN moiety of NAI-FN-NAI (BO) to a stronger electron withdrawing cyano group (C≡N) to obtain the compound NAI-FCN-NAI (BO) by keeping the same alkyl chain. The optical, electrochemical, and thermal properties of the new acceptors were studied. The materials exhibited higher to medium band gaps, low lowest unoccupied molecular orbital (LUMO) energy levels, and highly thermally stable properties. Organic solar cell devices employing conventional poly(3-hexylthiophene) (P3HT) a donor polymer and the newly designed small molecules as the acceptor were investigated. Among all new materials, organic solar cell devices based on NAI-FN-NAI (BO) as an acceptor exhibit the highest performance with an open circuit voltage (VOC) of 0.88 V, a short-circuit current density (JSC) of 9.1 mAcm-2, a fill factor (FF) of 45%, and an overall power conversion efficiency (PCE) of 3.6%. This is the first report of 9-fluorenone based nonfullerene acceptor with P3HT donor in organic solar cell devices with such a promising performance.
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Affiliation(s)
- Thu Trang Do
- School of Chemistry, Physics, and Mechanical Engineering, Queensland University of Technology (QUT) , 2 George Street, Brisbane, Queensland 4001, Australia
| | - Hong Duc Pham
- School of Chemistry, Physics, and Mechanical Engineering, Queensland University of Technology (QUT) , 2 George Street, Brisbane, Queensland 4001, Australia
| | - Sergei Manzhos
- Department of Mechanical Engineering, Faculty of Engineering, National University of Singapore , Block EA #07-08, 9 Engineering Drive 1, Singapore 117576, Singapore
| | - John M Bell
- School of Chemistry, Physics, and Mechanical Engineering, Queensland University of Technology (QUT) , 2 George Street, Brisbane, Queensland 4001, Australia
| | - Prashant Sonar
- School of Chemistry, Physics, and Mechanical Engineering, Queensland University of Technology (QUT) , 2 George Street, Brisbane, Queensland 4001, Australia
- Institute of Future Environment, GPO Box 2434, Brisbane Queensland 4001, Australia
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