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Polak DW, do Casal MT, Toldo JM, Hu X, Amoruso G, Pomeranc O, Heeney M, Barbatti M, Ashfold MNR, Oliver TAA. Probing the electronic structure and photophysics of thiophene-diketopyrrolopyrrole derivatives in solution. Phys Chem Chem Phys 2022; 24:20138-20151. [PMID: 35993400 PMCID: PMC9429679 DOI: 10.1039/d2cp03238d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Diketopyrrolopyrroles are a popular class of electron-withdrawing unit in optoelectronic materials. When combined with electron donating side-chain functional groups such as thiophenes, they form a very broad class of donor–acceptor molecules: thiophene–diketopyrrolopyrroles (TDPPs). Despite their widescale use in biosensors and photovoltaic materials, studies have yet to establish the important link between the electronic structure of the specific TDPP and the critical optical properties. To bridge this gap, ultrafast transient absorption with 22 fs time resolution has been used to explore the photophysics of three prototypical TDPP molecules: a monomer, dimer and polymer in solution. Interpretation of experimental data was assisted by a recent high-level theoretical study, and additional density functional theory calculations. These studies show that the photophysics of these molecular prototypes under visible photoexcitation are determined by just two excited electronic states, having very different electronic characters (one is optically bright, the other dark), their relative energetic ordering and the timescales for internal conversion from one to the other and/or to the ground state. The underlying difference in electronic structure alters the branching between these excited states and their associated dynamics. In turn, these factors dictate the fluorescence quantum yields, which are shown to vary by ∼1–2 orders of magnitude across the TDPP prototypes investigated here. The fast non-radiative transfer of molecules from the bright to dark states is mediated by conical intersections. Remarkably, wavepacket signals in the measured transient absorption data carry signatures of the nuclear motions that enable mixing of the electronic-nuclear wavefunction and facilitate non-adiabatic coupling between the bright and dark states. The interplay of two excited electronic states dictates the ultrafast dynamics and functionality of thiophene-diketopyrrolopyrrole derivatives.![]()
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Affiliation(s)
- Daniel W Polak
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, BS8 1TS, UK.
| | | | | | - Xiantao Hu
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, White City Campus, London, W12 0BZ, UK
| | - Giordano Amoruso
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, BS8 1TS, UK.
| | - Olivia Pomeranc
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, BS8 1TS, UK.
| | - Martin Heeney
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, White City Campus, London, W12 0BZ, UK
| | - Mario Barbatti
- Aix Marseille Université, CNRS, ICR, Marseille, France.,Institut Universitaire de France, 75231, Paris, France
| | - Michael N R Ashfold
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, BS8 1TS, UK.
| | - Thomas A A Oliver
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, BS8 1TS, UK.
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Manna B, Nandi A, Vats BG. Role of nanosize and defect trapping upon singlet fission yield and singlet fission dynamics of 1,6-Diphenyl-1,3,5-hexatriene nanoaggregates. J Photochem Photobiol A Chem 2021. [DOI: 10.1016/j.jphotochem.2021.113262] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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