Abstract
Singlet fission, the process of splitting a singlet exciton into two triplet excitons, has been proposed as a mechanism for improving the efficiency of future photovoltaic devices. In organic semiconductors exhibiting singlet fission, the geometric relationship between molecules plays an important role by setting the intermolecular couplings that determine the system energetics. Here, we spatially image TIPS-pentacene microcrystals using ultrafast two-dimensional white-light microscopy and discover a low-energy singlet state sparsely distributed throughout the microcrystals, with higher concentrations at edges and morphological defects. The spectra of these singlet states are consistent with slip-stacked molecular geometries and increased charge-transfer couplings. The picosecond-timescale kinetics of these low-energy singlet states matches that of the correlated triplet-pair state, which we attribute to singlet/triplet-pair interconversion at these sites. Our observations support the conclusion that small populations of geometries with favourable energetics can play outsized roles in singlet fission processes.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 12 print issues and online access
$259.00 per year
only $21.58 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Data availability
The experimental data with corresponding spectral simulations are available from the authors upon request.
Code availability
The MATLAB codes used for data analysis and simulations are available from the authors upon request.
References
Smith, M. B. & Michl, J. Singlet fission. Chem. Rev. 110, 6891–6936 (2010).
Shockley, W. & Queisser, H. J. Detailed balance limit of efficiency of p–n junction solar cells. J. Appl. Phys. 32, 510–519 (1961).
Ramanan, C., Smeigh, A. L., Anthony, J. E., Marks, T. J. & Wasielewski, M. R. Competition between singlet fission and charge separation in solution-processed blend films of 6,13-bis(triisopropylsilylethynyl)pentacene with sterically-encumbered perylene-3,4:9,10-bis(dicarboximide)s. J. Am. Chem. Soc. 134, 386–397 (2012).
Walker, B. J., Musser, A. J., Beljonne, D. & Friend, R. H. Singlet exciton fission in solution. Nat. Chem. 5, 1019–1024 (2013).
Congreve, D. N. et al. External quantum efficiency above 100% in a singlet-exciton-fission-based organic photovoltaic cell. Science 340, 334–337 (2013).
Yang, L. et al. Solution-processable singlet fission photovoltaic devices. Nano Lett. 15, 354–358 (2015).
Pazos-Outon, L. M. et al. A silicon-singlet fission tandem solar cell exceeding 100% external quantum efficiency with high spectral stability. ACS Energy Lett. 2, 476–480 (2017).
Zhu, T., Wan, Y., Guo, Z., Johnson, J. & Huang, L. Two birds with one stone: tailoring singlet fission for both triplet yield and exciton diffusion length. Adv. Mater. 28, 7539–7547 (2016).
Wan, Y. et al. Cooperative singlet and triplet exciton transport in tetracene crystals visualized by ultrafast microscopy. Nat. Chem. 7, 785–792 (2015).
Wong, C. Y. et al. Revealing exciton dynamics in a small-molecule organic semiconducting film with subdomain transient absorption microscopy. J. Phys. Chem. C 117, 22111–22122 (2013).
Wong, C. Y., Cotts, B. L., Wu, H. & Ginsberg, N. S. Exciton dynamics reveal aggregates with intermolecular order at hidden interfaces in solution-cast organic semiconducting films. Nat. Commun. 6, 5946 (2015).
Folie, B. D., Haber, J. B., Refaely-Abramson, S., Neaton, J. B. & Ginsberg, N. S. Long-lived correlated triplet pairs in a π-stacked crystalline pentacene derivative. J. Am. Chem. Soc. 140, 2326–2335 (2018).
Piland, G. B. & Bardeen, C. J. How morphology affects singlet fission in crystalline tetracene. J. Phys. Chem. Lett. 6, 1841–1846 (2015).
Tayebjee, M. J. Y. et al. Morphological evolution and singlet fission in aqueous suspensions of TIPS-pentacene nanoparticles. J. Phys. Chem. C 120, 157–165 (2016).
Pensack, R. D. et al. Exciton delocalization drives rapid singlet fission in nanoparticles of acene derivatives. J. Am. Chem. Soc. 137, 6790–6803 (2015).
Roberts, S. T. et al. Efficient singlet fission found in a disordered acene film. J. Am. Chem. Soc. 134, 6388–6400 (2012).
Schnedermann, C. et al. Sub-10 fs time-resolved vibronic optical microscopy. J. Phys. Chem. Lett. 7, 4854–4859 (2016).
Broch, K. et al. Robust singlet fission in pentacene thin films with tuned charge transfer interactions. Nat. Commun. 9, 954 (2018).
Eaton, S. W. et al. Singlet exciton fission in polycrystalline thin films of a slip-stacked perylenediimide. J. Am. Chem. Soc. 135, 14701–14712 (2013).
Sanders, S. N. et al. Quantitative intramolecular singlet fission in bipentacenes. J. Am. Chem. Soc. 137, 8965–8972 (2015).
Zirzlmeier, J. et al. Singlet fission in pentacene dimers. Proc. Natl Acad. Sci. USA 112, 5325–5330 (2015).
Kumarasamy, E. et al. Tuning singlet fission in π-bridge-π chromophores. J. Am. Chem. Soc. 139, 12488–12494 (2017).
Nagarajan, K., Mallia, A. R., Reddy, V. S. & Hariharan, M. Access to triplet excited state in core-twisted perylenediimide. J. Phys. Chem. C 120, 8443–8450 (2016).
Korovina, N. V. et al. Singlet fission in a covalently linked cofacial alkynyltetracene dimer. J. Am. Chem. Soc. 138, 617–627 (2016).
Bhattacharyya, K. & Datta, A. Polymorphism controlled singlet fission in TIPS-anthracene: role of stacking orientation. J. Phys. Chem C 121, 1412–1420 (2017).
Arias, D. H., Ryerson, J. L., Cook, J. D., Damrauer, N. H. & Johnson, J. C. Polymorphism influences singlet fission rates in tetracene thin films. Chem. Sci. 7, 1185–1191 (2016).
Mou, W. W., Hattori, S., Rajak, P., Shimojo, F. & Nakano, A. Nanoscopic mechanisms of singlet fission in amorphous molecular solid. Appl. Phys. Lett. 102, 173301 (2013).
Grieco, C. et al. Harnessing molecular vibrations to probe triplet dynamics during singlet fission. J. Phys. Chem. Lett. 8, 5700–5706 (2017).
Grieco, C. et al. Triplet transfer mediates triplet pair separation during singlet fission in 6,13-bis(triisopropylsilylethynyl)-pentacene. Adv. Funct. Mater. 27, 1703929 (2017).
Grieco, C. et al. Direct observation of correlated triplet pair dynamics during singlet fission using ultrafast mid-IR spectroscopy. J. Phys. Chem. C 122, 2012–2022 (2018).
Miyata, K., Conrad-Burton, F. S., Geyer, F. L. & Zhu, X. Y. Triplet pair states in singlet fission. Chem. Rev. 119, 4261–4292 (2019).
Bakulin, A. A. et al. Real-time observation of multiexcitonic states in ultrafast singlet fission using coherent 2D electronic spectroscopy. Nat. Chem. 8, 16–23 (2016).
Herz, J. et al. Unveiling singlet fission mediating states in TIPS-pentacene and its aza derivatives. J. Phys. Chem. A 119, 6602–6610 (2015).
Pensack, R. D. et al. Solution-processable, crystalline material for quantitative singlet fission. Mater. Horizons 4, 915–923 (2017).
Yong, C. K. et al. The entangled triplet pair state in acene and heteroacene materials. Nat. Commun. 8, 15953 (2017).
Grieco, C. et al. Dynamic exchange during triplet transport in nanocrystalline TIPS-pentacene films. J. Am. Chem. Soc. 138, 16069–16080 (2016).
Grechko, M. & Zanni, M. T. Quantification of transition dipole strengths using 1D and 2D spectroscopy for the identification of molecular structures via exciton delocalization: application to α-helices. J. Chem. Phys. 137, 184202 (2012).
Anthony, J. E., Brooks, J. S., Eaton, D. L. & Parkin, S. R. Functionalized pentacene: improved electronic properties from control of solid-state order. J. Am. Chem. Soc. 123, 9482–9483 (2001).
Gomar-Nadal, E., Conrad, B. R., Cullen, W. G. & Willams, E. A. Effect of impurities on pentacene thin film growth for field-effect transistors. J. Phys. Chem. C 112, 5646–5650 (2008).
Conrad, B. R. et al. Effect of impurities on pentacene island nucleation. Phys. Rev. B 77, 205328 (2008).
Monahan, N. & Zhu, X. Y. Charge transfer-mediated singlet fission. Annu. Rev. Phys. Chem. 66, 601–618 (2015).
Diao, Y. et al. Understanding polymorphism in organic semiconductor thin films through nanoconfinement. J. Am. Chem. Soc. 136, 17046–17057 (2014).
Wang, L., Olivier, Y., Prezhdo, O. V. & Beljonne, D. Maximizing singlet fission by intermolecular packing. J. Phys. Chem. Lett. 5, 3345–3353 (2014).
Wilson, M. W. et al. Ultrafast dynamics of exciton fission in polycrystalline pentacene. J. Am. Chem. Soc. 133, 11830–11833 (2011).
Tuan Trinh, M. et al. Distinct properties of the triplet pair state from singlet fission. Sci. Adv. 3, e1700241 (2017).
Pensack, R. D. et al. Observation of two triplet-pair intermediates in singlet exciton fission. J. Phys. Chem. Lett. 7, 2370–2375 (2016).
Loukianov, A. et al. Two-dimensional electronic stark spectroscopy. J. Phys. Chem. Lett. 8, 679–683 (2017).
Bussolotti, F., Kera, S. & Ueno, N. Potassium doping of single crystalline pentacene thin film. Phys. Rev. B 86, 155120 (2012).
Roth, F. & Knupfer, M. Impact of potassium doping on the electronic structure of tetracene and pentacene: an electron energy-loss study. J. Chem. Phys. 143, 154708 (2015).
McDonough, T. J. et al. Triplet exciton dissociation and electron extraction in graphene-templated pentacene observed with ultrafast spectroscopy. Phys. Chem. Chem. Phys. 19, 4809–4820 (2017).
Di, D. et al. Efficient triplet exciton fusion in molecularly doped polymer light-emitting diodes. Adv. Mater. 29, 1–7 (2017).
Burgos, J., Pope, M., Swenberg, C. E. & Alfano, R. R. Heterofission in pentacene-doped tetracene single crystals. Phys. Status Solidi B 83, 249–256 (1977).
Stern, H. L. et al. Identification of a triplet pair intermediate in singlet exciton fission in solution. Proc. Natl Acad. Sci. USA 112, 7656–7661 (2015).
Kearns, N. M., Mehlenbacher, R. D., Jones, A. C. & Zanni, M. T. Broadband 2D electronic spectrometer using white light and pulse shaping: noise and signal evaluation at 1 and 100 kHz. Opt. Express. 25, 7869–7883 (2017).
Sharifzadeh, S. et al. Relating the physical structure and optoelectronic function of crystalline TIPS-pentacene. Adv. Funct. Mater. 25, 2038–2046 (2015).
Yamagata, H. et al. The nature of singlet excitons in oligoacene molecular crystals. J. Chem. Phys. 134, 204703 (2011).
Kistler, K. A., Pochas, C. M., Yamagata, H., Matsika, S. & Spano, F. C. Absorption, circular dichroism and photoluminescence in perylene diimide bichromophores: polarization-dependent H- and J-aggregate behavior. J. Phys. Chem. B 116, 77–86 (2012).
Hestand, N. J. et al. Polarized absorption in crystalline pentacene: theory vs experiment. J. Phys. Chem. C 119, 22137–22147 (2015).
Hestand, N. J. & Spano, F. C. Molecular aggregate photophysics beyond the Kasha model: novel design principles for organic materials. Acc. Chem. Res. 50, 341–350 (2017).
Acknowledgements
This research was supported by NSF CHE 1665110 and AFOSR FA9550-15-1-0061.
Author information
Authors and Affiliations
Contributions
A.C.J., M.T.Z., N.M.K. and J.T.F. designed the experiment. A.C.J., N.M.K. and J.T.F. performed the measurements. A.C.J., N.M.K. and J.-J.H. performed the data analysis and modelling. A.C.J. and M.T.Z. wrote the manuscript.
Corresponding author
Ethics declarations
Competing interests
M.T.Z. is an owner of PhaseTech Spectroscopy, Inc., which sells 2D spectrometers and pulse shapers.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
Supplementary Information
Supplementary Figs. 1–16, Supplementary data and analysis and Supplementary methods.
Rights and permissions
About this article
Cite this article
Jones, A.C., Kearns, N.M., Ho, JJ. et al. Impact of non-equilibrium molecular packings on singlet fission in microcrystals observed using 2D white-light microscopy. Nat. Chem. 12, 40–47 (2020). https://doi.org/10.1038/s41557-019-0368-9
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41557-019-0368-9
This article is cited by
-
Ultrafast infrared nano-imaging of far-from-equilibrium carrier and vibrational dynamics
Nature Communications (2022)