Exciton diffusion lengths of organic semiconductor thin films measured by spectrally resolved photoluminescence quenching

Lunt, Richard R.; Giebink, Noel C.; Belak, Anna A.; Benziger, J.; Forrest, Stephen R.

doi:10.1063/1.3079797

Cited by 441 publications

(461 citation statements)

References 38 publications

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“…Exciton diffusion in SubPc is most likely based on self-Förster energy transfer, with an estimated selfFörster radius of 1.5 nm (ref. 43). Considering the obtained Förster radius of 7.5 nm, excitons at the SubNc/SubPc heterojunction are transferred more efficiently to SubNc by interlayer FRET compared with diffusion toward possible a-6T/ SubPc interfaces.…”

Section: Discussionmentioning

confidence: 99%

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer

et al. 2014

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In order to increase the power conversion efficiency of organic solar cells, their absorption spectrum should be broadened while maintaining efficient exciton harvesting. This requires the use of multiple complementary absorbers, usually incorporated in tandem cells or in cascaded exciton-dissociating heterojunctions. Here we present a simple three-layer architecture comprising two non-fullerene acceptors and a donor, in which an energy-relay cascade enables an efficient two-step exciton dissociation process. Excitons generated in the remote wide-bandgap acceptor are transferred by long-range Förster energy transfer to the smaller-bandgap acceptor, and subsequently dissociate at the donor interface. The photocurrent originates from all three complementary absorbing materials, resulting in a quantum efficiency above 75% between 400 and 720 nm. With an open-circuit voltage close to 1 V, this leads to a remarkable power conversion efficiency of 8.4%. These results confirm that multilayer cascade structures are a promising alternative to conventional donor-fullerene organic solar cells.

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Section: Discussionmentioning

confidence: 99%

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer

et al. 2014

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“…These results are the first direct spatial, temporal and spectral observation of exciton transport in a molecular system, which can be taken as an archetype for both natural and engineered, ordered and disordered systems that rely on exciton transport. In addition, the imaging technique developed for this study is a general tool that can be applied to exciton transport in a wide range of materials, including those dominated by singlet exciton diffusion, characterized by much shorter exciton diffusion lengths of 10 to 50 nm 4 . As only the change in exciton distribution width must be determined, no fundamental limit exists on the shortest diffusion length that can be measured with this technique.…”

Section: Discussionmentioning

confidence: 99%

“…Exciton transport is at the core of photosynthesis 2,3 and it similarly governs the operation of a wide array of nanostructured optoelectronic devices including molecular, polymeric and colloidal-quantumdot solar cells 4,5 , light-emitting diodes 6 and excitonic transistors 7 . For example, in molecular and polymeric solar cells, excitons are generated by absorption of sunlight, and must be moved efficiently to an interface where electron and hole are separated to produce charge buildup, leading to photovoltage and photocurrent.…”

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confidence: 99%

“…These techniques include optoelectronic device modelling 14 , exciton quenching at a surface or an interface 4,6,15,16 , and exciton-density-dependent excitonexciton annihilation 17 . Such approaches produce only an average 'diffusion length', L D , defined as the mean displacement of an exciton during its lifetime, but no direct evidence exists that exciton transport occurs by hopping-driven diffusion.…”

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confidence: 99%

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Visualization of exciton transport in ordered and disordered molecular solids

et al. 2014

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Transport of nanoscale energy in the form of excitons is at the core of photosynthesis and the operation of a wide range of nanostructured optoelectronic devices such as solar cells, lightemitting diodes and excitonic transistors. Of particular importance is the relationship between exciton transport and nanoscale disorder, the defining characteristic of molecular and nanostructured materials. Here we report a spatial, temporal and spectral visualization of exciton transport in molecular crystals and disordered thin films. Using tetracene as an archetype molecular crystal, the imaging reveals that exciton transport occurs by random walk diffusion, with a transition to subdiffusion as excitons become trapped. By controlling the morphology of the thin film, we show that this transition to subdiffusive transport occurs at earlier times as disorder is increased. Our findings demonstrate that the mechanism of exciton transport depends strongly on the nanoscale morphology, which has wide implications for the design of excitonic materials and devices.

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“…For example, the malaria drug artemisinin is commercially produced with a key photochemical step 6 . In organic electronics, the complex physics of excitations is critical to device function [7][8][9][10][11][12][13] . High efficiencies have been reached for both organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs) [14][15][16][17] , yet a major barrier to the deployment of organic semiconductors is their functional lifetime 17 .…”

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confidence: 99%

Temporal mapping of photochemical reactions and molecular excited states with carbon specificity

et al. 2016

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Photochemical reactions are essential to a large number of important industrial and biological processes. A method for monitoring photochemical reaction kinetics and the dynamics of molecular excitations with spatial resolution within the active molecule would allow a rigorous exploration of the pathway and mechanism of photophysical and photochemical processes. Here we demonstrate that laser-excited muon pump-probe spin spectroscopy (photo-μSR) can temporally and spatially map these processes with a spatial resolution at the single-carbon level in a molecule with a pentacene backbone. The observed time-dependent light-induced changes of an avoided level crossing resonance demonstrate that the photochemical reactivity of a specific carbon atom is modified as a result of the presence of the excited state wavefunction. This demonstrates the sensitivity and potential of this technique in probing molecular excitations and photochemistry.

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Exciton diffusion lengths of organic semiconductor thin films measured by spectrally resolved photoluminescence quenching

Cited by 441 publications

References 38 publications

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer

8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer

Visualization of exciton transport in ordered and disordered molecular solids

Temporal mapping of photochemical reactions and molecular excited states with carbon specificity

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