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Nonequilibrium site...
Nonequilibrium site distribution governs charge-transfer electroluminescence at disordered organic heterointerfaces
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- Melianas, Armantas (författare)
- Linköpings universitet,Biomolekylär och Organisk Elektronik,Tekniska fakulteten
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- Felekidis, Nikolaos (författare)
- Dept Phys Chem and Biol, Complex Mat and Devices, S-58183 Linkoping, Sweden
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- Puttisong, Yuttapoom (författare)
- Linköpings universitet,Biomolekylär och Organisk Elektronik,Tekniska fakulteten
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- Meskers, Stefan C. J. (författare)
- Eindhoven Univ Technol, Netherlands
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- Inganäs, Olle (författare)
- Linköpings universitet,Biomolekylär och Organisk Elektronik,Tekniska fakulteten
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- Chen, Weimin (författare)
- Linköpings universitet,Biomolekylär och Organisk Elektronik,Tekniska fakulteten
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- Kemerink, Martijn (författare)
- Linköpings universitet,Biomolekylär och Organisk Elektronik,Tekniska fakulteten
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(creator_code:org_t)
- 2019-11-05
- 2019
- Engelska.
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 116:47, s. 23416-23425
- Relaterad länk:
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https://www.pnas.org...
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- The interface between electron-donating (D) and electron-accepting (A) materials in organic photovoltaic (OPV) devices is commonly probed by charge-transfer (CT) electroluminescence (EL) measurements to estimate the CT energy, which critically relates to device open-circuit voltage. It is generally assumed that during CT-EL injected charges recombine at close-to-equilibrium energies in their respective density of states (DOS). Here, we explicitly quantify that CT-EL instead originates from higher-energy DOS site distributions significantly above DOS equilibrium energies. To demonstrate this, we have developed a quantitative and experimentally calibrated model for CT-EL at organic D/A heterointerfaces, which simultaneously accounts for the charge transport physics in an energetically disordered DOS and the Franck-Condon broadening. The 0-0 CT-EL transition lineshape is numerically calculated using measured energetic disorder values as input to 3-dimensional kinetic Monte Carlo simulations. We account for vibrational CT-EL overtones by selectively measuring the dominant vibrational phonon-mode energy governing CT luminescence at the D/A interface using fluorescence line-narrowing spectroscopy. Our model numerically reproduces the measured CT-EL spectra and their bias dependence and reveals the higher-lying manifold of DOS sites responsible for CT-EL. Lowest-energy CT states are situated similar to 180 to 570 meV below the 0-0 CT-EL transition, enabling photogenerated carrier thermalization to these low-lying DOS sites when the OPV device is operated as a solar cell rather than as a light-emitting diode. Nonequilibrium site distribution rationalizes the experimentally observed weak current-density dependence of CT-EL and poses fundamental questions on reciprocity relations relating light emission to photovoltaic action and regarding minimal attainable photovoltaic energy conversion losses in OPV devices.
Ämnesord
- NATURVETENSKAP -- Fysik -- Den kondenserade materiens fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Condensed Matter Physics (hsv//eng)
Nyckelord
- organic electronics; electroluminescence at organic interfaces; energetic disorder; Franck-Condon vibronic progression; 3D kinetic Monte Carlo model
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