Investigation of Energy Transfer in Organic Photovoltaic Cells and Impact on Exciton Diffusion Length Measurements

Luhman, Wade A.; Holmes, Russell J.

doi:10.1002/adfm.201001928

Cited by 139 publications

(133 citation statements)

References 49 publications

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“…13,14,37,38 Here, we apply Forster theory to describe exciton diffusion in SubNc as a function of dilution in UGH2. By assuming that exciton diffusion is dominated by nearest neighbor Forster energy transfer, predictions for the L D of SubNc as a function of concentration can be made.…”

Section: Resultsmentioning

confidence: 99%

Energy-Cascade Organic Photovoltaic Devices Incorporating a Host–Guest Architecture

Menke

Holmes

2015

ACS Appl. Mater. Interfaces

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In planar heterojunction organic photovoltaic devices (OPVs), broad spectral coverage can be realized by incorporating multiple molecular absorbers in an energy-cascade architecture. Here, this approach is combined with a host-guest donor layer architecture previously shown to optimize exciton transport for the fluorescent organic semiconductor boron subphthalocyanine chloride (SubPc) when diluted in an optically transparent host. In order to maximize the absorption efficiency, energy-cascade OPVs that utilize both photoactive host and guest donor materials are examined using the pairing of SubPc and boron subnaphthalocyanine chloride (SubNc), respectively. In a planar heterojunction architecture, excitons generated on the SubPc host rapidly energy transfer to the SubNc guest, where they may migrate toward the dissociating, donor-acceptor interface. Overall, the incorporation of a photoactive host leads to a 13% enhancement in the short-circuit current density and a 20% enhancement in the power conversion efficiency relative to an optimized host-guest OPV combining SubNc with a nonabsorbing host. This work underscores the potential for further design refinements in planar heterojunction OPVs and demonstrates progress toward the effective separation of functionality between constituent OPV materials.

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Section: Resultsmentioning

confidence: 99%

Energy-Cascade Organic Photovoltaic Devices Incorporating a Host–Guest Architecture

Menke

Holmes

2015

ACS Appl. Mater. Interfaces

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“…Modeling the experimental results allows to extract the Förster radius R 0 , as demonstrated in the work of Luhman and Holmes 41 . A three-layer structure is used to spatially separate the energy donor from the energy acceptor.…”

Section: Resultsmentioning

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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“…In addition, for the bi-component blend material that comprises the active layer of BHJ OPV devices (Figure 4) a non-continuous finely mixed system may form in which long-range energy transfer may have a significant effect on exciton transport and thus exciton dissociation. Thus, for OPV devices Förster theory should be used to model exciton diffusion since it considers long-range energy transfer in addition to purely diffusive transport and thus avoids an overestimation of the diffusion length, especially for small values of L [22,76,77]. …”

Section: Exciton Transportmentioning

confidence: 99%

Organic Solar Cells: Understanding the Role of Förster Resonance Energy Transfer

Feron

Belcher

Fell

et al. 2012

IJMS

114

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Organic solar cells have the potential to become a low-cost sustainable energy source. Understanding the photoconversion mechanism is key to the design of efficient organic solar cells. In this review, we discuss the processes involved in the photo-electron conversion mechanism, which may be subdivided into exciton harvesting, exciton transport, exciton dissociation, charge transport and extraction stages. In particular, we focus on the role of energy transfer as described by Förster resonance energy transfer (FRET) theory in the photoconversion mechanism. FRET plays a major role in exciton transport, harvesting and dissociation. The spectral absorption range of organic solar cells may be extended using sensitizers that efficiently transfer absorbed energy to the photoactive materials. The limitations of Förster theory to accurately calculate energy transfer rates are discussed. Energy transfer is the first step of an efficient two-step exciton dissociation process and may also be used to preferentially transport excitons to the heterointerface, where efficient exciton dissociation may occur. However, FRET also competes with charge transfer at the heterointerface turning it in a potential loss mechanism. An energy cascade comprising both energy transfer and charge transfer may aid in separating charges and is briefly discussed. Considering the extent to which the photo-electron conversion efficiency is governed by energy transfer, optimisation of this process offers the prospect of improved organic photovoltaic performance and thus aids in realising the potential of organic solar cells.

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Investigation of Energy Transfer in Organic Photovoltaic Cells and Impact on Exciton Diffusion Length Measurements

Cited by 139 publications

References 49 publications

Energy-Cascade Organic Photovoltaic Devices Incorporating a Host–Guest Architecture

Energy-Cascade Organic Photovoltaic Devices Incorporating a Host–Guest Architecture

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

Organic Solar Cells: Understanding the Role of Förster Resonance Energy Transfer

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