Understanding the effect of triplet sensitizers in organic photovoltaic devices

Angel, Felipe A.; Tang, Ching Wan

doi:10.1016/j.orgel.2016.01.005

Cited by 9 publications

(5 citation statements)

References 27 publications

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“…In principle, using triplet excitons instead of singlet excitons can increase L D . PHJs based on this strategy have been investigated; however, the long L D of triplet excitons has not been used to improve the performance of PHJs yet. Thermally activated delayed fluorescence, which allows the interconversion between singlet and triplet excitons, has been used to create highly efficient organic light‐emitting diodes, and may be another way to manage the excitons in PHJs, which should be investigated.…”

Section: Photophysical Processes In Organic Photovoltaics Based On Plmentioning

confidence: 99%

Organic Planar Heterojunctions: From Models for Interfaces in Bulk Heterojunctions to High‐Performance Solar Cells

2016

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Recent progress regarding planar heterojunctions (PHJs) is reviewed, with respect to the fundamental understanding of the photophysical processes at the donor/acceptor interfaces in organic photovoltaic devices (OPVs). The current state of OPV research is summarized and the advantages of PHJs as models for exploring the relationship between organic interfaces and device characteristics described. The preparation methods and the characterization of PHJ structures to provide key points for the appropriate handling of PHJs. Next, we describe the effects of the donor/acceptor interface on each photoelectric conversion process are reviewed by examining various PHJ systems to clarify what is currently known and not known. Finally, it is discussed how we the knowledge obtained by studies of PHJs can be used to overcome the current limits of OPV efficiency.

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Section: Photophysical Processes In Organic Photovoltaics Based On Plmentioning

confidence: 99%

Organic Planar Heterojunctions: From Models for Interfaces in Bulk Heterojunctions to High‐Performance Solar Cells

2016

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“…Prior work has demonstrated the ability to overcome the challenge of low optical absorption through the use of a host–guest, triplet-sensitized OPV. − In a triplet-sensitized OPV, a guest molecule capable of rapid singlet–triplet intersystem crossing is added to the donor layer in order to sensitize triplets on the fluorescent donor host. In this configuration, photogenerated host singlets undergo energy transfer to a triplet-sensitizing guest, which rapidly forms triplets that are subsequently transferred back to the long-lived host triplet state.…”

Section: Introductionmentioning

confidence: 99%

“…In this configuration, photogenerated host singlets undergo energy transfer to a triplet-sensitizing guest, which rapidly forms triplets that are subsequently transferred back to the long-lived host triplet state. In prior demonstrations, the guest is a heavy-metal-centered phosphor capable of rapid intersystem crossing. − For example, Luhman and Holmes used a host–guest pairing of N , N ′-bis(naphthalen-1-yl)- N , N ′-bis(phenyl)benzidine (NPD) and tris[2-phenylpyridinato-C2,N]iridium(III) (Ir(ppy) 3 ) to demonstrate an increase in L D from (6.5 ± 0.3) to (11.8 ± 0.6) nm at 5% doping . Rand et al investigated the host–guest pairing of phenyl-substituted poly( p -phenylene vinylene) (PPV) and platinum octaethylporphyrin (PtOEP) and demonstrated an increase in L D from (4 ± 1) to (9 ± 1) nm for an optimal doping of 5% .…”

Section: Introductionmentioning

confidence: 99%

“…This approach has been further applied to bulk heterojunction OPVs realizing significant increases in photocurrent . Similarly, Angel and Tang incorporated PtOEP into poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene (MEH-PPV) and found an increase in L D from 2.0 to 5.0 nm . Despite prior demonstrations of enhanced device performance using triplet sensitizers, there are several challenges associated with quantifying L D in these systems.…”

Section: Introductionmentioning

confidence: 99%

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Probing Enhanced Exciton Diffusion in a Triplet-Sensitized Organic Photovoltaic Cell

et al. 2020

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We examine exciton diffusion in a triplet-sensitized organic photovoltaic cell, where transport occurs via the long-lived triplet state of a fluorescent electron donor. While the triplet state is optically dark, it is populated via sensitization by a guest species capable of intersystem crossing. Here, the host material is metal-free phthalocyanine (H2Pc), and the triplet-sensitizing guest is copper phthalocyanine (CuPc). Optical excitation of H2Pc leads to the generation of singlet excitons which rapidly undergo energy transfer to CuPc. Excitons on CuPc undergo intersystem crossing to the triplet state followed by energy transfer back to the H2Pc triplet state. The exciton diffusion length (L D) is extracted using an internal quantum efficiency ratio methodology that permits accurate device-based measurements of exciton transport even in the presence of geminate recombination losses. The donor layer L D varies with composition with a maximum L D of (13.4 ± 1.6 nm) observed at 20 vol % CuPc, an almost 60% increase over the case of the mobile H2Pc singlet. Despite this increase, further improvements may be possible as the neat-film H2Pc triplet L D is estimated to exceed (20.7 ± 5.0) nm.

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“…Similar findings were obtained by Schulz et al., who introduced Ir complexes into a π‐conjugated polymer backbone forming long‐living triplet states, which increases the quantum efficiency by a factor of 10. Other systems exploiting triplet generation due to an enhanced intersystem crossing (ISC) are based on the heavy metal platinum or iron‐based nanoparticles …”

Section: Introductionmentioning

confidence: 99%

Impact of Phosphorescent Sensitizers and Morphology on the Photovoltaic Performance in Organic Solar Cells

Popp

Kaiser

Gagliardi

2018

Advcd Theory and Sims

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Phosphorescent sensitizers (PSs) are considered as a promising alternative for increasing the internal quantum efficiency (IQE) in organic solar cells (OSCs). By converting short-lifetime singlet into long-living triplet excitons, enhanced exciton diffusion and dissociation have been reported previously. However, only a limited increase in the OSC performance has been achieved. In this work, the interplay of the PS with both singlet and triplet excitons within organic blends is examined using kinetic Monte Carlo simulations including a comprehensive model of excitonic processes. Different morphologies of the conventional P3HT:PCBM solar cell are simulated, and the excitonic properties and their influence on the photovoltaic performance under doping are studied. The use of phosphorescent sensitization ensures high intersystem crossing and enlarges the diffusion length. An increase in the IQE of 34% is observed for a bilayer OSC. The increasing decay of triplets in proximity to the PS due to a strong spin-orbit coupling limits the IQE. Unlike expected, triplet-triplet annihilation does not provide a significant loss of excitons. A doped planar-mixed molecular heterojunction outperforms an undoped bulk-heterojunction OSC due to the enhanced exciton diffusion. A further study of optimal PS parameters predicts an increase in the IQE within bilayer solar cells by about 100%.

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Understanding the effect of triplet sensitizers in organic photovoltaic devices

Cited by 9 publications

References 27 publications

Organic Planar Heterojunctions: From Models for Interfaces in Bulk Heterojunctions to High‐Performance Solar Cells

Organic Planar Heterojunctions: From Models for Interfaces in Bulk Heterojunctions to High‐Performance Solar Cells

Probing Enhanced Exciton Diffusion in a Triplet-Sensitized Organic Photovoltaic Cell

Impact of Phosphorescent Sensitizers and Morphology on the Photovoltaic Performance in Organic Solar Cells

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