Dissociation processes of singlet and triplet excitons in organic photovoltaic cells

Zhihua Xu; Yue Wu; Bin Hu

doi:10.1063/1.2357584

Dissociation processes of singlet and triplet excitons in organic photovoltaic cells

Zhihua Xu, Yue Wu, Bin Hu

Chemical Engineering

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Abstract

The dissociation processes of singlet and triplet excitons are studied based on fluorescent aluminum (III) 8-hydroxyquinoline (Alq ₃) and phosphorescent fac-tris-(2-phenylpyridine) iridium [Ir(ppy) ₃] molecules. We find that phosphorescent Ir(ppy) ₃ shows a more efficient photovoltaic response as compared to fluorescent Alq ₃. The short-circuit photocurrent action spectra and magnetic-field-dependent photocurrents reveal that the triplet excitons dissociate directly into free charge carriers at the metal-electrode interface while the singlet excitons experience bulk dissociation through polaron-pair states. This interface dissociation of triplet excitons forms a mechanism for phosphorescent organic materials to yield efficient photovoltaic responses.

Original language	English (US)
Article number	131116
Journal	Applied Physics Letters
Volume	89
Issue number	13
DOIs	https://doi.org/10.1063/1.2357584
State	Published - 2006

Bibliographical note

Funding Information:
This research was supported by AFOSR (FA9550-06-10070), the NSF (ECS-SGER-0521474 and ECS-SGER-0551914), and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory under Contract No. DE-AC05-00OR22725.

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title = "Dissociation processes of singlet and triplet excitons in organic photovoltaic cells",

abstract = "The dissociation processes of singlet and triplet excitons are studied based on fluorescent aluminum (III) 8-hydroxyquinoline (Alq 3) and phosphorescent fac-tris-(2-phenylpyridine) iridium [Ir(ppy) 3] molecules. We find that phosphorescent Ir(ppy) 3 shows a more efficient photovoltaic response as compared to fluorescent Alq 3. The short-circuit photocurrent action spectra and magnetic-field-dependent photocurrents reveal that the triplet excitons dissociate directly into free charge carriers at the metal-electrode interface while the singlet excitons experience bulk dissociation through polaron-pair states. This interface dissociation of triplet excitons forms a mechanism for phosphorescent organic materials to yield efficient photovoltaic responses.",

author = "Zhihua Xu and Yue Wu and Bin Hu",

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AU - Wu, Yue

AU - Hu, Bin

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N2 - The dissociation processes of singlet and triplet excitons are studied based on fluorescent aluminum (III) 8-hydroxyquinoline (Alq 3) and phosphorescent fac-tris-(2-phenylpyridine) iridium [Ir(ppy) 3] molecules. We find that phosphorescent Ir(ppy) 3 shows a more efficient photovoltaic response as compared to fluorescent Alq 3. The short-circuit photocurrent action spectra and magnetic-field-dependent photocurrents reveal that the triplet excitons dissociate directly into free charge carriers at the metal-electrode interface while the singlet excitons experience bulk dissociation through polaron-pair states. This interface dissociation of triplet excitons forms a mechanism for phosphorescent organic materials to yield efficient photovoltaic responses.

AB - The dissociation processes of singlet and triplet excitons are studied based on fluorescent aluminum (III) 8-hydroxyquinoline (Alq 3) and phosphorescent fac-tris-(2-phenylpyridine) iridium [Ir(ppy) 3] molecules. We find that phosphorescent Ir(ppy) 3 shows a more efficient photovoltaic response as compared to fluorescent Alq 3. The short-circuit photocurrent action spectra and magnetic-field-dependent photocurrents reveal that the triplet excitons dissociate directly into free charge carriers at the metal-electrode interface while the singlet excitons experience bulk dissociation through polaron-pair states. This interface dissociation of triplet excitons forms a mechanism for phosphorescent organic materials to yield efficient photovoltaic responses.

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Dissociation processes of singlet and triplet excitons in organic photovoltaic cells

Abstract

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