Organic Salt Semiconductor with High Photoconductivity and Long Carrier Lifetime

Intrinsic photogeneration of charge carriers in organic semiconductors is generally attributed to high energy ionization or exciton dissociation by a strong electric field. Here, high bulk photoconductivity is reported in pristine pentamethine cyanine films with photocurrent onset at the band‐edge o...

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Bibliographic Details
Published in:Advanced functional materials 2018-04, Vol.28 (16), p.n/a
Main Authors: Wang, Lei, Jenatsch, Sandra, Ruhstaller, Beat, Hinderling, Christian, Gesevičius, Donatas, Hany, Roland, Nüesch, Frank
Format: Article
Language:English
Subjects:
aggregation
Carrier lifetime
Carrier recombination
charge carrier recombination
Computer simulation
Current carriers
Diodes
Electric contacts
Energy of dissociation
heptamethine cyanine dyes
Ionization
Luminous intensity
Materials science
Optoelectronic devices
organic salt semiconductors
Organic semiconductors
Photoconductivity
Photodiodes
Photoelectric effect
Photoelectric emission
quantum efficiency
Space charge
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Summary:Intrinsic photogeneration of charge carriers in organic semiconductors is generally attributed to high energy ionization or exciton dissociation by a strong electric field. Here, high bulk photoconductivity is reported in pristine pentamethine cyanine films with photocurrent onset at the band‐edge of the organic semiconductor. Single‐layer cyanine diodes with selective hole and electron contacts show linear dependence of photocurrent with reverse voltage and light intensity. Numerical drift‐diffusion simulations reveal that the linear resistor behavior stems from low and unbalanced carrier mobilities giving rise to negative space charge. Slow bimolecular recombination kinetics of photoinduced charges obtained by time delayed charge extraction measurements show strongly reduced Langevin recombination with long carrier lifetime of the order of a millisecond. Such reduced charge carrier recombination puts forward a materials concept to be exploited in photodiodes and more generally in optoelectronic devices. High photocurrent generation efficiency in the bulk of a pristine organic salt semiconductor in the absence of electric field and donor–acceptor heterointerface is reported. The long carrier lifetime puts forward a materials concept with reduced charge carrier recombination to be exploited in photodiodes and more generally in optoelectronic devices.
ISSN:1616-301X
1616-3028
DOI:10.1002/adfm.201705724