Polaron pair mediated triplet generation in polymer/fullerene blends

Stoichko D. Dimitrov; Scot Wheeler; Dorota Niedzialek; Bob C. Schroeder; Hendrik Utzat; Jarvist M. Frost; Jizhong Yao; Alexander Gillett; Pabitra S. Tuladhar; Iain McCulloch; Jenny Nelson; James R. Durrant

doi:10.1038/ncomms7501

Polaron pair mediated triplet generation in polymer/fullerene blends

Stoichko D. Dimitrov, Scot Wheeler, Dorota Niedzialek, Bob C. Schroeder, Hendrik Utzat, Jarvist M. Frost, Jizhong Yao, Alexander Gillett, Pabitra S. Tuladhar, Iain McCulloch, Jenny Nelson, James R. Durrant

Research output: Contribution to journal › Article › peer-review

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Abstract

Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well as spintronic applications relying on organic magnetoresistance. A mechanism for triplet excited state generation in such systems is by recombination of electron-hole pairs. However, the exact charge recombination mechanism, whether geminate or nongeminate and whether it involves spin-state mixing is not well understood. In this work, the dynamics of free charge separation competing with recombination to polymer triplet states is studied in two closely related polymer-fullerene blends with differing polymer fluorination and photovoltaic performance. Using time-resolved laser spectroscopic techniques and quantum chemical calculations, we show that lower charge separation in the fluorinated system is associated with the formation of bound electron-hole pairs, which undergo spin-state mixing on the nanosecond timescale and subsequent geminate recombination to triplet excitons. We find that these bound electron-hole pairs can be dissociated by electric fields.

Original language	English (US)
Journal	Nature Communications
Volume	6
Issue number	1
DOIs	https://doi.org/10.1038/ncomms7501
State	Published - Mar 4 2015

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title = "Polaron pair mediated triplet generation in polymer/fullerene blends",

abstract = "Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well as spintronic applications relying on organic magnetoresistance. A mechanism for triplet excited state generation in such systems is by recombination of electron-hole pairs. However, the exact charge recombination mechanism, whether geminate or nongeminate and whether it involves spin-state mixing is not well understood. In this work, the dynamics of free charge separation competing with recombination to polymer triplet states is studied in two closely related polymer-fullerene blends with differing polymer fluorination and photovoltaic performance. Using time-resolved laser spectroscopic techniques and quantum chemical calculations, we show that lower charge separation in the fluorinated system is associated with the formation of bound electron-hole pairs, which undergo spin-state mixing on the nanosecond timescale and subsequent geminate recombination to triplet excitons. We find that these bound electron-hole pairs can be dissociated by electric fields.",

author = "Dimitrov, {Stoichko D.} and Scot Wheeler and Dorota Niedzialek and Schroeder, {Bob C.} and Hendrik Utzat and Frost, {Jarvist M.} and Jizhong Yao and Alexander Gillett and Tuladhar, {Pabitra S.} and Iain McCulloch and Jenny Nelson and Durrant, {James R.}",

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AU - Dimitrov, Stoichko D.

AU - Wheeler, Scot

AU - Niedzialek, Dorota

AU - Schroeder, Bob C.

AU - Utzat, Hendrik

AU - Frost, Jarvist M.

AU - Yao, Jizhong

AU - Gillett, Alexander

AU - Tuladhar, Pabitra S.

AU - McCulloch, Iain

AU - Nelson, Jenny

AU - Durrant, James R.

N1 - KAUST Repository Item: Exported on 2020-10-01

PY - 2015/3/4

Y1 - 2015/3/4

N2 - Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well as spintronic applications relying on organic magnetoresistance. A mechanism for triplet excited state generation in such systems is by recombination of electron-hole pairs. However, the exact charge recombination mechanism, whether geminate or nongeminate and whether it involves spin-state mixing is not well understood. In this work, the dynamics of free charge separation competing with recombination to polymer triplet states is studied in two closely related polymer-fullerene blends with differing polymer fluorination and photovoltaic performance. Using time-resolved laser spectroscopic techniques and quantum chemical calculations, we show that lower charge separation in the fluorinated system is associated with the formation of bound electron-hole pairs, which undergo spin-state mixing on the nanosecond timescale and subsequent geminate recombination to triplet excitons. We find that these bound electron-hole pairs can be dissociated by electric fields.

AB - Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well as spintronic applications relying on organic magnetoresistance. A mechanism for triplet excited state generation in such systems is by recombination of electron-hole pairs. However, the exact charge recombination mechanism, whether geminate or nongeminate and whether it involves spin-state mixing is not well understood. In this work, the dynamics of free charge separation competing with recombination to polymer triplet states is studied in two closely related polymer-fullerene blends with differing polymer fluorination and photovoltaic performance. Using time-resolved laser spectroscopic techniques and quantum chemical calculations, we show that lower charge separation in the fluorinated system is associated with the formation of bound electron-hole pairs, which undergo spin-state mixing on the nanosecond timescale and subsequent geminate recombination to triplet excitons. We find that these bound electron-hole pairs can be dissociated by electric fields.

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SN - 2041-1723

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JO - Nature Communications

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Polaron pair mediated triplet generation in polymer/fullerene blends

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