Direct Observation of Structure and Dynamics of Photogenerated Charge Carriers in Poly(3-hexylthiophene) Films by Femtosecond Time-Resolved Near-IR Inverse Raman Spectroscopy

Tomohisa Takaya; Ippei Enokida; Yukio Furukawa; Koichi Iwata

doi:10.3390/molecules24030431

Direct Observation of Structure and Dynamics of Photogenerated Charge Carriers in Poly(3-hexylthiophene) Films by Femtosecond Time-Resolved Near-IR Inverse Raman Spectroscopy

Tomohisa Takaya^*, Ippei Enokida, Yukio Furukawa, Koichi Iwata

^*Corresponding author for this work

School of Advanced Science and Engineering

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

12 Citations (Scopus)

Abstract

The initial charge separation process of conjugated polymers is one of the key factors for understanding their conductivity. The structure of photogenerated transients in conjugated polymers can be observed by resonance Raman spectroscopy in the near-IR region because they exhibit characteristic low-energy transitions. Here, we investigate the structure and dynamics of photogenerated transients in a regioregular poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) blend film, as well as in a pristine P3HT film, using femtosecond time-resolved resonance inverse Raman spectroscopy in the near-IR region. The transient inverse Raman spectrum of the pristine P3HT film at 50 ps suggests coexistence of neutral and charged excitations, whereas that of the P3HT:PCBM blend film at 50 ps suggests formation of positive polarons with a different structure from those in an FeCl₃-doped P3HT film. Time-resolved near-IR inverse Raman spectra of the blend film clearly show the absence of charge separation between P3HT and PCBM within the instrument response time of our spectrometer, while they indicate two independent pathways of the polaron formation with time constants of 0.3 and 10 ps.

Original language	English
Article number	431
Journal	Molecules
Volume	24
Issue number	3
DOIs	https://doi.org/10.3390/molecules24030431
Publication status	Published - 2019 Jan 1

Keywords

Bulk heterojunction
Conjugated polymer
Femtosecond inverse Raman spectroscopy
Polaron

ASJC Scopus subject areas

Analytical Chemistry
Chemistry (miscellaneous)
Molecular Medicine
Pharmaceutical Science
Drug Discovery
Physical and Theoretical Chemistry
Organic Chemistry

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10.3390/molecules24030431

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@article{bce77a3cff404f98ae3a6cbcede123f1,

title = "Direct Observation of Structure and Dynamics of Photogenerated Charge Carriers in Poly(3-hexylthiophene) Films by Femtosecond Time-Resolved Near-IR Inverse Raman Spectroscopy",

abstract = "The initial charge separation process of conjugated polymers is one of the key factors for understanding their conductivity. The structure of photogenerated transients in conjugated polymers can be observed by resonance Raman spectroscopy in the near-IR region because they exhibit characteristic low-energy transitions. Here, we investigate the structure and dynamics of photogenerated transients in a regioregular poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend film, as well as in a pristine P3HT film, using femtosecond time-resolved resonance inverse Raman spectroscopy in the near-IR region. The transient inverse Raman spectrum of the pristine P3HT film at 50 ps suggests coexistence of neutral and charged excitations, whereas that of the P3HT:PCBM blend film at 50 ps suggests formation of positive polarons with a different structure from those in an FeCl3-doped P3HT film. Time-resolved near-IR inverse Raman spectra of the blend film clearly show the absence of charge separation between P3HT and PCBM within the instrument response time of our spectrometer, while they indicate two independent pathways of the polaron formation with time constants of 0.3 and 10 ps.",

keywords = "Bulk heterojunction, Conjugated polymer, Femtosecond inverse Raman spectroscopy, Polaron",

author = "Tomohisa Takaya and Ippei Enokida and Yukio Furukawa and Koichi Iwata",

note = "Funding Information: Funding: This research was funded by JSPS KAKENHI, grant number JP24750023 (T.T.), JP24350012 (K.I. and T.T.), MEXT KAKENHI, grant number JP26104534 (T.T.), JP16H00850 (T.T.), JP26102541 (K.I.), JP16H00782 (K.I.), JP18H05351 (K.I.) and MEXT-Supported Program for the Strategic Research Foundation at Private Universities, 2015–2019. Funding Information: This research was funded by JSPS KAKENHI, grant number JP24750023 (T.T.), JP24350012 (K.I. and T.T.), MEXT KAKENHI, grant number JP26104534 (T.T.), JP16H00850 (T.T.), JP26102541 (K.I.), JP16H00782 (K.I.), JP18H05351 (K.I.) and MEXT-Supported Program for the Strategic Research Foundation at Private Universities, 2015–2019. The authors are grateful to Jun Yamamoto (Waseda University, Japan) for preparation of a P3HT film for FeCl3 doping. Publisher Copyright: {\textcopyright} 2019 by the authors.",

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doi = "10.3390/molecules24030431",

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journal = "Molecules",

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T1 - Direct Observation of Structure and Dynamics of Photogenerated Charge Carriers in Poly(3-hexylthiophene) Films by Femtosecond Time-Resolved Near-IR Inverse Raman Spectroscopy

AU - Takaya, Tomohisa

AU - Enokida, Ippei

AU - Furukawa, Yukio

AU - Iwata, Koichi

N1 - Funding Information: Funding: This research was funded by JSPS KAKENHI, grant number JP24750023 (T.T.), JP24350012 (K.I. and T.T.), MEXT KAKENHI, grant number JP26104534 (T.T.), JP16H00850 (T.T.), JP26102541 (K.I.), JP16H00782 (K.I.), JP18H05351 (K.I.) and MEXT-Supported Program for the Strategic Research Foundation at Private Universities, 2015–2019. Funding Information: This research was funded by JSPS KAKENHI, grant number JP24750023 (T.T.), JP24350012 (K.I. and T.T.), MEXT KAKENHI, grant number JP26104534 (T.T.), JP16H00850 (T.T.), JP26102541 (K.I.), JP16H00782 (K.I.), JP18H05351 (K.I.) and MEXT-Supported Program for the Strategic Research Foundation at Private Universities, 2015–2019. The authors are grateful to Jun Yamamoto (Waseda University, Japan) for preparation of a P3HT film for FeCl3 doping. Publisher Copyright: © 2019 by the authors.

PY - 2019/1/1

Y1 - 2019/1/1

N2 - The initial charge separation process of conjugated polymers is one of the key factors for understanding their conductivity. The structure of photogenerated transients in conjugated polymers can be observed by resonance Raman spectroscopy in the near-IR region because they exhibit characteristic low-energy transitions. Here, we investigate the structure and dynamics of photogenerated transients in a regioregular poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend film, as well as in a pristine P3HT film, using femtosecond time-resolved resonance inverse Raman spectroscopy in the near-IR region. The transient inverse Raman spectrum of the pristine P3HT film at 50 ps suggests coexistence of neutral and charged excitations, whereas that of the P3HT:PCBM blend film at 50 ps suggests formation of positive polarons with a different structure from those in an FeCl3-doped P3HT film. Time-resolved near-IR inverse Raman spectra of the blend film clearly show the absence of charge separation between P3HT and PCBM within the instrument response time of our spectrometer, while they indicate two independent pathways of the polaron formation with time constants of 0.3 and 10 ps.

AB - The initial charge separation process of conjugated polymers is one of the key factors for understanding their conductivity. The structure of photogenerated transients in conjugated polymers can be observed by resonance Raman spectroscopy in the near-IR region because they exhibit characteristic low-energy transitions. Here, we investigate the structure and dynamics of photogenerated transients in a regioregular poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend film, as well as in a pristine P3HT film, using femtosecond time-resolved resonance inverse Raman spectroscopy in the near-IR region. The transient inverse Raman spectrum of the pristine P3HT film at 50 ps suggests coexistence of neutral and charged excitations, whereas that of the P3HT:PCBM blend film at 50 ps suggests formation of positive polarons with a different structure from those in an FeCl3-doped P3HT film. Time-resolved near-IR inverse Raman spectra of the blend film clearly show the absence of charge separation between P3HT and PCBM within the instrument response time of our spectrometer, while they indicate two independent pathways of the polaron formation with time constants of 0.3 and 10 ps.

KW - Bulk heterojunction

KW - Conjugated polymer

KW - Femtosecond inverse Raman spectroscopy

KW - Polaron

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Direct Observation of Structure and Dynamics of Photogenerated Charge Carriers in Poly(3-hexylthiophene) Films by Femtosecond Time-Resolved Near-IR Inverse Raman Spectroscopy

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Keywords

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