Abstract
We report femtosecond transient-absorption studies of a five-ring oligomer of polyphenylenevinylene (PPV) prepared in two different forms: As solid-state films and dilute solutions. Both types of samples exhibit a photoinduced absorption (PA) band with dynamics which closely match those of the stimulated emission (SE), demonstrating unambiguously that these features originate from the same species, namely from intrachain singlet excitons. Photochemical degradation of the solid-state samples is demonstrated to dramatically shorten the SE dynamics above a moderate incident pump fluence, whereupon the dynamics of the SE and the long-wavelength PA no longer coincide. In contrast to solutions, solid-state films exhibit an additional short-wavelength PA band with pump-independent dynamics, indicating the efficient formation of non-emissive inter-chain excitons. Correlations in the subpicosecond dynamics of the two PA features, as well as the pump intensity-dependence provide strong evidence that the formation of inter-chain excitons is mediated by intrachain two-exciton states. At high pump levels, we see a clear indication of interaction between excited states also in dilute solutions. This is manifested as a superlinear pump-dependence and shortening of the decay dynamics of the SE. We attribute this behavior to the formation of biexcitons resulting from coherent interaction between two excitons on a single chain.
| Original language | English |
|---|---|
| Title of host publication | Proceedings of SPIE - The International Society for Optical Engineering |
| Editors | Z.V. Vardeny, L.J. Rothberg |
| Pages | 58-68 |
| Number of pages | 11 |
| Volume | 3145 |
| DOIs | |
| Publication status | Published - 1997 |
| Event | Optical Probes of Conjugated Polymers - San Diego, CA, United States Duration: Jul 28 1997 → Jul 30 1997 |
Other
| Other | Optical Probes of Conjugated Polymers |
|---|---|
| Country | United States |
| City | San Diego, CA |
| Period | 7/28/97 → 7/30/97 |
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Keywords
- π-conjugated oligomers
- Biexcitons
- Excitons
- Transient absorption
ASJC Scopus subject areas
- Electrical and Electronic Engineering
- Condensed Matter Physics
Cite this
Exciton and biexciton signatures in femtosecond transient absorption of π-conjugated oligomers. / Klimov, Victor I; McBranch, D.; Barashkov, N.; Ferraris, J.
Proceedings of SPIE - The International Society for Optical Engineering. ed. / Z.V. Vardeny; L.J. Rothberg. Vol. 3145 1997. p. 58-68.Research output: Chapter in Book/Report/Conference proceeding › Conference contribution
}
TY - GEN
T1 - Exciton and biexciton signatures in femtosecond transient absorption of π-conjugated oligomers
AU - Klimov, Victor I
AU - McBranch, D.
AU - Barashkov, N.
AU - Ferraris, J.
PY - 1997
Y1 - 1997
N2 - We report femtosecond transient-absorption studies of a five-ring oligomer of polyphenylenevinylene (PPV) prepared in two different forms: As solid-state films and dilute solutions. Both types of samples exhibit a photoinduced absorption (PA) band with dynamics which closely match those of the stimulated emission (SE), demonstrating unambiguously that these features originate from the same species, namely from intrachain singlet excitons. Photochemical degradation of the solid-state samples is demonstrated to dramatically shorten the SE dynamics above a moderate incident pump fluence, whereupon the dynamics of the SE and the long-wavelength PA no longer coincide. In contrast to solutions, solid-state films exhibit an additional short-wavelength PA band with pump-independent dynamics, indicating the efficient formation of non-emissive inter-chain excitons. Correlations in the subpicosecond dynamics of the two PA features, as well as the pump intensity-dependence provide strong evidence that the formation of inter-chain excitons is mediated by intrachain two-exciton states. At high pump levels, we see a clear indication of interaction between excited states also in dilute solutions. This is manifested as a superlinear pump-dependence and shortening of the decay dynamics of the SE. We attribute this behavior to the formation of biexcitons resulting from coherent interaction between two excitons on a single chain.
AB - We report femtosecond transient-absorption studies of a five-ring oligomer of polyphenylenevinylene (PPV) prepared in two different forms: As solid-state films and dilute solutions. Both types of samples exhibit a photoinduced absorption (PA) band with dynamics which closely match those of the stimulated emission (SE), demonstrating unambiguously that these features originate from the same species, namely from intrachain singlet excitons. Photochemical degradation of the solid-state samples is demonstrated to dramatically shorten the SE dynamics above a moderate incident pump fluence, whereupon the dynamics of the SE and the long-wavelength PA no longer coincide. In contrast to solutions, solid-state films exhibit an additional short-wavelength PA band with pump-independent dynamics, indicating the efficient formation of non-emissive inter-chain excitons. Correlations in the subpicosecond dynamics of the two PA features, as well as the pump intensity-dependence provide strong evidence that the formation of inter-chain excitons is mediated by intrachain two-exciton states. At high pump levels, we see a clear indication of interaction between excited states also in dilute solutions. This is manifested as a superlinear pump-dependence and shortening of the decay dynamics of the SE. We attribute this behavior to the formation of biexcitons resulting from coherent interaction between two excitons on a single chain.
KW - π-conjugated oligomers
KW - Biexcitons
KW - Excitons
KW - Transient absorption
UR - http://www.scopus.com/inward/record.url?scp=0031288665&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031288665&partnerID=8YFLogxK
U2 - 10.1117/12.295539
DO - 10.1117/12.295539
M3 - Conference contribution
VL - 3145
SP - 58
EP - 68
BT - Proceedings of SPIE - The International Society for Optical Engineering
A2 - Vardeny, Z.V.
A2 - Rothberg, L.J.
ER -