P412
Photophysical Properties of Pentacene in Langmuir Blodgett film
Somobrata Acharya,
Tapan Kr. Parichha,
G. B. Talapatra
I. A. C. S., Calcutta 700 032
We have investigated photophysical properties of Langmuir Blodgett
film of nonamphiphilic polycyclic aromatic hydrocarbon, pentacene mixed
with Stearic acid (SA). Surface pressure versus area per molecule isotherms
(P-A) at different compositions are measured. With increase of molar concentration
of pentacene in the mixture, the area per molecule decreases. This is perhaps
due to accomodation of pentacene molecules within the stearic acid chains and
formation of aggregate. Langmuir monolayer formed at the air-water interface
was transferred to solid substrate. A comparison of spectroscopic properties
(UV-visible absorption and emission at both room temperature and 77K) with respect
to that in solution have been made. In solution, pentacene shows fluorescence with maxima
at ~510 nm. In LB film, high energy monomeric bands are quenched and a broad excimeric emission
with maximum at ~590 nm is found. this band is red shifted in comparison to the emission in
solution. This red shifted emission is supposed to be aggregation induced. Surface morphology
of LB films have been examined by Scanning Electron Microscopy (SEM). SEM pictures confirm the
formation of aggregates.
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