Investigation of photoinduced electron transport in electron sensitizer/relay/acceptor hetero-LB films using transient absorption technique

Kyung Sang Cho, Yun Suk Nam, Dongho Kim, Won Hong Lee, Jeong Woo Choi

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Photoinduced electron transport processes in hetero-Langmuir-Blodgett (LB) films composed of electron sensitizer (S), relay (R) and acceptor (A) molecules were investigated by femtosecond transient absorption technique. 7,8-Dimethyl-10-dodecyl isoalloxazine (flavin), N-allyl-N′-3-propylamido-N″, ″-di(n-octadecyl)-4,4′-bi pyridium dibromide (viologen) and N-docosilquinolinium tetracyanoquinodimethane (TCNQ) were employed as S, R and A units, respectively. Based on the time-resolved transient absorption spectra of S/R/A series hetero-LB films with different numbers of R layers, the optimum number of R layers for efficient photoinduced charge transport from S to A layers via R was determined to be two. Over two layers of R molecules in the S/R/A series LB films, the charge transport rate became slower due to an increase in the back electron transport from R to A layers. S(30 layers)/A(31 layers) (S(30)/A(31)) hetero-LB film exhibits nearly the same charge transport rate as S(30)/R(2)/A(31) hetero-LB film. But the charge recombination from A to S occurred in S(30)/A(31) hetero-LB film. In the S(30)/A(31) hetero-LB film, charge separated species were directly monitored in the transient absorption spectra. At 660 nm, a long decay component become manifest due to the contribution of bulk (TCNQ)2- species. At 740 and 840 nm, on the other hand, a slow rise and long-time decay components were observed due to the contribution of TCNQ- monomer existing at the interface between S and A layers.

Original languageEnglish
Pages (from-to)157-163
Number of pages7
JournalSynthetic Metals
Volume129
Issue number2
DOIs
Publication statusPublished - 2002 Jul 10

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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