Electron transport properties in fluorinated copper-phthalocyanine films: Importance of vibrational reorganization energy and molecular microstructure

Fu Chiao Wu, Horng Long Cheng, Chen Hsiang Yen, Jyu Wun Lin, Shyh Jiun Liu, Wei Yang Chou, Fu Ching Tang

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21 Citations (Scopus)

Abstract

Electron transport (ET) properties of a series of fluorinated copper-phthalocyanine (F16CuPc) thin films, which were deposited at different substrate temperatures (Tsub) ranging from 30 to 150 °C, have been investigated by quantum mechanical calculations of the reorganization energy (λreorg), X-ray diffraction (XRD), atomic force microscopy (AFM), and microRaman spectroscopy. Density functional theory calculations were used to predict the vibrational frequencies, normal mode displacement vectors, and electron-vibrational λreorg for the F16CuPc molecule. The electron mobilities (μe) of F16CuPc thin films are strongly dependent on the Tsub, and the value of μe increases with increasing Tsub from 30 to 120 °C, at which point it reaches its maximum value. The importance of electron-vibrational coupling and molecular microstructures for ET properties in F16CuPc thin films are discussed on the basis of theoretical vibrational λreorg calculations and experimental observations of resonance Raman spectra. We observed a good correlation between μe and the full-width-at-half-maximum of the vibrational bands, which greatly contributed to λreorg and/or which reflects the molecular microstructural quality of the active channel. In contrast, the crystal size analysis by XRD and surface grain morphology by AFM did not reveal a clear correlation with the ET behaviours for these different F 16CuPc thin films. Therefore, we suggest that for organic films with weak intermolecular interactions, such as F16CuPc, optimized microscopic molecular-scale parameters are highly important for efficient long-range charge transport in the macroscopic devices.

Original languageEnglish
Pages (from-to)2098-2106
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume12
Issue number9
DOIs
Publication statusPublished - 2010 Feb 26

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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