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Crystallization-Induced Charge-Transfer Change in TiOPc Thin Films Revealed by Resonant Photoemission Spectroscopy

Yu, Shun; Ahmadi, Sareh; Sun, Chenghua; Schulte, Karina LU ; Pietzsch, Annette LU ; Hennies, Franz; Zuleta, Marcelo and Gothelid, Mats (2011) In Journal of Physical Chemistry C 115(30). p.14969-14977
Abstract
Organic semiconductors usually demonstrate crystal structure dependent electronic properties, and through precise control of film structure, the performance of novel organic electronic devices can be greatly improved. Understanding the crystal structure dependent charge-transfer mechanism thus becomes critical. In this work, we have prepared amorphous titanyl phthalocyanine films by vacuum molecular beam evaporation and have further crystallized them through vacuum annealing. In the crystalline phase, an excited electron is rapidly transferred into neighboring molecules; while in the amorphous phase, it is mainly localized and recombines with the core hole as revealed by resonant photoemission spectroscopy (RPES). The fast electron... (More)
Organic semiconductors usually demonstrate crystal structure dependent electronic properties, and through precise control of film structure, the performance of novel organic electronic devices can be greatly improved. Understanding the crystal structure dependent charge-transfer mechanism thus becomes critical. In this work, we have prepared amorphous titanyl phthalocyanine films by vacuum molecular beam evaporation and have further crystallized them through vacuum annealing. In the crystalline phase, an excited electron is rapidly transferred into neighboring molecules; while in the amorphous phase, it is mainly localized and recombines with the core hole as revealed by resonant photoemission spectroscopy (RPES). The fast electron transfer time is determined to be around 16 fs in the crystalline film, which is in good agreement with the charge-transfer hopping time estimated from the best device performance reported. The crystallized film shows more p-type characteristics than the amorphous with all the energy levels shifting toward the vacuum level. However, the greatly improved charge transfer is assigned to the molecular orbital coupling rather than this shift. From density functional theory and RPES, we specify the contribution of two differently coordinated nitrogen atoms (N2c and N3c) to the experimental results and illustrate that the N3c related orbital has experienced a dramatic change, which is keenly related to the improved charge transfer. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physical Chemistry C
volume
115
issue
30
pages
14969 - 14977
publisher
The American Chemical Society
external identifiers
  • wos:000293192100067
  • scopus:79961039242
ISSN
1932-7447
DOI
10.1021/jp1100363
language
English
LU publication?
yes
id
8f6bbe04-3699-48a5-9a82-a91aadf6e02d (old id 2072113)
date added to LUP
2011-08-26 10:00:09
date last changed
2017-08-20 03:18:09
@article{8f6bbe04-3699-48a5-9a82-a91aadf6e02d,
  abstract     = {Organic semiconductors usually demonstrate crystal structure dependent electronic properties, and through precise control of film structure, the performance of novel organic electronic devices can be greatly improved. Understanding the crystal structure dependent charge-transfer mechanism thus becomes critical. In this work, we have prepared amorphous titanyl phthalocyanine films by vacuum molecular beam evaporation and have further crystallized them through vacuum annealing. In the crystalline phase, an excited electron is rapidly transferred into neighboring molecules; while in the amorphous phase, it is mainly localized and recombines with the core hole as revealed by resonant photoemission spectroscopy (RPES). The fast electron transfer time is determined to be around 16 fs in the crystalline film, which is in good agreement with the charge-transfer hopping time estimated from the best device performance reported. The crystallized film shows more p-type characteristics than the amorphous with all the energy levels shifting toward the vacuum level. However, the greatly improved charge transfer is assigned to the molecular orbital coupling rather than this shift. From density functional theory and RPES, we specify the contribution of two differently coordinated nitrogen atoms (N2c and N3c) to the experimental results and illustrate that the N3c related orbital has experienced a dramatic change, which is keenly related to the improved charge transfer.},
  author       = {Yu, Shun and Ahmadi, Sareh and Sun, Chenghua and Schulte, Karina and Pietzsch, Annette and Hennies, Franz and Zuleta, Marcelo and Gothelid, Mats},
  issn         = {1932-7447},
  language     = {eng},
  number       = {30},
  pages        = {14969--14977},
  publisher    = {The American Chemical Society},
  series       = {Journal of Physical Chemistry C},
  title        = {Crystallization-Induced Charge-Transfer Change in TiOPc Thin Films Revealed by Resonant Photoemission Spectroscopy},
  url          = {http://dx.doi.org/10.1021/jp1100363},
  volume       = {115},
  year         = {2011},
}