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Characterization of Carrier Transport and Trapping in Photorefractive Polymer Composites Using Photoemission Yield Spectroscopy in Air
Author(s) -
Tsujimura Sho,
Fujihara Takashi,
Sassa Takafumi,
Kinashi Kenji,
Sakai Wataru,
Ishibashi Koji,
Tsutsumi Naoto
Publication year - 2016
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201600070
Subject(s) - trapping , photorefractive effect , dipole , materials science , spectroscopy , molecular physics , yield (engineering) , chemical physics , analytical chemistry (journal) , composite material , chemistry , optoelectronics , organic chemistry , ecology , physics , quantum mechanics , biology
Carrier trapping in organic photorefractive (PR) composites is affected by the bulk state (which can be varied by modifying the molecule structure and processing method used) and the presence of dipolar molecules. Such situations complicate the understanding of carrier trapping in PR composites. The density of states (DOS) provides direct information about carrier trapping in materials. Here, the first attempt to directly measure the DOS in PR composites is performed to investigate the effect of the change of the bulk state on carrier trapping. The distribution of the DOS is measured using photoemission yield spectroscopy in air. The bulk state of the PR composites is tuned based on the crystallization of dipolar nonlinear optical dyes included as a component. Thus, the bulk with a different net dipole (spatially averaged dipole) moment is prepared with the same composition as the PR materials. The edge part of the DOS profile clearly changes upon tuning the bulk state. The diminished net dipole moment achieved by the bulk state tuning causes the suppression of carrier trapping, which is well supported by the dipole trapping model. This result coincides with those obtained using photocurrent and PR grating measurements.