Characterization of Carrier Transport and Trapping in Photorefractive Polymer Composites Using Photoemission Yield Spectroscopy in Air. Issue 16 (21st June 2016)

• Record Type: Journal Article
• Authors: Tsujimura, Sho; Fujihara, Takashi; Sassa, Takafumi; Kinashi, Kenji; Sakai, Wataru; Ishibashi, Koji; Tsutsumi, Naoto
• Is Part Of: Macromolecular chemistry and physics. Volume 217:Issue 16(2016:Aug.)
• Page Start: 1785
• Page End: 1791
• Publication Date: 2016-06-21
• Subjects: crystallization -- density of states -- dipole trap model -- organic photorefractive material -- photoemission spectroscopy in air; Polymers -- Periodicals; Polymerization -- Periodicals; Synthetic products -- Periodicals; Macromolecules -- Periodicals; 547.7
• DOI: 10.1002/macp.201600070
• Languages: English
• ISSNs: 1022-1352

Abstract

Abstract : 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. Abstract : 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. This approach would be useful for optimizing the carrier transport in many types of PR composites with crystalline NLO dyes.