Probing Internal Electric Field in Organic Photoconductors by Using Electric-Field-Induced Optical Second-Harmonic Generation

Dai TAGUCHI  Takaaki MANAKA  Mitsumasa IWAMOTO  Kazuko SAKUMA  Kaname WATARIGUCHI  Masataka KAWAHARA  

IEICE TRANSACTIONS on Electronics   Vol.E102-C   No.2   pp.113-118
Publication Date: 2019/02/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.2018OMP0002
Type of Manuscript: Special Section PAPER (Special Section on Recent Progress in Organic Molecular Electronics and Biotechnology)
electric-field-induced optical second-harmonic generation,  organic photoconductor,  internal electric field,  photo-conducting effect,  photovoltaic effect,  

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Organic photoconductors (OPC) have been an important research and development topics for high quality electrophotography. By using electric field induced optical second harmonic generation (EFISHG) measurement, we can probe carrier processes in electrophotographic processes such as photo carrier generation, carrier separation, and carrier transportation for copier image production. We here selectively probe charge generation and accumulation in charge generation layer and charge transport layer in multilayer structure OPCs. We studied charge accumulation in OPC under illumination (wavelength 635nm) of double-layer-type OPC with structure of hole transport layer coated on charge generation layer. The result showed that light absorption efficiently produces free holes and electrons in the charge generation layer, followed by excessive hole accumulation at the CG/CT interface due to photo-conducting effect of CG layer. The short-wavelength irradiation at 405nm induced photovoltaic effect. These results demonstrated that the EFISHG measurement is useful to selectively probe carrier process in one layer of the multilayer OPC and to the discussion of carrier process for electrophotographic image productions.