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Photorefractive Effect in NLC Cells Caused by Anomalous Electrical Properties of ITO Electrodes

Department of Nonlinear Phenomena, Institute of Physics, Otto von Guericke University, 39106 Magdeburg, Germany
Crystals 2020, 10(10), 900; https://doi.org/10.3390/cryst10100900
Received: 8 September 2020 / Revised: 29 September 2020 / Accepted: 2 October 2020 / Published: 4 October 2020
(This article belongs to the Special Issue Optical and Molecular Aspects of Liquid Crystals)
In a pure nematic liquid crystal (NLC) cell, optically induced charge carriers followed by transports in double border interfaces of orientant/LC and indium-tin-oxide (ITO)/orientant (or LC) can cause removal of screening of the static electric field inside the LC film. This is called surface photorefractive effect (SPR), which induces director field reorientation at a low DC electric field beyond the threshold at a reduced Fréedericksz transition and, as a result, a modulation of the LC effective refractive index. The studies conducted on the photoinduced opto-electrical responses in pure nematic LC cells biased with uniform static DC electric fields support the SPR effect (attributed to the photoelectric activation of the double interfaces). The SPR effect was further studied in LC cells with photoresponsive substrates, which act as a source of a bell-shaped electric field distribution in the LC film if no ITO electrode was employed. In an equipped cell with ITO, the photovoltaic electric field induces charge carrier redistribution in the ITO film, hence the SPR effect. This paper is aimed at highlighting all the evidences supporting ITO film as one of the fundamental sources of the SPR effect in pure NLC cells under the condition of applying low optical power and low DC voltage. An optically induced fringe electric field stemming from inhomogeneous photo-charge profiles near the electrode surfaces is expected in the LC film due to the semiconducting behavior of the ITO layer. View Full-Text
Keywords: nematic liquid crystal (NLC); ITO electrode; static DC electric field; photorefractive effect nematic liquid crystal (NLC); ITO electrode; static DC electric field; photorefractive effect
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MDPI and ACS Style

Habibpourmoghadam, A. Photorefractive Effect in NLC Cells Caused by Anomalous Electrical Properties of ITO Electrodes. Crystals 2020, 10, 900. https://doi.org/10.3390/cryst10100900

AMA Style

Habibpourmoghadam A. Photorefractive Effect in NLC Cells Caused by Anomalous Electrical Properties of ITO Electrodes. Crystals. 2020; 10(10):900. https://doi.org/10.3390/cryst10100900

Chicago/Turabian Style

Habibpourmoghadam, Atefeh. 2020. "Photorefractive Effect in NLC Cells Caused by Anomalous Electrical Properties of ITO Electrodes" Crystals 10, no. 10: 900. https://doi.org/10.3390/cryst10100900

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