Doping and photo-induced current in discotic liquid crystals thin films: Long-time and temperature effects

Abstract

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. b s t r a c tHere we address the problem of time and temperature instability of the electrical current related to parasitic doping effects in discotic liquid crystals (DLCs). We investigated the electrical transport in thin films of a phthalocyanine-based DLC in-dark and upon laser irradiation during long thermal cycles. Measuring the electrical transport between two electrodes we observed that in-dark the current is mostly due to doping levels while, upon laser irradiation, the photocurrent reflects the diffusion length of the photogenerated charge carriers and it is limited by the coherence length of a column. We prove here that the two contributions are completely independent. Our result experimentally supports the theoretical studies performed at the molecular level on discotic liquid crystals.

Multifunctional behaviors of an indium tin oxide/PbLa(ZrTi)O3/indium tin oxide wafer illuminated by ultraviolet light

“…Chang et al (2010) studied photoinduced excess carrier transport between surface states and two-dimensional electron gas channel in AlGaN/GaN structures. Calo et al (2011) investigated electrical transport in thin films of phthalocyanine-based discotic liquid crystals in dark and on laser irradiation during long thermal cycles. These materials may be used to develop advanced electric devices.…”

Organic Materials for Time–Temperature Integrator Devices

“…DLCs were originally proposed for electronic and photovoltaic applications; unfortunately, the high number of defects that spontaneously form in thin film limits their impact in their industrial development. 38 The alignment can be directly visualized using polarized optical microscopy; i.e., planar alignment results in a highly birefringent texture, whereas homeotropic alignment exhibits almost an absence of birefringence.…”

Recent Progress in Phthalocyanine Optoelectronic Materials

“…同时 Calò等 [79] 研究了烷基四取代酞菁盘状液晶(图 11)光生电流的性质. 在较弱的光照条件下, 产生柱状 相紊乱造成分子结构的重排, 进而产生光生电流; 而在 较强的光照条件下, 电子跃迁到激发态的过程较强, 电 子可以在柱状之间传递, 产生的光生电流稳定性较好.…”