Chiral Liquid Crystalline Electronic Systems

Abstract

Liquid crystals bearing extended π-conjugated units function as organic semiconductors and liquid crystalline semiconductors have been studied for their applications in light-emitting diodes, field-effect transistors, and solar cells. However, studies on electronic functionalities in chiral liquid crystal phases have been limited so far. Electronic charge carrier transport has been confirmed in chiral nematic and chiral smectic C phases. In the chiral nematic phase, consisting of molecules bearing extended π-conjugated units, circularly polarized photoluminescence has been observed within the wavelength range of reflection band. Recently, circularly polarized electroluminescence has been confirmed from devices based on active layers of chiral conjugated polymers with twisted structures induced by the molecular chirality. The chiral smectic C phase of oligothiophene derivatives is ferroelectric and indicates a bulk photovoltaic effect, which is driven by spontaneous polarization. This bulk photovoltaic effect has also been observed in achiral polar liquid crystal phases in which extended π-conjugated units are properly assembled. In this manuscript, optical and electronic functions of these chiral π-conjugated liquid crystalline semiconductors are reviewed.

Large Thermally Irreversible Photoinduced Shift of Selective Light Reflection in Hydrazone‐Containing Cholesteric Polymer Systems

“…Chiral liquid crystalline phases can be used in different fields of optoelectronics and photonics due to their ability to show dynamic changes or switching of optical properties in response to external stimuli, such as heat, light or electrical fields [12–14] …”

“…Chiral liquid crystalline phases can be used in different fields of optoelectronics and photonics due to their ability to show dynamic changes or switching of optical properties in response to external stimuli, such as heat, light or electrical fields. [12][13][14] Doping cholesteric liquid crystals (CLCs) with photochromic dyes makes it possible to control the pitch of the helix using light. [15] The phototuning mechanism is as follows: irradiation of photochrome leads to its isomerization with a change in its geometry.…”

Examining Energy Storage Potential in Weakly Polar Nematic Liquid Crystals Infused with Anthraquinone Dye: A Comprehensive Approach

“…In these applications, the host system also plays a crucial role. Therefore, the dispersion of dyes in different mesophases such as nematic [16][17][18], cholesteric [19,20], ferroelectric [21,22] and smectic [23][24][25] systems have already been tested for different application purposes. Nematic systems are the most fundamental and thoroughly investigated out of all other host mesophases.…”

Carrier transport characteristics of glass-forming chiral liquid crystalline dimers based on oligo(phenylenevinylene) units

“…22,23 For construction of electrically pumped systems, the N* liquid crystals comprising extended -conjugated units with large aspect ratios have been studied. 24 High quality CPL emission within the wide reflection band over 200 nm and enhancement of fluorescence at the reflection band edge have been reported only in optically pumped systems. [25][26][27][28] In order to realize electrically pumped systems, molecular design should be optimized for improvement of the carrier transport.…”