This book explores why the properties of liquid crystals make them ideal for use in photovoltaic applications. It achieves this by presenting a description of the properties of liquid crystals and how their electronic properties compare to that of polymers used in organic photovoltaics. It explores how the type of liquid crystal chosen can help in improving the efficiency of the photovoltaics. It compares experimental and theoretical ways in which the efficiency is directly or indirectly estimated between the organic photovoltaics and the organic photovoltaics that contain a liquid crystal. It first introduces liquid crystals and their different varieties, before reviewing their electronic transfer properties and how they can improve efficiency. It is an ideal text for graduate students and young researches considering entering the area of photovoltaics - specifically, organic photovoltaics – who do not yet have knowledge of this field. Introduces the field of liquid crystals and provides basic information to those new to the field, in a concise and visual manner Describes which characteristics of a liquid crystal are most advantageous to use in photovoltaics Provides basic knowledge of photovoltaics for those who do not have previous knowledge of how they behave electronically

The self-contained properties of discotic liquid crystals (DLCs) render them powerful functional materials for many semiconducting device applications and models for energy and charge migration in self-organized dynamic functional soft materials. The past three decades have seen tremendous interest in this area, fueled primarily by the possibility

This dissertation describes the use of discotic liquid crystals for two different areas of research, advances in new organic photovoltaic cell (OPVC) technologies and the development of new nanoporous membranes. Discotic liquid crystals (DLCs) generally consist of a central polycyclic aromatic hydrocarbon core that is generally ridged and crystalline in nature. The central core is decorated with alkyl chains in order to induce liquid crystallinity. Within their mesophase, DLCs spontaneously form columnar structures with close intracolumnar disc-disc distances. Due to the close disc-disc packing, the conjugated, aromatic cores act as one-dimensional charge carriers. The spontaneous alignment of DLCs is ideal for electronic applications, namely OPVCs. We describe the synthesis of a new boronic ester containing discotic liquid crystal that is highly electron deficient and displays high charge carrier mobilities. The scope of the boronic ester formation and its application to liquid crystals was explored with the development of two new boronic ester containing non-planar discotic liquid crystals. A new approach toward completely DLC-based OPVCs is described and explored. The miscibility of the non-planar discotic liquid crystals with planar discotic liquid crystals, which is a key requirement for the alignment of the desired OPVC was tested. In many membranes used for industrial applications a great deal of energy is put into forcing materials into certain alignments. However, in our approach toward a DLC-based nanoporous membrane we utilize the spontaneous alignment of liquid crystals in order to make desirable molecular architectures. By adding polymerizable units to the periphery of a DLC we "lock" the mesophase alignment upon polymerization. Due to the highly labile nature of the boron-oxygen bonds that surround the central core of our boronic ester-containing DLC were are able to then remove the DLC cores, revealing a nanoporous membrane templated by the DLC mesophase alignment. The polymerized material with the cores removed has a remarkably high pore density, contains only one pore size, and has linear pores templated by the columnar DLC mesophase.

The general theme of this thesis is organic photovoltaics. In more details it consists of two parts: Measuring the electrical mobility in a new compound showing liquid crystalline (LC) phase at room temperature. This LC whose abbreviated name is Pe4C8EH, is made up of disc-like molecules with flexible chains connected to the disc core. When disc-like cores pile-up upon each other, they form columns. We showed that along these columns the mobility of charge is enhanced, meaning that Pe4C8EH shows directional semiconducting properties. Measured values of mobility are 2.8 10-4 cm2/V.s and 8.5 10-5 cm2/V.s in the direction parallel and perpendicular to the columns, respectively. This property is interesting for solar cell and transistor applications. Mobility enhancement is attributed to the p-orbital overlapping along the columns. In the second part, the effect of 30nm spherical gold nanoparticles (AuNPs) on the efficiency of P3HT:PCBM solar cells was studied by adsorbing them on the surface of Indium Tin Oxide (ITO) electrode. Metallic nanoparticles can enhance the absorption efficiency of a cell by both scattering and absorption of the incident light at a special frequency, which is called Surface Plasmon Resonance (SPR). SPR depends on the metal, size and shape of nanoparticles. Our investigation showed that the positive effect of AuNPs on the efficiency of solar cells depends on their surface concentration. High concentration (215/μm2) of AuNPs almost suppresses the photocurrent generated by the solar cell while low concentration (8/μm2) has a positive effect on the efficiency of the cell.

Types and classification of liquid crystals. Theories of liquid crystals. Dynamic scattering mode LCDs.

This is an exciting stage in the development of organic electronics. It is no longer an area of purely academic interest as increasingly real applications are being developed, some of which are beginning to come on-stream. Areas that have already been commercially developed or which are under intensive development include organic light emitting diodes (for flat panel displays and solid state lighting), organic photovoltaic cells, organic thin film transistors (for smart tags and flat panel displays) and sensors. Within the family of organic electronic materials, liquid crystals are relative newcomers. The first electronically conducting liquid crystals were reported in 1988 but already a substantial literature has developed. The advantage of liquid crystalline semiconductors is that they have the easy processability of amorphous and polymeric semiconductors but they usually have higher charge carrier mobilities. Their mobilities do not reach the levels seen in crystalline organics but they circumvent all of the difficult issues of controlling crystal growth and morphology. Liquid crystals self-organise, they can be aligned by fields and surface forces and, because of their fluid nature, defects in liquid crystal structures readily self-heal. With these matters in mind this is an opportune moment to bring together a volume on the subject of ‘Liquid Crystalline Semiconductors’. The field is already too large to cover in a comprehensive manner so the aim has been to bring together contributions from leading researchers which cover the main areas of the chemistry (synthesis and structure/function relationships), physics (charge transport mechanisms and optical properties) and potential applications in photovoltaics, organic light emitting diodes (OLEDs) and organic field-effect transistors (OFETs). This book will provide a useful introduction to the field for those in both industry and academia and it is hoped that it will help to stimulate future developments.

The work focuses on recent developments of the rapidly evolving field of Non-conventional Liquid Crystals. After a concise introduction it discusses the most promising research such as biosensing, elastomers, polymer films , photoresponsive properties and energy harvesting. Besides future applications it discusses as well potential frontiers in LC science and technology.

The work focuses on recent developments of the rapidly evolving field of Non-conventional Liquid Crystals. After a concise introduction it discusses the most promising research such as biosensing, elastomers, polymer films , photoresponsive properties and energy harvesting. Besides future applications it discusses as well potential frontiers in LC science and technology.

The existence of liquid crystals has been known for nearly a centu ry; yet it is only in the last ten years that their unique optical, electri cal, electro-optic, and thermal properties have been exploited to any significant extent in such technological applications as digital d~ plays and thermography. Digital watches equipped with liquid-crys tal displays (LCD's) have recently made their debut in the electronic watch market, and the large-scale use of LCD's in a variety of other applications requiring reliable, low-power digital displays is immi nent. There is good reason to believe that liquid crystals will be the first electro-optic materials to find widespread commercial use. Apart from applications, liquid crystals are unique among the phases of matter. Lurking beneath their garish display of color and texture is a great complexity of physical and chemical interaction that is only now beginning to unfold in the face of a decade-old resurgence in all aspects of liquid~rystal research. RCA Laboratories has participated in this resurgence from its beginning in the early 1960's and at present maintains active liquid-crystal programs both in basic re search and in device engineering. In view of the widespread interest in liquid crystals at RCA Labo ratories, an in-house weekly seminar devoted to the subject of liquid crystals was organized in the fall of 1973. The resulting lectures were subsequently published in three issues of the RCA Review and, with the incorporation of much additional material, eventually grew into the present volume.