LIQUID CRYSTALLINE HYBRID DIELECTRICS FOR MONODOMAIN ORGANIC SEMICONDUCTORS

The twentieth century saw an explosion in semiconductor electronics from the first transistor, which was used in hearing aids, to the ultrafast computers of today. A similar surge is anticipated for Plastic Electronics based on a new type of semiconducting material which is soft and flexible rather than hard and brittle. Plastic Electronics is considered a disruptive technology, not displacing conventional electronics, but creating new markets because it enables the printing of electronic materials at low temperatures so that plastic, fabric, paper and other flexible materials can be used as substrates. Printing minimises the waste of materials and low cost roll-to-roll manufacturing can be used because the substrates are flexible. New applications include intelligent or interactive packaging, RFID tags, e-readers, flexible power sources and lighting panels. The organic field effect transistor (OFET) is the fundamental building block of plastic electronics and is used to amplify and switch electronic signals. The organic semiconducting channel connects the source and drain electrodes and is separated from the gate electrode by an insulating dielectric. A positive/negative gate voltage induces negative/positive charges at the insulator/semiconductor interface and so controls the conductivity of the semiconductor and consequently the current flowing between the source and drain. The future success of the industry depends on the availability of high performance solution processable materials and low voltage device operation. The semiconductors must have high electron and hole mobility (velocity/electric field) achieved by the hopping of carriers between closely spaced molecular sites. A new class of lamellar polymers, mostly developed in the UK, provides the required state-of the art performance because of their macromolecular self-organisation. However a major problem is that the materials are only well-ordered in microscopic domains; trapping in grain boundaries and poor interconnectivity between domains substantially reduce performance and reliability. The low voltage operation of OFETs requires that the gate insulators have a high dielectric constant.
We propose novel insulating dielectrics for OFETs to simultaneously align the plastic semiconductors and ensure low voltage operation. They will be solution processable at low temperatures for compatibility with printing and other large area manufacturing techniques. We will synthesise and characterise the new materials and test their performance using state of the art semiconductors. We will engage with industrial end-users to ensure that our technology is exploited so contributing to the high-tech economy in an area where the UK is already pre-eminent. We anticipate that our novel insulators will provide monodomain order over large areas to the overlying semiconductor and so will enhance OFET performance and stability. Hence we aim to hasten the commercialisation of Plastic Electronics.

Plastic Electronics is forecast to become a major disruptive technology, not replacing conventional electronics but opening new markets. It is considered disruptive because it enables the printing of electronic materials at low temperatures so that plastic, fabric, paper and other flexible materials can be used as substrates. Printing minimises the waste of materials and low cost roll-to-roll manufacturing can be used because the substrates are flexible. New applications include intelligent or interactive packaging, RFID tags, e-readers, flexible power sources, novelty items and lighting panels. The global market for Plastic Electronics is under $5 billion dollars now but is predicted to grow to over $330 billion by 2027 (IDTechEx). The future success of the industry depends on the availability of high performance, solution processable, insulating and semiconducting materials, which ensure high performance organic semiconductor devices with low voltage device operation. Very little work has been done on developing the insulating materials although high quality, semiconducting, organics are widely known. We aim to hasten the advent of Plastic Electronics by the development of a novel solution processable insulating film for use in low-voltage integrated circuits. The material has novel features to enhance device performance and reliability.
The entire supply chain of Plastic Electronics, from chemical companies through component fabrication and integration to high-volume product manufacturers, would benefit economically from our research. Chemical manufacturers and print companies would benefit by the synthesis and ink-formulation of large quantities of our novel materials. Our insulating materials are compatible with both polymer and small molecule semiconductors and so will be applicable no matter which material type dominates commercially. The UK is predominant in the area of organic semiconductors with a large patent base and SME activity and so will benefit particularly form the improved manufacturability of Plastic Electronics devices. The technologies involved are at a very early stage so that the UK may emerge as a manufacturing base. The general public will benefit from the availability of low cost and high specification products and the creation of high tech jobs. In the shorter term the demonstration of innovative research and the availability of researchers with interdisciplinary training will help ensure that the UK remains an attractive location to attract inward investment.
The new applications generated by Plastic Electronics would contribute to improved quality of life and health for the general public. For example, a new generation of flexible e-readers would be both ergonomic and energy efficient; medical sensors could be embedded in patches or dressings etc. There is also a potential cultural impact as Plastic Electronics has the potential to drive panelled displays with unusual shapes or aesthetics in architecture, fashion or art.