Solution processed thermoelectric materials for large area applications

Lead Research Organisation: Swansea University
Department Name: College of Engineering

Abstract

It is estimated that around one sixth of industrial energy usage is wasted as heat. In order to maximize energy efficiency, the waste heat represent a viable resource to reduce overall electricity demand, helping to mitigate CO2 emissions associated with the waste heat. One strategy for using waste heat would be to generate electrical energy with the use of Thermoelectric generators (TEGs).
TEGs are devices, which generate an electrical current driven by a difference in temperatures. TEGs consist of a hot side and a cold side and the difference in temperature between the two sides results in a potential difference (voltage) and current flow, and therefore the generation of electrical power. Until recently, thermoelectric materials capable of producing efficient TEGs at room temperatures, have been based on alloys of rare-Earth elements such as bismuth and tellurium which have draw- backs such as high cost of production, scarcity, and toxicity.
Very recent research has seen the emergence of organic thermoelectric materials which have advantages over inorganic materials, in that they are low cost, light weight and can be processed from solution at low temperatures, meaning they are less energy intensive to produce. This also means that manufacturing technologies such as printing produce organic TEGs over large areas, further reducing costs, but also leading to the possibility of flexible, building-integrated, or even wearable thermoelectric devices.
This project seeks to investigate the thermoelectric properties of potential candidate organic and polymer materials, to investigate improvements in materials' properties gained via process improvements, doping of pure materials, and the fabrication of organic/inorganic nanocomposites. It will also look at novel inorganic materials capable of being processed from solution such as intermetallics and perovskite-structured materials.
The primary objective of the project is to identify materials that are capable of being printed from solution in order to fabricate efficient TEGs on flexible substrates. Once suitable materials have been identified, processing conditions will be optimized and thermoelectric devices will be built and tested. We will also fabricate flexible TEG/photovoltaic tandem devices with the aim of harvesting waste heat from the PV devices under test conditions to generate electrical power photovoltaically and thermoelectrically in the same device.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509553/1 01/10/2016 30/06/2022
1815896 Studentship EP/N509553/1 01/10/2016 31/03/2020 Jonathan Atoyo
 
Description I have discovered several methods utilizing certain polar solvents and ionic liquids to improve the electrical conductivity of PEDOT:PSS polymer and thus the power factor of the material. The PEDOT:PSS polymer acts as a matrix by which it can be doped by either inorganic nano particles or solvents and acid. I have developed certain methods which can be useful and published to aid in the greater scope of research. Therein my most recent soon for publication (accepted manuscript) titled Enhanced electrical conductivity and Seebeck coefficient in PEDOT:PSS via a two-step Ionic liquid & NaBH4 treatment.
Thus far i have also discovered a novel method of using carbon nanotubes imbedded within PEDOT:PSS polymer matrix with a chemical treatment to formulate N type PEDOT:PSS thermoelectric materials and a novel method by using the ionic liquid post treatment for stability of the films to prevent oxygen doping in air which invariably turns the N type films back into P type films. This is significant because not only do N type thermoelectrics suffer from re oxidation stability issues but PEDOT:PSS based thermoelectrics are not reported in literature (only 3 papers currently).
I have also managed to answer the question of my thesis which is to similtanously improve the Seebeck coefficient and Electrical conductivity and thus increase the power factor significantly. I have done this by a novel three part system i developed using carbon nanotubes ionic liquid and a chemical post treatment which improved the electrical conductivity up to 4000 S/cm and seebeck coefficient up to 25 uv/k which results in a power factor above 240 uw/m/k. This chapter is significant. and will result in at least two papers
Exploitation Route it could be taken forward by other researchers because they can expand on the methods i have developed by mixing them with other methods. I have found a way to improve the electrical conductivity of PEDOT:PSS and others can engineer a way to improve the Seebeck coefficient as well mixing their approach and my approach to optimize the material efficiency. Finding a way to similtanously improve both the seebeck coefficient and electrical conductivity is vital for optimizing ZT and the discovery of an N type PEDOT:PSS is very significant to N type thermoelectrics research.
Sectors Energy,Environment