The vision of this synergy project is a large-area electronic platform suitable for low-cost production of energy components. The LEAP synergy project provide a contribution towards this vision by addressing the following core question: Which materials-processing combination will allow low-cost, large-area production of thermoelectric generators?
Three projects contribute to answer this core question:
Glass-on-paper is motivated by the lack of suitable substrates for electronic systems where the choice today is limited to plastic foils and paper and neither of them are ideal for electronics. Paper is an ideal choice in some respects but the sensitivity to moisture and poor barrier properties point to the need for an altered paper structure. This will be addressed in this project by taking the novel approach of coating a few micrometers thin layer of glass onto the paper. This laminate will be thin enough to have high flexibility, superior barrier properties, and very smooth surface - an ultimate flexible electronics substrate for certain applications such as OLED displays or outdoor devices. Laser-processing will be a key technology by post-processing of sol-gel coated paper to densify the film. Paper material with its high mechanical strength per mass and flexibility is advantageous as its excellent eco-friendly and recyclable properties. Glass-on-paper should also be of importance outside printed electronics in applications where good barriers are needed such as in packaging or wallpapers.
2) Printed Conductor
Printed conductors address the need for conducting structures in printed electronics. Metal films are usually made by coating or printing inks containing silver nanoparticles. Here, for the LEAP platform, we will use the novel technique of light induced reduction of copper oxide into pure copper. There are several advantages with this technique: copper is a more abundant material than silver and thus meets our eco-requirement, copper has 95% of the conductivity of Ag at 1% of the cost, and the technique allows high-speed deposition without the need for vacuum. Graphene is another conducting material and even if the conductivity is record high in a single flake the sheet resistance is high for such a single atom thick layer, about hundred Ω per square. The requirement in several of the printed electronics applications are more demanding, in particular for energy applications and radiofrequency antennas. We will explore way to intercalate (force molecules in between the graphite layers) the thin film to increase the conductivity.
3) Thermoelectric Generator
In project 3, Thermoelectric Generator, by adding to the materials developed in project 1 and 2, we will develop semiconducting materials to be printed in the form of a thermoelectric generator. The challenge is to produce a flexible thermoelectric generator with high efficiency that is possible to apply on a non-flat surface. The process should allow cost effective, large-area manufacturing. Moreover, the shaped panel must be possible to recycle and be made of environmentally friendly materials. The thermoelectric generator will be used in industrial field tests for waste-heat and thermal gradients conversion to electricity in two applications: heat exchange and off-grid street lights.
The synergy between these three projects aim at demonstrating a printed thermoelectric device suitable for waste-heat conversion to electrical energy thus providing means to answer the core question.
The question is important due to the large global need for harvesting (solar cells and thermoelectric generators) and storing (batteries and supercapacitors) green energy. This fast growing market attract companies from diverse fields. In the LEAP project, industry partners from different position along the value chain, from materials and processes to energy applications, are participating.