Rational design of manufacturing processes for next generation optoelectronically active nanocomposite films and coatings

Lead Research Organisation: University of Cambridge
Department Name: Physics

Abstract

Our research aims to develop plastic films or coatings that change the colour and other characteristics of the light that passes through them, not by absorbing certain wavelengths of light, as a simple colour filter would, but by converting light of one wavelength to another without losing any energy. Solar cells offer an example of why this would be useful: conventional silicon solar cells are more efficient at collecting the energy of red light than they are of blue light. So if we coated the solar cell with a film that would convert every blue photon into two red photons, without losing any energy in the process, in principle we could make the silicon solar cells 30% more efficient.

Our previous research at Cambridge has shown in principle how this could be done. Certain organic semiconductors will absorb a blue photon to produce an electron-hole pair, which then splits into two. Normally these two electron-hole pairs would annihilate and the energy would be lost, but if we can arrange for the organic semiconductor to be in molecular contact with an inorganic semiconductor quantum dot, then the electron-hole pairs can migrate to the quantum dot, where they will recombine and emit two red photons.

The problem we now want to solve is to work out how to turn this idea into a practical product that we can manufacture on a large scale. We need to be able to make semiconductor nanocrystals that won't clump together, and to coat them with a very thin layer of the organic semiconductor so the two materials are in molecular contact. Then we have to disperse these tiny particles in a clear plastic film, which we can use to coat a solar cell - and the whole process has to be designed so that it doesn't increase the cost or complexity of making the solar cell too much.

This coating for solar cells is just one example of the potential there now is for taking the latest materials from the laboratory with novel and interesting optical properties and turning them into useful products. Another example is provided by thin sheets of semiconductors only a few atoms thick. These can be very efficient at absorbing light (for example from a light emitting diode) and reemitting it as a single, purer, colour. This will help us make better optical communication devices and display devices. But once again, we need to learn how to encapsulate and embed these tiny, ultrathin sheets into a plastic film without them sticking together in stacks.

The key to solving these manufacturing problems is understanding the factors that make these tiny particles and sheets stick together and what treatments could keep them apart - often this will involve sticking special molecules to their surfaces. In the final products, these particles and sheets will be dispersed in a plastic sheet, and we need to understand how, as the plastic film dries or sets hard, the drying process affects the particles, and whether the processes that take place in the drying film makes the optical effects we're looking for less effective. We will be studying the films we make with techniques that allow us to see the individual molecular layers around the particles, as well as how well the particles are dispersed. In this way we'll understand the rules for manufacturing these sorts of films.

By the end of the project, we aim to be able to work with solar cell manufacturers to test our idea in the real world and get to the point where a product can be commercialised. If we are successful, we'll have demonstrated that we can go from understanding the fundamental science of these optical and electronic effects in these new kinds of materials to make useful products that will benefit UK industry and help solve problems of climate change.
 
Description FIG - FLUX INCREASING GLASS TO ENHANCE PHOTOVOLTAIC EFFICIENCY
Amount £600,000 (GBP)
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 11/2017 
End 10/2019
 
Description PINSTRIPE - PHOTON INCREASE BY SPLITTING TO REALISE IMPROVED PHOTOVOLTAIC EFFICIENCY
Amount £232,000 (GBP)
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 11/2017 
End 10/2018
 
Description Photon Management for Solar Energy Harvesting with Hybrid Excitonics - SolarX
Amount € 1,500,000 (EUR)
Organisation European Research Council (ERC) 
Sector Public
Country European Union (EU)
Start 04/2018 
End 03/2023
 
Description Eight19 
Organisation Eight19
Country United Kingdom 
Sector Private 
PI Contribution Expertise in singlet fission and photon-multiplier technology, photophysics, devices physics, synthesis of inorganic semiconductor nanocrystals
Collaborator Contribution Expertise in thin film processing and coating technology, commercialisation, manufacturing and product development.
Impact 3 Innovate UK projects, 1 completed successfully (SiFi - SInglet FIssion photon multiplier film to increase photovoltaic efficiency) and 2 ongoing (FIG - Flux Increasing Glass to enhance photovoltaic efficiency) & (PINSTRIPE: Photon Increase by Splitting to Realise Improved Photovoltaic Efficiency"). My team's work and collaboration with Eight19 has helped them raise significant investment to pursue the commercialisation of the Singlet Fission Photon Multiplier technology developed in my lab as part of this grant. Eight19 have a team of 3 scientists embedded in my group. 5+ patent applications filed.
Start Year 2015
 
Description NSG Pilkington 
Organisation Pilkington Glass
Country United Kingdom 
Sector Private 
PI Contribution We have an ongoing Innovate UK grant with two industrial partners Eight19 and NSG Pilkington , PINSTRIPE - PHOTON INCREASE BY SPLITTING TO REALISE IMPROVED PHOTOVOLTAIC EFFICIENCY. This is a 2 year grant helping to commercialise out singlet fission technology to improve conventional Si solar cells. We bring detailed photophysics, optoelectronics and device fabrication knowledge to the project.
Collaborator Contribution NSG Pilkington bring knowledge of manufacture of solar grade glass, encapsulants, glass processing, deposition of films on glass, environmental leaching tests
Impact Ongoing 2 year (11/2017-10/2019) Innovate UK project, PINSTRIPE - PHOTON INCREASE BY SPLITTING TO REALISE IMPROVED PHOTOVOLTAIC EFFICIENCY
Start Year 2017
 
Description Total - Sunpower 
Organisation Total E & P
Country Unknown 
Sector Private 
PI Contribution Singlet fission photon multipler research
Collaborator Contribution Sunpower part of the Total group is the 2nd largest Si PV manufacturer in the world. They are providing us Si modules and solar glass samples to test our photon multipler film on
Impact Currently confidential
Start Year 2016