Energy Harvesting Devices
Solar energy ~10 000 times today’s total global energy consumption impignes on Earth. Could we only convert a small fraction of all this energy to useful energy forms, our future energy supply is secured. Photovoltaics converts light to electricity and NW technologies have the potential to provide multi-bandgap materials otherwise not feasible and low material-consumption devices.
Nanowire tandem cells
By use of nanowires, we have taken on the challenge to create high-performance photovoltaics (PV) at low cost, simultaneously being sustainable with concern for the limited abundance of materials on the planet. The main objective is to exploit the advantages of III-V semiconductor nanowires to develop novel PV devices with high conversion efficiency at moderate production cost. The project aims to achieve a step jump towards designing and developing a novel solar conversion system based on nanowire technology. Initially, we aim for efficiencies >20% at a fraction of the materials used in thin film technology: sustainable energy harvesting for coming generations.
The axial geometry offers greater flexibility with respect to materials combinations and we are working towards multi-junction technology where different materials are stacked on top of each other for more efficient harvesting of a larger part of the solar spectrum, combined with open circuit voltage addition of the junctions separated by Esaki tunneling diodes. This opens up the venue for even higher efficiencies >40%. Challenges are overcoming the barrier of single to tandem junction performance, control over materials composition and doping for designed p-i-n and tunneling diodes between materials in a tandem (multi) junction NW PV device, and limitations set by surface recombination leading to loss of carriers intended for carrying the current.
Nanowire/perovskite solar cells
We aim to develop nanowire-perovskite tandem junction solar cells with high solar energy harvesting efficiency. Our main focus will be to combine efficient III-V nanowire devices with emerging hybrid materials to form nanostructured tandem junctions.
This is a relatively new project where we will identify the most feasible approach to make integrated hybrid tandem devices based on III-V nanowires and solution-processable semiconductors like metal-halide perovskites. Then we will learn how to match photocurrents of sub-cells by optimizing the NW band gap and pitch as well as adjusting the perovskite band gap, assisted by numerical modeling. Laterally integrated hybrid tandem devices are considered, for which a contract strategy for perovskite-nanowire tandem junctions has to be developed in order to be able to make and test the perovskite-nanowire architectures with respect to feasibility and energy harvesting efficiency.
Hot carrier solar cells
When a photon is absorbed by a semiconductor and generates an electron-hole pair, part of the photon’s energy is converted to kinetic energy. Being able to extract work from high-energy (hot), photon-generated electron-hole pairs would create an alternative path towards high power conversion efficiencies. Nanowires are a promising system for such hot-carrier solar cells because their one-dimensional nature allows for high-power, high-efficiency thermoelectric harvesting of heat, and their geometry, combined with photonic or plasmonic effects, makes it possible to tailor the location of light absorption. A key aim of our research is to explore and understand the full potential of nanowire-based hot-carrier photovoltaics