Solar energy ~10 000 times today’s total global energy consumption impinges 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 to 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.
Aerotaxy is a method to produce nanowires in the gas phase. It is much faster than substrate-based methods. You will find a short description in the Materials Research section.
Read more about aerotaxy
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.Different architectures integrating hybrid perovskite semiconductors with III-V nanowire based solar cell devices. Image by Eva Unger.
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.
Understanding InP Nanowire Array Solar Cell Performance by Nanoprobe-Enabled Single Nanowire Measurements. Otnes, G.; Barrigon, E.; Sundvall, C.; Svensson, K. E.; Heurlin, M.; Siefer, G.; Samuelson, L.; Åberg, I.; Borgström, M. T., Nano Letters, 2018, 18 (5), 3038-3046. DOI: 10.1021/acs.nanolett.8b00494
See article understanding InP nanowire array at publisher's site
Towards Nanowire Tandem Junction Solar Cells on Silicon. Borgström, M. T.; Magnusson, M. H.; Dimroth, F.; Siefer, G.; Hohn, O.; Riel, H.; Schmid, H.; Wirths, S.; Bjork, M.; Aberg, I.; Peijnenburg, W.; Vijver, M.; Tchernycheva, M.; Piazza, V.; Samuelson, L., IEEE J Photovolt, 2018, 8 (3), 733-740. DOI: 10.1109/Jphotov.2018.2816264
See article towards nanowire tandem at publisher's site
InP nanowire array solar cells achieving 13.8% efficiency by exceeding the ray optics limit. Wallentin, J.; Anttu, N.; Asoli, D.; Huffman, M.; Aberg, I.; Magnusson, M. H.; Siefer, G.; Fuss-Kailuweit, P.; Dimroth, F.; Witzigmann, B.; Xu, H. Q.; Samuelson, L.; Deppert, K.; Borgström, M. T., Science, 2013, 339 (6123), 1057-60. DOI: 10.1126/science.1230969
See article InP nanowire array at publisher's site
Single-nanowire, low-bandgap hot carrier solar cells with tunable open-circuit voltage. S. Limpert, A. Burke, I-J. Chen, N. Anttu, S. Lehmann, S. Fahlvik, S. Bremner, G. Conibeer, C. Thelander, M. -E. Pistol and H. Linke, Nanotechnology 2017, 28, 434001. DOI: 10.1088/1361-6528/aa8984
See article single-nanowire, low-bandgap hot carrier at publisher's site
Gaute Otnes, III-V Nanowire Solar Cells: Growth and Characterization PhD thesis, Lund University 2018
See Gaute Otnes' thesis at the Research Portal
Xulu Zeng, InP/GaInP Nanowires for Tandem Junction Solar Cells : Growth, Processing, and Characterization PhD thesis, Lund University 2018
See Xulu Zeng's doctoral thesis at the Research Portal
Vilgaile Dagyte, Growth and optical properties of III-V semiconductor nanowires: Studies relevant for solar cells PhD thesis, Lund University 2018
See Vilgaile Dagyte's thesis at the Research Portal
Research focussed on nanowires and molecular engineering to find new solutions for energy
Other Major Projects
Swedish energy agency project on nanowire tandem cells. Project number 36454-3
Swedish energy agency project on nanowire/perovskite tandem junction solar cells. Project number 46655-1
Swedish research council, x-ray characterization of nanowire solar cells Swedish research council, RÅC, framework program.