As a part of Nordic Top-level Research Initiative, NANORDSUN researches solar cell material that has potential for high conversion efficiency at a lower material cost.
This consortium will target research and development of radial p-n junction III-V semiconductor nanowire solar cells. The advantage of a radial p-n junction nanowire is that electrons and holes only have to move across a very short distance (< 50 nm) to reach the contacts. Good optical absorption is achieved since the light is mainly absorbed along the direction of the nanowire. The ability to collect carriers and light orthogonally is a unique feature of a radial p-n junction nanowire.
In addition, the nanowire concept offers several other advantages compared with bulk or thin films:
- They can be produced with self-assembly techniques, providing complex structures with relatively simple processing.
- Strain is easily accommodated without creating defects detrimental to the device, hence more freedom to optimize material combinations for efficiency.
- Can potentially be grown on any other substrate, e.g. Si or glass hence substantial cost savings can be made.
- Nanowires can be designed to have photonic crystal effects, which could lead to very efficient light trapping.
The nanowires will be fabricated using catalyst-assisted and catalyst-free growth methods. Processing of full nanowire solar cell arrays will be made, including the design of passivation layers and transparent contacts. Non III-V substrate growth as well as substrate-free methods will be tried out in order to find a substantial low cost advantage. The design of the solar cells will be accompanied by modeling of the nanowires unique light harvesting and anti-reflecting properties.
The objective is to find the most energy efficient nanowire solar cell with an optimum design solution for low cost.
Helge Weman (Project manager)
NTNU, Norwegian University of Science and Technology
KTH Royal Institute of Technology
Sol Voltaics AB