Project: Topological optimization of near-field-enhancing nanostructures
Main supervisor: Associate Professor, Ph.d., Søren Peder Madsen, Dept. Of Eng., Aarhus University
Co-supervisor(s): Professor, dr. Techn., Ole Sigmund, Mech. Eng., DTU
Project period: 1/5 2015 - 31/5 2018
The total radiation from the Sun on the surface of the earth is almost 10,000 times more powerful than our global power consumption. The exploitation of solar energy is, however, still not cost-effective compared to nuclear or fossil fuels. To improve this, one may reduce the production cost of solar cells and/or increase their efficiency. Silicon (Si) based solar cells are widely used today, however in commercial Si-based devices the efficiency is typically 15-20 %, with a theoretical limit of 30% for simple Si-cells.
This low efficiency is mainly caused by the fact that the very wide spectrum of solar light (photon energies) is simply not fully absorbed and converted into electricity.
Si-based solar cells mainly generate current by absorbing photons within the visible and near infrared spectrum (400-1100nm). Thus a majority of the solar light spectrum does not contribute to the power generation, as the low energy photons (wave length > 1100nm) simply pass though the cell while high energy photons (300 - 400nm wave length) mainly contributes to heat dissipation.
By applying an additional material layer to the back of the Si-cell, it is possible to convert two low energy photons to one photon with a higher energy, which can be absorbed in Si and thereby contribute to current production. This process is named upconversion and can e.g. take place in some rare-earth doped materials. The efficiency of upconversion is naturally weak and careful nanostructuring of the material is needed for practical applications.
The aim of this PhD project is to develop advanced numerical models for upconversion and utilize the models for topology optimization of the nano-structures in the up-converting layer to maximize the efficiency while keeping production and environmental constraints in mind.
External partners/project that the PhD is part of
This PhD project is a part of the SunTune project. http://projects.au.dk/suntune/