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James Walshe

PhD Researcher
Host University: School Of Physics, Dublin Energy Lab, Dublin Institute Of Technology



Plasmonic and structure enhanced luminescent down shifting for photovoltaics

Keywords: sustainable energy development; nanotechnology; solar energy; luminescent down shifting; plasmonics; efficiency enhancement; theoretical modelling; ray tracing simulation.

The combination of the depletion of conventional carbon based forms of energy, the continuous need to expand energy production to keep up with demand and the need to consider more efficient and environmentally friendly forms of energy production has made the investigation into alternative forms of energy production ever more pertinent. The solution to the current energy crisis will likely come in the form of renewable energy resources such as solar energy, with the area showing considerable interest over the past few decades as countries around the world attempt to ween their energy grids dependence on conventional form of energy generation.


However one of the major barriers preventing solar energy from becoming a viable alternative to conventional forms of energy production is its cost per unit of power produced (normally expressed in $/W) with the technology currently available. The heart of this problem lies in the limited spectral response of the photovoltaic technologies (PV) currently available.  This problem can be addressed via the introduction of a luminescent down shifting (LDS) layer onto the cell, with the layer containing a luminescent material which absorbs short wavelength photons and re-emitted them at a longer wavelength where the cells efficiency is higher.

The introduction of this LDS layer also introduces additional loss mechanisms within the device, which must be overcome in order to achieve an enhancement in the cells efficiency. Some material combinations have shown premise in their ability to offer a sizeable increase in the conversion efficiency achievable with a range of different PV technologies. The possibility of further enhancement with existing PV technology was recognized via the novel approach of incorporating metal nanoparticles (MNP’s) directly into the LDS layer, with the Plasmon interaction between the MNP’s and the luminescent species exploited in a controlled manner. Despite the reported success of this novel approach the question remains of how far can the limits of the enhancement gained via this approach be extended. It is believed that a greater enhancement can be achieved through further refinement in the MNP’s geometry and distribution within the LDS layer.


The project aim is to develop a detailed theoretical model which will allow the resultant optical properties of such a plasmonic-enhanced LDS (PLDS) layer to be investigated, and the maximum achievable enhancement factor possible with such an approach identified. The model will help identify the role played by the MNP’s geometry, size and distribution within a PLDS layer, in the enhancement reported for such devices, as well as providing a deeper understanding of the limitations of such devices.  The possibility of further enhancement through the recycling of photons and/or the exploitation of the field mode enhancement observed within cavity structures, via additional more speculative optical design will also be investigated during the course of the project.


Project Supervisors: Dr John Doran (DIT) & Associate Prof. Sarah McCormack