Lefteris research interests encompass the field of photovoltaics and solar energy conversion. In particular he is interested in developing light harvesting and photon management structures for applications in high efficiency low cost solar cells. Light harvesting structures can be fabricated based on ultra-thin film organic architectures for increased absorption of light and better solar energy utilization. Efficient spectral management of the solar spectrum can be applied to existing solar cell devices towards lower cost of solar electricity.

A range of projects are available and we welcome applications from self-funded students or from students seeking external funding. • Photonic Luminescent Solar Concentrator. • Silicon Photosensitisation using organic molecular layers. • Photo-Electrochemical Characterisation of Organic/Silicon Interfaces. • Photophysics of functional and solar cell materials. • Photon Frequency Management Materials for Efficient Solar Energy Collection.

Luminescent Solar Concentrators

This area of research involves the development of Luminescent Solar Concentrators (LSC) and Luminescence Down Shifting (LDS) structures for efficient spectral management and light trapping in solar cells for indoor and outdoor applications. An LSC usually consists of a flat plate, doped with a luminescent species, which absorbs the incident sunlight (direct or diffuse). A large fraction of the emitted light is then trapped within the collector by total internal reflection (TIR) and is directed to a solar cell at the edge of the collector where the remaining edges of the collector can be covered by mirrors. 

Light Harvesting 

The term ”light harvesting” describes the process occurring in photosynthesis which enhances the absorption cross section of the photosynthetic reaction complex by excitation energy transfer, often called resonance energy transfer. The proposed research aims to develop a light harvesting framework as a means of sunlight energy collection with application towards the photosensitisation of silicon solar cells. Previous experimental results have revealed the existence of a similar energy transfer mechanism between a molecule and a semiconductor, as demonstrated by quenching of molecular fluorescence in proximity to silicon for Langmuir-Blodgett (LB) films. We use Time Resolved Fluorescence Spectroscopy and Fluorescence Lifetime Imaging Microscopy on the light harvesting structures to determine energy transfer and photon collection efficiencies.

Silicon Surface Chemistry

Silicon photosensitisation using light harvesting structures represents an attractive solution for reducing the amount of semiconductor material needed by up to two orders of magnitude in the manufacture of solar cells. The direct covalent attachment of alkyl layers and chromophores on the silicon surface offers exciting chemistry that combine the strong optical absorption of dye molecules with the excellent electronic properties of thin silicon converters. The above approach divides the photovoltaic conversion process into two processes consisting of an energy collector (light harvesting) which absorbs light with a high optical absorption cross-section, and transfers energy to a semiconductor converter (silicon) which efficiently separates the photo-generated charges and produces electricity. The resulting organic-inorganic structure presents a step change in thinking in photovoltaic energy conversion.