Photovoltaic (PV) cells remain an expensive source of electrical power. Our work addresses the cost of PV energy. We follow the example of photosynthesis by separating the two functions of a solar cell: absorbing light and generating charge. This allows us to improve efficiency and potentially lower costs. For example, it is wasteful to employ large areas of intensively engineered PV cells merely to absorb light. A simple film of organic dyes, for example, is cheaper and more absorptive.

Our initial work employed biological materials extracted from plants and photosynthetic bacteria. This was perhaps the first demonstration of the integration of photosynthetic protein-molecular complexes in solid state devices. These first devices focused on the charge generation function of solar cells. Subsequently, we have worked on the light gathering function since this offers the greatest opportunity for cost savings and gains in performance.

The light gathering function in photosynthesis is performed by structures known as ‘antennas’. We have worked on antennas for conventional and organic solar cells. The aim is to use a film of organic dyes to absorb light. The energy must then be transferred to the charge generating structure. We have investigated two approaches to this problem:

Antennas for organic solar cells: We have demonstrated the use of surface plasmon polaritons to transfer energy across the contact of an organic solar cell. This approach has demonstrated enhancements in the quantum efficiency of solar cells at selected regions of the spectrum.

Antennas for conventional solar cells: We have built solar concentrators that collect light using organic dyes and concentrate it on solar cells. The architecture is known as a luminescent solar concentrator (LSC). It enables high optical concentration without excess heating in a stationary system. LSCs consist of a dye dispersed in a transparent waveguide. Incident light is absorbed by the dye and then re-emitted into a waveguide mode. The energy difference between absorption and emission prevents re-absorption of light by the dye, isolating the concentrated photon population in the waveguide. In this way, LSCs can achieve high optical concentrations without solar tracking. Unfortunately, the performance of LSCs has been limited by self-absorption losses that restrict the maximum possible concentration factor. Our work has focused on demonstrating an efficient variant of an LSC that exhibits optical concentrations suitable for practical applications. We call this an ‘organic solar concentrator’ (OSC) because it draws upon the organic semiconductor technology. We have developed solar concentrators using both synthetic dyes and photosynthetic materials known as phycobilisomes.

See our work on:
- Integration of Photosynthetic Complexes with Solid-State Photovoltaics
- Surface Plasmon Polariton Mediated Energy Transfer in Organic Photovoltaic Devices
- Organic Solar Concentrators