Traditional solar cells convert light into electricity by exploiting the photovoltaic effect that occurs at the junction of semiconductors. They are therefore devices akin to transistors or integrated circuits. The semiconductor simultaneously performs the functions of absorbing light and separating the resulting electrical discharge. For both processes to be effective, the cells have to be made from high-purity materials. They are therefore expensive to produce, which limits their use in large-scale electricity generation. The cells we have discovered in our research work on a different principle, which differentiates between the functions of light absorption and electrical charge separation [1].
By imitating the principles used by green plants in photosynthesis, we have developed a new solar cell that succeeds in harvesting light very efficiently by means of a molecular layer of sensitizers attached to the surface of a film consisting of nanocrystals of a semiconducting oxide with a wide band gap and high roughness [2]. In this way, it becomes possible to convert visible light into electric current with an external quantum efficiency close to 100 %.
At present, the overall efficiency of converting solar energy into electricity is 12.3 % [3]. Thanks to their unique optical properties, these cells will find new application niches, such as power windows for buildings. By virtue of their good stability, low production costs and wide range of applications, as well as their environmental compatibility, these cells have become credible candidates for large-scale electricity generation from solar radiation.
