A method for improving the efficiency of electron emission in solar conversion devices is presented in this week’s Nature Communications. The method demonstrates an important step for solar energy convertors based on the photon-enhanced thermionic emission scheme, which makes use of thermal energy that is not available to conventional photovoltaic cells.

Hot carrier harvesting is an approach for overcoming limits to solar energy efficiency that captures electrons that have been heated up by light before they lose their energy to the surrounding material. In photon-enhanced thermionic emission - a recent method for hot carrier harvesting - the electrons and the underlying crystal lattice are heated to the same temperature, so it is no longer necessary to capture the electrons before they lose their energy. This means there is more time to convert the electrons into useful energy. However, the efficiency for this process is currently too low to be practical. Nick Melosh and colleagues address this problem by building a structure from two semiconductors and showing that the resulting interface dramatically enhances the efficiency. They show that further improvements are possible by using different coatings on the surface of the device.