Quantum-dot intermediate-band solar cells with inverted band alignment

The intermediate-band concept was proposed over a decade ago as a possible route to increase the efficiency of single-junction solar cells. Despite a number of experimental attempts to realize this concept, no efficiency improvement over conventional single-junction solar cells has so far been demonstrated. This is likely due to the fact that the intermediate band itself acts to enhance electron–hole recombination. In this work we propose a novel intermediate-band solar-cell architecture based on doped semiconductor nanostructures having an inverted type-I band alignment with the surrounding host. The recombination of carriers in the nanostructures is prevented by ultra-fast charge transfer to the host, thereby removing the main obstacle to achieve high conversion efficiency.