Semiconductor Quantum Dots and Quantum Dot Arrays and Applications of Multiple Exciton Generation to Third-Generation Photovoltaic Solar Cells

Several classes of semiconductor quantum dots (QD), including groups II-VI, III-V, IV-VI, IV, and their alloys as well as various intergroup and intragroup core-shell configurations, and nanocrystal shapes have been synthesized. One approach to enhance efficiency in QD-based PV cells compared to conventional bulk semiconductor-based PV is to create efficient multiple exciton generation from a large fraction of the photons in the solar spectrum. Three generic types of QD solar cells that could utilize MEG to enhance conversion efficiency can be defined. They include photoelectrodes composed of QD arrays that form either Schottky junctions with a metal layer, a hetero p-n junction with a second NC semiconductor layer, or the i-region of a p-i-n device, QD-sensitized nanocrystalline TiO₂ films, and QDs dispersed into a multiphase mixture of electron- and hole-conducting matrices, such as C₆₀ and hole conducting polymers.