Understanding of energy and charge transfer processes at the semiconductor/liquid junction interfaces is important for design of new type of electronic and photovoltaic devices. We have investigated interfacial energy and charge transfer processes in assemblies consisting of CdSe NQDs and Ru-polypyridine complexes. We show that in the NQD/Ru-complex assemblies the NQD photoluminescence (PL) is quenched with efficiencies up to 100%. The mechanism of quenching is either ET or CT, depending on NC size. In the case of small NCs, the dominant interaction mechanism is dipole-dipole type ET due to the large overlap of the NC PL and the absorption spectrum of the complex. For large NCs, the overlap of the NC PL and the absorption spectrum of the complex is small and the dominant interaction mechanism is rapid CT. Demonstrated sensitization of complexes with NQDs opens interesting opportunities for designing new types of photocatalytic materials for solar energy conversion applications.