Surface/interfacial engineering plays a significant role in improving the transport of photo-generated electrons and photovoltaic performance of quantum dot sensitized solar cells (QDSCs). In this work, a new approach involving introduction of an ultrathin aluminum nitride (AlN) coating ( < 1 nm) to modify the TiO2/quantum dots (QDs)/electrolyte interfaces is explored with the aid of plasma-enhanced atomic layer deposition (PEALD) technology. The surface morphology, chemical composition as well as deposition temperature of the AlN coating are studied in detail. Significantly enhanced open-voltage (V-oc) is achieved after introducing AlN coating, and the 5 ALD cycles of AlN modified CdSexTe1-x QDSCs achieve the best efficiency of 9.31% with a V(oc )of 679 mV, which is higher than the efficiency of 8.27% and V-oc of 619 mV for the reference cell. Detailed investigation on the electron transport processes in AlN-modified devices reveals that as-prepared AlN can passivate the surface defects of TiO2/QDs while inhibiting photo-generated electron recombination occurring M both TiO2/electrolyte and QDs/electrolyte interfaces. This study opens up the door constructing nitrides interface layers to improve the performance of QDSCs.