High fluorescence efficiency is desired for the practical applications of semiconductor nanocrystals (NCs) in many fields. However, reducing photoluminescence (PL) efficiency is usually observed after ligand exchanges on nanocrystal surfaces due to the generation of surface defects. Here, we report the preparation of polyvinylpyrrolidone-capped CdSe NCs (CdSe/PVP), and show the PL enhancement of CdSe/PVP NCs under UV radiation in the air. The experimental results indicate that the PL-enhanced mechanism of the NCs in methanol results from passivation of the lyates in that they act as the hole-acceptors. By screening of hole scavenger, furthermore, it is found that ditertbutyl peroxide is a better passivators of surface defects, and promotes the PL efficiency of CdSe/PVP NCs to achieve a value 110 times higher than that of as-prepared CdSe/PVP NCs. The photopassivation in the presence of organic molecules provides a prefertial, inexpensive path to harvest NCs with high PL efficiency. (C) 2012 Elsevier B.V. All rights reserved.