In this work, the record for a photoluminescence (PL) quantum yield (QY) of positively-charged CdTe nanocrystals (NCs) was brought up to 31%, by using a water–ethanol mixture as a new medium for NC synthesis. A series of water–ethanol feed ratios were investigated, with the maximal PL QY achieved in 50% ethanol solvent mixtures. A photoluminescence lifetime measurement and element analysis demonstrated an improved NC surface modification via the synthesis in the water–ethanol solvent mixtures.