Abstract A great deal of attention has been directed towards the development of facile synthetic methods for semiconductor materials that allow for doping. In this work, Cu-doped CdSeTe-alloyed quantum dots (QDs) were synthesized via a non-injection one pot synthesis route and used as a sensitizer in solar cells. The lattice incorporation of CdSeTe QDs with Cu2+ was evidenced by X-ray diffraction (XRD) analysis and ab initio simulation. We have performed characterization on the relaxed geometry structure, bonding character, and band alignment of the Cu-doped CdSeTe QDs based on rigorous ab initio calculations. Our main objective is to fully understand the effect of the Cu2+ dopant on the physical properties of CdSeTe QDs, which would be very useful to further understand the mechanism of photoelectric conversion. HR-TEM analysis showed ~7 nm and ~9 nm particles for CdSeTe and Cu-doped CdSeTe nanocrystals (NCs), respectively. It was found that the open circuit voltage (Voc) of Cu-doped CdSeTe NCs decreases with respect to that of the undoped ones. The QD-based solar cell with Cu-doped Cu0.2Cd0.8Se0.6Te0.4 exhibited a photo-conversion efficiency of 1.25% (VOC=0.593 V, JSC=3.78 mA/cm2, FF=55.5%), which was higher than the reference CdSeTe NCs under AM1.5 G at 100 mW/cm2 simulated sunlight radiation conditions.