One of the main factors affecting the performance of quantum dot sensitized solar cells (QDSSCs) is charge recombination caused by surface traps. It is important to passivize the surface traps of the synthesized QDs as much as possible in order to raise the power conversation efficiency (PCE). Therefore, in this study, the effects of chloride passivation on the performance of CdSeTe QDSSCs were tested. CdSeTe QDs synthesized by the hot injection method were passivized with chlorine ions in different proportions (10-70%) by mass and CdSeTe(Cl) QDSSCs were designed. In order to detect the effects of chloride treatment, chloride passivation was applied to CdSeTe QDs with different growth time. The absorbance and emission characterizations of the synthesized CdSeTe and CdSeTe(Cl) QDs were removed, HR-TEM and X-ray diffraction (XRD) studies were performed. Photovoltaic, incident-photo-to-carrier conversation (IPCE), electrochemical impedance spectroscopy (EIS) measurements were performed for all designed CdSeTe QDSSCs. As a result of the analyses, it was determined that chloride treatment increased the PCE of CdSeTe (Cl) QDSSCs by 2.456 times compared to untreated CdSeTe QDSSCs. The average value of PCE for CdSeTe(Cl) (60% Cl) (5 min) QDSSCs was 3.379 +/- 0.08%, while J(SC) and V-OC values were measured as 10.048 mA/cm(2) and 0.664 V, respectively.