The photovoltaic performance of alloyed CdTe_0.6S_0.4 quantum dot sensitized solar cells (QDSSCs) is investigated. Fluorine doped Tin Oxide (FTO) substrates were coated with 20 nm-diameter TiO₂ nanoparticles (NPs). Presynthesized colloidal solution of alloyed CdTe_0.6S_0.4 quantum dots (QDs) of 4.2 nm was deposited onto TiO₂ NPs substrates using direct adsorption (DA) technique, by dipping for different times at ambient conditions. The FTO counter electrodes were coated with platinum, while the electrolyte containing I^-/I^-3 redox species was sandwiched between the two electrodes. Compared to pure CdTe QDs and CdS QDs, CdTe_0.6S_0.4 QDs showed better photovoltaic performance. The J-V characteristic curves of the assembled QDSSCs were measured at AM 1.5 simulated sunlight. The short current density (J_sc) and efficiency (η) increase with dipping time. At 24 h dipping time, the open-circuit photovoltage V_oc, J_sc, fill factor (FF), and η were 0.46 volts, 1.54 mA/cm², 0.43% and 0.31%, respectively.