The photoelectronic properties of quantum dots (QDs) have a critical impact on the performance of quantum dot-sensitized solar cells (QDSCs). Currently, I-III-VI group QDs have become the mainstream light-harvesting materials in high-performance QDSCs. However, it is still a great challenge to achieve satisfactory efficiency for light-harvesting, charge extraction, and charge collection simultaneously in QDSCs. Herein, we design and prepare Zn0.4Cu0.7In1.0SxSe2-x (ZCISSe) quinary alloyed QDs by cation/anion co-alloying strategy. The critical photoelectronic properties of target QDs, including bandgap, conduction band energy level, and density of defect trap states, can be conveniently tailored. Experimental results demonstrate that the ZCISSe quinary alloyed QDs can achieve an ideal balance among light-harvesting, photogenerated electron extraction, and charge collection efficiencies in QDSCs compared to its single anion or cation quaternary alloyed QD counterparts. Consequently, the quinary alloyed QDs boost the certified efficiency of QDSCs to 14.4%, which is a new efficiency record for liquid-junction QD solar cells.