The challenge of boosting the efficiency of QDSSCs lies in the rational development and design of economical, stable and efficient counter electrode (CE) catalysts for fast and efficient electron transport at the CE/electrolyte interface. Here, we creatively construct Co9S8/Cu7S4 heterostructure composite CEs using CuCo-Prussian blue analogs (PBA) as precursor by one-step in-situ solvothermal vulcanization method. Work function analysis and systematic electrochemical characterizations reveal that the presence of heterojunctions in the Co9S8/Cu7S4 can increase the interfacial electric field driving force inside the material, thereby reducing the Rct at CE/electrolyte interface, promoting the efficient transfer of electrons. Correspondingly, the Co9S8/Cu7S4 composite CE can improve the stability and compensate for the deficiency of the single component CE through a decent synergistic catalytic effect. Remarkably, the Mn-CdS/CdSe/ZnS co-sensitized QDSSC equipped with Co9S8/Cu7S4 heterostructure composite CE delivers an optimal conversion efficiency of 8.43% with Jsc = 23.42 mA/cm2, Voc = 0.672 V; FF = 0.54, which was significantly superior to physically mixed CE (PM-Co9S8/Cu7S4, 6.55%), single-component CE (Cu7S4, 5.60%; Co9S8, 5.13%) and conventional Brass/Cu2S CE (4.96%). In briefly, the advanced heterostructure engineering and the abundant, tunable chemical elemental composition of PBA provide new views for the purposeful design of economical and outstanding heterostructured composite CEs.