Iron sulfide has been proved to be a promising material for counter electrode (CE) of QDSCs in our previous work. However, the fill factor is still much below expectation, owing to the poor catalytic activity. Herein, iron sulfide nanosheets are embedded into porous carbon. This structure exhibits good interfacial contact between iron sulfide and carbon. As a result, it improves the stability of the CE, promotes the interfacial electron transfer rate between iron sulfide and carbon, and increases active sites leading to superior catalytic activity. Consequently, the QDSC based on this optimal structure obtains a power conversion efficiency of 5.61% with higher FF (0.64) compared with those with Pt or other conventional sulfide based CEs. Besides, we developed a novel facile, reproducible and printable preparation process: compositing and chemical conversion (3C). (C) 2017 Elsevier Ltd. All rights reserved.