Low-cost porous Cu2ZnSnSe4 film remarkably superior to noble Pt as counter electrode in quantum dot-sensitized solar cell system

► Cu2ZnSnS(Se)4 nanoparticles as efficient counter electrodes in quantum dot-sensitized solar cells. ► The catalytic activity is sensitive to the composition and thermal annealing condition. ► Porous Cu2ZnSnSe4 film sintered at 450 °C at Ar atmosphere was remarkably superior to traditional Pt. ► A high solar conversion efficiency of 4.35% was obtained.