Anchoring Spinel MnCo2S4 on Carbon Nanotubes as Efficient Counter Electrodes for Quantum Dot Sensitized Solar Cells

Ternary spinel MnCo2S4 was anchored on carbon nanotubes (CNTs) via a two-step method of precursor preparation followed by ion exchange, and employed as efficient counter electrodes for quantum dot sensitized solar cells (QDSSCs). Electrochemical tests show that the interface charge transfer resistance (Rct) of MnCo2S4 is only 2.86 Ω and the Rct of MnCo2S4/CNTs further decrease to 1.09 Ω, suggesting both MnCo2S4 and its composite exhibit excellent catalytic activity for Sn2– reduction. The power conversion efficiencies of QDSSC assembled CdS/CdSe QD photoanodes with MnCo2S4 and MnCo2S4/CNTs counter electrodes reach 2.98 and 4.85%, respectively. The better photovoltaic performance of the QDSSC based on MnCo2S4/CNTs is mainly ascribed to the synergistic effect of the excellent electrocatalytic activity of MnCo2S4 itself and the conductivity of CNTs. The addition of CNTs not only significantly reduces the size of MnCo2S4 and increases catalytic activity sites, but also forms a cross-linked conductive network to accelerate the delivery of electrons. Due to the excellent reducing ability for Sn2–, MnCo2S4/CNTs is expected to be a competitive counter electrode material for efficient QDSSCs.