Few-Layer MoS2 Flakes as Active Buffer Layer for Stable Perovskite Solar Cells

Solution-processed few-layer MoS2 flakes are exploited as an active buffer layer in hybrid lead-halide perovskite solar cells (PSCs). Glass/FTO/compact TiO2/mesoporous-TiO2/CH3NH3PbI3/MoS2/Spiro-OMeTAD/Au solar cells are realized with the MoS2 flakes having a twofold function, acting both as a protective layer, by preventing the formation of shunt contacts between the perovskite and the Au electrode, and as a hole transport layer from the perovskite to the Spiro-OMeTAD. As prepared PSC demonstrates a power conversion efficiency (eta) of 13.3%, along with a higher lifetime stability over 550 h with respect to reference PSC without MoS2 (Delta eta/eta = -7% vs. Delta eta/eta = -34%). Large-area PSCs (1.05 cm(2) active area) are also fabricated to demonstrate the scalability of this approach, achieving eta of 11.5%. Our results pave the way toward the implementation of MoS2 as a material able to boost the shelf life of large-area perovskite solar cells in view of their commercialization.