Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)–molybdenum oxide composite films as hole conductors for efficient planar perovskite solar cells

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)–molybdenum oxide (MoOx) composite films are used as hole transport layers in planar perovskite solar cells (PSCs) by simply incorporating solution-processed MoOx powders into a PEDOT:PSS solution. Compared to PEDOT:PSS based PSCs, the PEDOT:PSS–MoOx based PSC exhibits an obvious improvement in conversion efficiency, open circuit voltage, and fill factor. The morphology of perovskite films indicates that the film coverage has been improved due to the introduction of MoOx nanospots into the underlayer, which are regarded as the growing sites of the crystal nucleus of the perovskites during annealing. A PEDOT:PSS–MoOx based device with a power conversion efficiency of over 15% has been achieved, suggesting that the PEDOT:PSS–MoOx film is efficient as a hole transport layer in obtaining highly efficient planar perovskite solar cells.