As a key precursor for perovskite layer, we developed a complex of CH3NH3PbI3(dmf). The higher solubility of this complex in DMSO compared to the conventional PbI2 and CH3NH3I (1:1) mixture enables the fabrication of thick perovskite layer to give higher short-circuit current density (Jsc) in perovskite solar cells. In addition, the use of less volatile DMSO solution of this complex than DMF allows us to fabricate perovskite layer with a wide process window. In this presentation, we will report our optimized fabrication protocol of perovskite solar cells that gives high PCEs (∼19.8%) with good reproducibility.