Perovskite solar cells have emerged one of the promising next generation power source. Perovskite solar cells achieved power conversion efficiency beyond 20 % within 7 years since its discovery. The new perovskite materials with an ABX3-crystal structure are commonly based on an organic cation as A, lead as B and halides as X compound. The most common perovskite solar cell structure is FTO/TiO2/mp-TiO2+CH3NH3PbI3/spiro-OMeTAD/Au. The poor coverage and the presence of hysteresis in the voltage-dependent photocurrent are the main issues of this type of perovskite solar cells. Here, we demonstrate high-performance perovskite solar cell by introducing small amounts of GITC as an A compound to control the morphology in perovskite precursor solution. The incorporated guanidinium cation which has three NH2 groups results in a symmetrical structure and therefore has zero dipole moment. As a result, the power conversion efficiency of 12.7% (pristine perovskite solar cell: 10.6 %), highly homogeneous film morphology, and no hysteresis effect are achieved. This study represents that guanidinium thiocyanate helps the formation of smooth film and reducing the hysteresis of the voltage-current curve, therefore, provide efficient way to fabricate a high efficiency perovskite solar cells.