(Figure Presented) Tin-doped indium oxide (ITO) sputtering is known as a damaging cause on organic hole transporting material in solar cells. In order to gain more insights into the reasons for poor device performance of perovskite solar cells by the ITO sputtering on Spiro-OMeTAD, here we present an in-depth study by I-V simulation analysis using corresponding equivalent circuit models. First, experimental I-V data were obtained for the perovskite solar cells with 'FTO/TiO2(dense)/TiO2(mesoporous)/CH3NH3PbI3/Spiro-OMeTAD/ITO/Au' configuration. An Au layer (t = 50 nm) was deposited on the ITO as a contact layer. The simulation studies indicated that sputtering of ITO onto Spiro-OMeTAD introduced a reverse Schottky diode and an additional diode to the device that could be relating the sputtering damage of the Spiro-OMeTAD layer. By considering the parameter of the reverse diode element as a function of sputtering time, it was found that the barrier height of the reverse Schottky diode was enhanced by the sputtering damage against Spiro-OMeTAD, which could be the key reason for the reduced fill factor of the devices.