In this report, a modeling approach is employed to study the effect of the grain boundaries (GBs) and their electronic activity on the performance parameters of the perovskite solar cells (PSCs). Our model is based on the 1- dimensional drift-diffusion framework to engage the electron (hole) defects formed in the GBs and the GB's location through the perovskite layer. Power conversion efficiency (PCE) of the PSC is optimized with regards to the perovskite layer thickness, GBs location and perovskite layer band offset with GBs layer. The results shows that the location or the distribution of the GBs can vary the PCE of PSCs from 12% to around 21%, thereby making proper morphology engineering and passivation of GBs is a chief requirement for achieving high efficiency. PCEs larger than 21% require GB defect densities below 10(15) cm(-2). It is demonstrated that the band offset of about 100 meV with GB width of 1 nm could effectively suppress the negative impact of the GBs throughout the entire perovskite layer. Interestingly, GBs location at closer points to electron transport layer (ETL)/perovskite interface may give rise to higher PCEs, however, relatively stronger hysteresis in current values is observed. The results here provide insight into the effect of the GBs location and their corresponding type of defects on the hysteresis and the PSC performance and opens up new horizons to find solutions for current PSC's shortcomings.