Interfaces are crucial for high-performance perovskite solar cells. Here, phenyltrichlorosilane (PTS) and octadecyltrichlorosilane (OTS) were used to modify the interface between perovskite layer and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) layer in an inverted layered perovskite device. Such treatments facilitated the formation of a high-quality PCBM film and effectively decreased the density of surface traps that induce undesirable electron-hole recombination. As a result, the average power conversion efficiency of PTS (and OTS) modified devices was improved from 9.60% to 11.96% (and 11.08%), with a highest value of 12.63% (and 11.87%). Therefore, this study provides an attractive mothed to improve the quality of PCBM film on top of perovskite layer and finally the performance of inverted perovskite solar cells.