In this research work, for the first time, we introduced amino-substituted perylene diimide derivative (N-PDI) as an alternative electron transport layer (ETL) to replace the commonly used TiO2 in planar heterojunction perovskite solar cells. Two types of device structures i.e., glass/FTO/N-PDI/CH3NH3PbI3-xClx/spiro-MeOTAD/Au, and polyethylene terephthalate (PET)/ITO/N-PDI/CH3NH3PbI3-xClx/spiro-MeOTAD/Au, were fabricated on both rigid and flexible substrates using room-temperature solution processing technique. Based on the proposed device structures, the power conversion efficiency (PCE) of 17.66% was obtained based on glass/FTO rigid substrates, and a PCE of 14.32% was achieved based on PET/ITO flexible substrates. Results revealed that the terminal amino group in N-PDI resulting in the enhanced wetting capability of surfaces to perovskite, and the lower the surface work function of FTO substrate as well as passivate the surface trap states of perovskite films. Our results confirm that small molecule semiconductor N-PDI can serve as an effective electron-transport material for achieving high-performance perovskite solar cells and draw molecular design guidelines for electron-selective contacts with perovskite.