Interface engineering of compact-TiOx in planar perovskite solar cells using low-temperature processable high-mobility fullerene derivative

Interface engineering plays a promising strategy to produce highly efficient planar heterojunction (PHJ) perovskite solar cells. The deep trap states on the compact-TiOx surface leading to a large leakage current and recombination of charge carriers. To solve the problems, interfacial engineering of electron collecting layer (ECL) compact-TiOx by a thin-layer of one-step solution-processed and low-cost organic material is applied. In contrast, commonly used PCBM is still expensive material. Herein, a new, low-temperature processable higher potential of [60]fulleropyrrolidine derivatives named as N-phenyl[60]fulleropyrrolidines (PNP) was introduced as an interfacial modification of ECL compact-TiOx with the varying thickness of 10, 20, and 30 nm to replace the commonly used PCBM in PHJ perovskite solar cells. The modified surface morphology was achieved by introducing PNP interfacial layers that enhanced the surface-energy properties of the cells in terms of enhanced photocurrent. Compared with PCBM, PNP features a higher electronic mobility and stronger hydrophobic nature. The enhancement of power conversion efficiency was obtained from 5.12% to 8.23%, with an increase in short-circuit current density (J(sc)) from 11.90 to 21.44 mA cm(-2) and fill factor (FF) from 0.49 to 0.56 owing to insertion of optimum 10-nm-thickness PNP that led to more efficient electron transport and charge extraction in the solar cell performances. The present work provides an important sign in the aspects to the low-cost mass production of perovskite solar cells.