Elucidating the Roles of TiCl4 and PCBM Fullerene Treatment on TiO2 Electron Transporting Layer for Highly Efficient Planar Perovskite Solar Cells

With the fast development of the perovskite solar cell, its energy conversion efficiency has improved rapidly. In this paper, a CH3NH3PbI3–x Cl x organic–inorganic perovskite solar cell (PSC) was successfully prepared by the one-step solvent engineering method, and the planar heterojunction perovskite solar cell was optimized by interface engineering of the cathode interlayers. It was found that TiCl4 treatment could effectively reduce the TiO2 surface roughness, decrease the surface defects, improve the perovskite thin film crystallinity, and reduce the charge carrier recombination; hence, the short-circuit current density of PSCs and charge extraction and collection efficiencies were enhanced. Furthermore, PC60BM fullerene treatment could optimize the contact condition and reduce the interfacial potential loss. The device hysteresis effects after PCBM treatment were also reduced. The combination of TiCl4 and PC60BM treatments could largely improve the PSC device performance with a power conversion efficiency of 16.4% due to the synergetic effect.