Performance enhancement of mesoporous TiO2-based perovskite solar cells by ZnS ultrathin-interfacial modification layer

Interfacial modification (IM) plays a vital role in boosting the performance of perovskite solar cells. Herein, we demonstrate a new strategy in which zinc sulfide (ZnS) is used as an interfacial modifier between mesoporous-TiO2 (mp-TiO2) and a CH3NH3PbI3 absorber layer via the successive ionic layer adsorption and reaction method. The layer thickness of ZnS was optimized, and its effects on the conduction band position, interfacial charge recombination, and photovoltaic performance were investigated. Our results revealed that an ultrathin ZnS layer on mp-TiO2 helps in suppressing backflow of electrons, effectively reducing interfacial charge recombination and facilitating electron transfer. Our best performing perovskite solar cell device using the mp-TiO2-ZnS achieved a power conversion efficiency of 14.9%, with an open-circuit voltage of 1.02 V, short-circuit current density of 19.05 mA cm−2, and fill factor of 75.43%. Our simple ZnS IM approach proves that interface engineering could be a key strategy in improving the performance of perovskite solar cells.