Highly efficient and low hysteresis methylammonium-free perovskite solar cells based on multifunctional oteracil potassium interface modification

• A novel multifunctional buffer molecule is developed to modify the interface of MA-free perovskite films. • The bulk and interfacial nonradiative recombination losses are reduced simultaneously. • The long-term operational stability and efficiency are enhanced simultaneously after modifying with OP. • The infamous hysteresis factor was inhibited significantly. Bulk and interface defects are the culprits of power conversion efficiency (PCE) loss of the perovskite solar cells (PSCs). Meanwhile, notorious hysteresis is also an obstacle on the road of the PSCs commercialization process. Consequently, it is urgently needed to develop a multifunctional modification strategy to address the above issues. Herein, we report a multifunctional buffer molecule (oteracil potassium, OP) for suppressing hysteresis and passivating defect in stable and efficient methylammonium-free PSCs (Rb 0.02 (FA 0.95 Cs 0.05 ) 0.98 PbI 2.91 Br 0.03 Cl 0.06 ). Experimental and theoretical results prove that multi-functional OP has strong chemical interaction with SnO 2 and the perovskite layer. It can not only reduce the oxygen vacancy defects in SnO 2 film but also passivate the under coordinated Pb 2+ in perovskite. At the same time, it can significantly inhibit hysteresis. Due to these beneficial effects, the PCE of the OP-modified device is over 22%, and the unencapsulated modified device exhibits more excellent humidity stability. This work provides guidance for the development of multifunctional modified molecules for high PCE, stable, and non-hysteresis PSCs.