Surface treatment of the perovskite via self-assembled dipole layer enabling enhanced efficiency and stability for perovskite solar cells

Surface “molecule treatment” has been widely used to promote the performance of perovskite solar cells (PSCs). However, the low tolerance in thickness and difficulty in energy level matching restrict its applications in large-scale manufactures in the future. In this work, a mono-molecule layer (MML) of Tetrabutylammonium chloride (TBAC) was introduced, which can self-assemble onto the surface of perovskite by means of a facile solution method. TBAC MML possesses a strong interface dipole pointing outward of the surface of perovskite, which promotes the built-in electric field and reduces the contact barrier for hole extraction. Accordingly, the carrier extraction rate and recombination resistance are enhanced by 1.5 and 4 times, respectively. PSCs treated by TBAC (TBAC-PSCs) induced a champion efficiency of 23.50% with fill factor (FF) of over 82%. In addition, TBAC MML can prevent the adsorption of H2O and O2 onto the surface of perovskite, and thereby enhance the stability of PSCs. After being aged in ambient air for 1000 h, TBAC-PSCs sustained the initial efficiency of over 90% which is only 58% for the control devices.