Mechanism of bifunctional p-amino benzenesulfonic acid modified interface in perovskite solar cells

Abstract

• ABSA is firstly used to synergistically modify the interface between SnO 2 and perovskite layer. • The acidic sulfonic acid groups in ABSA connect to the under-coordinated Sn ions. • The alkaline amino groups passivate the defects on surface of perovskite. • The energy band model for SnO 2 nanoparticle and interface is established. • The mechanism of significantly improved PCE is analyzed. The n-type metal oxide SnO 2 exists surface energy band bending due to massive vacancy oxygen. The bending will cause unnecessary electron accumulation and recombination at the interface between electron transport layer (ETL) and perovskite layer. Besides, there exist massive deep-level defects (Pb I , Pb i , I Pb ) for solution-processed polycrystalline perovskite films, which will aggravate the energy band uncoordinated and non-radiative recombination, limiting device efficiency and stability. Herein, amphoteric linking molecule p-amino benzenesulfonic acid (ABSA) is firstly used to synergistically modify the interface between SnO 2 ETL and perovskite layer. The acidic sulfonic acid groups in ABSA modify SnO 2 ETL by inactivating the under-coordinated Sn ions, which reduces the energy band barrier on the surface of SnO 2 film, increasing the conduction and reduces charge recombination. Besides, the alkaline amino groups also passivate the deep-level defects on surface of perovskite to lessen intermediate energy level and non-radiative recombination. The power conversion efficiency (PCE) of perovskite solar cells (PSCs) based on MAPbI 3 is obviously increased from 18.02% to 20.32% after 0.10 mg ml −1 ABSA modification. Simultaneously, the modified devices show better stability due to improved perovskite crystallization and the reduced defects. The energy band model for SnO 2 nanoparticle and interface between perovskite layer and SnO 2 ETL is established to explain the interfacial engineering from a new physical perspective.