Multifunctional zwitterion modified SnO2 nanoparticles for efficient and stable planar perovskite solar cells

Abstract

SnO 2 nanoparticles (NPs) have been widely employed as electron transport layers (ETLs) in planar n-i-p perovskite solar cells (PSCs). Perfect SnO 2 ETL/perovskite interface plays a key role in high efficiency PSCs, however, the main issues caused by the self-aggregation of the SnO 2 NPs and the interface recombination limit the further improvement of device performance. Here, l -carnitine hydrochloride (L-ch) zwitterion with multiple functional groups has been incorporated into SnO 2 NP solution for high-efficiency PSCs. The results demonstrate that the unique coordination complexes assembled between L-ch zwitterion and SnO 2 NPs can inhibit the aggregation of SnO 2 NPs, benefiting for the formation of more compact film with reduced roughness. Simultaneously, the L-ch zwitterion can adjust the electronic properties of SnO 2 and promote the carrier transport between perovskite and SnO 2 ETL with well aligned energy level. Moreover, the -COO - and –N + (CH 3 ) 3 groups can passivate uncoordinated Pb 2+ and MA vacancies defects in the perovskite film, respectively. Therefore, by using SnO 2 /L-ch as the ETL, the efficiency of champion MAPbI 3 PSCs can be increased from 18.77% to 20.56%, with reduced hysteresis and improved stability. A novel multifunctional L-ch zwitterion is introduced to inhibit the aggregation of SnO 2 NPs and passivate interfacial defects in PSCs. • A novel L-ch zwitterion with multiple functional groups is introduced into SnO 2 nanoparticles (NPs). • The unique coordination complexes can inhibit the aggregation of SnO 2 NPs, benefiting for the formation of compact film. • The L-ch can adjust the electronic properties of SnO 2 and promote the carrier transport with well aligned energy level. • The -COO - and –N + (CH 3 ) 3 groups can passivate uncoordinated Pb 2+ and MA vacancies defects, respectively.