MDABCO-NH4l3 bridged between SnO2 and α-FAPbI3 for efficient and stable perovskite solar cells

Abstract

For perovskite solar cells (PSCs) based on the SnO₂ electron transport layer (ETL), the massive defects accumulated at the interface between the perovskite absorber layer and the SnO₂ ETL greatly limit the device efficiency and stability. Optimizing the SnO₂/perovskite interface can be a useful strategy to improve PSCs’ performance. Here, an all-organic perovskite (AOP), MDABCO-NH₄I₃, was employed to modify SnO₂ ETL for α-FAPbI₃ PSCs. MDABCO-NH₄I₃ could integrate ETL and perovskite layer together to form a favorable interface contact. Meanwhile, I⁻ and NH₄⁺ can covalently bond with α-FAPbI₃ to passivate the defects located in ETL/perovskite interface, reduce the recombination centers in the system, and finally obtain uniform perovskite films with low defect concentration. In addition, the presence of MDABCO²⁺ cation improves the energy level alignment at the perovskite/ETL interface by dipole movements, which also facilitates photogenerated carriers’ separation and transfer. The SnO₂-AOP ETL with reduced trap density and improved carrier transport boosted the open-circuit voltage of target PSC near to 1.18 V and achieved an inspiring PCE over 24 %. Related PSCs without encapsulation store at room temperature can maintain 80 % of their initial PCE over 3000 h. Moreover, the target PSCs could retain more than 90 % and 85 % of their initial efficiency after 600 h of heat testing (65 60 ± 5 °C in Ar) and humidity testing (60 ∼ 65 % RH in air), respectively.