Enhancing the Performance of the Half Tin and Half Lead Perovskite Solar Cells by Suppression of the Bulk and Interfacial Charge Recombination.

In this article it is investigated how the hole extraction layer (HEL) influence the charge recombination and performance in half tin and half lead (FASn0.5 Pb0.5 I3 ) based solar cells (HPSCs). FASn0.5 Pb0.5 I3 film grown on PEDOT:PSS displays a large number of pin-holes and open grain boundaries, resulting in a high defect density and shunts in the perovskite film causing significant bulk and interfacial charge recombination in the HPSCs. By contrast, FASn0.5 Pb0.5 I3 films grown on PCP-Na, an anionic conjugated polymer, show compact and pin-hole free morphology over a large area, which effectively eliminates the shunts and trap states. Moreover, PCP-Na is characterized by a higher work function, which determines a favorable energy alignment at the anode interface, enhancing the charge extraction. Consequently, both the interfacial and bulk charge recombination in devices using PCP-Na HEL are considerably reduced giving rise to an overall improvement of all the device parameters. The HPSCs fabricated with this HEL display power conversion efficiency up to 16.27%, which is 40% higher than the efficiency of the control devices using PEDOT:PSS HEL (11.60%). Furthermore, PCP-Na as HEL offers superior performance in larger area devices compared to PEDOT:PSS.