Dual passivation of SnO2/Perovskite heterogeneous interfacial defects for efficient perovskite solar cells

The presence of heterogeneous interfacial defects limits the efficiency and long-term stability of the perovskite solar cells (PSCs). Rational passivation of interfacial defects and reduction of nonradiative recombination at the perovskite active layer are effective ways to achieve efficient PSCs. Here, a heterointerface engineering strategy is presented by employing a multifunctional molecule of reduced l-glutathione (GSH). The introduction of GSH improves the crystallization of SnO2, resulting in a continuous and conformal coverage of SnO2 on the FTO surface. And the GSH buffer layer improves the affinity between SnO2 and perovskite, resulting in the formation of large grains of perovskite. In addition, GSH bridges the perovskite to SnO2 through multi-dentate ligands (-COOH, –NH2, –CONH–, –HS), which passivates the multiple defects at the heterogeneous interfaces while accelerates the electron transport. As a result, the PCE of the GSH-SnO2 ETL based PSC significantly increases to 21.66% with no noticeable hysteresis. Meanwhile, compared with the control PSC, the unencapsulated GSH-SnO2 based PSC exhibits better environmental stability, which maintains more than 80% of its initial PCE after 600 h of placement in atmospheric environment.