Deactivation of Interfacial Recombination Center for Thermally Stable Perovskite Solar Cells

We report here on deactivation of the recombination center at the perovskite/Spiro-MeOTAD interface for thermally stable perovskite solar cells (PSCs). Investigation into the chemical reactivity of oxidized Spiro-MeOTAD (Spiro-MeOTAD^•+) reveals that the Spiro-MeOTAD^•+-induced interfacial recombination center is a key factor contributing to lowering open-circuit voltage (V_OC) and thereby power conversion efficiency (PCE) of PSCs under thermal stress. To deactivate the recombination center via suppressing chemical reactivity, a functional molecule of 3-aminopropyltriethoxysilane (APTES) is inserted between the perovskite film and the Spiro-MeOTAD-based hole transporting layer (HTL). The alkoxy head in APTES is found to coordinate with the perovskite, and the amino tail reacts with the triphenylamine moiety of Spiro-MeOTAD^•+, which effectively captures the excess oxidized Spiro-MeOTAD. As a result, the nonradiative recombination of perovskite is deactivated and the oxidation level of HTL is modulated, leading to a significant increase in V_OC from 1.032 to 1.19 V after introducing APTES, along with a certified PCE of 25.6%. Thermal stability tests at 85 °C for 1000 h following the ISOS-D2I protocol show that 82% of the initial PCE is retained by the deactivation approach.