Development of Robust Perovskite Solar Cells Using Interfacial Materials

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has risen rapidly from 3.8% to a certified 25.7%. However, their relatively short operational lifetime remains a critical hurdle for commercialization. Herein, we present two simple ways to enhance the environmental stability of PSCs. In the first approach, a tiny amount (0.01 wt%) of exfoliated montmorillonite (<i>ex</i>MMT) was incorporated into the perovskite precursor solution and these <i>ex</i>MMT nanoplates were able to self-organize into an ultra-dense top layer with a thickness of around 50 nm and strongly bonded to the perovskite crystalline grains through cationic exchange with organic cations during the spin-drying process. Such self-assembled layer acted as an effective protection shell that retarded the penetration of gases and moisture into the perovskite during environmental aging, achieving extremely stable photovoltaic cells against moisture, thermal and photo stresses. The thus prepared unencapsulated devices exhibited exceptionally steady PCE, which showed negligible degradation after 4680 h of storage in 50% relative humidity and room temperature. In the second route, a fluorine-containing fullerene adduct (5F-PCBP) was introduced to replace PCBM as an electron-transporting layer (ETL) to establish PSCs that delivered an excellent PCE of 21.27%. The fluorinated ETL not only increased the surface hydrophobicity but also filled the surface iodine vacancy and immobilized the ion migration, thus protecting the solar devices against harsh environment. As a result, The CsFAMA perovskite solar devices with 5F-PCBP ETL without physical encapsulation exhibited a T₈₀ over 1920 hours under industrial relevant conditions i.e., relative humidity of 85% and heat stress at 85^○C.