Determining the bonding–degradation trade-off at heterointerfaces for increased efficiency and stability of perovskite solar cells

The heterointerfaces between perovskite and charge-transporting layers pose a major limitation to the durability of perovskite solar cells (PSCs), largely due to complex and conflicting chemical and mechanical interactions. Here we introduce an effective debonding technique to thoroughly analyse heterointerface behaviour during both crystal growth and ageing phases of PSCs. Our analysis reveals a strong correlation between interface bonding (fracture energy ranging from ~2.49 J m⁻² to ~0.38 J m⁻²), proton transfer interactions and degradation, highlighting a critical trade-off between mechanical and chemical stability in PSCs. To address these stability challenges, we mixed Me-4PACz and DCZ-4P molecules, which introduced additional phosphonic acid anchoring groups to enhance bonding at both the metal oxide and the perovskite interfaces. With a high efficiency of 25.6%, the devices retained 90% of their initial performance after 1,000 h of testing under ISOS-L-1I and ISOS-D-2I standard protocols. Under thermal cycling conditions, our PSCs sustained 95% of their efficiency over 500 cycles, exceeding the IEC 61215 and ISOS-T-3I standards.