Researchers from China's Northwestern Polytechnical University, Chinese Academy of Sciences (CAS) and Henan University have addressed the stability challenge of flexible perovskite solar cells (FPSCs). Inspired by the exceptional wet adhesion of marine mussels via adhesive proteins (dopamine, DOPA), the scientists proposed a multidentate-cross-linking strategy, which combines multibranched structure and adequate dopamine anchor sites in three-dimensional hyperbranched polymer to directly chelate perovskite materials in multiple directions.
Schematics of key components for the underwater adhesion feature of marine mussels and HPDA adhesive in perovskite films and interfaces. Image from: Nature Communications
This constructs a vertical scaffold across the bulk of perovskite films from the bottom to the top interfaces, that intimately binds to the perovskite grains and substrates with a strong adhesion ability, and enhances mechanical durability under high humidity.
The team designed and synthesized a hyperbranched polymer dopamine adhesive (HPDA) with dopamine end groups strategy that can intimately bind to the perovskite grains and substrates with a strong adhesion force, thus enforcing the perovskite grain boundaries and device interfaces. The HPDA self-assemble in the perovskite films to construct a vertical scaffold across the bulk of perovskite films from the bottom to the top interfaces. The oxygen functional groups present in HPDA coordinated with Pb2+ and binds the grain boundaries, suppressing the formation and propagation of intergranular cracks.
Moreover, the interactions between HPDA and the two charge transport layers SnO2 and spiro-OMeTAD47 result in stronger interface toughness at the fragile ETL/PVK and HTL/PVK interfaces. The dopamine end-groups allow HPDA to achieve strong adhesion in humidity environment, thereby inhibiting the accelerated degradation of FPSCs by cooperative interactions of water and mechanical stress.
Consequently, the modified rigid PSCs achieved PCE of up to 25.92%, while flexible PSCs exhibited a PCE of 24.43% and maintained 94.1% of initial PCE after 10,000 bending cycles with a bending radius of 3 mm exposed to 65% humidity.
This work describes a comprehensive and multidimension fracture toughness reinforcement strategy for highly stable flexible perovskite photovoltaics.
