Interconnected Grains via Buffer Engineering: a Bioinspired Route toward Flexible Inverted Perovskite Solar Cells

Natural evolution has led to long-term interactions between biology and the environment, with many excellent functions and perfect structures existing in nature. Inspired by the vertebral column structure, we developed a buffer-engineered nucleation strategy for inserting a buffer component into adjacent perovskite grains. This strategy synchronously tailors the perovskite crystallization of perovskite films and improves the flexibility of inverted perovskite solar cells. The rigid and high-quality perovskite grains that efficiently absorb photons correspond to the vertebrae of vertebrates, whereas fullerene, as a flexible buffer, can serve as an intervertebral disk to interconnect neighboring vertebra-like grains. In addition to functioning as a buffer to enhance the flexibility of the film, the fullerene inserted between the perovskite grains was also employed to passivate the uncoordinated lead ions in the perovskite and promote interfacial contacts, enhancing the efficiency of charge extraction at the interface. As a result, the power conversion efficiency of a methylammonium-based flexible perovskite solar cell, fabricated on a flexible polyethylene terephthalate substrate, was significantly enhanced from the pristine device’s value of 14.58% to 18.21%. Moreover, the FPSCs successfully survived a harsh dynamic mechanical bending test owing to the reasonable inspiration from the vertebral column. This strategy could prove highly beneficial for future FPSC fabrication processes because of the significant enhancement in the elasticity and flexural strength of the perovskite films at the nanoscale, as well as the effective passivation of defects achieved by the embedded materials.