A multi-institution team of researchers, led by the Davidson School of Chemical Engineering at Purdue University, has reported a breakthrough in the flexible solar cell field that may contribute to the development of solar cells on flexible surfaces, including ultra-flexible and wearable energy-harvesting devices.

Perovskite composite material heals after mechanical damage and is demonstrated in flexible solar cells image

“Our research is unique in that we have created the first mechanically self-healing perovskite material,” says Blake Finkenauer, lead author of the study and a fourth-year graduate student with Dr. Letian Dou, the Charles Davidson Assistant Professor of Chemical Engineering at Purdue. “Self-healing mechanical damage has only been realized in the organic materials field, typically with insulating materials. By joining dissimilar perovskite and polymer materials, a composite material with both semiconducting and self-healing properties is realized. The polymer acts as a molecular bonding agent with the crystals, which improves both the thermal and mechanical stability compared to the pure perovskite material".

The team focused on incorporating a molecularly tailored self-healing polymer into polycrystalline halide perovskite thin films to form a healable composite that can be used in flexible devices. Surface cracks and abrasions in the thin films were healed using moderate temperature, and the composite solar cells retained 94% of their power conversion efficiency after 3000 bending cycles and 80% recovery after extreme bending.

The researchers synthesized a mechanically tough and self-healing polymer because it contains functional groups which readily bond with perovskite materials. Already the team is looking forward to improving the material through new polymer design and device engineering.

“Next steps in our research include using more fluid polymers to lower the composite healing temperature,” explained Finkenauer. “By reducing the molecular weight and tuning the polymer backbone, we can change the polymers thermal and mechanical properties. Changes to the perovskite and polymers may reduce the composite healing temperature, resulting in a more durable material for high performance, smart, ultra-flexible and wearable devices.”

The team included researchers from Purdue, Zhejiang University, Lawrence Berkeley National Laboratory, University of California-Los Angeles, and Chinese Academy of Sciences.