New polymer-based hole transport layer to push forward perovskite-based flexible and wearable electronics

A team of researchers led by Nanchang University in China tested a polymer-based hole transport layer for flexible perovskite solar cells, using a glue to attach it to the active perovskite. The team was able to assemble the cells into a small flexible module suitable for wearable solar applications, and says its design was inspired by the structure and movements of human vertebrae.

Bio-inspired vertebral design for scalable and flexible perovskite solar cells. Image from Nature Communications

The team reported that the solar cell measured 1.01cm² and achieved a stabilized efficiency of 19.87%. The cell was tested for 3000 hours under one-sun illumination at room temperature and was shown to retain 85% of its initial efficiency.

These results, according to the group from Nanchang University, were achieved thanks to the use of an interface layer of a polymer material known as PEDOT:EVA, which was glued in place between the perovskite film and indium-tin-oxide electrode film. This served to facilitate uniform crystal formation in the perovskite layer and also to improve the flexibility of the brittle ITO layer.

The group used these cells to fabricate a flexible module measuring 36cm², which achieved a stable efficiency of 14.91%.

In developing these cells and seeking to boost their flexibility, the group says it took inspiration from the human vertebrae. 'In nature, vertebrae can adapt to complex human movements, because of the oriented crystallization of robust skeleton and the flexible structure,' states the paper. 'Inspired by the biological crystallization and flexible structure of vertebrae, we synthesize the PEDOT:EVA ink by miniemulsion.'

The scientists further explain that in this analogy, the PEDOT:EVA layer plays a similar role to cartilage in a vertebrae joint, serving to evenly distribute force and protect the perovskite and ITO layers from stress and damage during movement.

Further microscope imaging revealed good potential for scaling the devices up to even larger sizes, and the group believes it may open up a new approach for the development of flexible and wearable electronics.