Video of the week: Flexible organic PV cells could power wearable tech

Described in the American Chemical Society journal Chemistry of Materials, the cells rely on organic carbon-based polymers rather than inorganic silicone. Rather than develop solar-harvesting organics from scratch, the Rice team began with rigid organics that were known to work, tweaking their composition in order to add mechanical flexibility. This was achieved using sulphur-based thiol-ene reagents where the molecules blend with the polymers and then crosslink with each other to provide elasticity.

"If you stretch or bend things, you get cracks in the active layer and the device fails," said Rice chemical and biomolecular engineer Rafael Verduzco.

"Our idea was to stick with the materials that have been carefully developed over 20 years and that we know work, and find a way to improve their mechanical properties.”

The amount of thiol-ene is key to determining the level of flexibility while also having an impact on the cells’ conductivity. Too little thiol-ene leaves the crystalline polymers prone to cracking under stress, while too much dampens the material's efficiency. After extensive testing, the team found that 20 per cent thiol-ene allowed the cells to retained their efficiency while also gaining flexibility.