Making organic solar cells stretchier

Plastic solar cells made from low-cost organic liquids via large-area printing methods hold the promise of turning ordinary fabrics and other surfaces into power generators. Some of these thin-film devices generate electricity from light with upward of 17% conversion efficiency, close to that of rigid silicon solar cells. But the plastic kind, commonly touted for flexibility, often starts to fail when flexed and stretched. Some researchers have tried mitigating the problem by fabricating organic cells on highly flexible substrates or by making the electrodes more bendable. A group led by Rice University’s Rafael Verduzco has taken a different approach. The team increased the flexibility of the photoactive layer—the region that absorbs light and transports charged particles—by imbuing it with an elastic cross-linked network (Chem. Mater. 2018, DOI: 10.1021/acs.chemmater.8b03791). Improving the active layer’s mechanical stability often weakens its electronic properties, causing poor device performance. But the Rice team found that modifying that layer by adding up to 20% by weight of cross-linking thiol and alkene compounds provides roughly 20% improvement in fracture resistance during strain and stretching tests without reducing conversion efficiency.