A General Strategy for Stretchable Organic Photovoltaics through Interpenetrating Thiol-Ene Networks

Thin films of semiconductive polymers and small molecules exhibit a low crack-onset strain and poor mechanical properties under deformation, limiting their viability for flexible organic electronic devices. Molecular engineering of the semiconductive material can enhance mechanical properties but oftentimes is detrimental to electronic properties and overall device performance. Here, we present a general approach to fabricating flexible bulk heterojunction organic photovoltaics (OPVs) through the incorporation of an elastic and mechanically robust interpenetrating network. Reactive small molecule thiol-enes are incorporated in the active layer through solution blending, casting, and post-deposition crosslinking. A thiol-ene network is formed through short, one-minute exposure to UV light or with an amine catalyst. This results in fully functional devices with significantly increased crack-to-onset strain and flexibility. The approach is compatible with a variety of donors and acceptors and results in significant enhancement of mechanical properties and device flexibility.