UC San Diego

This thesis describes the use of a transparent, stretchable gas barrier film used to encapsulate organic devices in order to protect them from chemical degradation. One of the major issues with current organic semiconductor materials is that they are susceptible to degradation when exposed to oxygen and water vapor in the ambient atmosphere. In order to take advantage of these materials, stretchable barrier films must also be developed.

Solar cell devices were fabricated using an organic bulk heterojunction blend of poly(3-heptylthiophene) and phenyl-C61-butyric acid methyl ester (P3HpT:PCBM). Stretchable barrier films were fabricated with graphene and polyurethane (PU) using a simple dip coating process. Devices encapsulated with an unstrained graphene/PU barrier film retained 60.6 ± 3.7% efficiency after 10 days, exhibiting barrier properties similar to that of a control device encapsulated with glass (61.1 ± 3.2%). Measurements over the course of 1 day showed that graphene/PU films strained up to 20% were still able to maintain 91.5 ± 2.8% efficiency. Electrical resistance measurements showed that graphene cracks around 6% strain. This work highlights the potential impact graphene/PU barrier films may have on stretchable electronics.