New Strategy to Improve Thermal Stability of Small-Molecule-Based Bulk-Heterojunction Organic Photovoltaics

Using flexible aliphatic chains to link conjugated molecular semiconductors Andrea Gasperini devloped a polymeric material that possesses defined conjugated segments but extended covalent connectivity that enhances crystallinity and thermal stability in field-effect transistors and bulk heterojunction solar-cell devices when used as an additive. The results are pulished in Advanced Materials.

Solution-processed organic photovoltaics (OPV) have recently reached the target 10% power conversion efficiency expected to signal their viable commercialization as an inexpensive and scalable energy conversion technology. However, obtaining devices with suitable long-term stability remains an unsolved challenge. Here we present a new strategy to improve the thermal stability of small-molecule-based bulk-heterojunction OPVs by including a custom additive specifically designed to interact with the device active layer components. Our results indicate that active layer degradation under continuous thermal stress can be inhibited due to the formation of more robust thin film microstructure with the additive present. Since our additive employs the identical semiconductor core used in the active layer, but linked by aliphatic chains into a flexible polymer, this straightforward strategy can reasonably be applied to stabilize a wide variety of semiconducting small molecules in solution-processed molecular OPVs, transistors and light emitting diodes.