High-performance materials for organic electronics
Advancements in the microelectronics industry have brought small-sized products of increased performance and decreased price to a wide range of users. Facing intense competition from all over the world, Europe is increasingly investing in organic electronics as a potential route to getting innovative products at low costs. Spurred by the potential of organic semiconductors, scientists initiated the BLEND (Stability of blended organic semiconductors under various environments) project. Unlike their inorganic counterparts, organic semiconductors are lighter, more robust and can be easily manufactured. Despite their promise, stability issues pose a severe threat to organic semiconductor reliability. To improve stability, BLEND members resorted to blending organic semiconductors with commodity polymers having good insulating properties. By preparing organic multicomponent systems comprising at least one insulator component, the team gained further insight into how these materials behave under different circumstances. Work was mainly geared towards applying heat treatment to several material combinations to ultimately study morphology under different temperatures. Research focused on polyethylene (PE), poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl butyric acid methyl ester (PCBM) systems that are commonly used in organic photovoltaics. The casting temperature was found to greatly affect film morphology. Results also demonstrated that PE may cause long-term reliability issues because of PCBM clustering. To help determine the long-term effects of stress levels within a shorter time, scientists performed accelerated ageing tests, exposing the materials to different temperatures and humidity levels. Using ultraviolet-visible spectroscopy, they noticed that light absorption of the films decreased over time and then calculated the rate at which materials decay. Results clearly showed that the rate of degradation increased markedly with the increase of the ageing temperature. In addition, insulating polymers were found to affect the long-term behaviour of films, which needs to be considered if they are used in organic electronics devices. Further studies are necessary to better elucidate the material stability under accelerated ageing conditions. The option that BLEND investigated, blending of organic semiconductors, can help cut down the costs of organic electronics mainly due to the low cost of bulk commodity polymers.
Keywords
Organic electronics, organic semiconductors, stability, solar cells, accelerated ageing
