It was observed that bi-directional phase changes can be triggered by genuine photoexcitation between two phases with different bond structures in polydiacetylenes. The observed photoinduced phase transition was found to be mediated by photogeneration of charge carriers (and not of excitons). The extremely high efficiency is perhaps due to cooperative interaction between the locally photoconverted domains.

• Received 16 September 1991

DOI:https://doi.org/10.1103/PhysRevLett.68.1148