Lasing in substituted polythiophene between dielectric mirrors

We report photopumped lasing in a microcavity device with a polythiophene layer as emitter. The microcavity is made of a polymer film between two dielectric Bragg reflecting mirrors (DBR). The microcavity devices is built by joining two polymer coated DBR mirrors at elevated temperature. When photopumping the film, a lasing threshold is observed at 120 nJ/cm 2. Comparative studies with fast pump-probe spectroscopy of thin polythiophene films and the same polymer in photopumped lasing studies, indicate that the gain coefficient is 80±20 cm 2, and that the exciton concentration is 2x10 17 cm 2 at the lasing transition, well below the exciton-exciton recombination level.