Surface-emitting vertical cavity with vapor-grown single crystal of cyano-substituted thiophene/phenylene co-oligomer

Photoluminescence from an organic microcavity is investigated using vapor-grown single crystals of 5,5'-bis(4'-cyano-biphenyl-4-yl)-2,2'-bithiophene (BP2T-CN). A vertical half-cavity structure is fabricated with thin platelet crystals of BP2T-CN placed on a distributed Bragg reflector (DBR). Lying orientation of the BP2T-CN molecules is suitable for effective surface emission from the cavity. Angle-resolved photoluminescence spectra show anticrossing splits, suggesting the formation of cavity polaritons induced by coupling between confined photons and excitons. Phenomenological analysis well reproduces the dispersion characteristics with a Rabi splitting energy of 90 meV at room temperature. With increasing excitation fluence under optical pumping, one of the cavity photon modes is gain-narrowed, and amplified emission is obtained from the surface-emitting half-cavity structure. (C) 2017 The Japan Society of Applied Physics