Non-Langevin bimolecular recombination in low-mobility materials

We have investigated the bimolecular recombination coefficient (B) of charge carriers in low-mobility materials, in which the Langevin recombination is reduced: inorganic a-Si:H, μc-Si:H and the organic regioregular poly(3-hexylthiophene)/1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (RR-PHT/PCBM) blend. We have been using a multitude of experimental techniques, namely space-charge-limited current (SCLC), photogenerated charge carrier extraction by linearly increasing voltage (photo-CELIV) and double injection (DoI) current transient techniques for investigation of temperature and electric field dependencies of B. For RR-PHT/PCBM blends, we observed a weak dependence of B on electric field and the most significant reduction of Langevin recombination.