Recombination of photogenerated and injected charge carriers in π-conjugated polymer/fullerene blends

In regioregular poly(3-hexylthiophene) /1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (RR P3HT/PCBM) bulk heterojunction structures the recombination features of photogenerated and of double injection charge carriers are compared. The investigations have been made using time-of-flight (TOF), charge extraction by linearly increasing voltage (CELIV), and double injection transient methods. In both cases when electric field is absent (photogeneration case) and in various electric fields (double injection case) the bimolecular recombination coefficient (β) has been estimated 103 ÷ 104 times lower than Langevin's one (βL). The weak dependence of β on electric field was obtained and activation energy of β lower than of βL one was estimated.