Trap-limited bimolecular recombination in poly(3-hexylthiophene): Fullerene blend films

• The dependence of the photoexcitation density, PC61BM composition, thermal annealing and thickness on Trap-limited bimolecular recombination has been investigated by photo-CELIV method in P3HT and PC61BM blend films.
• The trap-limited bimolecular recombination is strongly affected by the distribution of the density of trap state (trap DOS).
• The higher trap-limited bimolecular recombination rate means the trap DOS centered at lower energy which is beneficial to the releasing of trapped charge carriers, and leading to better charge carrier transportation.

Trap-limited bimolecular recombination in poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) blend films has been investigated by using photo-induced charge extraction by linearly increasing voltage (photo-CELIV) method. The bimolecular recombination rate is strongly dependent on the photoexcitation density, the PC61BM composition and the thermal annealing process, but it slightly depends on the thickness of the blend film. The results show that the trap-limited bimolecular recombination is strongly affected by the distribution of the density of trap state (trap DOS). The higher trap-limited bimolecular recombination rate means the trap DOS centered at lower energy which is beneficial to charge carriers transportation, due to the lower activation energy and faster release rate. On the other hand, the trap-limited bimolecular recombination rate is mainly controlled by the slower species of charge carriers in the blend film when the transport of electrons and holes are strongly unbalanced, and the recombination rate will increase when the transport of electrons and holes becomes more balanced.

Figure optionsDownload as PowerPoint slide