Solar Cells Based on Colloidal Nanocrystals by Holger Borchert

Author:Holger Borchert
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Also shown in Fig. 8.2 are PL spectra of films made of donor/acceptor systems when blending the polymer with CdSe nanocrystals or PCBM as electron acceptor, respectively. In both cases, the PL intensity is reduced (said to be “quenched”). This can be interpreted as an indication that charge transfer is possible at the material interface, because after electron transfer to the acceptor, the electron can obviously no longer recombine radiatively from the LUMO level of the donor polymer. Thus, PL quenching is a useful tool to probe charge transfer processes in donor/acceptor solar cells. However, care must be taken in the interpretation, because under certain conditions, the PL intensity can also be reduced by processes concurring with charge transfer. If the acceptor material has a lower energy gap than the donor, it is also possible that the entire electron–hole pair is transferred to the acceptor by Förster resonance energy transfer (FRET). If this is possible, it becomes difficult to distinguish between both processes in simple PL quenching experiments.

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