1 research outputs found
Tuning Non-Langevin Recombination in an Organic Photovoltaic Blend Using a Processing Additive
The effect of altering the acceptor
and exchanging a key atom in
the polymer structure on the extent of non-Langevin (suppressed) recombination
has been examined using the polymer/fullerene photovoltaic blend PDTSiTTz:PC60BM.
Time-of-flight data show that changing the acceptor from PC60BM to
PC70BM maintains the non-Langevin recombination. In contrast, altering
the donor polymer by exchanging the silicon bridging atom for a carbon
considerably reduces the non-Langevin behavior. Importantly, the addition
of a processing additive, diiodooctane (DIO), allows a partial recovery
of this non-Langevin recombination. The addition of DIO also decreases
the ionization potential of the polymer, which not only explains the
drop in open circuit voltage but may also contribute to the partial
recovery of non-Langevin behavior observed. It is proposed that localized,
more crystalline areas of lower ionization potential (or higher electron
affinity) within a mixed/amorphous phase may act as energy sinks for
the holes (electrons), thus potentially inhibiting bimolecular recombination.
Such a phenomenon could contribute to non-Langevin behavior in organic
photovoltaic blends