Abstract
In this paper, we use magnetic field effects of photocurrent
(MFEPC ) to study the photovoltaic processes in pristine
conjugated polymer, bulk heterojunction, and double-layer
solar cells, respectively, based on poly(3-alkylthiophene) (P3HT).
The MFEPC reveals that the photocurrent generation undergoes
the dissociation in polaron pair states and the charge reaction
in excitonic states in pristine conjugated polymers. As for the
bulk-heterojunction solar cells consisting of electron donor P3HT
and electron acceptor [6,6]-phenyl C61-butyric acid methyl ester
(PCBM), the MFEPC indicates that the dissociated electrons and
holes inevitably form the intermolecular charge-transfer (CT) complexes
at donor and acceptor interfaces. Essentially, the photocurrent
generation relies on the further dissociation of intermolecular
CT complexes. Moreover, we use double-layer solar cell to further
study the intermolecular CT complexes with well-controlled
donor–acceptor interfaces based on double-layer P3HT/TiOx design.
We find that the increase in free energies can significantly
reduce the density of CT complexes upon thermal annealing.
