ja2104747_si_001.pdf (1021.9 kB)
Time-Resolved Structural Evolution of Additive-Processed Bulk Heterojunction Solar Cells
journal contribution
posted on 2012-02-15, 00:00 authored by James
T. Rogers, Kristin Schmidt, Michael F. Toney, Guillermo C. Bazan, Edward J. KramerSolution deposition using high-boiling-point additives
such as
octanedithiol (ODT) provides a simple and widely used fabrication
option for improving the power conversion efficiencies of solar cells
composed of narrow-band-gap conjugated polymer donor/fullerene acceptor
blends. Previous examination of the resulting device active layers
has shown that the use of additives influences the degree of phase
segregation within the bulk heterojunction (BHJ) blend and also improves
ordering within the polymeric domains. In this work, in situ grazing-incidence
wide-angle X-ray scattering as a function of time was used to explore
the dynamics of the BHJ evolution. These studies showed that a small
percentage of ODT in chlorobenzene (CB) induced the nucleation of
polymeric crystallites within 2 min of deposition, increased the orientational
order of specific polymorphs, and promoted further crystallite nucleation
over a period longer than 40 min after casting. Similar structural
changes did not occur when the same BHJ blend was cast from pure CB.