Interplay Between Side Chain Pattern, Polymer Aggregation, and Charge Carrier Dynamics in PBDTTPD:PCBM Bulk‐Heterojunction Solar Cells

摘要: Poly(benzo[1,2-b:4,5-b′]dithiophene–alt–thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymer donors with linear side-chains yield bulk-heterojunction (BHJ) solar cell power conversion efficiencies (PCEs) of about 4% phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor, while a PBDTTPD combination branched and substituents yields doubling PCE to 8%. Using transient optical spectroscopy it is shown that exciton dissociation ultrafast charge generation steps are not strongly affected by side chain modifications, chains exhibits decreased rate nongeminate recombination lower fraction sub-nanosecond geminate recombination. In turn long-lived carriers increases, resulting in 33% increase short circuit current (J sc). parallel, two polymers show distinct grazing incidence X-ray scattering spectra indicative presence stacks different orientation patterns optimized thin-film BHJ devices. Independent packing pattern spectroscopic data also reveals existence aggregates pristine films well both blends which trap excitons hinder their dissociation.