Identification of a bridge-specific intramolecular exciton dissociation pathway in donor–?–acceptor alternating conjugated polymers

Abstract Intramolecular exciton dissociation is critical for high efficient mobile charge carrier generations in organic solar cells. Yet despite much attention, the effects of ? bridges on dynamics donor–?–acceptor (D-?-A) alternating conjugated polymers remain still unclear. Here, using a combination femtosecond time-resolved transient absorption (TA) spectroscopy and steady-state spectroscopy, we track ultrafast intramolecular relaxation three D-?-A which were synthesized by Qin's group named HSD-A, HSD-B, HSD-C. It found that addition thiophene unit as will lead to red shift spectrum. Importantly, reveal existence new pathway mediated bridge-specific transfer (CT?) state with TA fingerprint peak at 1200 nm ?-bridged HSD-B This CT? results higher electron capture rates HSD-C compared HSD-A. Depending proportion nongeminate recombination are important step understanding power conversion efficiencies than We propose this plays an role photovoltaic material polymers.