Excited-State Dynamics Study of Ternary Blend Organic Solar Cells Containing a Low-Bandgap Non-Fullerene Acceptor
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To clarify the effect of a low-bandgap non-fullerene acceptor (NFA) on a power conversion efficiency (PCE) of ternary blend organic solar cells (OSCs), we investigated the excited-state dynamics in ternary blend systems composed of a donor-acceptor wide-bandgap polymer based on a benzodithiophene backbone (PBT-OTT), PC71BM, and ITIC using femtosecond transient absorption (fsTA) spectroscopy. We found the unique formation-pathway of ITIC-generated free carriers, which increases the PCE of ternary blend NFA OSCs more effectively than does the hole transfer from ITIC to PBT-OTT. Our findings of the charge-carrier dynamics in the ternary blend system may provide the important information that may lead to further increase in the PCE of OSCs.