Growing interests have been devoted to the synthesis of polymer acceptors as alternatives to fullerene derivatives to realize high-performance and stable all-polymer solar cells (all-PSCs). So far, one of the key factors that limit the performance of all-PSCs is low photocurrent density (normally < 2 14 mA/cm 2). One potential solution is to improve the dielectric constants (ε r) of polymer:polymer blends, which tend to reduce the binding energy of excitons, thus boosting the exciton dissociation efficiencies. Nevertheless, the correlation between ε r and photovoltaic performance has been rarely investigated for all-PSCs. In this work, five fluorinated naphthalene diimide (NDI)-based acceptor polymers, with different content of fluorine were synthesized. The incorporation of fluorine increased the ε r of the acceptor polymers and blend films, which improved the charge generation and overall photocurrent of the all-PSCs. As a result, the PTB7-Th:PNDI-FT10 all-PSC attained a high power conversion efficiency (PCE) of 7.3% with a photocurrent density of 14.7 mA/cm 2 , which surpassed the values reported for the all-PSC based on the non-fluorinated acceptor PNDI-T10. Interestingly, similarly high photovoltaic performance was maintained regardless of a large variation of donor:acceptor ratios, which revealed the good morphological tolerance and the potential for robust production capability of all-PSCs.

A ternary strategy could combine the advantages of incorporated materials as an encouraging approach to achieve high power conversion efficiency (PCE) polymer solar cells (PSCs).

A diketopyrrolopyrrole-based small bandgap polymer (DPPT-TT) with high mobility is introduced as an additive to D–A1–D–A2 type thieno[3,4-b]thiophene-based random copolymer (P3):(6,6)-phenyl-C70-butyric acid methyl ester (PC71BM) polymer solar cells (PSCs).

No abstract