Self-doped polymer with fluorinated phenylene as hole transport layer for efficient polymer solar cells

Two new pH neutral Conjugated polyelectrolytes (CPEs), PCPDPhSO3K and PCPDffPhSO3K, based on 3,4-dithia-7H-cyclopenta[a]pentalene alternatively copolymerized with benzene and 1,4-difluorobenzene units respectively were designed and synthesized as hole-transporting layers (HTLs) for polymer solar cells (PSCs). The single-junction PSC based on PCPDffPhSO3K HTL showed a power conversion efficiency of 9.50%, which was much better than that of PEDOT:PSS-modified device (PCE = 8.60%), due to the improved conductivity and better energy alignment by incorporation of F atom into the backbone. These results demonstrated that CPEs developed as efficient HTLs can be realized by precise backbone engineering for highly performance PSCs.235