New anthracene-based organic dyes: the flexible position of the anthracene moiety bearing isolation groups in the conjugated bridge and the adjustable cell performance

Three organic sensitizers (LI-65–LI-67), featuring a 9,10-diarylsubstituted anthracene unit as part of the conjugated bridge, were designed and employed in dye-sensitized solar cells (DSCs). The two phenyl groups on the 9 and 10 positions of the anthracene ring acted as isolation groups, to suppress possible dye aggregation and electron recombination. With the flexible position of the isolation group in the conjugated bridge, interesting structure–property relationships were obtained: the isolation groups (the phenyl rings on the anthracene unit), close to the donor, were beneficial to the enhancement of the short circuit current (Jsc) values, with the highest Jsc value of 13.95 mA cm−2 (LI-65); once located in the middle of the π-bridge, the highest resistance of charge recombination and the longest electron lifetime were achieved and contributed to the enhanced open circuit voltage (Voc) of 722 mV, with the highest conversion efficiency (η) of 6.44% (LI-66, 25% higher than the lowest).