posted on 2023-03-23, 14:34authored byHonglin Tang, Junhua Ning, Ke Wang, Heng Liu, Xinhui Lu, Songting Tan, Meihua Huang, Bin Zhao
Two polymer donors with dithieno[3,2-e:2′,3′-g]-2,1,3-benzoselenadiazole
(DTBSe) as electron-deficient
(A) units and alkylthiophene derivatives as conjugated π units
between A units and electron-rich units, named as PSe-BO and PSe-HD,
respectively, have been designed and synthesized, and the effects
of branched alkyl side chains of alkylthiophene derivatives on molecular
aggregation, photophysical properties, and photovoltaic performance
have been studied. The results indicate that PSe-HD with 2-hexyldecyl
side chains possesses a lower HOMO energy level, a smaller bandgap,
and a more complementary absorption spectrum than PSe-BO with 2-butyloctyl
side chains. Moreover, the PSe-HD:Y6 blend film also shows a better
nanofibrous structure and a more orderly molecular orientation than
the PSe-BO:Y6 blend film, which leads to higher charge mobility, more
balanced charge transport, and less charge recombination of the former.
Therefore, the polymer organic solar cell based on PSe-HD:Y6 blends
achieves a higher power conversion efficiency of 14.85% than the device
based on PSe-BO:Y6 blends owing to thoroughly improved photovoltaic
parameters. This study provides an efficient strategy to design polymer
donors by introducing DTBSe as A units and synchronously applying
side-chain engineering.