In addition, the donors play a critical function in light harvesting and electron injection.30e34 In this study, we designed and synthesized a series of DB dyes SDD1e4 and a reference sensitizer with single DepeA system (RD)(Fig. 1). As shown in Scheme 1, SDD1e4 were designed with the
following characteristics: (i) two DepeA branches were linked by
non-conjugated alkyl chain, resulting in two separate light-harvesting
units, which might enhance the absorption intensity due to
the absorption overlap of both the same donors and p-spacers. (ii)
Indole and phenoxazine donors were introduced into the DepeA
branches as the electron donor units. As a consequent, the photovoltaic
performance of the cells based on these dyes would be
influenced by the structure of the linkages, such as different length
of flexible alkyl chains and the rigid alkyl chain. Moreover, the
HOMO and LUMO energy levels of the dyes would be tuned by the
different donors, as a result, the conversion efficiencies of the DSSCs
would be affected due to the changed absorption range and intensity
of the dyes.