Boosting performance of D-A-D type hole-transporting materials for perovskite solar cells via tuning the acceptor group

In this work, two novel electron-deficient groups of phenanthrothiadiazole (PT) and triphenylenobisthiadiazole (TBT) are utilized to construct donor-acceptor-donor (D-A-D) typed hole-transporting materials (HTMs). The electronic, optical and charge transport properties are evaluated by performing quantum chemical calculations. Our results show that, in comparison with that of the benzothiadiazole (BT, SM-1 in Fig.1) unit, the new designed SM-2 and SM-3 display more deep highest occupied molecular orbital (HOMO) energy levels. Meanwhile, the blue-shifted light absorption spectra are also obtained, which will be helpful to enhance the absorption of perovskite layer. Unfortunately, the hole mobilities of the SM-2 and SM-3 are slightly lower than that of the SM-1 due to the weak intermolecular electronic coupling. In addition, we also find that the better solubility and stable dimeric configuration are shown for the new HTMs. Overall, this work provides some useful clues for designing of new acceptor structure in D-A-D-typed HTMs, and a potential HTM SM-3 is proposed.