[1]Benzothieno[3,2-b][1]benzothiophene-Phthalocyanine Derivatives: A Subclass of Solution-Processable Electron-Rich Hole Transport Materials

The [1]benzothieno[3,2-b][1]benzothiophene (BTBT) planar system was used to functionalize the phthalocyanine ring aiming at synthesizing novel electron-rich ?-conjugated macrocycles. The resulting ZnPc-BTBT and ZnPc-(BTBT)4 derivatives are the first two examples of a phthalocyanine subclass having potential use as solution-processable p-type organic semiconductors. In particular, the combination of experimental characterizations and theoretical calculations suggests compatible energy level alignments with mixed halide hybrid perovskite-based devices. Furthermore, ZnPc-(BTBT)4 features a high aggregation tendency, a useful tool to design compact molecular films. When tested as hole transport materials in perovskite solar cells under 100 mAcm-2 standard AM 1.5G solar illumination, ZnPc-(BTBT)4 gave power conversion efficiencies as high as 14.13%, irrespective of the doping process generally required to achieve high photovoltaic performances. This work is a first step toward a new phthalocyanine core engineerization to obtain robust, yet more efficient and cost-effective materials for organic electronics and optoelectronics.