Molecularly Engineered Phthalocyanines as Hole-​Transporting Materials in Perovskite Solar Cells Reaching Power Conversion Efficiency of 17.5​%

Easily accessible tetra-​5-​hexylthiophene-​, tetra-​5-​hexyl-​2,​2'-​bisthiophene-​substituted zinc phthalocyanines (ZnPcs) and tetra-​tert-​Bu ZnPc are employed as hole-​transporting materials in mixed-​ion perovskite [HC(NH2)​2]​0.85(CH3NH3)​0.15Pb(I0.85Br0.15)​3 solar cells, reaching the highest power conversion efficiency (PCE) so far for phthalocyanines. Results confirm that the photovoltaic performance is strongly influenced by both, the individual optoelectronic properties of ZnPcs and the aggregation of these tetrapyrrolic semiconductors in the solid thin film. The optimized devices exhibit PCE of 15.5​% when using tetra-​5-​hexyl-​2,​2'-​bisthiophene substituted ZnPcs, 13.3​% for tetra-​tert-​Bu ZnPc, and a record 17.5​% for tetra-​5-​hexylthiophene-​based analog under std. global 100 mW cm-​2 AM 1.5G illumination. These results boost up the potential of soln.-​processed ZnPc derivs. as stable and economic hole-​transport materials for large-​scale applications, opening new frontiers toward a realistic, efficient, and inexpensive energy prodn.