Title: Dopant‐Free Hole‐Transporting Layer Based on Isomer‐Pure Tetra‐Butyl‐Substituted Zinc(II) Phthalocyanine for Planar Perovskite Solar Cells
Abstract: Herein, the important role of the isomer purity of hole‐transporting materials (HTMs) in achieving high‐performance perovskite solar cells (PSCs) is highlighted. The isomer‐pure 2,9,16,24‐tetra‐n‐butyl‐Zn(II) phthalocyanine (RE‐ZnBu4Pc) is directly synthesized through a ring expansion method, without any further purification. The ground‐state absorption, fluorescence and thermal properties of RE‐ZnBu4Pc and the isomer mixture ZnBu4Pc, along with their hole mobilities and film morphologies are investigated, proving that RE‐ZnBu4Pc can be the more efficient HTM. The devices based on RE‐ZnBu4Pc, as dopant‐free HTMs, achieve a higher average power conversion efficiency (PCE of 11.49% ± 0.67%) and more stability at 25 °C and under 75% relative humidity than that of isomer mixture ZnBu4Pc (PCE of 9.51% ± 1.15%). RE‐ZnBu4Pc‐based PSCs also show better reproducibility in the fabrication process. This study demonstrates that better device performance can be expected for PSCs with isomer‐pure HTM materials.