Tetra‐Propyl‐Substituted Copper (II) Phthalocyanine as Dopant‐Free Hole Transporting Material for Planar Perovskite Solar Cells

Solution‐processed hole transporting materials (HTMs) that are dopant‐free show promise for use in low‐cost, high‐performance perovskite solar cells (PSCs). In this study, a new HTM of copper (II) phthalocyanine with tetra‐propyl‐substituted function groups ( CuPrPc ) is reported. It is found that CuPrPc could form face‐on molecular orientation when spin‐coated on perovskite, resulting in high hole mobility and hydrophobic surface. These properties are more favorable for hole transport and moisture resistance applications in PSCs. Solution‐processed planar PSCs utilizing CuPrPc as HTM are fabricated and tested. PSC with CuPrPc exhibited highest power conversion efficiency of 17.8%. Furthermore, beneficial from the hydrophobic nature of CuPrPc , the devices with CuPrPc as HTM show improved stability and retain over 94% of their initial efficiency even after storage in humidity about 75% for 800 h without encapsulation, which is much better than the performance of PSCs based on Spiro‐OMeTAD HTM.