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 800h without encapsulation, which is much better than the performance of PSCs based on Spiro-OMeTAD HTM.