A study of different central metals in octamethyl-substituted phthalocyanines as dopant-free hole-transport layers for planar perovskite solar cells

摘要

We demonstrate two octamethyl-substituted phthalocyanines, HMe2Pc and ZnMe2Pc, as dopant-free hole-transport layers for planar pervoskite solar cells. HMe2Pc illustrated a very similar HOMO energy level and a slightly smaller band gap compared with that of ZnMe2Pc, resulting in perovskite photovoltaic devices with very close open circuit voltage (VOC) values based on different phthalocyanine hole transporting materials. Varying the central metals also leads to the HMe2Pc film exhibiting higher carrier mobility, better film coverage, and stronger surface hydrophobicity than the ZnMe2Pc film, which is consistent with higher short circuit current density (JSC) and fill factor (FF) values, and better long-term film stability for HMe2Pc-based devices. When employed as hole-transport layers by vacuum deposition, the HMe2Pc-based devices showed the highest photo conversion efficiency (PCE) of up to 15.59%, which is slightly higher than the 14.88% PCE for ZnMe2Pc-based devices. These properties make the easily-synthesized and highly stable octamethyl-substituted phthalocyanines promising candidates as hole-transport materials in perovskite solar cells.