Non-peripherally octaalkyl-substituted nickel phthalocyanines used as non-dopant hole transport materials in perovskite solar cells

This report presents two non-perihperally octaalkyl-substituted nickel phthalocyanines(NiPcs),namely,NiEt2Pc and NiPr_(2)Pc,for use as dopant-free hole transport materials in perovskite solar cells(PSCs).The length extension of the alkyl chains from ethyl to propyl significantly tunes the NiPcs’energy levels,thus reducing charge carrier recombination at the perovskite/hole transport layer(HTL)interface and leading to higher open-circuit voltage(VOC)and short-circuit current density(JSC)observed for the NiPr_(2)Pc-based PSC.And higher charge carrier mobility,higher thin film crystallinity,and lower surface roughness of the NiPr_(2)Pc HTL compared with that of the NiEt2Pc one also lead to higher JSC and fill factor(FF)observed for the NiPr_(2)Pc-based device.Consequently,the NiPr_(2)Pc-based PSC exhibits a higher power conversion efficiency(PCE)of 14.07%than that of the NiEt2Pc-based device(8.63%).