Boosting efficiency and stability of perovskite solar cells with nickel phthalocyanine as a low-cost hole transporting layer material

The efficiency of perovskite solar cells (PSCs) has increased from around 4% to over 22% following a few years of intensive investigation. For most PSCs, organic materials such as 2,2′,7,7′-tetrakis(N,N-pdimethoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD) are used as the hole transporting materials (HTMs), which are thermally and chemically unstable and also expensive. Here, we explored nickel phthalocyanine (NiPc) as a stable and cost-effective HTM to replace the conventionally used spiro-OMeTAD. Because of its high carrier mobility and proper band alignments, we achieved a PCE of 12.1% on NiPc based planar device with short-circuit current density (Jsc) of 17.64 mA cm−2, open circuit voltage (Voc) of 0.94 V, and fill factor (FF) of 73%, outperforming the planar device based on copper phthalocyanine (CuPc) that is an outstanding representative of metal phthalocyanines (MPcs) reported. Moreover, the device with NiPc shows much improved stability compared to that based on the conventional spiro-OMeTAD as a result of NiPc's high stability. Photoluminescence (PL) and Impedance spectroscopy analysis results show that thermally deposited NiPc has good hole-extraction ability. Our results suggest that NiPc is a promising HTM for the large area, low cost and stable PSCs.