Using commercially available cost-effective Zn(II) phthalocyanine as hole-transporting material for inverted type perovskite solar cells and investigation of dopant effect

Commercially available, low-cost, and stable unsubstituted zinc phthalocyanine (ZnPc) was introduced as both dopant-free and doped hole-transporting material (HTM) in inverted type (p-i-n) perovskite solar cells (PSCs). A simple solution process was applied to the fabrication of PCSs with a device structure of ITO/HTM/CH₃NH₃Pbl₃/PCBM/Al, in which ZnPc and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) were used as HTM, methylammonium lead iodide (MAPbI₃) as an active layer, [6,6]-phenyl-C61-butyric acid methyl ester (PC₆₁BM) as the electron transport material (ETM), and aluminum as the counter electrode. PEDOT:PSS based cell was used as a reference and a power conversion efficiency (PCE) of 14.3% was achieved. A PCE of 4.4% was achieved for dopant-free ZnPc and 7.7% for doped-ZnPc. Although lower efficiency than the reference was obtained for ZnPc-based cells, we observed that the stability of inverted cells drastically improved when ZnPcs were used as HTM instead of PEDOT-PSS.