Dopant-free Tert-butyl Zn (II) Phthalocyanines: Impact of Substitution on Photo-Physical Properties in Their Role in Perovskite Solar Cells

Abstract

We synthesized molecular hole-transporting materials (HTMs) featuring a zinc phthalocyanine (ZnPc) central core and modulated the non-perypheral position with different numbers of tert-butyl groups. The synthesized molecules were also integrated into the fabrication of perovskite solar cells to evaluate their efficacy. We studied four undoped different ZnPcs with four (ZnPc 1), three (ZnPc 2), two (ZnPc 3), and one (ZnPc 4) tert-butyl group as hole transport material in n-i-p configuration. Among them, ZnPc 1 registered the best power conversion efficiency with 15.50%, an open-circuit voltage (Voc) of 932.9 mV, a short-circuit current density (Jsc) of 24.26 mA/cm2, and a fill factor (FF) of 68.46%. This was followed by ZnPc 2 which achieved a modest 7.98% of performance. The surface microstructure is greatly influenced by the type of molecules and it evolves from compact granular to fibril structure. Furthermore, the devices with ZnPc 1 showed enhanced stability under an ambient atmosphere comparable to Spiro-OMeTAD.