Efficient organic macrocyclic photosensitizers and hole transporting materials based on corrole-eugenol and phthalocyanine-eugenol conjugates: Synthesis, excited state properties, and solar cell applications

Three macrocyclic aromatic compounds which are porphyrin analogues (triazatetrabenzocorrole-eugenol and phthalocyanine-eugenol conjugates) have been synthesized. The three compounds are 2,9(10),16(17),23(24)-Tetra(4-allyl-2-methoxyphenoxy)-metal free phthalocyanine [H2Pc(β-Eu)4], 2,9(10),16(17),23(24)-Tetra(4-allyl-2-methoxyphenoxy)-silicon phthalocyanine [v-SiPc(β-Eu)4], and 2,9(10),16(17),23(24)-Tetra(4-allyl-2-methoxyphenoxy)- phosphorous triazatetrabenzcorrole [POTBC(β-Eu)4]. We have examined their light absorbing ability, fluorescence emission efficiency, fluorescence lifetime length, excited triplet state formation properties, singlet oxygen production yield, and the application as hole transporting materials in metal halide perovskite solar cells. The techniques used are UV–Vis electronic absorption, steady state and time resolved UV–Vis and NIR fluorescence, laser flash photolysis, singlet oxygen chemical trapping by DPBF, J-V measurements, and EQE measurements. The results show that the triazatetrabenzocorrole-eugenol conjugate has much better total light absorbing ability and the highest fluorescence quantum yield. Eugenol attachment significantly improves the fluorescence and singlet oxygen formation efficiency. All three compounds show both good singlet oxygen formation quantum yield up to 0.60 and balanced fluorescence quantum yield up to 0.40, which makes them well applicable both as singlet oxygen photosensitizer and fluorescence imaging agent. We have explained the experimental results by revealing their photophysical kinetic processes. We have also applied the compounds as non doped hole transporting material in metal halide perovskite solar cells. Without doping lithium salt, the power conversion efficiency (PCE) value of the non-optimized devices can be 13.4% which are much larger than the best PCE for organic or dye-sensitized solar cells based on PCs or TBCs reported. The TBC compounds can be good HTM for PSC since further analysis shows that its PCE value has a large space to be increased.