Redox-Active β-Tetrathiophenyl Porphyrins as Next-Generation Hole-Transport Materials in Perovskite Photodetectors

We report the design, synthesis, and comprehensive characterization of a series of electron-rich β-tetrathiophenyl porphyrins, MTPP(SPh)₄ (M = 2H, Co, Ni, Cu, and Zn), developed as solution-processable hole-transporting materials (HTMs) for perovskite photodetectors. Single-crystal XRD and DFT calculations reveal prominent macrocyclic nonplanarity induced by bulky -SPh substituents, resulting in red-shifted optical transitions, reduced HOMO-LUMO gaps, and multiple reversible redox processes. When integrated as interfacial hole transport layers (HTLs) in FA_0.9Cs_0.1Pb(I_0.94Br_0.06)₃-based lateral photodetectors, these porphyrins significantly suppress dark current, enhance charge extraction, and reduce transport resistance, as supported by J-V analysis and impedance spectroscopy. Among the series, ZnTPP(SPh)₄ and NiTPP(SPh)₄ porphyrins exhibit the highest performance, achieving broadband responsivity (400-720 nm) with maximum detectivities of 1.43 × 10¹¹ and 1.10 × 10¹¹ Jones, respectively. These results establish β-tetrathiophenyl porphyrins as a structurally tunable and efficient class of HTMs, offering a minimalistic yet powerful strategy for high-performance, stable perovskite photodetectors.