H/F substitution activating tunable dimensions and dielectric–optical properties in organic lead-bromide hybrids

Abstract

Hybrid organic–inorganic halide perovskites as solution-processable semiconductors have progressed to be a promising class of optoelectronic materials. In this manuscript, we utilized H/F substitution to achieve structural dimension tailoring at the molecular level and tunable phase transition, dielectric, and optical features in organic lead-bromide hybrids, which have been rarely reported. The parent [piperidinium]PbBr₃ ([PD]PbBr₃) has a one-dimensional (1D) chain-like perovskite structure and shows successive solid–solid structural phase transitions. After monofluoride substitution, [4-FPD]₆Pb₅Br₁₆ (4-FPD = 4-fluoro-piperidinylaminium) presents a two-dimensional (2D) wave-like stacking and a significantly enhanced phase transition temperature, mainly attributed to the new C–F bonds generating extra intermolecular interactions. Exceptionally, difluoride substituted [4,4-DFPD]₂PbBr₄ (4,4-DFPD = 4,4-difluoro-piperidinylaminium) with a 2D layered perovskite structure demonstrates interestingly irreversible to reversible structural phase transitions, accompanied by evident dielectric and nonlinear optical transformations. Moreover, the three hybrids show tunable semiconducting bandgaps and photoluminescence. This work provides great inspiration for the design of desired functional materials by rational chemical strategies and the intriguing properties of the new hybrids would also reveal promising applications in optoelectronic devices, data storage, etc.