Optical Properties of Two-Dimensional Perovskite Films\nof (C₆H₅C₂H₄NH₃)₂[PbI₄] and (C₆H₅C₂H₄NH₃)₂ (CH₃NH₃)₂[Pb₃I₁₀]

Abstract

The\ntemperature dependence of absorption and photoluminescence\n(PL) spectroscopies were used to study the optical properties of 2D\nperovskite films, including <i>n</i> = 1 and 3 of (PEA)₂(CH₃NH₃)_<i>n</i>−1[Pb_<i>n</i>I_3<i>n</i>+1] (PEA = C₆H₅(CH₂)₂NH₃). In (PEA)₂[Pb₁I₄] (PEPI),\nexcitons coupling to optical phonons with an average energy of ∼30\nmeV dominate the photophysics of absorption and PL. (PEA)₂(CH₃NH₃)₂[Pb₃I₁₀] (shortened as PMPI₃), nominally prepared as <i>n</i> = 3, actually was a mixture of multiple layered perovskites\nwith various <i>n</i>. In absorption, a PMPI₃ film presents respective <i>n</i> materials’ excitonic\nfeatures, coupling to phonons with an average energy of ∼30\nmeV; in analyzing PL peaked singly at ∼1.6 eV and its width\nas a function of temperature, we found that PMPI₃ behaves\nlike PEPI at around 80 K but like 3D perovskite near room temperature,\nwith three times larger electron–phonon interaction strength\ncompared to that in PEPI.