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

The temperature dependence of absorption and photoluminescence (PL) spectroscopies were used to study the optical properties of 2D perovskite films, including n = 1 and 3 of (PEA)(2)(CH3NH3)(n-1)[PbnI3n+1] (PEA = C6H5(CH2)(2)NH3). In (PEA)(2)[Pb1I4] (PEPI), excitons coupling to optical phonons with an average energy of similar to 30 meV dominate the photophysics of absorption and PL. (PEA)(2)(CH3NH3)(2)[Pb3I10] (shortened as PMPI3), nominally prepared as n = 3, actually was a mixture of multiple layered perovskites with various n. In absorption, a PMPI3 film presents respective n materials' excitonic features, coupling to phonons with an average energy of similar to 30 meV; in analyzing PL peaked singly at similar to 1.6 eV and its width as a function of temperature, we found that PMPI3 behaves like PEPI at around 80 K but like 3D perovskite near room temperature, with three times larger electron-phonon interaction strength compared to that in PEPI.