Time-Resolved Photoluminescence Measurement of One-Dimensional Lead Bromide Organic- Inorganic Hybrid Perovskites

摘要

One-dimensional (1D) lead halide hybrid perovskites are attractive materials because they areexpected to show high and fast optical nonlinear effects owing to the enhanced electron density ofstates and electron-phonon interaction. The 1D perovskites are a low dimensional class of hybridperovskites in which octahedrons are connected in a chain and surrounded by organic cations. Thus,they can be considered as the crystalline bulk assemblies of 1D quantum confined materials. In ourprevious report, the structural dependence of the photoluminescence spectra of 1D lead bromideperovskites with three different structures was examined, where broadband luminescence due to selftrappedexcitons was observed in all the materials. To understand the detailed mechanism of thephotoluminescence we performed the time-resolved photoluminescence (PL) measurements of 1D leadbromide hybrid perovskite crystals with 4-ethylpyridine organic molecules. The orange curve in Fig. 1shows the photoluminescence spectrum of the specimen at 300 K. The absorption spectrum is alsopresented as a blue curve, showing that the absorption edge is around 3.4 eV. The luminescencelooked yellow and the spectrum was very broad with a large Stokes shift, which are characteristic forluminescence from self-trapped excitons (STE). In addition, at a temperature the same decay profileswere observed for the peak at 2.0 eV (620 nm) and 1.9, 1.8 eV, indicating that the photoluminescenceof the specimen due to STE with single nature. Fig. 2 depicts the decay profiles at the peak around 2.0eV at temperatures of 5, 100, and 200 K. As seen from the figure the experimental data were wellfitted using a single-exponential function: I(t)=I_(0exp)( t/τ), where I is the phosphorescence intensity,I_0 is the constants, and τ is the decay constant. As temperature increases the decay constant decreases,which were 4.9, 3.6, and 0.8 μs, at 5, 100, and 200 K, respectively. This behavior is similar to other 1Dlead halide perovskites.