Surface Effects on Anisotropic Photoluminescence in One-Dimensional Halide Perovskites

One-dimensional (1D) hybrid organic-inorganic perovskites exhibit strongly anisotropic optical properties, highly efficient light emission, and large Stokes shift, holding promises for novel photo-detection and lighting applications. However, the fundamental mechanisms governing their unique optical properties and in particular the impacts of surface effects are not understood. Here, we investigate C₄N₂H₁₄PbBr₄ by polarization dependent time-averaged and time-resolved PL (TRPL) spectroscopy, as a function of photoexcitation energy. Surprisingly, we found that the emission under photoexcitation polarization parallel to the 1D molecular chain can be either stronger or weaker than that under perpendicular polarization, depending on the excitation energy. We attribute the excitation energy dependent anisotropic PL to fast nonradiative surface recombination, as supported by TRPL measurements and first principles calculations. Our comprehensive studies provide a more complete picture for a deeper understanding of the optical anisotropy in 1D perovskites.