  One-dimensional (1D) organic metal halide hybrids exhibit strongly
anisotropic optical properties, highly efficient light emission, and large
Stokes shift, holding promises for novel photodetection 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 1D C4N2H14PbBr4 by polarization-dependent
time-averaged and time-resolved photoluminescence (TRPL) spectroscopy, as a
function of photoexcitation energy. Surprisingly, we find that the emission
under photoexcitation polarized parallel to the 1D metal halide chains can be
either stronger or weaker than that under perpendicular polarization, depending
on the excitation energy. We attribute the excitation-energy-dependent
anisotropic emission to fast surface recombination, supported by
first-principles calculations of optical absorption in this material. The fast
surface recombination is directly confirmed by TRPL measurements, when the
excitation is polarized parallel to the chains. Our comprehensive studies
provide a more complete picture for a deeper understanding of the optical
anisotropy in 1D organic metal halide hybrids.
