Surface Effects on Anisotropic Photoluminescence in One-Dimensional Organic Metal Halide Hybrids

TL;DR

This study investigates how surface effects influence the anisotropic photoluminescence in 1D organic metal halide hybrids, revealing excitation-energy-dependent emission behavior and the role of surface recombination.

Contribution

It provides new insights into the impact of surface effects on optical anisotropy in 1D organic metal halide hybrids using polarization-dependent spectroscopy and first-principles calculations.

Findings

Surface recombination affects emission intensity depending on excitation polarization.

Fast surface recombination is confirmed by time-resolved PL measurements.

Optical absorption calculations support the role of surface effects in anisotropic emission.

Abstract

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.