White Light Emission from Mixed Composition Low Dimensionality Halide Perovskites

Hybrid halide perovskites are a novel class of semiconductor materials with promising and versatile optoelectronic properties enabled by their chemically adjustable structures and dimensionality. The diversity in the metal ions, halide anions, and organic spacers enables a wide range of materials with highly tunable properties and variable dimensionalities. These materials are studied for various applications, such as photovoltaics, detectors, and light-emitting devices. The chemical and structural agility of halide perovskites, enabling the adjustment of the optical and electronic properties for a desired application, is significant. In our research, we seek to gain additional information regarding the correlation between structure and composition to optoelectronic properties in low-dimensionality halide perovskites.<br/>Specifically, we study low-dimensionality hybrid halide perovskites that exhibit broad-spectrum, white-light emission at room temperature, associated with self-trapped excitons (STE). These compounds are ideal candidates for illumination applications. We study the correlation between structural and chemical motifs of low-dimensionality halide perovskites and their STE emission.<br/>In this research, we have studied how exchanging the halide anions while maintaining the structure affects the STE properties. We have focused on a unique 1D perovskite structure based on edge-sharing dimers, exhibiting strong, broad emission with PLQY of approximately 40%. By changing the halide from I to Br and Cl, we observe an increase in the bandgap energy, as expected. However, the broad emission shows an anti-correlated behavior, resulting in red-shifted broad emission for the Cl sample, with a significantly larger stokes shift. We further study how mixing Br and Cl in a single structure affects the broad emission properties and how different synthetic approaches can be utilized to fabricate these compounds.<br/>To gain additional information regarding the STE properties with different compositions we have studied the temperature-dependent photoluminescence of these compounds. We utilize combined spectrally and temporally resolved photoluminescence measurements, allowing us to study the transition from band-edge to STE emission upon excitation. We observed how this transition, along with additional properties of the STE emission, evolved with temperature and composition.