Tuning Hot Carrier Cooling Dynamics by Dielectric Confinement in Two-Dimensional Hybrid Perovskite Crystals.
basic_science · Level V
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- Record sourced from PubMed, PMID 31613089.
- Also identified by DOI 10.1021/acsnano.9b04085.
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Abstract
Hot carrier (HC) cooling is a critical photophysical process that significantly influences the optoelectronic performance of hybrid perovskite-based devices. The hot carrier extraction at the device interface is very challenging because of its ultrashort lifetime. Here, ultrafast transient reflectance spectroscopy measurements and time-domain <i>ab initio</i> calculations show how the dielectric constant of the organic spacers can control and slow the HC cooling dynamics in single-crystal 2D Ruddlesden-Popper hybrid perovskites. We find that (EA)<sub>2</sub>PbI<sub>4</sub> (EA = HOC<sub>2</sub>H<sub>4</sub>NH<sub>3</sub><sup>+</sup>) that correspond to a high dielectric constant organic spacer has a longer HC cooling time compared to that of (AP)<sub>2</sub>PbI<sub>4</sub> (AP = HOC<sub>3</sub>H<sub>6</sub>NH<sub>3</sub><sup>+</sup>) and (PEA)<sub>2</sub>PbI<sub>4</sub> (PEA = C<sub>6</sub>H<sub>5</sub>C<sub>2</sub>H<sub>4</sub>NH<sub>3</sub><sup>+</sup>). The slow HC relaxation process in the former case can be ascribed to a stronger screening of the Coulomb interactions, a small nonradiative internal conversion within the conduction bands, as well as a weak electron-phonon coupling. Our findings provide a strategy to prolong the hot carrier cooling time in low-dimensional hybrid perovskite materials by using organic spacers with reduced dielectric confinement.