Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28106061.
- Also identified by DOI 10.1038/ncomms14120 and PMC identifier 5263885.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The hot-phonon bottleneck effect in lead-halide perovskites (APbX<sub>3</sub>) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA<sup>+</sup>/MA<sup>+</sup>/Cs<sup>+</sup>, X=I<sup>-</sup>/Br<sup>-</sup>) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI<sub>3</sub>. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials.