Superradiance Emission and Its Thermal Decoherence in Lead Halide Perovskites Superlattices

Self-assembled nanocrystals (NCs) into superlattices (SLs) are alternative materials to polycrystalline films and single crystals, which can behave very differently from their constituents, especially when they interact coherently with each other. This work concentrates on the Superradiance (SR) emission observed in SLs formed by CsPbBr3 and CsPbBrI2 NCs. Micro-Photoluminescence spectra and transients in the temperature range 4-100 K are measured in SLs to extract information about the SR states and uncoupled domains of NCs. For CsPbBr3 SLs with mostly homogeneous SR lines (linewidth 1-5 meV), this work measures lifetimes as short as 160 ps, 10 times lower than the value measured in a thin film made with the same NCs, which is due to domains of near identical NCs formed by 1000 to 40 000 NCs coupled by dipole-dipole interaction. The thermal decoherence of the SR exciton state is evident above 25 K due to its coupling with an effective phonon energy of approximate to 8 meV. These findings are an important step toward understanding the SR emission enhancement factor and the thermal dephasing process in perovskite SLs.