Crown size effect on the light amplification features of core/crown (Cdse/Cds) nanoplatelets

CdSe/CdS core-crown nanoplatelets display minimal shifts in optical features relative to their respective CdSe core, but yield higher stability and photoluminescence quantum efficiencies,1 imperative for cutting-edge photonic applications including lasing. In the present work, using femtosecond pump-probe spectroscopy we assessed the influence of crown (CdS) lateral area on the optical gain threshold, gain lifetime and gain bandwidth of CdSe/CdS core-crown nanoplatelets. Our results demonstrate that thin CdS crowns lowers the gain threshold twofold compared to the CdSe core, achieving gain close to 1 exciton per nanoplatelet. The lower gain thresholds for the thin-crown nanoplatelets is likely a consequence of efficient surface trap passivation, as we also observed an increasing gain lifetime of 700 ps, nearly threefold longer than CdSe cores for similar exciton densities. Further increase of the crown lateral area increased the gain threshold to an exciton density similar to the core nanoplatelets, yet the threshold is obtained at a fourfold lower photon flux, as a result of higher absorption cross section. The gain lifetime of 400 ps is also still twofold longer than core nanoplatelets. Furthermore, the thick crown broadened the gain bandwidth to 105 nm. The maximum material gain obtained from the core and core-crown nanoplatelets are similar and reach 15000 cm-1. Our studies confirm that core-crown nanoplatelets are promising materials for light amplification.

Jaar van publicatie:2022

Toegankelijkheid:Open