Giant Quantum Yield Enhancement in CdS/MgF₂/Ag Hybrid Nanobelt under Two-Photon Excitation

Abstract

We demonstrate a giant quantum yield (QY) enhancement (230 times) in a single CdS/MgF2/Ag hybrid nanobelt under the two-photon excitation at 800 nm. The power-dependent two-photon photoluminescence (TPL) and the time-resolved photoluminescence (TRPL) measurement are performed in a single half-covered CdS/MgF2/Ag nanobelt, offering a direct comparison between the CdS nanobelt with and without MgF2/Ag coating. The quantitative theoretical analysis based on the free carrier dynamic model indicates the defect concentration is reduced from (3.7 ± 0.9) × 1019 cm–3 (in bare) to (3.9 ± 0.6) × 1018 cm–3 (in hybrid CdS nanobelt) due to the surface passivation, and the radiative recombination rate is increased from (1.7 ± 0.2) × 10–11 cm3 s–1 (in bare) to (7.1 ± 1.3) × 10–11 cm3 s–1 (in hybrid CdS nanobelt) due to the Purcell effect. Moreover, combined with the enhancement of the local field at the excitation wavelength (6.3×) and the signal collection efficiency (1.42×), a total 1800× enhancement of the TPL signal is achieved in experiment. Our work provides a quantitative characterization on free carrier dynamics of the surface defect passivation in semiconductor nanostructures, which has potentials in photovoltaics and photodetectors with high performance.

Tunable Quantum Photoinitiators for Radical Photopolymerization

“…The charge carriers effectively control the concentration of oxidative species generated and also retard the annihilating function of the oxygen species. Quantum PIs are also used for two-photon (2P) absorption-based printing approaches [ 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ]. In addition, 2P polymerization processes involve the use of femtosecond laser radiation at a wavelength below the bandgap to excite the quantum PI.…”