Luminescence and Amplified Stimulated Emission in CdSe–ZnS‐Nanocrystal‐Doped TiO₂ and ZrO₂ Waveguides

Abstract

A reproducible route for the preparation of high‐quality CdSe–ZnS‐doped titania and zirconia waveguides is presented. The optical properties of the resultant composite materials are found to be sensitive to the semiconducting properties of the host matrix. Titania‐based composites are seen to be inherently photounstable because of photoelectron injection into the bulk matrix and subsequent nanocrystal (NC) oxidation. In comparison, zirconia composites are significantly more robust with high photoluminescence (PL) retained for annealing temperatures up to 300 °C. Both titania and zirconia composite waveguides exhibit amplified stimulated emission (ASE); however only zirconia‐based waveguides exhibit long‐term photostability (loss of less than 30 % ASE intensity after more than 40 min continuous excitation). We conclude that the low electron affinity of zirconia and its inherent high refractive index makes it an ideal candidate for NC‐based optical waveguides.

Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

“…Similar results were obtained by embedding CdSe/ZnS QDs in TiO 2 [53]. Then, Jasieniak et al studied the optical properties of planar waveguides made by the incorporation of CdSe/ZnS QDs (emission at 630 nm) in TiO 2 , and ZrO 2 [54]. Although a similar ASE threshold (0.33 mJ/cm 2 under fs pulses) was found for both kind of matrices (TiO 2 , and ZrO 2 ), the later demonstrated longer term stability.…”

Quantum yield excitation spectrum (UV-visible) of CdSe/ZnS core-shell quantum dots by thermal lens spectrometry

“…12,13 It is established that capping a core material with a shell reduces nonradiative recombination, when the shell inorganic material is a semiconductor with wider band gap than the core semiconductor. 14,15 Fluorescence quantum efficiency and related aging and photodegradation effects are therefore of utmost importance in the development and applications of the QDs materials.…”

Photothermal Spectroscopic Characterization in CdSe/ZnS and CdSe/CdS Quantum Dots: A Review and New Applications

“…The inset shows the nanostructure of the QD Type I, with a CdSe core surrounded by a ZnS shell. In this case electrons (e -) and holes (h + ) are confined to the core of the core-shell QDs (Jasieniak et al, 2007;Kim et al, 2003).…”

“…CdSe/ZnS core-shell nanocrystals have been shown to be useful for tailoring the fluorescence of dental resin composites (Alves et al, 2010). Core-shell quantum dots (CS) have been used as heteronanocrystals, structures that allow optical amplification because of their stimulated emission of single-exciton states (Klimov et al, 2007), and highquality CdSe/ZnS doped titania and zirconia optical waveguides have been prepared (Jasieniak et al, 2007).…”

“…CdSe/ZnS and CdSe/CdS core-shell semiconductor nanocrystallites are II-VI semiconductor systems and Type I QDs; i.e., both electrons and holes are confined to the core of the core-shell QDs (Jasieniak et al, 2007;Kim et al, 2003). A CdSe nanocrystal core with band gap of (1.7-1.76) eV (Kortan et al, 1990;Lee et al, 2006) is often covered by another semiconductor shell with a high-energy band gap, such as ZnS or CdS, to improve the radiative quantum efficiency by passivating the nonradiative recombination sites at the surface (Dabbousi et al, 1997;Kortan et al, 1990).…”