High-Q Microcavity Enhanced Optical Properties of CuInS₂/ZnS Colloidal Quantum Dots toward Non-Photodegradation

Abstract

We report on a temporal evolution of photoluminescence (PL) spectroscopy of CuInS 2 /ZnS colloidal quantum dots (QDs) by drop-casting on SiO 2 /Si substrates and high quality factor microdisks (MDs) under different atmospheric conditions. Fast PL decay, peak blueshift and linewidth broadening due to photooxidation have been observed at low excitation power. With further increasing of the excitation power, the PL peak position shows a redshift and linewidth becomes narrow, which is ascribed to the enhanced Förster resonant energy transfer between different QDs by photoinduced agglomeration. The oxygen plays an important role in optically induced PL decay which is verified by reduced photobleaching effect in vacuum. When the QDs drop-casted on MDs, photooxidation and photobleaching are accelerated because the excitation efficiency is greatly enhanced with coupling the pumping laser with the cavity modes. However, when the emitted photons couple with cavity modes, a PL enhancement by more than 20 times is achieved because of the increased extraction efficiency and Purcell effects of MDs at room temperature (RT), and 35 times at 20 K. The photobleaching can be avoided with a small excitation power but with a strong PL intensity by taking advantages of high quality factor cavities. The high efficient PL emission without photodegradation is very promising for using CuInS 2 QDs as high efficient photon emitters at RT, where the photodegradation has always been limiting the practical applications of colloidal quantum dots.

Optical Properties and Reliability Studies of Gradient Alloyed Green Emitting (CdSe)x(ZnS)1–x and Red Emitting (CuInS2)x(ZnS)1–x Quantum Dots for White Light-Emitting Diodes

“…As previously, we observe a clear depreciation of the luminescence of the (CuInS 2 ) x (ZnS) 1– x composite films upon the action of temperature and of the incoming irradiation power. These degradations are presumably caused by the damage to the dodecanethiol (DDT) capping ligand, which generates defects on the surface of QDs and quenches the luminescence. The degradation of CuInS 2 /ZnS QDs may occur by the ligand detachment followed by the oxidation of ZnS shell and CuInS 2 core .…”

Advances and prospects of lasers developed from colloidal semiconductor nanostructures

“…More issues remain in other heavy metal-free CQDs for laser applications. For example, the ternary I-III-VI2 chalcogenide CQDs, such as CuInS2 and, CuInSe2, suffer from the intra-band defects due to the wide range of stoichiometric variations and complex crystal structure [181,194,195]. As for the earth-abundant silicon-based CQDs, the different synthetic methods, precursors, and posttreatment will result in greatly distinct optical properties, and the emission mechanism from silicon nanocrystals still remains unclear to date [196][197][198].…”

Flexible Manipulation of Lasing Modes in an Erbium-Doped Microcavity via an Add–Drop Configuration

“…Whispering-gallery-mode (WGM) microcavities are an excellent platform for realizing a low-threshold and narrow-linewidth laser due to its high quality ( Q ) factor (i.e., low loss) and small footprint (i.e., small mode volume ( V m )). − Up to now, there are many kinds of gain materials used for WGM lasing emission, such as dyes, semiconductors, − conjugated polymers, gold nanorods, and rare earth elements. − Rare earth elements have captured much interest because of the large quantum efficiency and ease of emitting in the infrared wavelength band…”