The effect of annealing and photoactivation on the optical transitions of band–band and surface trap states of colloidal quantum dots in PMMA

Abstract

For optoelectronic applications, colloidal CdSe quantum dots (QDs) have been integrated into solid devices by using optically transparent polymer matrices that embedded the colloidal QDs. We systematically studied the effect of annealing and photoactivation on the band-band (BB) and surface trap state (STS) transitions of colloidal CdSe QDs embedded in polymethylmethacrylate (QDs-PMMA). The QDs-PMMA composites demonstrate enhancement of the STS emissions while their annealing leads to an intensity quench of both BB and STS emissions. The annealing process also causes the red shift of the BB emission. By contrast, photoactivation of QDs-PMMA composites results in the remarkable recovery of luminescence intensity accompanied by blue shift of the emissions. Furthermore, it is found in the photoactivation process that the STS emission can be saturated earlier than the BB emission, which renders it possible to tune the light color of the emissions. The combination of annealing and photoactivation could undoubtedly provide an effective way to precisely tune the colors of light-emitting devices that use colloidal CdSe QDs.

Temperature and Wavelength Dependence of Energy Transfer Process Between Quantized States and Surface States in CdSe Quantum Dots

“…Recently, some experimental results demonstrate that the emission of surface trap states with the wide visible light range can be applied to white LEDs [20–22]. Hu et al have realized the fluorescent color tuning by post-synthesis thermal annealing method which enhances the PL intensity of surface trap states for CdSe QDs on polymethyl methacrylate (PMMA) silver films [23, 24]. …”

Physical approaches to tuning luminescence process of colloidal quantum dots and applications in optoelectronic devices

“…Baker et al tuned the SSEs and the intensity ratio of BEE to SSE of the CdSe CQDs via modulating the 3-mecaptopropionic acid (MPA) concentration, thereby obtaining different fluorescence colors (Baker and Kamat, 2010). Hu et al studied the effect of annealing and photooxidation on the recombination of both band-to-band (BB) and SSs of colloidal CdSe QDs in PMMA (Hu et al, 2011). The fabrication of the devices commonly requires annealing process.…”

“…By contrast, photooxidation of QDs-PMMA composites resulted in blue shifts accompanied by the remarkable enhancement of luminescence intensity (Hu et al, 2011). The combination of these physical operations can be applied for designed luminescence color.…”

Study of the propagation of solitary waves produced by an assembly of quantum dots through optical fibers.

“…Some of the most recent investigations indicate that this type of heterostructures can undergo abrupt changes in the spectral response with minimal variations in their size and morphology, offering important applications to optics, among which are the lasers of new generations, diodes. light emitters, optical multiplexers, biosensors, spectral tuners, quantum computing, logic gates, among others [1][2][3][4][5][6]. Nowadays, it has been possible to combine nanostructures with other polymeric materials such as optical fibers, giving rise to nanocomposites, which are generally composed of several phases such as SiO2, where one or several of its dimensions are found at the nanoscale [6][7][8][9][10].…”

“…light emitters, optical multiplexers, biosensors, spectral tuners, quantum computing, logic gates, among others [1][2][3][4][5][6]. Nowadays, it has been possible to combine nanostructures with other polymeric materials such as optical fibers, giving rise to nanocomposites, which are generally composed of several phases such as SiO2, where one or several of its dimensions are found at the nanoscale [6][7][8][9][10]. The optical fibers are a important elements for the propagation of light waves with water and for the propagation of electromagnetic waves in the optical, infrared and ultraviolet range, however, there are other important applications for optical fibers in the area of sensors and in the study of nonlinear optical phenomena.…”