Efficient, Stable, and Photoluminescence Intermittency-Free CdSe-Based Quantum Dots in the Full-Color Range

Abstract

Colloidal semiconductor CdSe-based quantum dots (QDs) show undesirable photoluminescence (PL) intermittency with frequent and long-lasting dark states due to positively charged states, significantly limiting QD optoelectronic and photonics applications. Here, we show that p-phenylenediamine (PPD) can completely suppress the long-lasting dark states in the PL intensity trajectories for single CdSe-based QDs in the full-color emission range from 459 to 800 nm, while hardly influencing any other PL properties of the QDs, such as the PL intensity, lifetime, and emission spectra. The suppression mechanism is investigated by comparing PPD to another amine compound, N,N-dimethylaniline. With a reasonable highest occupied molecular orbital energy, PPD facilitates electron transfer from PPD to the positively charged QDs, thus, neutralizing the extra hot holes via an Auger-assisted process. Therefore, the positively charged states of QDs and the PL intermittency could be eliminated. Moreover, we demonstrate that PPD can effectively suppress the photobleaching of CdSe-based QDs, and the average survival time of single QDs can be extended from a few minutes to more than 1 h. Finally, we demonstrate the application of PPD-stabilized QDs to single-particle tracking and HeLa cell imaging under relevant biological conditions and show their promising potential in various biomedical applications.

Exciton Dynamics in Colloidal CdS Quantum Dots with Intense and Stokes Shifted Photoluminescence in a Single Decay Channel

“…Semiconductor quantum dots (QDs) have attracted significant attention over the last few decades, due to their excellent optical properties that arise due to quantum confinement effect, − and pave the way for a myriad of potential applications. − Cadmium chalcogenide QDs constitute an important class of these materials, with facile size, shape, and capping group-dependent wavelength tunability of emission across the visible region of the spectrum. ,− Besides, high photoluminescence quantum yields (PLQYs) and ease of chemical processability makes this particular class of QDs attractive. ,,− Optical amplification and lasing, demonstrated in these materials, − form one class of potential applications. Competition from efficient nonradiative processes of Auger recombination (AR) and surface trapping are important issues that need to be addressed in this context. , While surface trapping can be reduced effectively by growing a passivating shell of a higher band gap material around the emitting dot, AR poses a more formidable challenge.…”

Role of Aspect Ratio in the Photoluminescence of Single CdSe/CdS Dot-in-Rods

“…The normalized on-state and off-state probability densities for these DR samples show truncated power-law distribution P on ( t ) = A on t –α on exp­(−μ on t ) and power-law distribution P off ( t ) = A off t –α off , respectively, as shown in Figure g–i. The fitting parameters are summarized in Table , where α on and α off are the power-law exponents, and μ on is the saturation rate. − From the on-state and off-state probability densities, we find that when the aspect ratios increase, the α on values reduce and the 1/μ on values increase, which indicate the increased probability densities of long on-state events with the increased aspect ratios. This indicates that the larger aspect ratio can suppress the PL blinking.…”

Charge and energy transfer dynamics in single colloidal quantum dots/monolayer MoS2 heterostructures

“…The increase in the on-state may originate from the decrease of the charging rate or the increase of the discharging rate. In order to quantitatively investigate the effect of MoS 2 on the charging and discharging process of single QDs, we calculate the statistical distribution 44 of on- and off-time of PL intensity traces.…”