Near-Unity Photoluminescence Quantum Yield and Highly Suppressed Blinking in a Toxic-Metal-Free Quantum Dot

Abstract

There is no literature report of simultaneously achieving near-unity PLQY (ensemble level) and highly suppressed blinking (ultrasensitive single-particle spectroscopy (SPS) level) in a toxic-metal-free QD. In this Letter we report accomplishing near-unity PLQY (96%) and highly suppressed blinking (>80% ON fraction) in a toxic-metal-free CuInS 2 / ZnSeS Core/Alloy-Shell (CAS) QD. In addition, (i) gigantic enhancement of PLQY (from 15% (Core) to 96% (CAS QD)), (ii) ultrahigh stability over 1 year without significant reduction of PLQY at the ensemble level, (iii) high magnitude (nearly 3 times) of electron detrapping/trapping rate, and (iv) very long ON duration (∼2 min) without blinking at the SPS level enable this ultrasmall (∼3.3 nm) CAS QD to be quite suitable for single-particle tracking/bioimaging. A model explaining all these excellent optical properties has been provided. This ultrabright CAS QD has been successfully utilized toward fabrication of lowcost microcontroller-based stable and bright yellow and white QD-LEDs.

Carrier Dynamics in Alloyed Chalcogenide Quantum Dots and Their Light‐Emitting Devices

“…Thus far, there are many reports on suppressed PL blinking behavior of alloyed QDs. [26,[139][140][141] In 2009, Wang et al [26] studied the single QD PL intensity time traces of CdZnSe/ZnSe alloyed core/shell QDs and CdSe/ZnSe core/shell QDs. It has been found that CdZnSe/ZnSe alloyed core/shell QDs exhibit complete suppression of PL blinking, whereas CdSe/ZnSe core/ shell QDs show PL blinking.…”

Core-Size-Dependent Trapping and Detrapping Dynamics in CdSe/CdS/ZnS Quantum Dots

“…Larger k d values compared to k t have been reported earlier in several semiconductor QD systems indicating that the trapped electron stays only for a shorter duration in the trap-states. 43,45 Semiconductor QDs such as CdSe and PbS possess shallow trap-states, and the depth of the trap-state increases as the core size decreases. 10,25 In other words, the energy gap between the trap-state and the conduction band edge in CdSe QDs having a smaller core size is wider compared to QDs having a large size.…”

“…Semiconductor QDs exhibit mysterious episodes of emission intermittency often called blinking when explored using single-particle PL spectroscopy. − Indeed, blinking is a universal feature of all single emitters. This is manifested as a finite occurrence of emission, followed abruptly by periods wherein no light is emitted. − These extreme states are narrated as ON-states (bright) and OFF-states (dark). In the OFF-state, QDs lose the absorbed energy through nonradiative pathways instead of emitting photons and are hence considered as a disadvantage for various applications. , Apart from the completely dark state, a low-intensity gray state is also observed during the blinking process .…”

Effect of Lead:Halide Precursor Ratio on the Photoluminescence and Carrier Dynamics of Violet- and Blue-Emitting Lead Halide Perovskite Nanocrystals

“…Because of their great potential in diverse applications like in photovoltaics, LEDs, display technologies, lasing, and so on, the cesium lead halide (CsPbX 3 , X = Cl, Br, I) perovskite NCs continue to receive great attention of the researchers. − High PLQY and ease of tunability of the PL band position across the entire visible region make these substances quite attractive for optoelectronic applications. − ,, In this family of perovskites, CsPbCl 3 and CsPb­(Cl/Br) 3 NCs are considered indispensable due to their violet and blue emission, which are essential color components for fabrication of white LEDs. − Unlike the conventional metal chalcogenide semiconductor NCs, the halide perovskites generally exhibit high PLQY due to their defect-tolerant nature. ,− However, compared to their green- and red-emitting counterparts, CsPbBr 3 and CsPbI 3 , the large-bandgap perovskites such as violet- and blue-emitting CsPbCl 3 and CsPb­(Cl/Br) 3 NCs most often exhibit much lower PLQY due to competing nonradiative recombination of the photogenerated charge carriers through the deep trap states generated by halide vacancies and distorted [PbX 6 ] 4– octahedral units. ,,− Since the first synthesis of these NCs by the hot-injection (HI) method, several methodologies have been developed for the preparation of violet- and blue-emitting CsPCl 3 and CsPb­(Cl/Br) 3 NCs with higher PLQY. ,,− Doping with different bivalent metal ions ,,,,,,,, and a variety of postsynthetic treatments of the as-synthesized NCs ,,,,,, are the most common practices for improving the PLQY of these NCs. Considering that, in the first synthesis of the CsPbX 3 NCs PbX 2 was used as pr...…”