Tunable Emission of Bluish Zn–Cu–Ga–S Quantum Dots by Mn Doping and Their Electroluminescence

Abstract

On the basis of bluish-emitting double-shelled quantum dots (QDs) of Zn–Cu–Ga–S (ZCGS)/ZnS/ZnS, Mn doping into ZCGS host with different Mn/Cu concentrations is implemented via surface adsorption and lattice diffusion. The resulting double-shelled Mn-doped ZCGS (ZCGS/Mn) QDs exhibit a distinct Mn2+ 4T1–6A1 emission as a consequence of effective lattice incorporation simultaneously with host intragap states-involving emissions of free-to-bound and donor–acceptor pair recombinations. The relative contribution of Mn emission to the overall photoluminescence (PL) is consistently proportional to its concentration, resulting in tunable PL from bluish, white, to reddish white. Regardless of Mn doping and its concentration, all QDs possess high PL quantum yield levels of 74–79%. Those undoped and doped QDs are then employed as an emitting layer (EML) of all-solution-processed QD-light-emitting diodes (QLEDs) with hybrid charge transport layers and their electroluminescence (EL) is compared. Compared to undoped QDs, doped analogues give rise to a huge spectral disparity of EL versus PL, specifically showing a near-complete quenching of Mn2+ EL. This unexpected observation is rationalized primarily by considering unbalanced carrier injection to QD EML on the basis of energetic alignment of the present QLED and rapid trapping of holes injected at intragap states of QDs.

Macroporous Hydrogels for Fast and Reversible Switching between Transparent and Structurally Colored States

“…The exact combinatorial code is only revealed when the water–ethanol mixture agreed in advance is used, providing advanced security in anti‐counterfeiting applications. The macroporous hydrogel can be further tailed to have a microparticle format with various shapes including microdisks and microspheres through micro‐molding, [ 10,42 ] photolithography, [ 41,43,44 ] and microfluidic system, [ 45–47 ] which will further expand the applications beyond the sensors and security materials.…”

“…In particular, the colloidal photonic crystals can be designed to show structural‐color change or disclose hidden patterns under external chemical or mechanical stimuli, which makes them appealing as colorimetric sensors and user‐interactive anti‐counterfeiting materials. [ 11–13 ] For example, the colloidal lattices embedded in the polymeric matrix responsive to the external conditions, such as mechanical strain, humidity, pH, temperature, organic solvents, and specific molecules, exhibit the condition‐dependent structural colors, serving as colorimetric sensors. [ 14–20 ] In addition, a temperature‐responsive matrix can provide light‐sensitive structural colors through the incorporation of photothermal agents.…”

“…[ 22–25 ] Alternatively, colloidal particles made of stimuli‐responsive materials are assembled to form crystalline lattices, which also show the condition‐dependent color change. [ 26–28 ] The stimuli‐responsive colloidal crystals can be micropatterned to show condition‐dependent and regioselective color change, [ 12,13 ] which is able to disclose hidden optical and graphical codes, verifying the authenticity. [ 29–36 ] However, there is room to further improve the property of the photonic materials for practical applications.…”

Cephalopod‐Inspired High Dynamic Range Mechano‐Imaging in Polymeric Materials

“…Separately, spiropyran cross‐linker is incorporated in a PDMS elastomer (see Experimental Section and Supporting Information); the spiropyran is functionalized with two alkene groups, which allow it to be covalently coupled into the PDMS network via hydrosilylation. [ 33–36 ] The photonic film is then positioned on top of the cured spiropyran‐PDMS. To reduce diffuse scattering from the photonic film which makes the color appear pale, a separately cured film of PDMS containing 5 wt% carbon black nanoparticles is placed on top of the photonic film; alternatively, 0.5 wt% carbon black nanoparticles can be added to the PEGPEA/silica pre‐polymer mixture prior to photo‐curing.…”

New Encryption Strategy of Photonic Crystals with Bilayer Inverse Heterostructure Guided from Transparency Response

“…The response mode of the responsive colloidal photonic crystals (CPCs) provide a large number of encryption methods for information security due to their strong capability to control and manipulate the light propagation with tunability . In order to obtain more advanced encryption methods, a variety of response strategies of CPCs have been proposed, such as thermoresponse, photoresponse, pressure response, and solvent response .…”