Constructing Gradient Energy Levels to Promote Exciton Energy Transfer for Photoluminescence Controllability of All-Inorganic Perovskites and Application in Single-Component WLEDs

Photoluminescence tunability is exceedingly crucial to all-inorganic halide perovskite (CsPbX3, X = Cl, Br, I) quantum dots (QDs) for high-resolution display. However, up to now, the wide-range color tunability could only be achieved by varying the halide ratio. A drawback in this approach is the color instability caused by inevitable halide ion exchange. Therefore, it is of great significance to exploit the new train of thought to tune the emission color in a wide range. Herein, we designed a novel exciton energy-transfer strategy by introducing the 1G4 energy level of Tm to construct the intermediate gradient energy levels between the conduction band of the host perovskite and the 4T1 energy level of Mn for efficiently promoting the exciton energy transfer from the host perovskite to Mn. Thus, the emission color could be accurately tuned from green to orange, and the corresponding correlated color temperature changed from 12 400 to 1800 K. Most strikingly, the single-component pure white light QDs with a record photoluminescence quantum yield (PLQY) of 54% were obtained based on this strategy. Additionally, white light-emitting diodes with a color rendering index up to 91 and a CIE color coordinate of (0.33, 0.34) are further fabricated. Therefore, we believe that this novel exciton energy-transfer strategy will possibly open up a new avenue for efficient emission controllability of all-inorganic perovskites, promoting the higher PLQY of single-component white light QDs and facilitating practical application

Harvesting Broadband Kinetic Impact Energy from Mechanical Triggering/Vibration and Water Waves

We invented a triboelectric nanogenerator (TENG) that is based on a wavy-structured Cu–Kapton–Cu film sandwiched between two flat nanostructured PTFE films for harvesting energy due to mechanical vibration/impacting/compressing using the triboelectrification effect. This structure design allows the TENG to be self-restorable after impact without the use of extra springs and converts direct impact into lateral sliding, which is proved to be a much more efficient friction mode for energy harvesting. The working mechanism has been elaborated using the capacitor model and finite-element simulation. Vibrational energy from 5 to 500 Hz has been harvested, and the generator’s resonance frequency was determined to be ∼100 Hz at a broad full width at half-maximum of over 100 Hz, producing an open-circuit voltage of up to 72 V, a short-circuit current of up to 32 μA, and a peak power density of 0.4 W/m2. Most importantly, the wavy structure of the TENG can be easily packaged for harvesting the impact energy from water waves, clearly establishing the principle for ocean wave energy harvesting. Considering the advantages of TENGs, such as cost-effectiveness, light weight, and easy scalability, this approach might open the possibility for obtaining green and sustainable energy from the ocean using nanostructured materials. Lastly, different ways of agitating water were studied to trigger the packaged TENG. By analyzing the output signals and their corresponding fast Fourier transform spectra, three ways of agitation were evidently distinguished from each other, demonstrating the potential of the TENG for hydrological analysis

Harvesting Broadband Kinetic Impact Energy from Mechanical Triggering/Vibration and Water Waves

We invented a triboelectric nanogenerator (TENG) that is based on a wavy-structured Cu–Kapton–Cu film sandwiched between two flat nanostructured PTFE films for harvesting energy due to mechanical vibration/impacting/compressing using the triboelectrification effect. This structure design allows the TENG to be self-restorable after impact without the use of extra springs and converts direct impact into lateral sliding, which is proved to be a much more efficient friction mode for energy harvesting. The working mechanism has been elaborated using the capacitor model and finite-element simulation. Vibrational energy from 5 to 500 Hz has been harvested, and the generator’s resonance frequency was determined to be ∼100 Hz at a broad full width at half-maximum of over 100 Hz, producing an open-circuit voltage of up to 72 V, a short-circuit current of up to 32 μA, and a peak power density of 0.4 W/m². Most importantly, the wavy structure of the TENG can be easily packaged for harvesting the impact energy from water waves, clearly establishing the principle for ocean wave energy harvesting. Considering the advantages of TENGs, such as cost-effectiveness, light weight, and easy scalability, this approach might open the possibility for obtaining green and sustainable energy from the ocean using nanostructured materials. Lastly, different ways of agitating water were studied to trigger the packaged TENG. By analyzing the output signals and their corresponding fast Fourier transform spectra, three ways of agitation were evidently distinguished from each other, demonstrating the potential of the TENG for hydrological analysis

Simultaneous Photoluminescence and Photothermal Investigation of Individual CH₃NH₃PbBr₃ Microcrystals

The photoluminescence (PL) of CH3NH3PbBr3 (MAPbBr3), from thin films to nanoparticles, has been widely studied, providing information about charge carrier dynamics. However, the other energy dissipative channel, nonradiative relaxation, has not been thoroughly investigated due to a lack of proper technology. In this work, we simultaneously investigated the PL and photothermal (PT) properties of single MAPbBr3 microcrystals (MCs) by a home-built PL and PT microscope. In addition to the direct observation of the heterogeneity of the PL and PT images and kinetics of different MCs, we demonstrated the variation in the absorption of single MAPbBr3 MCs, which was believed to be constant. We also proved that more absorbed energy dissipated from the nonradiative channel at higher heating power. These results show that PL and PT microscopy is an effective and convenient method to investigate the charge carrier behaviors of optoelectronic materials at the single particle level for a deep understanding of their photophysical processes

Highly Enantioselective Synthesis of 2,6-Disubstituted and 2,2,6-Trisubstituted Dihydropyrones: A One-Step Synthesis of (<i>R</i>)-(+)-Hepialone and Its Analogues

An efficient enantioselective approach to chiral dihydropyrones has been developed by the hetero-Diels−Alder (HDA) reactions of (E)-4-methoxy-2-trimethylsiloxy-penta-1,3-diene (diene 1) with aldehydes and pyruvates. It has been found that the readily accessible (R)-BINOL-Ti(OiPr)4 (1.1:1) complex was a very effective catalyst for this reaction. Aromatic, heteroaromatic, conjugated, and aliphatic aldehydes afforded the corresponding products in moderate to high isolated yields (up to 99%) with excellent enantioselectivities (up to 99% ee). The first example of highly enantioselective synthesis of 2,2,6-trisubstituted dihydropyrones by the catalytic reaction of diene 1 with pyruvates was reported. The isolated intermediates indicated that this asymmetric HDA reaction proceeded in a Mukaiyama aldol pathway. On the basis of the absolute configurations of the products, a possible mechanism was proposed. Moreover, the catalytic system could be used to synthesize a series of enantioenriched β-hydroxyketones 4. Finally, this methodology was successfully applied for the one-step synthesis of the important natural product (R)-(+)-Hepialone with 88% isolated yield and 94% enantioselectivity

Highly Enantioselective Synthesis of 2,6-Disubstituted and 2,2,6-Trisubstituted Dihydropyrones: A One-Step Synthesis of (<i>R</i>)-(+)-Hepialone and Its Analogues

An efficient enantioselective approach to chiral dihydropyrones has been developed by the hetero-Diels−Alder (HDA) reactions of (E)-4-methoxy-2-trimethylsiloxy-penta-1,3-diene (diene 1) with aldehydes and pyruvates. It has been found that the readily accessible (R)-BINOL-Ti(OiPr)4 (1.1:1) complex was a very effective catalyst for this reaction. Aromatic, heteroaromatic, conjugated, and aliphatic aldehydes afforded the corresponding products in moderate to high isolated yields (up to 99%) with excellent enantioselectivities (up to 99% ee). The first example of highly enantioselective synthesis of 2,2,6-trisubstituted dihydropyrones by the catalytic reaction of diene 1 with pyruvates was reported. The isolated intermediates indicated that this asymmetric HDA reaction proceeded in a Mukaiyama aldol pathway. On the basis of the absolute configurations of the products, a possible mechanism was proposed. Moreover, the catalytic system could be used to synthesize a series of enantioenriched β-hydroxyketones 4. Finally, this methodology was successfully applied for the one-step synthesis of the important natural product (R)-(+)-Hepialone with 88% isolated yield and 94% enantioselectivity

Highly Enantioselective Synthesis of 2,6-Disubstituted and 2,2,6-Trisubstituted Dihydropyrones: A One-Step Synthesis of (<i>R</i>)-(+)-Hepialone and Its Analogues

An efficient enantioselective approach to chiral dihydropyrones has been developed by the hetero-Diels−Alder (HDA) reactions of (E)-4-methoxy-2-trimethylsiloxy-penta-1,3-diene (diene 1) with aldehydes and pyruvates. It has been found that the readily accessible (R)-BINOL-Ti(OiPr)4 (1.1:1) complex was a very effective catalyst for this reaction. Aromatic, heteroaromatic, conjugated, and aliphatic aldehydes afforded the corresponding products in moderate to high isolated yields (up to 99%) with excellent enantioselectivities (up to 99% ee). The first example of highly enantioselective synthesis of 2,2,6-trisubstituted dihydropyrones by the catalytic reaction of diene 1 with pyruvates was reported. The isolated intermediates indicated that this asymmetric HDA reaction proceeded in a Mukaiyama aldol pathway. On the basis of the absolute configurations of the products, a possible mechanism was proposed. Moreover, the catalytic system could be used to synthesize a series of enantioenriched β-hydroxyketones 4. Finally, this methodology was successfully applied for the one-step synthesis of the important natural product (R)-(+)-Hepialone with 88% isolated yield and 94% enantioselectivity

Highly Enantioselective Synthesis of 2,6-Disubstituted and 2,2,6-Trisubstituted Dihydropyrones: A One-Step Synthesis of (<i>R</i>)-(+)-Hepialone and Its Analogues

An efficient enantioselective approach to chiral dihydropyrones has been developed by the hetero-Diels−Alder (HDA) reactions of (E)-4-methoxy-2-trimethylsiloxy-penta-1,3-diene (diene 1) with aldehydes and pyruvates. It has been found that the readily accessible (R)-BINOL-Ti(OiPr)4 (1.1:1) complex was a very effective catalyst for this reaction. Aromatic, heteroaromatic, conjugated, and aliphatic aldehydes afforded the corresponding products in moderate to high isolated yields (up to 99%) with excellent enantioselectivities (up to 99% ee). The first example of highly enantioselective synthesis of 2,2,6-trisubstituted dihydropyrones by the catalytic reaction of diene 1 with pyruvates was reported. The isolated intermediates indicated that this asymmetric HDA reaction proceeded in a Mukaiyama aldol pathway. On the basis of the absolute configurations of the products, a possible mechanism was proposed. Moreover, the catalytic system could be used to synthesize a series of enantioenriched β-hydroxyketones 4. Finally, this methodology was successfully applied for the one-step synthesis of the important natural product (R)-(+)-Hepialone with 88% isolated yield and 94% enantioselectivity

Highly Enantioselective Synthesis of 2,6-Disubstituted and 2,2,6-Trisubstituted Dihydropyrones: A One-Step Synthesis of (<i>R</i>)-(+)-Hepialone and Its Analogues

An efficient enantioselective approach to chiral dihydropyrones has been developed by the hetero-Diels−Alder (HDA) reactions of (E)-4-methoxy-2-trimethylsiloxy-penta-1,3-diene (diene 1) with aldehydes and pyruvates. It has been found that the readily accessible (R)-BINOL-Ti(OiPr)4 (1.1:1) complex was a very effective catalyst for this reaction. Aromatic, heteroaromatic, conjugated, and aliphatic aldehydes afforded the corresponding products in moderate to high isolated yields (up to 99%) with excellent enantioselectivities (up to 99% ee). The first example of highly enantioselective synthesis of 2,2,6-trisubstituted dihydropyrones by the catalytic reaction of diene 1 with pyruvates was reported. The isolated intermediates indicated that this asymmetric HDA reaction proceeded in a Mukaiyama aldol pathway. On the basis of the absolute configurations of the products, a possible mechanism was proposed. Moreover, the catalytic system could be used to synthesize a series of enantioenriched β-hydroxyketones 4. Finally, this methodology was successfully applied for the one-step synthesis of the important natural product (R)-(+)-Hepialone with 88% isolated yield and 94% enantioselectivity