Efficient Er/O‐Doped Silicon Light‐Emitting Diodes at Communication Wavelength by Deep Cooling

A silicon light source at the communication wavelength is the bottleneck for developing monolithically integrated silicon photonics. Doping silicon with erbium and oxygen ions is considered one of the most promising approaches to produce silicon light sources. However, this method suffers from a high concentration of defects in the form of nonradiative recombination centers at the interface between the crystalline silicon and large Er2O3/ErSi1.7 precipitates during the standard rapid thermal treatment. Here, a deep cooling process is applied to suppress the growth of these precipitates by flushing the high‐temperature Er/O‐doped silicon substrates with helium gas cooled in liquid nitrogen. The resultant light‐emitting efficiency at room temperature is enhanced by two orders of magnitude in comparison with that of the sample treated via standard rapid thermal annealing. The deep‐cooling‐processed Si samples are further processed into light‐emitting diodes. Bright electroluminescence with a main spectral peak at 1536 nm is also observed from the silicon‐based diodes with the external quantum efficiency reaching ≈0.8% at room temperature. Based on these results, the development of electrically driven silicon optical amplifiers or even lasers at communication wavelengths is promising for monolithically integrated silicon photonics.A deep cooling technique is developed for silicon light sources by suppressing the growth of Er/O‐related precipitates. The resultant near‐infrared emission shows efficiency enhancement by two orders of magnitude. Bright electroluminescence with a main spectral peak at 1536 nm is also observed. The external quantum efficiency can reach 0.8% at room temperature.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/162702/3/adom202000720.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162702/2/adom202000720-sup-0001-SuppMat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162702/1/adom202000720_am.pd

Boosting the High Working Voltage of an Aqueous Symmetric Supercapacitor by a Phosphotungstic Acid-Based Coordination Polymer Coating with Polypyrrole

The low working voltage limits the energy density and feasibility of practical applications of aqueous supercapacitors (SCs) to some extent. Herein, new CuPW12@PPy (n, n = 1, 2, 3) nanocomposites were designed and fabricated by involving the hydrothermal synthesis of crystalline H4[Cu2(bix)4][PW12O40]2·8H2O (CuPW12) and subsequently pyrrole in situ oxidation polymerization on the CuPW12 surface. These were then used as electrode materials to widen the working voltage of SC. As expected, CuPW12@PPy (n, n = 1, 2, 3) can operate stably within −0.6 to 1.0 V while inhibiting the hydrogen evolution reaction, which exhibits higher specific capacitance in 2 M H3PO4. Specifically, CuPW12@PPy (2) shows a 711.2 F g–1 specific capacitance at 1.5 A g–1, attributed to the high ion/electron transportation and their synergy from the conductive PPy covering the CuPW12 surfaces. Finally, the assembled symmetric SC cell can operate at 1.6 V and deliver a 43.67 Wh kg–1 energy density and 1280 W kg–1 power density at 1.0 A g–1 and a 91.3% capacitance retention at 5 A g–1 after 10,000 cycles

Isomeric organic ligand dominating polyoxometalate-based hybrid compounds: synthesis and as electrocatalysts and pH-sensitive probes

<p>By introducing isomeric organic ligands into polyoxometalate (POM) systems, two new POM-based hybrid compounds, [Cu₆(<i>m</i>-pyttz)₂(H₂O)][HPMo₁₂O₄₀] (<b>1</b>) and [Ag₃(<i>p</i>-H₂pyttz)(<i>p</i>-Hpyttz)Cl][H₂PMo₁₂O₄₀]·6H₂O (<b>2</b>) (<i>m</i>-/<i>p</i>-H₂pyttz = 3-(pyrid-3/4-yl)-5(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), have been hydrothermally synthesized and characterized. Single-crystal structural analysis shows the <i>m</i>-pyttz ligands link Cu^I ions to generate a two-dimensional layer with hanger-like rhombus, which is pillared by the PMo₁₂ anions in <b>1</b>. Compound <b>2</b> exhibits a three-dimensional supramolecular framework, in which PMo₁₂ anions are building blocks facilitating the extension of the whole structure. The influence of the coordination modes of <i>m</i>-/<i>p</i>-H₂pyttz on the structures is discussed in detail. Furthermore, electrochemical properties of <b>1</b> and <b>2</b> have been studied and they display excellent electrocatalytic activities toward the reduction of nitrite and hydrogen peroxide and pH-dependent electrochemical behaviors.</p

Synthesis and polypyrrole-loading study of antifungal medicine fluconazole functionalized Keggin polyoxotungstates

<p>To rich the coordination polymer and polyoxometalate (POM) chemistry, two new hybrid compounds based on Keggin POMs with antifungal medicine fluconazole (Hfkz = [1-(2,4-difluorophenyl)-1,1-bis [(1H-1,2,4-triazol-1-yl)-methyl]methanol]), [Ag₄(Hfkz)₂][PW₁₂O₄₀] (AgFkzPW₁₂) and [Ag₄(Hfkz)₂][SiW₁₂O₄₀] (AgFkzSiW₁₂), have been successfully synthesized and structurally characterized. Moreover, to improve the photogenerated electron-hole pair separation properties, the surface of hybrid compounds was loaded by polypyrrole (PPy) through a chemical oxidation polymerization process <i>in situ</i> fabricating hybrid nanocomposites AgFkzPW₁₂@PPy and AgFkzSiW₁₂@PPy. As a result, the Hfkz molecules were successfully grafted onto the surface of the Keggin polyoxoanions, and their nanocomposites exhibit better photocatalytic activity than the respective matrix compounds under the irradiation of visible light.</p