Hydrolysis and DFT structural studies of dinuclear Zn(II) and Cu(II) macrocyclic complexes of <i>m</i>-12N₃O-dimer and the effect of pH on their promoted HPNP hydrolysis rates

<p>The synthesis of the ligand, <i>m</i>-12N₃O-dimer (1,3-bis(1-oxa-4,7,10-triazacyclododecan-7-yl)methyl)benzene, L), and the stability and hydrolysis constants of its dinuclear Zn(II) and Cu(II) complexes are reported, in addition to the effect of pH on HPNP (2-hydroxypropyl-4-nitrophenylphosphate) hydrolysis reaction rates promoted by these complexes. Various structural possibilities of the [Zn₂L] and [Cu₂L] hydrolytic species derived from solution equilibrium modeling are predicted from density functional theory (DFT) studies to correlate with the promoted HPNP hydrolysis reaction rates and to establish the structure–function–reactivity relationship. Upon deprotonation [Zn₂L(OH)]³⁺ tends to form a structure with a “closed-form” conformation where it is not possible for <i>para</i>-isomers. At pH >8, the formation of the closed-form [Zn₂L(OH)₂]²⁺ and [Zn₂L(<i>μ</i>-OH)(OH)₂]⁺ species led to faster promoted HPNP hydrolysis rates than the [Zn₂L(OH)]³⁺ species. On the other hand, the observed rates of the Cu₂L-promoted HPNP hydrolysis reaction were much slower than those of the [Zn₂L]-promoted ones due to formation of the inactive, di-<i>μ</i>-OH⁻ bridged closed-form [Cu₂L(<i>μ</i>-OH)₂]²⁺ structure at high pH. The effects of solvent molecules and the use of higher DFT computation levels, i.e., M06 and M06–2X, in conjunction with cc-pVDZ and cc-pVTZ basis sets on the DFT-predicted structures for both [Cu(12N₄)(H₂O)]²⁺ and [Zn(12N₃O)(H₂O)₂]²⁺ complexes were also evaluated and compared with those using the B3LYP/6–31G* method.</p

Large-Scale Micro- and Nanopatterns of Cu(In,Ga)Se₂ Thin Film Solar Cells by Mold-Assisted Chemical-Etching Process

A reactive mold-assisted chemical etching (MACE) process through an easy-to-make agarose stamp soaked in bromine methanol etchant to rapidly imprint larger area micro- and nanoarrays on CIGS substrates was demonstrated. Interestingly, by using the agarose stamp during the MACE process with and without additive containing oil and triton, CIGS microdome and microhole arrays can be formed on the CIGS substrate. Detailed formation mechanisms of microstructures and the chemical composition variation after the etching process were investigated. In addition, various microand nanostructures were also demonstrated by this universal approach. The microstructure arrays integrated into standard CIGS solar cells with thinner thickness can still achieve an efficiency of 11.22%, yielding an enhanced efficiency of ∼18% compared with that of their planar counterpart due to an excellent absorption behavior confirmed by the simulation results, which opens up a promising way for the realization of high-efficiency micro- or nanostructured thin-film solar cells. Finally, the complete dissolution of agarose stamp into hot water demonstrates an environmentally friendly method by the mold-assisted chemical etching process through an easy-to-make agarose stamp

Improved Efficiency of a Large-Area Cu(In,Ga)Se₂ Solar Cell by a Nontoxic Hydrogen-Assisted Solid Se Vapor Selenization Process

A nontoxic hydrogen-assisted solid Se vapor selenization process (HASVS) technique to achieve a large-area (40 × 30 cm²) Cu­(In,Ga)­Se₂ (CIGS) solar panel with enhanced efficiencies from 7.1 to 10.8% (12.0% for active area) was demonstrated. The remarkable improvement of efficiency and fill factor comes from improved open circuit voltage (<i>V</i>_oc) and reduced dark current due to (1) decreased interface recombination raised from the formation of a widened buried homojunction with n-type Cd_Cu participation and (2) enhanced separation of electron and hole carriers resulting from the accumulation of Na atoms on the surface of the CIGS film. The effects of microstructural, compositional, and electrical characteristics with hydrogen-assisted Se vapor selenization, including interdiffusion of atoms and formation of buried homojunction, were examined in detail. This methodology can be also applied to CIS (CuInSe₂) thin film solar cells with enhanced efficiencies from 5.3% to 8.5% (9.4% for active area) and provides a facile approach to improve quality of CIGS and stimulate the nontoxic progress in the large scale CIGS PV industry