Constructing (super)alkali–boron-heterofullerene dyads: an effective approach to achieve large first hyperpolarizabilities and high stabilities in M₃O–BC₅₉(M = Li, Na and K) and K@n-BC₅₉(n = 5 and 6)

Abstract

Using DFT methods, the electronic properties and the first hyperpolarizabilities of boron-heterofullerene-(super)alkali dyads: M3O-BC59 (M = Li, Na and K) and K@n-BC59 (n = 5 and 6) were systematically investigated. It is found that both M3O and K can effectively bind to BC59 with high binding energies (2.50-2.69 eV for K and 4.24-5.14 eV for M3O). The interaction between K and BC59 in K@n-BC59 is identified as primarily ionic in nature, whereas that between the superalkali M3O unit and BC59 becomes much stronger owing to the formation of a strong chemical bond (B-O bond). Moreover, compared with the sole parent cluster BC59 (619 au), both K@n-BC59 (n = 5 and 6) and M3O-BC59 (M = Li, Na and K), possess large first hyperpolarizabilities (β0), which are 3352, 2621 and 4921, 5440 and 7800 au, respectively, where the superalkali doped dyads (M3O-BC59) are much superior to the simple alkali exo-hedral species (K@n-BC59), and heavier superalkali can be more powerful in enhancing the β0 values of M3O-BC59. Clearly, these superalkali doped dyads M3O-BC59, formal donor-acceptor (DA) chromophores, exhibit not only excellent stability but also large first hyperpolarizability; therefore, they are expected to be potential candidates for excellent second-order NLO materials.

High efficiency bifacial Cu2ZnSnSe4 thin-film solar cells on transparent conducting oxide glass substrates

“…1(a) and 1(b) present cross-sectional SEM images of the metal precursors with thicknesses of 350 nm on the FTO and ITO substrates, respectively. Since a Cu-Sn alloy can be easily formed at room temperature due to the diffusion of Cu element during precursor deposition, 15 it is hard to observe each layer of Cu, Sn, and Zn on TCO substrate. Figs.…”

Intermetallic Layer Growth Kinetics in Sn‐Ag‐Cu System using Diffusion Multiple and Reflow Techniques

“…[46][47][48]56,57] The interfaces identified by the SEM/EDS measurements between the Cu and IMC, and between IMC themselves at any stage of the annealing are linear because the interfacial processes take place in the solid state and the Cu 3 Sn grows out of the Cu 6 Sn 5 phase. [9,[15][16][17] The exception is the interface between initially liquid solder and a Cu 6 Sn 5 layer (scallop-like morphology) formed during the early stage of annealing. [54,58,59] The scallop-type interface is an effect of the fast diffusion of Cu into the solder during reflow process (a process called liquid grooving) as well as solidification after the reflow process.…”

“…[13,16,26,28,31,44,47,49,58,[61][62][63][64] Activation energy, E A , values for the Cu 3 Sn growth in Cu|Sn multiples and reflow samples range from 22.4 and 94.54 kJ mol À 1 , respectively, and for Cu 6 Sn 5 from 9.1 to 69.3 kJ mol À 1 . The remarkable scatter of the activation energy values obtained by previous studies compared to this work may be caused by the difficulty of measuring an accurate layer thickness.…”

“…Wang et al [5] studied the microstructural evolution of Cu/Sn-Ag($5 mm)/Cu Cu-bump-on-line (CuBOL) joints during isothermal annealing at 180°C for up to 72 h. According to their work, both IMCs are formed at the interface during the early stages of the Cu/Sn liquid phase reaction. The formation of Cu 3 Sn takes place at the expense of Cu 6 Sn 5 [9,[15][16][17] ; its standard Gibbs energy of formation is lower (À 8.25 kJ mol À 1 ) than that of Cu 6 Sn 5 (À 7.00 kJ mol À 1 ) at room temperature. [18,19] Sunwoo et al [12] postulated that absence of a Cu 3 Sn phase at the Cu/Sn interface is due to the limited nucleation rate of this phase.…”

“…A marker study by Tu et al, [13] has proven that the diffusion of Cu is dominant in Cu 6 Sn 5 and Cu 3 Sn IMCs. Since most of the Kirkendall voids [16,[32][33][34][35][36] arise in close proximity of the Cu 3 Sn or directly at the interface, it was concluded that the main diffusing element is Cu, however the diffusion of Sn occurs as well. The diffusion multiples (DM) method enables the study of phase diagrams, kinetics, and composition-structure properties of bulk solids.…”