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A novel hierarchical MoS2@SnO2 hetero-nanoflower was successfully synthesized by a facile, two-step hydrothermal method without using any additives or surfactants. One possible growth mechanism of the hetero-nanostructure was presented in detail based on OH-ion-dependent experimental facts. Due to the formation of the p-n junctions and the increased specific surface area in the composites, an outstanding photocatalytic activity of the as-prepared sample was obtained by monitoring the photodegradation of methylene blue (MB). According to the data, after irradiation for 100 min, the remaining MB in solution is about 26% for MoS2 nanoflowers and 9.5% for MoS2@SnO2 hetero-nanoflowers. Moreover, an excellent field-emission performance was obtained from MoS2@SnO2 hetero-nanoflower relative to the pure MoS2 with the turn-on field decreasing from 4.2 V μm-1 to 3.4 V μm-1 and the threshold field decreasing from 6.2 V μm-1 to 5.2 V µm-1, which is mainly attributed to the increased field-emission points and MoS2-SnO2 heterojunction. [ABSTRACT FROM AUTHOR]

Cu2O-TiO2-ZnO ternary nano-heteroarchitectures were designed and successfully fabricated using titanium (IV) oxideacetylacetonate (TiO(acac)2) as a precursor and polyethyleneimine (PEI) as a binding agent. Field emission and photocatalytic activities of pure Cu2O nanopines, Cu2O-TiO2 core-shell nanopines and Cu2O-TiO2-ZnO ternary composites were investigated and compared. The results revealed that the as-prepared nano-heterojunctions and nanoparticles at the surface remarkably enhanced the field emission and photocatalytic activities of pure Cu2O nanopines. The as-prepared nano-heterojunctions induced interfacial states and energy band differentials, which caused electron transition and the inhibition of photo-induced electron-hole pair recombination. The nanoparticles at the surface formed thousands of surface nano-protrusions and active sites for photocatalytic chemical reactions. [ABSTRACT FROM AUTHOR]

The optical properties of Al0.44Ga0.56N/Al0.59Ga0.41N multiple quantum well structures with an InxAl1-xN insertion layer between the barrier layer and the well layer are investigated by using the effective mass theory. The numerical results show the TE-dominated emission can be realized by using the InxAl1-xN insertion layer, which can be mainly attributed to the larger separation of the electron-hole wave-function for the TM-dominated transition. Note that the rearrangement of valence subbands is also an important factor to enhance the TE polarization emission for the InxAl1-xN insertion layer with the lower In-content. The ratios of TE-polarized total spontaneous emission rate between the InxAl1-xN insertion layer structures (x = 0.11, 0.13, 0.15) and the conventional structure can reach 1.76–2.05 in the current density range of 2–300 A cm−2 due to the larger product of Fermi–Dirac distribution functions of electron and hole. Furthermore, the InxAl1-xN insertion layer structures with x = 0.15–0.17 show the largest TE polarization emission. [ABSTRACT FROM AUTHOR]

The optical properties of the type-II lineup InxAl1−xN–Al0.59Ga0.41N/Al0.74Ga0.26N quantum well (QW) structures with different In contents are investigated by using the six-by-six K–P method. The type-II lineup structures exhibit the larger product of Fermi–Dirac distribution functions of electron and hole and the approximately equal transverse electric (TE) polarization optical matrix elements ( for the c1–v1 transition. As a result, the peak intensity in the TE polarization spontaneous emission spectrum is improved by 47.45%–53.84% as compared to that of the conventional AlGaN QW structure. In addition, the type-II QW structure with has the largest TE mode peak intensity in the investigated In-content range of 0.13–0.23. It can be attributed to the combined effect of and for the c1–v1, c1–v2, and c1–v3 transitions. [ABSTRACT FROM AUTHOR]

Temperature dependence of the optical properties of InGaN/GaN single quantum well light-emitting diodes (LEDs) with different indium (In) contents is investigated by using the effective mass theory taking into account the band-gap shrinkage and lattice thermal expansion. The peak intensity of the spontaneous emission spectrum is decreased by 30.6%, 30.4%, and 30.3% for the violet, blue, and green LEDs in the temperature range 300 K–400 K, while the reductions of internal quantum efficiency (η) with temperature are ~0.13, ~0.11, and ~0.1 respectively at the injection current density of 100 A cm−2. Moreover, two different slopes for all the η–T curves are observed: a lower absolute value of the slopes at T  =  300–350 K; a larger absolute value of the slopes at T  =  350–400 K. The numerical results also indicate that the efficiency droop effect with increasing the temperature becomes more serious, especially for the InGaN/GaN LED structures with the lower In-content. [ABSTRACT FROM AUTHOR]