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The catalytic solid-phase synthesis of self-organized nanoporous tin sulfide (SnS) with enhanced absorption, manipulative transmittance and depolarization features is demonstrated. Using an ultralow radio-frequency (RF) sputtering power, the variation of the orientation angle between the anodized aluminum oxide (AAO) membrane and the axis of the sputtered ion beam detunes the catalytically synthesized SnS from nanorod to nanoporous morphology, along the sidewall of the AAO membrane. The ultraslow catalytic sputtering synthesis on the AAO at the RF plasma power of 20 W and the orientation angle of 0° regulates the porosity and integrality of nanoporous SnS, with average pore diameter of 80-150 nm. When transferring from planar to nanoporous structure, the phase composition changes from SnS to SnS2-Sn2S3, and the optical bandgap shrinks from 1.43 to 1.16 eV, due to the preferred crystalline orientation, which also contributes to an ultralow reflectance of1% at 200-500 nm when both the transmittance and the surface scattering remain at their maxima. The absorption coefficient is enhanced by nearly one order of magnitude with its minimum of5 × 10(4) cm(-1) at the wavelength between 200 and 700 nm, due to the red-shifting of the absorption spectrum to at least 100 nm. The catalytically self-organized nanoporous SnS causes strong haze and beam divergence of 20°-30° by depolarized nonlinear scattering at the surface, which favors the solar energy conversion with reduced surface reflection and enhanced photon scattering under preserved transmittance.

To meet the demand of all-optical data processing applications, the SiNx layer with enriching Si quantum dots (Si-QDs) for achieving strong optical nonlinearity is demonstrated with its χ(3) coefficient enhanced by three orders of magnitude larger than that of stoichiometric Si3N4. With excessive Si concentration enriched from 16.3% to 23.4%, the dense Si-QDs apparently self-assemble in the SiNx matrix with an average size of ∼0.95 nm and volume density of 5 × 1019 # cm−3. The Si-QD doped Si-rich SiNx not only enlarges its third-order nonlinear absorption coefficient from 0.01 to 1.8 m GW−1, but also increases its nonlinear refractive index from 5.7 × 10−13 to 9.2 × 10−12 cm2 W−1 at a wavelength of 800 nm, as attributed to the localized excitons with decreased effective Bohr radius in quantum confined Si-QDs. Such a SiNx:Si-QD material enables strong optical nonlinearity in compact nonlinear nanophotonic waveguide devices developed for future all-optical data processors.

Carrier injection and charge loss characteristics of nonvolatile memories with chemically-synthesized (CS) and vacuum-deposited (VD) gold nanoparticles (Au-NPs) have been investigated. Compared to CS counterparts, the memories with VD Au-NPs exhibit a higher dot density of 3.77 × 1011 cm−2, leading to a larger memory window. Further, the energy from valence-band edge to vacuum level (EVB_vac) of tunneling oxide for the samples with CS and VD Au-NPs is found to be 9.04 and 9.85 eV respectively. The small EVB_vac value of the memories with CS Au-NPs is resulted from the formation of a thin chemical oxide (SiOx) on thermally-grown SiO2 tunneling layer during the chemically synthesized process, contributing to a slow erasing behavior. Besides, the programming of the memories with VD Au-NPs is saturated at high gate bias, which has been well-explained by the electrons induced potential coupling between Au-NPs. Superior data retention property and high temperature dependence of charge loss are observed for the memories with CS Au-NPs, which can be ascribed to the thick tunneling oxide layer by the additional SiOx film.

All silicon-rich silicon carbide (Si-rich SixC1−x)-based single p–i–n junction photovoltaic solar cells (PVSCs) were fabricated by growing nonstoichiometric Si-rich SixC1−x films through medium-temperature hydrogen-free plasma enhanced chemical vapor deposition. The Si-rich SixC1−x-based thin-film p–i–n junction PVSCs exhibit improved power conversion efficiency when an intrinsic Si-rich SixC1−x absorbing layer with a low C/Si composition ratio is added; amorphous Si (a-Si) particles are embedded in this absorbing layer. Lowering the [CH4]/[CH4 + SiH4] fluence ratio from 0.5 to 0.3 reduces the C/Si composition ratio of Si-rich SixC1−x films from 0.74 to 0.665. The absorbance of these films in the visible light region (400–800 nm) is substantially enhanced to 3.8 × 105 cm−1 by reducing the [CH4]/[CH4 + SiH4] fluence ratio, which is up to one order of magnitude larger than that of crystalline Si. The open-circuit voltage and short-circuit current density of the indium tin oxide/p-SixC1−x/i-SixC1−x/nSixC1−x/Al PVSCs are enhanced to 0.51 V and to 19.7 mA cm−2, respectively, raising the conversion efficiency and filling factor to 2.24% and 0.264, respectively. Through hydrogen-free deposition of the Si-rich SixC1−x p–i–n cells on a-Si based p–i–n cells, Si-rich SixC1−x/a-Si hybrid tandem PVSCs exhibit enhanced conversion efficiency and an enhanced filling factor of 6.47% and 0.332, respectively.

Enhanced nonlinear refractive indices and absorption coefficients of nonstoichiometric SixC1−x with varying C/Si composition ratios from 0.51 to 1.83 grown by low-temperature plasma-enhanced chemical vapor deposition are demonstrated. When increasing the [CH4]/[CH4 + SiH4] fluence ratio from 70% to 92%, two Raman scattering signals at 795 and 970 cm−1 contributed by transverse and longitudinal optical modes of Si–C bonds are simultaneously enhanced in stoichiometric and C-rich SixC1−x samples, whereas the Si-associated Raman peak at 520 cm−1 decreases with increasing C/Si composition ratio. The C-rich SixC1−x film shows additional Raman scattering peaks at 1330 and 1580 cm−1, which are individually contributed by the diamond-like C–C bonds and the G peak of the graphite-like C–C bonds, respectively. The nonlinear refractive index increases to 1 ± 0.1 × 10−11 cm2 W−1 upon increasing the C/Si composition ratio up to 1.83, which is four orders of magnitude higher than that of bulk SiC. The increased C/Si composition ratio reduces the lattice constant and the effective mass of the SixC1−x film and enhances its nonlinear refractive index effectively. In comparison with the sp3-orbital C–C bond, the sp2-orbital C–C bond in SixC1−x films dominates the enhancement of nonlinear refractive index. By contrast, the nonlinear absorption coefficient changes sign and decreases magnitude when transferring the SixC1−x film from Si-rich to C-rich conditions. This sign reversal is primarily attributed to the conversion in the absorption mechanism from two-photon absorption to nonlinear saturable absorption. Unlike Si–Si bonds which favor two-photon absorption, the sp2-orbital C–C bonds with delocalized π-electrons essentially enhance the saturable absorbance. Hence, a higher nonlinear refractive index and a higher saturable absorption coefficient can be obtained by enriching the sp2-orbital C–C bonds in C-rich SixC1−x films.

The epitaxy of high-power gallium nitride (GaN) light-emitting diode (LED) on amorphous silicon carbide (a-SixC1−x) buffer is demonstrated. The a-SixC1−x buffers with different nonstoichiometric C/Si composition ratios are synthesized on SiO2/Si substrate by using a low-temperature plasma enhanced chemical vapor deposition. The GaN LEDs on different SixC1−x buffers exhibit different EL and C-V characteristics because of the extended strain induced interfacial defects. The EL power decays when increasing the Si content of SixC1−x buffer. The C-rich SixC1−x favors the GaN epitaxy and enables the strain relaxation to suppress the probability of Auger recombination. When the SixC1−x buffer changes from Si-rich to C-rich condition, the EL peak wavelengh shifts from 446 nm to 450 nm. Moreover, the uniform distribution contour of EL intensity spreads between the anode and the cathode because the traping density of the interfacial defect gradually reduces. In comparison with the GaN LED grown on Si-rich SixC1−x buffer, the device deposited on C-rich SixC1−x buffer shows a lower turn-on voltage, a higher output power, an external quantum efficiency and an efficiency droop of 2.48 V, 106 mW, 42.3% and 7%, respectively.

Graphene thin films have great potential to function as transparent electrodes in organic electronic devices, due to their excellent conductivity and high transparency. Recently, organic light-emitting diodes (OLEDs)have been successfully demonstrated to possess high luminous efficiencies with p-doped graphene anodes. However, reliable methods to fabricate n-doped graphene cathodes have been lacking, which would limit the application of graphene in flexible electronics. In this paper, we demonstrate fully solution-processed OLEDs with n-type doped multilayer graphene as the top electrode. The work function and sheet resistance of graphene are modified by an aqueous process which can also transfer graphene on organic devices as the top electrodes. With n-doped graphene layers used as the top cathode, all-solution processed transparent OLEDs can be fabricated without any vacuum process.

We demonstrate the fabrication of solution-processed MoOx-treated (s-MoOx) silver nanowire (AgNW) transparent conductive electrodes (TCEs) utilizing low-temperature (sub-100 °C) processes. The s-MoOx aggregates around the AgNW and forms gauze-like MoOx thin films between the mesh, which can effectively lower the sheet resistance by more than two orders of magnitude. Notably, these s-MoOx-treated AgNW TCEs exhibit a combination of several promising characteristics, such as a high and broad transmittance across a wavelength range of 400 to 1000 nm, transmission of up to 96.8%, a low sheet resistance of 29.8 ohm sq(-1), a low haze value of 0.90%, better mechanical properties against bending and adhesion tests, and preferable gap states for efficient hole injection in optoelectronic applications. By utilizing these s-MoOx-treated AgNW TCEs as the anode in ITO-free organic light emitting diodes, promising performance of 29.2 lm W(-1) and 10.3% external quantum efficiency are demonstrated. The versatile, multi-functional s-MoOx treatment presented here paves the way for the use of low-temperature, solution-processed MoOx as both a nanowire linker and a hole injection interfacial layer for future flexible optoelectronic devices.

We demonstrate an alternating current (AC)-driven organic light emitting diodes (OLED) with lithium fluoride (LiF) insulating layers fabricated using simple thermal evaporation. Thermal evaporated LiF provides high stability and excellent capacitance for insulating layers in AC devices. The device requires a relatively low turn-on voltage of 7.1 V with maximum luminance of 87 cd/m(2) obtained at 10 kHz and 15 Vrms. Ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy are employed simultaneously to examine the electronic band structure of the materials in AC-driven OLED and to elucidate the operating mechanism, optical properties and electrical characteristics. The time-resolved luminance is also used to verify the device performance when driven by AC voltage.