The effects of a strain relief layer (SRL) employed in the InGaN/GaN light-emitting diodes (LEDs) was demonstrated. The wavelength shift was reduced to as small as 2.5 nm by inserting a SRL between n-GaN and InGaN/GaN multiple quantum wells (MQWs). For the improvement of optical properties, a proper Si-doped layer was simultaneously added in the last several barriers of In0.08Ga0.92N/GaN SRL. It can be found that the output power was increased more than 25% as the Si doping level was increased up to 5 times in the last three barriers of SRL at an injection current of 20 mA. Furthermore, the forward voltages at 20 mA were almost the same for all LEDs with different doping levels and positions.

Well-dispersed gold nanodumbbells (GNDs) in an aqueous phase have been successfully fabricated by an electrochemical method using a micelle template formed by two surfactants with the addition of acetone solvent during electrolysis, the primary surfactant being cetyltrimethylammonium bromide (CTABr) and the cosurfactant being tetradecyltrimethylammonium bromide (TTABr). The role of acetone solvent is found to change the gold nanoparticles' shape from a rod to a dumbbell. The shape of the GNDs is fatter at the two ends and thinner in the middle section. The GNDs have been determined to be pure gold with a single-crystalline face-centred cubic (FCC) structure from selected area electron diffraction (SAED) patterns. Morphology features of GNDs in cross-section have also been investigated by dark field (DF) transmission electron microscopy (TEM) images. These GNDs exhibit octagonal structure in cross-section and an aspect ratio of around 3.

In this study, we prepared different shapes of gold nanoparticles by seed-mediated growth method and applied them on the photoelectrodes of dye-sensitized solar cells (DSSCs) to study the surface plasma resonant (SPR) effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells. The analyses of field emission scanning electron microscopy show that the average diameter of the spherical gold nanoparticles is 45 nm, the average length and width of the short gold nanorods were 55 and 22 nm, respectively, and the average length and width of the long gold nanorods were 55 and 14 nm, respectively. The aspect ratio of the short and long gold nanorods was about 2.5 and 4, respectively. The results of ultraviolet–visible absorption spectra show that the absorption wavelength is about 540 nm for spherical gold nanoparticles, and the absorption of the gold nanorods reveals two peaks. One is about 510 to 520 nm, and the other is about 670 and 710 nm for the short and long gold nanorods, respectively. The best conversion efficiency of the dye-sensitized solar cells with spherical gold nanoparticles and short and long gold nanorods added in is 6.77%, 7.08%, and 7.29%, respectively, and is higher than that of the cells without gold nanoparticles, which is 6.21%. This result indicates that the effect of gold nanoparticles on the photoelectrodes can increase the conductivity and reduce the recombination of charges in the photoelectrodes, resulting in the increase of conversion efficiency for DSSCs. In addition, the long gold nanorods have stronger SPR effect than the spherical gold nanoparticles and short gold nanorods at long wavelength. This may be the reason for the higher conversion efficiency of DSSCs with long gold nanorods than those of the cells with spherical gold nanoparticles and short gold nanorods.

In this work, we investigate the metal organic chemical vapor deposition (MOCVD) growth of GaAsN/InGaAs straincompensated superlattice cells in view of their application in solar cells. The compressive strain in InGaAs layers is matched by the tensile strain in GaAsN layers, overcoming the lattice-mismatch limitation. GaAsN/InGaAs strained layer superlattice cells, lattice-matched to GaAs, are proposed to extend the long-wavelength absorption of the bottom cell in a cascade solar cell structure. A strain-compensated superlattice solar cell with 0.6 mm GaAsN/InGaAs incorporated in the intrinsic region of p-in GaAs cells was fabricated. Compared with the fabricated InGaAs and InGaNAs cells, it was found that the GaAsN/ InGaAs superlattice cell can lower the band gap energy and extend the absorption the most, followed by the InGaAs cell. In addition, the efficiency of the GaAsN/InGaAs superlattice cell was 4.3%, which is comparable to that of the InGaNAs cell. The GaAsN/InGaAs strain-compensated superlattice structure shows many characteristics required to make it a candidate for the next-generation multijunction solar cells, which means this design can be used as the third junction of future-generation ultrahigh-efficiency three-and four-junction devices.

The conductivity of poly(3,4-thylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) films by adding various molar concentrations of sulfuric acid (H2SO4) was improved and studied in this paper. The sheet resistance of the doped PEDOT: PSS film was enhanced with increasing the ratio of H2SO4, but it drops after the maximum sheet resistance. The reason for this phenomenon is resulting from the fact that the H2SO4preferentially react with the sorbitol which is so-called the pinacol rearrangement. The nonconductive anions of some PSS−were substituted by the conductive anions of hydrogen sulfate (HSO4-) when the residual H2SO4reacted with PSS. In addition to the substitution reaction, PEDOT chains were increasingly aggregated with increasing the ratio of H2SO4. After doped H2SO4, the sheet resistance of H2SO4-doped PEDOT: PSS film is improved nearly 36%; the surface roughness is reduced from 1.268 nm to 0.822 nm and the transmittance is up to 91.9% in the visible wavelength range from 400 to 700 nm.