Sungm Cho

Tungsten trioxide (WO3) films with a mesoporous morphology, high transparency, and monoclinic phase crystallinity were prepared using polyethyleneglycol (PEG) as a surfactant and their photoelectrochemical properties were measured. By controlling the weight ratio of the tungsten precursor to PEG, a sphere-like WO3 nanoparticle film with high transparency can be synthesized. The photocurrent responses of the films under 1 sun solar light illumination were measured. Due to the high transparency of

Preventing reactive gas species such as oxygen or water is important to ensure the stability and durability of organic electronics. Although inorganic materials have been predominantly employed as the protective layers, their poor mechanical property has hindered the practical application to flexible electronics. The densely packed hexagonal lattice of carbon atoms in graphene does not allow the transmission of small gas molecules. In addition, its outstanding mechanical flexibility and optical

We have successively fabricated inverted bulk heterojunction polymer solar cells employing ZnO and MoO3as electron and hole selective layers, respectively. The device structure is ITO/ZnO/P3HT: PCBM/MoO3/Al. Differently from conventional polymer solar cells, ITO and Al work as electron and hole collecting electrodes in this inverted structure, respectively. We have found the optimal thickness of ZnO and MoO3 to be 100 nm and 5 nm, respectively. The highest PCE was obtained to be 3.32% under AM 1

An approximate solution of the Boltzmann transport equation is used to arrive at an expression for the electron energy distribution function. All major scattering mechanisms, including intervalley scattering, are included, and a distinction is made between nonpolar (Si, Ge) and polar (GaAs) optical phonon scattering. Numerically calculated impact ionization coefficients for electrons and holes in Ge, Si, and GaAs compare favorably with almost all experimental results reported in the literature.

Enhanced efficiency of white polymer light-emitting diodes (PLEDs) was observed by incorporating polysilicic acid (PSA) nanodots into the hole-injection layer (HIL). The PLEDs employed three different phosphorescent dyes in a single emissive layer with a host polymer of poly(vinylcarbazole) (PVK). The optimal composition of the phosphorescent dyes has been found to accomplish the white emission. By incorporating 1.5 wt% of PSA nanodots into the HIL, the maximum efficiency has been found to incre