Current density–voltage (J-V) characteristics of hole-only devices using indium tin oxide (ITO) anode and N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) layers were measured with various thicknesses of a molybdenum trioxide (MoO3) buffer layer inserted between ITO and α-NPD. The device with a 0.75-nm-thick MoO3 layer forms Ohmic hole injection at the ITO∕MoO3∕α-NPD interfaces and J-V characteristics of this device are controlled by a space-charge-limited current. Results of X-ray photoelectron and ultraviolet/visible/near-infrared absorption studies revealed that this Ohmic hole injection is attributable to an electron transfer from ITO and α-NPD to MoO3.

The authors report the systematic control of $V_{\mathrm{oc}}$ as a function of the film thickness of molybdenum trioxide $\left(\mathrm{Mo}{\mathrm{O}}_3\right)$ buffer layer in the organic solar cells. The open-circuit voltage $\left(V_{\mathrm{oc}}\right)$ increased from $0.57\text{to}0.97\mathrm{V}$ as the thickness of $\mathrm{Mo}{\mathrm{O}}_3$ film is increased from $0\text{to}50\mathrm{nm}$ in the device structure of indium-tin-oxide $\left(\mathrm{ITO}\right)∕\mathrm{Mo}{\mathrm{O}}_3$ $\left(x\mathrm{nm}\right)$ /tetraphenylporphine $\left(10\mathrm{nm}\right)∕{\mathrm{C}}_{60}$ $\left(40\mathrm{nm}\right)$ /bathocuproine $\left(10\mathrm{nm}\right)∕\mathrm{Ag}$ $\left(100\mathrm{nm}\right)$ . The values between $V_{\mathrm{oc}}$ and the ionization potential $\left(I_p\right)$ of $\mathrm{Mo}{\mathrm{O}}_3$ $\left(x\mathrm{nm}\right)$ on ITO exhibit linear relationship, where the $I_p$ values change from $4.92\text{to}5.92\mathrm{eV}$ as they increase from $0\text{to}50\mathrm{nm}$ . The enhancement of $V_{\mathrm{oc}}$ was achieved without affecting short-circuit current density and fill factor. Consequently, the power conversion efficiency of the device increases from 1.24% to 1.88% primarily due to the increase in $V_{\mathrm{oc}}$ .

Supramolecular nanorods of 5,15-diaryl-substituted porphyrins prepared by sonication method exhibit a broad absorption property, which is confirmed by photocurrent generation measurement in a photoelectrochemical cell.

A blue phosphorescent organic light emitting device fabricated under the ultra high vacuum (UHV) condition of 6.5 × 10⁻⁷ Pa decreases the initial luminance drop upon lifetesting under a constant dc current of 15 mA/cm² by 3 times compared to a device fabricated under a high vacuum (HV) condition of 7.6 × 10⁻⁶ Pa resulting in a 23% increase in half lifetime. We calculate a water content of 10⁻⁴ mol. % in the UHV device emissive layer (EML) and 10⁻² mol. % in the HV device EML. We discuss the effects of water on luminance loss and voltage rise for the devices.