In order to enhance energy density, a hybrid type pseudocapacitor/electric double layer capacitor ͑EDLC͒ was considered and its electrochemical properties were investigated. At various current densities, stable charge/discharge behaviors were observed with much higher specific capacitance values of 530 F/g compared with that of EDLC ͑230 F/g͒, by introducing Ni͑OH͒ 2 as a cathode material. By using the modified cathode of a Ni͑OH͒ 2 /activated carbon composite electrode, the specific capacitance was less sensitive to charge/discharge current density exhibiting stable power characteristics.

The potential use of polymer light-emitting diodes is ultimately limited by their low quantum efficiency as well as by their poor stability due to oxygen. We report experiments on polymer light-emitting diodes made with poly(9,9′-dioctylfluorene)/gold nanocomposites to solve these drawbacks. Blue polymer light-emitting diodes with enhanced luminescent stability were obtained by incorporating 5-10-nm gold nanoparticles as the quenchers of the triplet states of blue emitting polymer. The nanocomposite light-emitting diodes exhibited an enhanced quantum efficiency due to the roughening of the surface onto which the Al cathode is deposited and to balanced charge injection.

This review discusses interfacial layers in organic photovoltaic devices. The first part of the review focuses on the hole extraction layer, which is located between a positive electrode and an organic photoactive material. Strategies to improve hole extraction from the photoactive layer include incorporation of several different types of hole extraction layers, such as conductive polymeric materials, self-assembled molecules and metal oxides, as well as surface treatment of the positive electrodes and the conductive polymeric layers. In the second part, we review recent research on interlayers that are located between a negative electrode and a photoactive layer to efficiently extract electrons from the active layer. These materials include titanium oxides, metal fluorides and other organic layers.

Efficient white‐light‐emitting diodes (WLEDs) have been developed using a polyfluorene‐type blue‐emitting conjugated polymer doped with green and red phosphorescent dyes. The emission spectrum of the conjugated polymer, which has a very high luminescent efficiency, shows a large spectral overlap with the absorbance of green and red iridium complexes. Also, efficient energy transfer from the conjugated polymer to the iridium complexes is observed. Poly(N‐vinyl carbazole) is used to improve the miscibility between conjugated polymer and iridium complexes because of their poor chemical compatibility and phase separation. A white emission spectrum is easily obtained by varying the contents of the three materials and controlling the phase morphology. Moreover, these WLEDs show a voltage‐independent electroluminescence owing to the threshold and driving voltage of the three materials being similar as a result of energy transfer.