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This study investigates the effect of chemical surface termination on the electrochemical characteristics of boron-doped diamond powder (BDDP). The aim is to realize highly sensitive electrochemical detection of ciprofloxacin (CIP) on BDDP-printed electrodes. To this end, we prepared oxygen-terminated BDDP (O-BDDP) and hydrogen-terminated BDDP (H-BDDP), and mixed them with an insulating polyester (PES) resin binder to obtain BDDP ink for the printed electrode. Scanning electron microscopy of the BDDP-printed electrodes revealed that the O-BDDPs were partially covered with PES resin, while the H-BDDPs were entirely covered with resin. This structural difference might explain the lower charge-transfer resistance of the Ru(NH3)62+/3+ redox reaction at the O-BDDP-printed electrode than at the H-BDDP-printed electrode. The slope of the calibration curve of the linear sweep voltammogram of CIP was steeper at the O-BDDP-printed electrode than at the H-BDDP-printed electrode and the O-BDD thin-film electrode, and was similar to that at the H-BDD thin-film electrode. Using the O-BDDP-printed electrode, we determined the CIP in artificial buffer-diluted urine in the concentration range 1–30 μM with a recovery of 107%. We conclude that the O-BDDP-printed electrodes provide a highly sensitive and disposable electrochemical sensor for CIP detection.

Boron-doped diamond powder (BDDP) was prepared using various sizes of diamond powder (DP) core (300–2600 nm), and the electrochemical properties of a screen-printed electrode obtained using the BDD...

Organic solar cells were fabricated by stacking aromatic amine and C60 layers. The energy conversion efficiency of these solar cells was low because of poor photoabsorption by these layers and short diffusion length of excitons. However, the photocurrent density was increased by about 3 times by the application of heat treatment to the stacked organic layers at 140 °C, and the maximum energy conversion efficiency reached 1.1 % under AM 1.5, 100 mW cm–2 simulated solar light. The internal quantum efficiency of the photocurrent after the annealing reached about 45 %. When the aromatic amine layer was about 100 nm thick, the organic layers after the annealing showed a wrinkled structure under an optical microscope. The annealing temperature needed for the formation of this structure was in good agreement with the temperature needed for the increase in the photocurrent. The morphological change caused by the annealing was attributed to infiltration of the amorphous aromatic amine compound into grain boundaries of the microcrystalline C60 layer, resulting in expansion of the C60 layer and the wrinkled structure of the organic layers. From observation by electron microscopy, the mixed form of these two compounds near the interface was found to be suited to solar cells because the C60 and aromatic amine phases wedge each other in a direction normal to two electrodes. However, the annealing slightly lowered photovoltage of the solar cell. This effect was attributed to a partial contact of the C60 layer with a counter electrode through the aromatic amine layer.

The photo-active region in the solar cells consisting of Cu-phthalocyanine (CuPc) and perylene-derivative (PV) layers was determined by using exciton blocking layers (EBLs) inserted in these layers. The photocurrent density was low when the EBL was placed near the CuPc/PV interface. With the increase of the distance between the EBL and the CuPc/PV interface, the photocurrent increased. However, when the distance reached a certain value, it leveled off owing to the limited diffusion length of excitons. From the analysis of the relationship between the position of EBL and the photocurrent density, the photo-active regions in the CuPc and PV layers were estimated to be 8 and 12 nm thick from the interface, respectively.

Photocurrent–voltage characteristics for organic solar cells with a heterojunction formed between copper phthalocyanine and a perylene derivative (or C60) were studied. The photocurrent was observed under both reverse and forward biases. From the analysis of the photocurrent action spectra, the origin of the reverse photocurrent was attributed to the excitons formed in both the organic layers, whereas that of the forward photocurrent was attributed to the excitons formed in the perylene derivative (or C60) layer. The photocurrent density under reverse bias increased at higher temperatures, suggesting that the charge recombination possibility was lowered at higher temperatures. On the basis of the time responses of the photocurrents observed after pulsed photoirradiation, the charge separation and transport processes are discussed.

The mechanism of photocurrent generation for organic solar cells with a heterojunction formed between metal phthalocyanine and C60 (or a perylene derivative) was studied. Photocurrent was observed under both reverse and forward biases. Under reverse biases, photocurrent action spectra showed that excitons generated in both organic layers contribute to photocurrent, whereas under forward biases, the excitons generated in only one of them contributed to photocurrent. Forward photocurrent was attributed to the electron transfer reaction between excitons and charge carriers accumulated at the organic/organic junction, the charge carriers depending on the rate of carrier injection from the electrodes. Forward photocurrent showed quantum efficiencies higher than 100% under very weak irradiation, and was attributed to current multiplication at the organic/electrode interface. Since this phenomenon is closely associated with the interfacial structure, it can be used as a measure of interface quality.

Organic solar cells were fabricated by stacking aromatic amine and C 60 layers. The energy conversion efficiency of these solar cells was low because of poor photoabsorption by these layers and short diffusion length of excitons. However, the photocurrent density was increased by about 3 times by the application of heat treatment to the stacked organic layers at about 140 °C, and the maximum energy conversion efficiency reached 1.1% under AM 1.5, 100 mW/cm 2 simulated solar light. The effect of the heat treatment was attributed to the infiltration of the amorphous aromatic amine compound into grain boundaries of the microcrystalline C 60 layer. From observation by electron microscopy, the mixed form of these two compounds near the interface was found to be suited to solar cells because the C 60 and aromatic amine phases wedge each other in a direction normal to two electrodes.

The effect of magnetic field on the intensity of electroluminescence from devices made of a poly-$p$-phenylenevinylene (PPV) copolymer was investigated. The emission intensity was enhanced by the application of magnetic field, and the magnitude of the increase depended on operational voltages. When the device was operated under application of low voltages, the intensity increased with magnetic field and reached an 8.5% increase at about $100\phantom{\rule{0.3em}{0ex}}\mathrm{mT}$. With the increase of the operational voltage, the effect of magnetic field was lessened. In addition, when measured at high voltages with increasing magnetic field, the emission intensity started to decrease after passing a maximum, then leveled off. This saturation value was slightly higher than that observed in the absence of magnetic field. These findings suggest that two processes sensitive to magnetic field are included in the emission processes. They are assigned to the charge recombination (CR) of anion and cation radicals and triplet-triplet annihilation (TTA) processes. From the analysis of the effects of magnetic field on the emission intensity based on a kinetic model, we quantitatively determined the fractions of singlet and triplet excitons generated through the CR process to be 0.17 and 0.83, respectively. With the increase of the concentration of triplet excitons in the organic layer, production of singlet excitons through the TTA process was enhanced, and the total yield of the singlet excitons exceeded 0.5 under normal device operational conditions. We conclude that this high yield is responsible for the high emission efficiency observed in the light-emitting devices based on PPVs.

Solid-state dye-sensitized solar cells (DSSCs), consisting of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] (MEHPPV) as a hole-transporting material, an indium tin oxide (ITO) electrode, and a titanium dioxide (TiO2) electrode, were studied with respect to the factors affecting their properties. The morphology of TiO2 electrodes, which was controlled by changing preparation conditions, affected the performance of solid-state DSSCs, and cells with a TiO2 electrode having a smooth surface showed better properties. The carrier transportation between the TiO2 layer and the MEHPPV layer was one of the most important factors that determined the overall efficiency of the solar cells. This carrier transportation process was improved by the addition of an interlayer consisting of potassium iodide (KI) and iodine (I2). In addition to improving the carrier transportation, this KI/I2 blend interlayer also improved the pore filling of the solid-state DSSC. By controlling these parameters, a solid-state DSSC was obtained, with a short-circuit current density of about 1.51 mA/cm2, an open circuit voltage of about 0.65 V, a fill factor of about 0.5, and an energy conversion efficiency of about 0.51%.

CuO x films were prepared on glass plates by the vacuum sublimation of Cu films followed by an oxygen-plasma treatment. These CuO x films showed a strong hole-injection ability and found to be applicable to organic light-emitting devices as anodes, although their optical transmittance and conductivity were slightly lower than those of indium–tin-oxide layers. The most important merit of employing the films as the anodes lies in that they are easily shaped in patterns by vacuum sublimation using shadow masks in device fabrication.