Method for Estimating the Charge Density Distribution on a Dielectric Surface

High-quality color output from digital photocopiers and laser printers is in strong demand, motivating attempts to achieve fine dot reproducibility and stability. The resolution of a digital photocopier depends on the charge density distribution on the organic photoconductor surface; however, directly measuring the charge density distribution is impossible. In this study, we propose a new electron optical instrument that can rapidly measure the electrostatic latent image on an organic photoconductor surface, which is a dielectric surface, as well as a novel method to quantitatively estimate the charge density distribution on a dielectric surface by combining experimental data obtained from the apparatus via a computer simulation. In the computer simulation, an improved three-dimensional boundary charge density method (BCM) is used for electric field analysis in the vicinity of the dielectric material with a charge density distribution. This method enables us to estimate the profile and quantity of the charge density distribution on a dielectric surface with a resolution of the order of microns. Furthermore, the surface potential on the dielectric surface can be immediately calculated using the obtained charge density. This method enables the relation between the charge pattern on the organic photoconductor surface and toner particle behavior to be studied; an understanding regarding the same may lead to the development of a new generation of higher resolution photocopiers.

Evaluation of Optoelectronic Performance of Four Organic Photo Detectors Structures

Organic photosensor made of poly [N-9′′-heptadecanyl-2,7-carbazole-alt-5,5-(4′, 7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) are promising candidates for bio-sensing applications. This paper investigates the optoelectronic characteristics of 4 different structures through simulation, utilizing PCDTBT as the active absorption layer. The scheme 1 is formed by placing the PCDTBT layer on top of a SiO2layer, and then interdigitated electrodes made of aluminium are placed onto PCDTBT. As to the scheme 2, the semiconductor layer is placed between an aluminium layer (bottom) and glass (top) layer coated with thick transparent interdigitated electrodes made of indium tin oxide (ITO). Regarding to scheme 3, layers from bottom to top are SiO2, cathode, PCDTBT and anode. Cathode has the same area as SiO2and PCDTBT layers, but anode covers only partial of the semiconductor. Finally, in the scheme 4, the semiconductor layer is also placed over SiO2layer but here the anode and cathode are limiting the PCDTBT layer sides, having the same area for both sides. All schemes have same volume of semiconductor. The simulations have been realized in dark conditions and under light intensities 100 mW/cm2in the wavelength range of 400-550 nm. The best results were obtained for scheme 2, organic photoconductor with Metal-Semiconductor-Metal structure. For in this scheme which is under the conditions of 2 V bias, 500 nm wavelength and 100 mW/cm2illumination, the photocurrent, the internal and external quantum efficiency obtained were 8.53 μA, 88% and 45% respectively. As a conclusion, the scheme 2 Glass/PCDTBT/Aluminium with transparent electrodes has reached high performance desirable for bio-sensing.

Charging and Discharging Phenomena in Organic Photoconductors Observed Using Electron Holography

The Phenomenon of Laser-Induced Discharging in an Organic Photoconductor Sample Was Directly Observed Using Electron Holography and Sophisticated Techniques for In Situ Observations. Mechanical Friction Was Used to Induce Negative Tribocharges on the Surface of the Photoconductor Sample. the Observation of Equipotential Contour Lines (i.e., the Electric Potential Distribution) outside the Specimen Revealed that the Amount of Tribocharges Was Reduced by the Laser Exposure. Computer Simulations of the Equipotential Lines Provided Useful Information for Evaluating the Quantity of Tribocharges.

Theory Study of the Geometrical Isomerism Influence on Hole-Transport Material’s Residual Potential of Organic Photoconductive

Residual potential is a very important performance index of organic photoconductor (OPC). At present, research shows that the purity of charge transport material will seriously influence residual potential of OPC. But in past research we found that some OPC used charge transport material with very high purity still has very high residual potential. With quantum calculation and x-ray diffraction we found that some materials are optical isomer and some have cis-trans isomerism. So in order to improve performance of OPC we should separate isomerism.