Gold Nanoshell Bioconjugates Used for Molecular Imaging in Living Cells
- PDF / 263,593 Bytes
- 2 Pages / 612 x 792 pts (letter) Page_size
- 114 Downloads / 211 Views
RESEARCH/RESEARCHERS
Organic Photodiodes Deposited on Newspaper Organic semiconductors have received significant interest recently and are under serious consideration for use in flexible electronics on a wide variety of substrates. In particular, organic photodiodes have seen rapid improvements in properties and performance. In a recent study, B. Lamprecht and co-workers at Günther Leising’s Institute of Nanostructured Material and Photonics in Weiz, Austria, a division of Joanneum Research, have demonstrated the fabrication and characterization of organic photodiodes deposited on ordinary newspaper sheets. They reported their results in the April issue of Physica Status Solidi A (p. R50; DOI: 10.1002/pssa.200510010). The paper samples, taken from the German newspaper Die Zeit, were mounted on glass substrates during the fabrication process. The newspaper substrates were coated with a parylene C barrier layer (5–10 µm thick), which is an effective chemical and moisture barrier. Since the newspaper surface is rough, and the parylene coating does not provide a smoothing effect, an ORMOCER coating, which is a new class of silicate-based inorganic– organic hybrid polymer materials, was applied. The ORMOCER coating, ~100 µm thick, provided surface planarization and was inert to subsequent depositions of metal and organic layers. The rms surface roughness at this point was less than 3 nm. The organic charge-generating layers were then deposited, sandwiched between a 55-nm-thick gold bottom electrode and a 25-nm-thick semitransparent silver top electrode. The fabricated organic photodiode, similar to the well-understood Tang-type pn-heterojunction device, consisted of a p-type conducting copper phthalocyanine (CuPc) and an n-type perylene tetracarboxylic bisbenzimidazole. The organic and metal layers were deposited using room-temperature, high-vacuum sublimation. The fabricated devices were removed from the glass substrates prior to characterization. The current–voltage characteristics of the devices were measured in the dark and under illumination using a halogen lamp, with white light passing through the semitransparent Ag electrode. In the dark, the devices showed a well-pronounced rectification ratio of about 104 at ±1 V. On illumination, the devices yielded a photocurrent exceeding the dark current by about six orders of magnitude when operated near a zero bias condition. No hysteresis effect was observed. The photodiodes yielded very good diode behavior. Also, in order to determine the spectral re418
sponse of the device, measurements of spectrally resolved external quantum efficiency were carried out using a tungsten halogen lamp and a monochromator. The devices yielded a spectral response covering the complete ultraviolet and visible light range. The researchers said that although newspaper was used as an example, from a wider perspective, this study demonstrated that organic photodiode devices may likely be fabricated on almost any user-defined substrate. GOPAL RAO
Al-Based Tunnel Junctions Form Solid-State Re
Data Loading...
