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Photosensitive Materials

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From 07/11/2014 through 4/14/2013

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3. A photodetector, PV device or related optoelectronic device is based on a junction formed by a pair of two different types of semiconductors (e.g., an n-type and a p-type material, or an electron acceptor and an electron donor material).  When a photon's energy is higher than the band gap value of the semiconductor, the photon can be absorbed in the semiconductor and the photon's energy excites a negative charge (electron) and a positive charge (hole).  For the excited electron-hole pair to be successfully utilized in an external electrical circuit, the electron and the hole must first be separated before being collected at and extracted by respective opposing electrodes.  This process is called charge separation and is required for photoconductive and photovoltaic effects to occur.  If the charges do not separate they can recombine and thus not contribute to the electrical response generated by the device.

Quantum efficiency, includes both external quantum efficiency (EQE) and internal quantum efficiency (IQE). EQE corresponds to the percentage of total incident photons that are converted to electrical current, and IQE corresponds to the percentage of total absorbed photons that are converted to electrical current.

Signal-to-noise (S/N) ratio is maximized by maximizing the EQE and minimizing the dark current.

Charge carrier mobility describes the velocity of a charge carrier in the presence of an electric field.  A larger value of mobility means that charge carriers move more freely and can be extracted from the device more efficiently.

Exciton diffusion length is the average distance that an exciton (a bound electron-hole pair) will travel before the charge carriers recombine. In a photodetector or related device where excitons play a significant role, a larger value means that there is a higher probability that photogenerated excitons will reach a charge separation region prior to recombination, and also leads to a higher device performance as compared to a photodetector device with a lower exciton diffusion length.

Klem and Lewis, US Patent 8,742,398 (6/3/2014)

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2. “A photosensitive resin composition for use in a transflective LCD is required to meet processing characteristics for forming more complex and finer patterns than patterns of existing structures. Another requirement of the photosensitive resin composition is good adhesion to an underlying substrate while forming narrow patterns. In contrast, conventional photosensitive resin compositions cannot simultaneously meet the requirements for the adhesion to underlying substrates and the formation of high resolution fine patterns. That is, some conventional photosensitive resin compositions sacrifice adhesion to underlying substrates to form high resolution fine patterns. Some conventional photosensitive resin compositions with good adhesiveness have difficulty in forming high resolution patterns.” [Kim et al, US Patent 8,399,176 (3/19/2013)]

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1. “Chemicals that are photosensitive may undergo chemical reactions when exposed to light. These chemicals, such as hydrogen peroxide and many prescription drugs, are stored in tinted or opaque containers until they are needed to prevent photodegradation. Devices that are photosensitive include the human retina and photographic film; their photosensitive materials undergo a chemical reaction when struck by light”  (Photosensitive Materials, Wikipedia, 4/14/2013)

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Interested!!
Bookmark this page to follow future developments!.
(RDC 6/5/2012)

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Roger D. Corneliussen
Editor
www.maropolymeronline.com

Maro Polymer Links
Tel: 610 363 9920
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E-Mail: cornelrd@bee.net  

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Copyright 2013 by Roger D. Corneliussen.
No part of this transmission is to be duplicated in any manner or forwarded by electronic mail without the express written permission of Roger D. Corneliussen
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* Date of latest addition; date of first entry is 4/14/2013.