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Thin film organic position sensitive detectorsRelated Patent Categories: Active Solid-state Devices (e.g., Transistors, Solid-state Diodes), Organic Semiconductor MaterialThin film organic position sensitive detectors description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070176165, Thin film organic position sensitive detectors. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application is a continuation of U.S. application Ser. No. 10/607,211, filed Jun. 25, 2003, which claims priority to Provisional Patent Application Ser. No. 60/454,836, filed Mar. 14, 2003, herein incorporated by reference. The contents of those applications are incorporated herein in their entirety by reference. RESEARCH AGREEMENTS [0003] The claimed invention was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university corporation research agreement: Princeton University, The University of Southern California, and Universal Display Corporation. The agreement was in effect on and before the date the claimed invention was made, and the claimed invention was made as a result of activities undertaken within the scope of the agreement. FIELD OF THE INVENTION [0004] The present invention relates to position sensitive detectors and more particularly to organic thin film photosensitive optoelectronic devices used as a high-resolution position sensitive detector. BACKGROUND OF THE INVENTION [0005] Optoelectronic devices rely on the optical and electronic properties of materials to either produce or detect electromagnetic radiation electronically or to generate electricity from ambient electromagnetic radiation. Photosensitive optoelectronic devices convert electromagnetic radiation into electricity. Solar cells, also known as photovoltaic (PV) devices, are specifically used to generate electrical power. PV devices are used to drive power-consuming loads to provide, for example, lighting, heating, or to operate electronic equipment such as computers or remote monitoring or communications equipment. These power generation applications also often involve the charging of batteries or other energy storage devices so that equipment operation may continue when direct illumination from the sun or other ambient light sources is not available. As used herein the term "resistive load" refers to any power consuming or storing device, equipment or system. [0006] Traditionally, photosensitive optoelectronic devices have been constructed of a number of inorganic semiconductors, e.g. crystalline, polycrystalline and amorphous silicon, gallium arsenide, cadmium telluride and others. Herein the term "semiconductor" denotes materials that can conduct electricity when charge carriers are induced by thermal or electromagnetic excitation. The term "photoconductive" generally relates to the process in which electromagnetic radiant energy is absorbed and thereby converted to excitation energy of electric charge carriers so that the carriers can conduct, i.e., transport, electric charge in a material. The terms "photoconductor" and "photoconductive material" are used herein to refer to semiconductor materials which are chosen for their property of absorbing electromagnetic radiation of selected spectral energies to generate electric charge carriers. Solar cells are characterized by the efficiency with which they can convert incident solar power to useful electric power. Devices utilizing crystalline or amorphous silicon dominate commercial applications and some have achieved efficiencies of 23% or greater. However, efficient crystalline-based devices, especially of large surface area, are difficult and expensive to produce due to the problems inherent in producing large crystals without significant efficiency-degrading defects. On the other hand, high efficiency amorphous silicon devices still suffer from problems with stability. Present commercially available amorphous silicon cells have stabilized efficiencies between 4 and 8%. [0007] Recently, organic materials have attracted considerable interest for use in photovoltaic cells and photodetectors. (C. W. Tang, "Two-layer organic photovoltaic cell," Appl. Phys. Lett., vol. 48, no. 2, pp. 183-185, January 1986; P. Peumans and S. R. Forrest, "Very-high-efficiency double-heterostructure copper phthalocyanine/C.sub.60 photovoltaic cells," Appl. Phys. Lett., vol. 79, no. 1, pp. 126-128, July 2001; P. Peumans, V. Bulovic, and S. R. Forrest, "Efficient, high-bandwidth organic multilayer photodetectors," Appl. Phys. Lett., vol. 76, no. 26, pp. 3855-3857, June 2000, each of which are herein incorporated by reference.) [0008] The ability to make large area, ultrathin devices due to a small optical absorption length of .about.500 .ANG. in the visible spectrum and the ability to obtain acceptable photovoltaic conversion efficiencies with economical production costs are among many reasons for interest in these devices. In addition, their compatibility with rugged, conformable, or flexible substrates opens up many applications that cannot be addressed using other conventional detector technologies. A typical known photovoltaic device configuration is the organic bilayer cell. In the bilayer cell, charge separation predominately occurs at the organic hetero-junction. The built-in potential is determined by the HOMO-LUMO energy levels for such a hetero-junctions produce a gap offset between the donor and acceptor layers and produce an electric field around the donor/acceptor interface. [0009] Position sensitive detectors (PSDs) are an important class of photodetectors that use the lateral photoeffect to detect the position of a focused incident light beam. (J. T. Wallmark, "A new semiconductor photocell using lateral photoeffect," Proc. IRE, vol. 45, no. 4, pp. 474-483, April 1957.) Position sensitive detectors are commonly used in robotic vision, machine tool alignment, and guidance system applications. [0010] PSDs are commonly configured as photodetector arrays fabricated from silicon. A disadvantage of this configuration is the inability to continuously detect a signal without their resolution being limited by detector size. This problem can be overcome by configuring a thin film one dimensional PSD, which has the further advantage of requiring only two outputs, whereas arrays require data output from each detector. [0011] Hydrogenated amorphous silicon (a-Si:H) films have been widely studied for use in large-area PSDs. (S. Arimoto, H. Yamamoto, H. Ohno, and H. Hasegawa, "Hydrogenated amorphous silicon position sensitive detector," J. Appl. Phys., vol. 57, no. 10, pp. 4778-4782, May 1985; E. Fortunato, G. Lavareda, R. Martins, F. Soares, and L. Fernandes, "Large-area 1 D thin-film position-sensitive detector with high detection resolution," Sensor Actuat. A: Phys., vol. 51, no. 2-3, pp. 135-142, February 1996; J. Henry and J. Livingstone, "Thin-film amorphous silicon position-sensitive detectors," Adv. Mater., vol. 13, no. 12-13, pp. 1023-1026, July 2001.) [0012] The a-Si:H films are advantageous over previously used crystalline silicon since they can be made at lower cost and with higher surface area than the crystalline PSDs, however, the size limitation and fabrication cost of a-Si:H films still substantially limits the usefulness of silicon-based PSDs. [0013] A biological substrate, bacteriorhodopsin, has been used to create a motion sensitive detector which can measure the position of a moving light stripe over a film of a protein treated with a high-pH buffer by changes in the photocurrent response. (K. Fukuzawa "Motion-sensitive position sensor using bacteriorhodopsin" Applied Optics vol. 33 no. 31, pp. 7489-7495, November 1994.) [0014] However, this device is limited to having a single biological material that must be buffered with a high pH, and has a low spatial resolution (approximately +1 mm error) which decreases with increased width of the detector which make this device unusable for many applications. [0015] The advantage of using organic thin film PSDs over those fabricated from photodetector arrays is the ability to continuously detect a signal without their resolution being limited by detector size. Furthermore, a thin film one-dimensional PSD requires only two outputs, whereas arrays require data output from each detector. [0016] Therefore, it would be advantageous to provide an organic hetero-junction PSD (OPSD) with performance equal or superior to that found in many a-Si:H detectors, that can be produced as either a one dimensional PSD or a two dimensional PSD. This PSD would have a high operational bandwidth capable of tracking rapidly scanned optical beams, a resolution substantially similar to or better than the silicon-based detectors, and be produced more economically than existing PSDs. SUMMARY OF THE INVENTION [0017] The present invention is directed to organic photosensitive optoelectronic devices and methods of use for determining the position of a light source. Therefore, it is an object of the present invention to provide an organic position sensitive detector comprising: a first electrode, which is resistive and may be either an anode or a cathode; a first contact in electrical contact with the first electrode; a second contact in electrical contact with the first electrode; a second electrode disposed near the first electrode; a donor semiconductive organic layer disposed between the first electrode and the second electrode; and an acceptor semiconductive organic layer disposed between the first electrode and the second electrode and adjacent to the donor semiconductive organic layer. A hetero-junction is located between the donor layer and the acceptor layer, and at least one of the donor layer and the acceptor layer is light absorbing. [0018] More specifically, it is an object of the present invention to provide a OPSD where the donor semiconductive organic layer comprises copper phthalocyanine (CuPc) and the acceptor semiconductive organic layer comprises 3,4,9,10-perylenetetracarboxylic-bis-benzimidazole (PTCBI). It is a still more specific object of the present invention to provide an OPSD with an exciton-blocking layer that may comprise 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP). The OPSD may comprise a polymer layer such as a 3,4-polyethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) layer. In a preferred embodiment, the OPSD has an optical beam spatial resolution of less than 50 .mu.m, 30 .mu.m, or more preferably 20 .mu.m. [0019] Yet another object of the current invention is to provide a method of determining the position of incident radiation comprising: obtaining an OPSD such as the OPSD described hereinabove, placing the OPSD in the path of the incident radiation; and measuring a current at the first contact and a current at the second contact, wherein the currents are used to determine the position of the incident radiation. BRIEF DESCRIPTION OF THE DRAWINGS [0020] The foregoing and other features of the present invention will be more readily apparent from the following detailed description of exemplary embodiments taken in conjunction with the attached drawings. It will be noted that for convenience all illustrations of devices show the height dimension exaggerated in relation to the width. Continue reading about Thin film organic position sensitive detectors... 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