Patent Application
20090294761
This application claims the benefit of Korean Patent Application No. 10-2008-0049678, filed on May 28, 2008, in the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
Disclosed herein is an organic photoelectric conversion film for an image sensor, and a photoelectric conversion device having the organic photoelectric conversion film.
2. Description of the Related Art
Photoelectric conversion devices convert light into an electrical signal using the photoelectric effect. Photoelectric conversion devices are widely used for various optical sensors for automobiles or in the home, or solar batteries, in particular for complementary metal-oxide semiconductor (CMOS) image sensors.
Photoelectric conversion films formed from an inorganic material are mainly used in commercial photoelectric conversion devices. However, since an inorganic photoelectric conversion film exhibits an inferior selectivity in relation to the wavelength of light, a CMOS image sensor using the inorganic photoelectric conversion film needs a color filter that decomposes incident light into red light, green light, and blue light. However, the use of the color filter generates a Moire defect and an optical low pass filter is therefore used to address this defect. The use of the optical filter causes degradation in the resolution of the device. As a result, research aimed at manufacturing a photoelectric conversion film using an organic material has recently been performed.
In general, a color filter, a microlens, and a photodiode are used as in commercially available photoelectric conversion devices for CMOS image sensors. This combination also produces problems in that the color filter generates a Moire defect and the compensating microlens reduces the amount of light arriving at the photodiode. To address these problems, the development of a photoelectric conversion device for a CMOS image sensor having a new structure without using the color filter, microlens, or photodiode is desirable.
Disclosed herein is an organic photoelectric conversion film having an improved n-type material layer, and a photoelectric conversion device and an image sensor, each having the organic photoelectric conversion film.
Disclosed herein too is an organic photoelectric conversion film including a p-type material layer formed of an organic material; and an n-type material layer formed on the p-type material layer, and formed of naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTCDA).
A co-deposition layer may be further formed between the p-type material layer and the n-type material layer, by co-depositing the organic material forming the p-type material layer and the NTCDA forming the n-type material layer.
The p-type material layer may be formed of at least one material selected from the group comprising phthalocyanine derivatives, triarylamine derivatives, bezidine derivatives, pyrazoline derivatives, styrylamine derivatives, hydrazine derivatives, carbazole derivatives, thiophene derivatives, pyrrole derivatives, phenanthrene derivatives, tetracence derivatives, perylene derivatives, and naphthalene derivatives.
Disclosed herein too is a photoelectric conversion device including a first electrode and a second electrode which are separated from each other; and an organic photoelectric conversion film formed between the first electrode and the second electrode, wherein the organic photoelectric conversion film includes a p-type material layer formed on the first electrode, and formed of an organic material; and an n-type material layer formed on the p-type material layer, and formed of NTCDA.
A buffer layer may be formed between the first electrode and the p-type material layer, or between the second electrode and the n-type material layer.
The first electrode may be formed of an optically transparent electrically conductive material including indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and tin oxide (SnO2). Also, the second electrode may be formed of a transparent conductive material, or a thin film metal including Al, Cu, Ti, Au, Pt, Ag, and Cr.
Disclosed herein too is an image sensor including a plurality of photoelectric conversion devices, wherein each of the plurality of photoelectric conversion devices includes a first electrode and a second electrode which are separated from each other; and an organic photoelectric conversion film formed between the first electrode and the second electrode, wherein the organic photoelectric conversion film includes a p-type material layer formed on the first electrode, and formed of an organic material; and an n-type material layer formed on the p-type material layer, and formed of NTCDA.
A plurality of photoelectric conversion devices may be stacked above and below each other on a substrate.
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. Like reference numerals in the drawings denote like elements. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present.
Referring to
The first electrode 110 may be an anode electrode. Such a first electrode 110 may be formed on a transparent substrate (not shown), which is formed of a glass or a plastic. The first electrode 110 may be formed of an optically transparent electrically conductive material. Here, examples of the transparent conductive material may be ITO, IZO, ZnO, SnO2 or a combination comprising at least one of the foregoing transparent conductive materials. The material used for the electrode is not limited to the foregoing list of materials and other electrically conductive materials can be used. For example, a thin metal can be used as the electrode. Similarly a thin layer of an electrically conducting polymer can also be used as the electrode. Suitable examples of electrically conducting polymers are polythiophenes, polypyrrole, polyaniline, or the like, or a combination comprising at least one of the foregoing electrically conductive polymers. The second electrode 120 may be a cathode electrode, and may be formed from the aforementioned optically transparent electrically conductive material or a thin metal. In the case where the second electrode 120 is formed of the metal, the second electrode 120 may be formed to have a thickness of approximately (hereinafter, “appx.”) 15 to 20 nanometer (nm). Examples of the metal used in the electrode may be Al, Cu, Ti, Au, Pt, Ag Cr, or the like, or a combination comprising at least one of the foregoing metals, but the present invention is not limited thereto.
The organic photoelectric conversion film is formed between the first electrode 110 and the second electrode 120. The organic photoelectric conversion film converts light into an electrical signal by using a photoelectric effect. Such an organic photoelectric conversion film includes a p-type material layer 112 formed on the first electrode 110, and an n-type material layer 114 formed on the p-type material layer 112. In the current embodiment, the n-type material layer 114 is formed of naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTCDA) that is a transparent organic material. Here, NTCDA that is an n-type material, generates and transports charge.
The p-type material layer 112 may be formed of phthalocyanine which can absorb light having the wavelength of visible light (appx. 550 to 700 nm).
In addition to phthalocyanine, the p-type material layer 112 may be formed of at least one of phthalocyanine derivatives, triarylamine derivatives, bezidine derivatives, pyrazoline derivatives, styrylamine derivatives, hydrazine derivatives, carbazole derivatives, thiophene derivatives, pyrrole derivatives, phenanthrene derivatives, tetracence derivatives, perylene derivatives, naphthalene derivatives, or a combination comprising at least one of the foregoing, depending on the absorbing wavelength required. However, the present invention is not limited thereto, and other various materials may be used for the p-type material layer 112.
A buffer layer (not shown) may be further formed between the first electrode 110 and the p-type material layer 112, or between the second electrode 120 and the n-type material layer 114. Here, the buffer layer enables charge to be more easily transported. The buffer layer may be formed of a charge transport material (e.g., an aryl compound, and the like), which is generally used in organic light emitting diodes (OLED). The photoelectric conversion device according to the current embodiment of the present invention uses NTCDA as the n-type material, so that a quantum efficiency may be improved. A description thereof will be described later.
Referring to
The photoelectric conversion device of
The photoelectric conversion devices having the aforementioned structures were each manufactured using the following methods. First, a glass substrate on which an ITO electrode was formed is cleaned using water and ultrasonic sonication, and then cleaned using methanol and acetone. After that, oxygen plasma processing was performed on a surface of the glass substrate. After that, an organic layer (deposition speed: 2 Å/sec) (either the n-type material or the p-type material or both) and a metal electrode (deposition speed: 5 Å/sec) were successively deposited on the ITO electrode, under a 1×10−5 Torr pressure, by using a thermal evaporator. Here, NTCDA was used as the n-type material, and phthalocyanine was used as the p-type material.
In order to measure electrical features of such manufactured photoelectric conversion devices, forward bias or reverse bias was applied to the photoelectric conversion devices, when monochromatic light was irradiated on the first electrode 110 (see
Referring to
According to the aforementioned results, it is possible to see that the photoelectric conversion device having the improved quantum efficiency may be realized when NTCDA is used as the n-type material. Meanwhile, unlike
The photoelectric conversion device described herein may be widely used for various optical sensors for automobiles or in the home, or solar batteries. In particular, it may be used for a CMOS (complementary metal-oxide semiconductor) image sensor. By applying a plurality of photoelectric conversion devices to the CMOS image sensor, high quality image can be realized. Here, the plurality of photoelectric conversion devices forming the CMOS image sensor may be stacked in a vertical direction with respect to a substrate (that is, stacked above and below each other on the substrate). For each of the plurality of photoelectric conversion devices, the p-type material capable of absorbing light in a predetermined wavelength range is used. For example, when a photoelectric conversion device, which uses phthalocyanine (that has an absorbing wavelength area of about 550 to about 700 nm) as the p-type material, is positioned below other photoelectric conversion devices, the photoelectric conversion device can be used as a pixel, which absorbs red light. In this manner, by manufacturing such a CMOS image sensor in which the plurality of photoelectric conversion devices are arranged stacked in the vertical direction, image quality with higher definition can be realized, compared to a conventional CMOS image sensor.
While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The exemplary embodiments should be considered in a descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2008-0049678 | May 2008 | KR | national |
