| 초록 |
An image sensor is a photoelectric conversion device using semiconductor materials used in cameras, photocopiers, and medical diagnostic devices. Currently, an image sensor uses a Si photodiode as a core conversion element for a unit pixel. However, in recent years, the demand for ultra-high-definition image sensors now requires sub-micron-sized image pixels, which cannot be realized with Si photodiodes. Since the Si photodiode has a low absorption coefficient for visible light due to an indirect band gap, an active layer of several μm, which is undesirable, must be formed thickly in order to secure a sufficient amount of light absorption. In addition, color filters are required to impart color selectivity to each pixel due to the chromatic absorptive properties of Si. Since the color filter itself absorbs the incident light to some extent, the quantum efficiency of the final device is greatly reduced. In addition, installing color filters expands the light path and increases the overall volume of the image sensor, reducing the integrity of the image pixels. Recently, organic semiconductors have been reported to replace the role of Si in the field of photodiodes in order to overcome the disadvantages of Si. Since the organic semiconductor absorbs light through the HOMO-LUMO transition of electrons, the absorption coefficient for the entire visible light is high, so that the thickness of the active layer can be made low thickness. Also, there is the potential for color-selective absorption for R/G/B because organic semiconductors can fine-tune the absorption range. This is a great advantage compared to Si as a photoactive layer in a photodiode because it does not require a color filter. In this work, we synthesized a donor with novel green selectivity. The general characteristics of the unit are its planar molecular structure, high atmospheric pressure stability and strong electron donating ability, all of which can be related to its excellent electrical properties. It has been found that with appropriate acceptor units and synthesis, it is possible to have a narrow absorption band for the green range. |
