半導体デバイスはシリコンに代表されるような無機固体材料によって構成されているものが一般的ですが、近年有機材料を半導体として用いたデバイスが注目を集めています。有機半導体材料は印刷や蒸着といったシンプルなプロセスで成膜することが可能であり、0.1ミクロンオーダーの薄膜で機能するため、フィルムや極薄ガラス上に素子形成を行うことで、薄い、軽い、曲げられるといった自由度の高いデバイスを実現することが可能です。
当社では、センサとして用いる有機受光素子(organic photodiode: OPD)および光源として用いる有機発光素子(organic light-emitting diode: OLED)といった光学デバイスの研究を行っています。
図1. 有機半導体デバイス
図2. OPDおよびOLEDの動作原理
有機デバイスの基本的な構造は、受光、発光いずれのデバイスも有機半導体材料を電極で挟み込んだサンドイッチ構造となっています。OPDの場合は電子供与性(ドナー型)、電子受容性(アクセプター型)の2種の有機分子が含まれており、それらの分子に光が吸収された後、ドナー-アクセプター分子界面に励起状態が移動することで電荷分離が誘起されます。その後、生成したホールと電子がそれぞれの電極に捕集されることで電流が発生し、シグナルとして検出されます。本来有機材料は絶縁体に近い特性を持っていますが、薄膜化することで半導体としての機能させています。そのため素子の垂直方向に対しては導電可能である一方で、水平方向に対しては高抵抗となります。つまり、一般的な無機半導体を用いた受光デバイスと比較して、電気的なクロストークが本質的に起こりにくいデバイスであるということが言えます。さらに光吸収係数が非常に高いために、0.1ミクロンという薄膜でも高い光電変換効率を得ることができ、これも薄膜デバイスとしての性能を支持する特長となっています。
一方、OLEDの場合は、電極から有機層に向かってホールと電子がそれぞれ注入され、内部の発光性有機分子内においてキャリア再結合することで発光が観測されます。一般的にOLEDでは透明電極を用いるため、面発光源であるという特長を有しています。そのため広いエリアにおいて均一な光を出すことが可能であり、できるだけ強度分布の小さい光源を使いたいといったニーズに応えることが可能です。また、発光面において任意のパターンを形成するのも容易であるため、自由度の高いデザインが可能となります。
当社で開発したフレキシブルOPDは近赤外領域に受光感度を有しており、生体センシング用デバイスへの応用を目指しています。この波長帯は水やヘモグロビンといった生体を構成する要素の吸収が小さく、光の振る舞いとしては散乱現象が支配的となるため「生体の窓」と呼ばれ、生体内の多くの情報を得ることが可能です。そのセンサ部にフレキシブルOPDを用いることで、装着感のない、生体にフィットする新しいデバイスが創製できると考えています。
図3(a)フレキシブルOPD
図3(b)受光感度
図4. 生体の光学的窓
発光素子に関しては、センチメートルオーダーという大面積かつ任意のパターンで発光する近赤外OLEDが得られており、分析用の光源や暗視野用の照明としての応用を目指しています。当社製の近赤外OLEDはmWオーダーの発光出力に加え、優れた駆動耐久性を有していることを特長としており※、面発光源としての特長を活かすことによって、対象物を均一に照射する新しい光源を提供可能と考えています。
■大面積OLEDの近赤外カメラ像
図5. 大面積OLEDの発光スペクトル
図6(a)一般的なLED
図6(b)面発光OLED
※参考文献:T. Yamanaka, H. Nakanotani, S. Hara, T. Hirohata, C. Adachi, “Near-infrared organic light-emitting diodes for biosensing with high operating stability,” Appl. Phys. Express 10, 074101 (2017).
It looks like you're in the . If this is not your location, please select the correct region and country below.
You're headed to Hamamatsu Photonics website for JP (Japanese). If you want to view an other country's site, the optimized information will be provided by selecting options below.
In order to use this website comfortably, we use cookies. For cookie details please see our cookie policy.
This website or its third-party tools use cookies, which are necessary to its functioning and required to achieve the purposes illustrated in this cookie policy. By closing the cookie warning banner, scrolling the page, clicking a link or continuing to browse otherwise, you agree to the use of cookies.
Hamamatsu uses cookies in order to enhance your experience on our website and ensure that our website functions.
You can visit this page at any time to learn more about cookies, get the most up to date information on how we use cookies and manage your cookie settings. We will not use cookies for any purpose other than the ones stated, but please note that we reserve the right to update our cookies.
For modern websites to work according to visitor’s expectations, they need to collect certain basic information about visitors. To do this, a site will create small text files which are placed on visitor’s devices (computer or mobile) - these files are known as cookies when you access a website. Cookies are used in order to make websites function and work efficiently. Cookies are uniquely assigned to each visitor and can only be read by a web server in the domain that issued the cookie to the visitor. Cookies cannot be used to run programs or deliver viruses to a visitor’s device.
Cookies do various jobs which make the visitor’s experience of the internet much smoother and more interactive. For instance, cookies are used to remember the visitor’s preferences on sites they visit often, to remember language preference and to help navigate between pages more efficiently. Much, though not all, of the data collected is anonymous, though some of it is designed to detect browsing patterns and approximate geographical location to improve the visitor experience.
Certain type of cookies may require the data subject’s consent before storing them on the computer.
This website uses two types of cookies:
This website uses cookies for following purposes:
Cookies help us help you. Through the use of cookies, we learn what is important to our visitors and we develop and enhance website content and functionality to support your experience. Much of our website can be accessed if cookies are disabled, however certain website functions may not work. And, we believe your current and future visits will be enhanced if cookies are enabled.
There are two ways to manage cookie preferences.
If you don’t want to receive cookies, you can modify your browser so that it notifies you when cookies are sent to it or you can refuse cookies altogether. You can also delete cookies that have already been set.
If you wish to restrict or block web browser cookies which are set on your device then you can do this through your browser settings; the Help function within your browser should tell you how. Alternatively, you may wish to visit www.aboutcookies.org, which contains comprehensive information on how to do this on a wide variety of desktop browsers.
Occasionally, we may use internet tags (also known as action tags, single-pixel GIFs, clear GIFs, invisible GIFs and 1-by-1 GIFs) at this site and may deploy these tags/cookies through a third-party advertising partner or a web analytical service partner which may be located and store the respective information (including your IP-address) in a foreign country. These tags/cookies are placed on both online advertisements that bring users to this site and on different pages of this site. We use this technology to measure the visitors' responses to our sites and the effectiveness of our advertising campaigns (including how many times a page is opened and which information is consulted) as well as to evaluate your use of this website. The third-party partner or the web analytical service partner may be able to collect data about visitors to our and other sites because of these internet tags/cookies, may compose reports regarding the website’s activity for us and may provide further services which are related to the use of the website and the internet. They may provide such information to other parties if there is a legal requirement that they do so, or if they hire the other parties to process information on their behalf.
If you would like more information about web tags and cookies associated with on-line advertising or to opt-out of third-party collection of this information, please visit the Network Advertising Initiative website http://www.networkadvertising.org.
We use third-party cookies (such as Google Analytics) to track visitors on our website, to get reports about how visitors use the website and to inform, optimize and serve ads based on someone's past visits to our website.
You may opt-out of Google Analytics cookies by the websites provided by Google:
https://tools.google.com/dlpage/gaoptout?hl=en
As provided in this Privacy Policy (Article 5), you can learn more about opt-out cookies by the website provided by Network Advertising Initiative:
http://www.networkadvertising.org
We inform you that in such case you will not be able to wholly use all functions of our website.
Close