Organic optoelectronic materials and devices are nowadays found in many devices such as smart phone displays or solar panels. The advantages of this already mature technology are clear: The large oscillator strengths of the materials enable bright and colorful, low-power displays with extremely high contrast or relatively high photo conversion efficiencies in solar cells while the fabrication costs tend to further decrease.
However, organic optical sensors are not common in application although they would benefit from similar advantages but cannot compete with silicon detectors in the visible spectral range. However, in the near infrared (NIR) spectral region the situation is different: The standard inorganic material for detectors and LEDs is Indium-Gallium-Arsenide (InGaAs), which has many drawbacks: They are expensive due to epitaxial growth and contain reasonable amounts of highly toxic arsenic.
We developed a new type of organic photovoltaic detector based on blends of electron accepting and donating molecules. We exploit the properties of the weakly absorbing charge transfer state formed at the donor-acceptor interface and combine the device with an optical microcavity. This allows us to spectrally-selective detect light up to 1600 nm. We show a prototype of a miniaturized spectrometer with basic calibration allowing for simple food screening applications and liquid analysis.
Robert Brückner, Matthias Jahnel, Ronny Timmreck, Karl Leo, and Koen Vandewal, "Near-infrared organic spectroscopic sensors for food quality sensing (Conference Presentation)," Proc. SPIE 10529, Organic Photonic Materials and Devices XX, 105290T (Presented at SPIE OPTO: February 01, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2286627.5752212924001.
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