No abstract

Solution-processed organic diodes based on bulk heterojunctions are attractive for large area photodetection. We report a general approach for fully spray-coated organic photodiodes with outstanding characteristics in comparison to bladed or spin-coated devices. Despite the high surface roughness and the less defined morphology of the spray-deposited organic layers, we observe organic photodetectors with responsivities of 0.36 A/W and noise equivalent powers of 0.2 pW/H(1/2) in the visible spectrum at high reverse biases of -5 V. Furthermore, we demonstrate device lifetimes beyond 1 year as well as superior yield and reproducibilties for the dark current and photocurrent densities.

The active pixel concept is a promising architecture for imaging systems. We report on the electrooptical characterization of a hybrid organic active pixel sensor (APS) where an organic photodiode is integrated on top of an amorphous silicon thin-film transistor circuitry, which drives the image sensor and performs the signal processing. The active pixel approach provides an on-pixel amplification of the signal with a charge gain of up to 10. A fill factor that is close to 100% is obtained by embedding all transistors underneath the organic photodetector. We show that, as compared with organic passive pixels, the organic APS shows a higher sensitivity, making the detection of smaller signals possible.

Inorganic/organic hybrid photodiodes, based on a solution-processed ternary blend containing PbS quantum dots (QDs), a fullerene derivative, and a conjugated polymer, have been reported to exhibit external quantum efficiencies in the infrared of up to 51% [T. Rauch et al., Nat. Photonics 3, 332 (2009)]. Temperature dependent experiments reveal the high sensitivity of the photoresponse on the energy level alignment between the QDs and the fullerene derivative, resulting in quenching of the photoresponse at low temperatures for 5.2 nm QDs in size. With smaller QDs the optimum operation temperature is found between room temperature and 72 °C, making these photodiodes promising for various applications.

No abstract

No abstract

Measurements of current transients are used to gain insight into the mechanism of charge transport and extraction of photodiodes based on bulk heterojunction blends of poly-3-hexyl-thiophene and [6,6]-phenyl C-61 butyric acid methyl ester. It is shown that the implementation of an appropriate hole conducting layer leads to a reduction of the dark current in the reverse direction. It is observed that the dynamic response to light excitation is strongly influenced by the thickness of the hole conducting layer, the light intensity, and the applied bias. Charge accumulation at the interface is assumed to result in the characteristic shape of the transients. The shape of the switch-off transient can be understood qualitatively by an equivalent circuit diagram. (c) 2007 American Institute of Physics

Convolutional neural network (CNN)-based approaches have recently led to major performance steps in visual recognition tasks. However, only a few industrial applications are described in the literature. In this paper, an object detection application for visual quality evaluation of X-ray scatter grids is described and evaluated. To detect the small defects on the 4K input images, a sliding window approach is chosen. A special characteristic of the selected approach is the aggregation of overlapping prediction results by applying a 2D scalar field. The final system is able to detect 90% of the relevant defects, taking a precision score of 25% into account. A practical examination of the effectiveness elaborates the potential of the approach, improving the detection results of the inspection process by over 13%.