Organic based photodetectors: Suitability for X- and Γ-rays sensing application

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 624; no. 2; pp. 443 - 448
• Main Authors: Binda, M., Natali, D., Sampietro, M., Agostinelli, T., Beverina, L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 11.12.2010
• Subjects: Bulk heterojunction; Detector; Organic detector; Organic semiconductor; Detector; Bulk heterojunction; Organic semiconductor; Organic detector
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2010.04.026

X- and Γ-rays sensing application might benefit from the development of detectors based on organic semiconductors. Their processing from solution and at room temperature envisages large area coverage of, in principle, any substrate. The intrinsic low yield in the photogeneration of free charge pairs, due to the low intermolecular interaction resulting in localized excited states, has been reasonably overcome by suitable donor/acceptor molecule blends. Instead, as a consequence of the presence of two mixed moieties in the active layers, efficient transport and collection of photogenerated charges and, at the same time, suppression of dark injected charge are still subject of intense research. In this paper we show that the entangled issues regarding leakage currents, quantum efficiency, response speed, and device lifetime can be effectively addressed: at a chemical level by suitably tailoring the organic molecules, and at a device level by optimizing the metal–semiconductor interface and the morphology of photosensitive blend layer. Leakage current <1 nA/cm 2, external quantum efficiency in the visible spectrum range >10% and stability to air and moisture in more than one year can be achieved. Radiation hardness (>500 Gy) for such devices has also been demonstrated.