Hybrid nanostrucutured organic/inorganic systems Motivations. Bright prospects are offered by solution processable semiconductor materials for applications in electronic devices due to the ease of processing, the ability to deposit them as thin films on a large variety of substrates and the low cost of fabrication technologies. Colloidal semiconductor nanocrystals hold great promise, owing to their narrow-band, efficient luminescence in the visible and near-infrared, their broad absorption spectrum, and their high stability in ambient conditions. However, when complex functions as charge transport or charge transfer are needed, semiconducting nanocrystals show severe limitations due to difficulties of interfacing individual entities. Linking semiconducting nanocrystals to each other is thus a basic challenge. Hybrid organic/inorganic materials represent a novel class of materials in which the role of the functional linker is played by molecular/polymeric semiconductors. Our research activities. We performed pioneer experimental studies on hybrid inorganic/organic systems as active materials for near-infrared photoconductive detectors . In these composites, electron transport is carried out by a soluble derivative of fullerene (PCBM), while quantum dots act as efficient sensitizer in the nearinfrared. Our experimental studies were focussed on: • Photophysics of charge separation, investigated by time-resolved photoluminescence and transient femtosecond pump&probe spectroscopy • Fabrication and testing of NIR photoconductive detectors Nanocrystal/fullerene inorganic/organic hybrid photodetectors with high detectivity in the near infrared and linear power dependence are demonstrated. The ultrafast electron transfer from the PbS crystals to fullerene opens a new alternative towards efficient photodetectors.
Ongoing activities and challenges. • Control over film morphology and stability • Control over charge separation and transport properties to improve current gain and sensitivity , K. Szendrei, F. Cordella, M. V. Kovalenko, M. Böberl, G. Hesser, M. Yarema, D. Jarzab, O. V. Mikhnenko, A Gocalinska, M. Saba, F. Quochi, A. Mura, G. Bongiovanni, P. W. M. Blom, W. Heiss and M. A. Loi, in press Adv. Mater.