BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:69db5c7820f2b DTSTART:20220204T100000Z SEQUENCE:0 TRANSP:OPAQUE DTEND:20220204T120000Z LOCATION:Online (Teams) and ICFO Auditorium SUMMARY:ICFO | ONUR ÖZDEMI CLASS:PUBLIC DESCRIPTION:In the infrared\, photodetectors are the key components in a wi de-variety of applications such as thermal imaging\, remote sensing\, spec troscopy with newer technologies added to the list such as LiDaR and deep tissue imaging. As the demand for photodetectors increase with a shift tow ards longer wavelengths\, we need high-performance\, scalable and low-powe r consuming alternatives to current infrared photodetector technologies.Co lloidal Quantum Dots (CQDs) are nanoscale-sized semiconductors with quantu m-confined charges in all 3 dimensions. They can be synthesized in solutio n and can easily be deposited onto a desired substrate as a quantum dot (Q D) film which allows easy integration with current silicon-based technolog ies. QDs are efficient light absorbers and their bandgap can accurately be tuned by controlling their size during synthesis. Lead chalcogenide QDs\, such as PbS and PbSe\, have tunable bandgaps covering the near-infrared ( NIR) and short-wave infrared (SWIR) up to 3 µ\;m\, making them ideal sensitizers for photodetectors.In this thesis\, we utilize PbS QDs with an excitonic bandgap around 1.8 µ\;m in combination with 2-dimensional transition metal dichalcogenides (TMDCs) to form hybrid photodetectors ope rating in the infrared. With their layered structure similar to graphene a nd semiconducting character\, TMDCs have outstanding electronic properties . Incorporating few-layers of TMDCs in our PbS QD detectors allows fast an d efficient charge transfer from the QDs to the photodetector contacts thr ough the TMDC layer\, boosting detector responsivity. By combining PbS QDs with two types of TMDCs\, WS2 and MoS2\, we are able to reach detectiviti es exceeding 1012 Jones at room temperature with a response up to 2 µ \;m.Probing further into the infrared\, we extend the spectral response of our hybrid detectors up to 3 µ\;m by utilizing narrower-bandgap PbSe QDs with MoS2 layers.After a careful analysis and using strategies such a s oxide-isolation of metallic contacts\, we reached detectivities of 7.7 x 1010 Jones at 2.5 µ\;m at RT. With their low-noise and high responsi vities\, our detectors improve the potential of hybrid detectors and demon strate a performance comparable to commercial detectors without the need o f external cooling\, costly vapor deposition techniques or complex integra tion with silicon technology.Broadening the reach of PbS QDs even further\ , even beyond the limit of their bulk bandgap\, up to 9 µ\;m by using a novel doping method\, we demonstrate the first PbS QD intraband photode tectors. Having developed this air-stable high n-doping method for PbS QDs \, observation of intraband transitions taking place between the first two conduction levels becomes possible. These intraband transitions have lowe r energies compared to the bandgap\, opening up another degree of freedom in tunable optical response of our QDs between 6-9 µ\;m. We study how the doping works across a wide range of QD sizes and at different tempera tures. Our photodetectors utilizing the intraband transitions in highly-do ped PbS QD films have detectivities approaching 105 Jones.To sum up\, we d emonstrated lead chalcogenide QD based photodetectors with improved perfor mance and spectral responses progressively shifting deeper into the infrar ed. Our TMDC-QD hybrid detectors reveal the potential of these systems as alternatives to commercial detectors. Whereas\, surpassing the bandgap lim it with high doped QDs and intraband transitions opens up new ways to real ize optoelectronic devices further in the infrared. DTSTAMP:20260412T084856Z END:VEVENT END:VCALENDAR