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Ligand Exchange Optimization for Quantum Dot Based Infrared Thin-film Photodetectors
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Image in the infrared wavelength range offers several advantages when compared with the visible
range. The information that is impossible to acquire with our naked eyes can be used for different
industries such as quality control, surveillance, augmented and virtual reality, medical diagnostics, and
others. Colloidal quantum dots (QDs) have been gathering increased attention and becoming one of the
most promising candidates for infrared optoelectronic devices, being praised for their size-dependent
bandgap tunability, low-cost manufacturing when comparing to III-V semiconductors, and suitability
for deposition on large and flexible substrates. However, the main challenge to accomplish is precise
control over their material properties through surface passivation.
The work performed in this thesis is focused on exploring the effect of different strategies of surface
ligand treatments to colloidal QDs for further integration as an active layer of thin-film photodetectors.
Therefore, thin-films made from solution-phase ligand exchange lead sulfide (PbS) QDs deposited on
glass substrates were analyzed in terms of their optical and morphological properties through multiple
characterization techniques. Full processing and fabrication of thin-film photodiode detectors were then
carried out, pursuing the highest devices performance according to their electrical characterization.
In the end, the developed PbS QD-based photodiode stack successfully completed the proposed
optimization by reaching dark currents values close to 10-5 A/cm2
at -3 V and external quantum
efficiency of 29% at 1450 nm.
Descrição
Palavras-chave
infrared image sensor colloidal quantum dots ligands thin-film photodiode