Diogo Almeida

III–V nanocrystals (NCs) are emerging as a leading platform for short‐wave infrared sensing, yet a deeper understanding of their electronic structure is still needed. Paradoxically, although the corresponding bulk materials have been extensively studied, the evolution of optical properties at low temperatures (relevant to boost performances), and under pressure (likely induced by a shell introduced to prevent oxidation) has been scarcely investigated in NCs. We therefore conduct structural and spectroscopic studies to explore the (P;T) electronic phase diagram of InAs NCs with various sizes. Cooling induces a blue shift of the optical spectrum, thus reducing the spectral window. The temperature dependence shows an increase in dE/dT with the optical band gap, from which we derive an empirical law capable of predicting the temperature dependence for InAs NCs over a broad size range. Under pressure, we show that the zinc blende phase remains stable up to 12 GPa in nanocrystalline InAs, well above the pressure induced by a ZnSe shell. The pressure dependence of the band gap is found to be around 50 meV/GPa, with no significant size dependence. The 30‐band k.p model is used to quantify how the quantum confinement impacts the temperature and pressure dependence of the optical features.

Colloidal lead sulfide (PbS) nanocrystals (NCs) are emerging as cost-effective and solution-processable materials for infrared (IR) detection. Their use in a space environment is conditioned by their radiation tolerance. This study investigates the intrinsic robustness of PbS NC-based photoconductive devices to high-dose x-ray irradiation (up to 1.6 Grad [PbS]), far above the requirements for deep-space operation. PbS NC films exhibit gradual performance degradation without abrupt thresholds, attributed to their polycrystalline nature, which localizes defects and mitigates long-range lattice disruption. Optoelectronic measurements reveal a drop in both the dark and illuminated response, yet the signal-to-noise ratio improves due to the faster decay of the dark current. Spectroscopic analyses (x-ray photoemission spectroscopy/hard x-ray photoemission spectroscopy) confirm that the conductivity change can be attributed to x-ray-induced oxidation, which affects both Pb and S, forming sulfate and lead hydroxide phases that propagate throughout the NC volume. This oxidation reduces the effective NC size, blue-shifting the excitonic peak. Despite this, PbS NCs exhibit exceptional radiation hardness, comparable to that of radiation-hardened CMOS devices. These findings position PbS NCs as viable candidates for spaceborne IR detection, especially in oxygen-free environments where oxidation is naturally limited.