Colloidal quantum dots (QDs) in the visible spectral range have become key materials for next-generation displays, particularly III–V indium phosphide (InP) and II–VI ZnSeTe-based core–shell nanocrystals. These systems provide tunable, high-purity emissions while avoiding the toxicity concerns of cadmium-based QDs. Despite their promise, conventional synthetic routes often suffer from broad size distributions and interfacial trap states that limit photoluminescence quantum yield (PLQY) and color purity.

Our group has recently demonstrated that precise reaction-kinetic control in a two-step growth process enables the formation of highly monodisperse InP cores. Coupled with rationally designed ZnSeS/ZnS multishell passivation, these structures achieve PLQYs exceeding 90% and ultra-narrow full width at half maximum (FWHM) values (<33 nm) for both green and red emission. In parallel, we have advanced ZnSeTe alloyed QDs, which allow fine tuning of band structure and lattice strain, enabling high-efficiency blue quantum dots through controlled Te incorporation and optimized core/shell compositions.

Beyond synthesis, we developed direct optical patterning strategies using photoacid generators and carbene-based crosslinkers that enable sub-micron resolution patterning without damaging the QD surfaces. This approach is fully compatible with both InP and ZnSeTe QDs and is critical for high-resolution QLED pixels and micro-LED color-conversion layers.

Finally, I will discuss integration of these high-quality QDs into QLED device architectures, focusing on charge-balance engineering, interfacial defect suppression, and efficiency roll-off mitigation. This talk will highlight our recent progress in visible-range III–V and ZnSeTe QD synthesis, direct patterning, and QLED device implementation toward environmentally friendly, high-performance display technologies.

Indium antimonide (InSb) quantum dots are emerging as highly promising materials for short-wave infrared optoelectronics, owing to their intrinsically narrow bandgap and excellent charge-transport properties. Yet, achieving precise control over their size and structural quality has remained difficult, largely due to incomplete understanding of their growth pathways. In this work, we uncover a two-step formation mechanism in which metal-halide precursors first undergo room-temperature reduction to yield discrete indium and antimony nanocrystals. Upon heating, these mobile intermediates react to nucleate and grow InSb quantum dots. We show that the size and diffusivity of these metallic intermediates govern the overall growth kinetics and final quantum-dot dimensions, enabling systematic size control through judicious selection of precursor chemistry and ratios. This mechanism is further confirmed by independently synthesizing indium and antimony nanocrystals and reacting them at elevated temperature to directly form InSb quantum dots with tunable sizes. Understanding this mechanism, we obtain highly uniform quantum dots with absorption spanning 1160 to >2200 nm, exhibiting pronounced size-dependent photoluminescence and excellent long-term stability. These insights clarify the fundamental growth chemistry of InSb quantum dots and provide a scalable route to producing size-engineered nanocrystals for next-generation infrared technologies.

Colloidal quantum dots (QDs) with infrared (IR) absorption and emission are promising candidates for next-generation optoelectronic applications, including machine vision (e.g., object, food, pharmaceutical, and plastic-recycling inspection), anticounterfeiting, biometric authentication, fog and smoke visors, light detection and ranging (LIDAR), theranostics, and optical communications. Among RoHS-compliant IR materials, InAs QDs are particularly attractive thanks to the tunability of their optical bandgap, which can span from 700 to more than 1700 nm, thus covering a relevant spectral range for the aforementioned applications.

Despite their potential, the use of InAs QDs in optoelectronic devices is still largely unexplored, mainly because their synthetic approaches still need optimization. In particular, efficient control over their size and size distribution has been achieved only recently by employing tris(trimethylsilyl)arsine (TMS-As), which enables the production of InAs QDs with narrow excitonic absorption peaks tunable down to 1600 nm and efficient photoluminescence up to ~950 nm. Another emerging synthetic route is based on tris(dimethylamino)arsine (amino-As), recently introduced as an alternative to TMS-As, because the latter is a pyrophoric, expensive, and commercially limited arsenic precursor, making it non suitable for large-scale production of InAs QDs for consumer applications.

The current challenges are to further advance the optical properties of amino-As-based InAs QDs via: i) the use of innovative ad-hoc reducing agents capable of tuning the reduction rate of As³⁺, present in amino-As, to As^3-, which is essential for improving control over QDs size and size distribution and, thus, over the excitonic peak position and width; ii) improved control over the overgrowth of shell materials capable of delivering InAs@shell QDs with enhanced PL efficiency and, ideally, reduced Auger recombination. Achieving this requires the identification of appropriate shell materials and a detailed understanding of their overgrowth on InAs cores.

In our recent work, we began addressing these challenges by employing a novel reducing agent, trioctylamino-alane, synthesized in our laboratory. This enabled improved control over the growth of amino-As-based InAs QDs, whose absorption could be tuned up to ~1300 nm. Careful optimization of the ZnSe shelling procedure yielded samples exhibiting PLQYs as high as 75% at 905 nm, 60% at 1000 nm, 46% at 1160 nm, 38% at 1250 nm, 32% at 1335 nm, and 23% at 1430 nm. These results were made possible by the use of ZnCl₂ as a crucial additive in the synthesis of the InAs cores. We elucidated the role of ZnCl₂ through combined experimental characterization and computational modeling. Our study indicates that ZnCl₂ is not simply passivating the surface of InAs QDs by acting as a Z-type ligand, but that its use leads to the inclusion of Zn atoms into the InAs QD surface, thereby passivating surface trap states, which are mainly located on As-rich (–1 –1 –1) facets.

These results pave the way for further advancements in InAs QDs, which will necessarily require a deeper understanding of how shell materials grow onto pre-formed InAs cores and how the band alignment between core and shell materials can be possibly optimized.

Short-wave infrared (SWIR) semiconductor materials are essential for the development of consumer optoelectronic applications such as telecommunication, sensing and biological imaging. Indium arsenide (InAs) quantum dot (QD) materials are not restricted and offer bandgap tunability throughout the whole SWIR, making them very promising for such applications. Active imaging applications such as sensing require both a SWIR source and a detector, for example a QD-light emitting diode (QLED) and a QD-photodetector (QDPD) respectively. However, because of the lack of high photoluminescence quantum yield (PLQY) InAs-based QDs, QLED development lags behind QDPD development. Strong advancements have been made for the synthesis of InAs/ZnSe core/shells to enhance PLQY of these materials in the SWIR.[1,2] However, further improvement is needed as efficiency rapidly declines with longer emission wavelengths and PL features remain broad. An appealing core/shell combination for emission at longer wavelengths is InAs/InP. InAs and InP have a common cation and a relatively small lattice mismatch, enabling the formation of a low-defect interface in core/shell structures. However, little work has been done on the development of these InAs/InP-based structures.[3,4] In this work we present work done on the In(As,P) alloy synthesis route published by Leemans et al.[5] Using amino-arsine and -phosphine for In(As,P) core synthesis gives a tunable method for particles with band-edge transition (BET) between 1150 - 1600 nm. Firstly, we present a synthesis method for In(As,P) with BET features between 1250 - 1650 nm, with FWHM as low as 90 meV. The synthesis has a chemical yield between 30 - 50 % and does not require any size-selective precipitation steps, making it more easily reproducible. However, the photoluminescence quantum yield (PLQY) of these core QDs remains low without surface treatment or shell growth (< 1%). Secondly, in this work we present a novel synthesis route for the growth of tetrahedral In(As,P)/InP core/shell structures. This synthesis enables In(As,P)/InP with variable thickness of 1 - 5 monolayers (ML) and core sizes used between 5 - 10 nm in edge length. The synthesis can be done in both 2- and 1-pot fashion. The BET is not broadened and PLQY is enhanced from << 1 % to roughly 1 %. Compared to the InAs/ZnSe materials, this is a relatively small increase. Through ab initio density functional theory calculations we can attribute this low PLQY to surface states on the InP shell. Finally, we present a synthesis route for facile ZnSe overgrowth of the In(As,P)/InP core/shell structure demonstrating luminescent materials with centre of emission between 1200 and 1550 nm. The material PLQY is between 12 - 16 % and the PL FWHM is typically between 120 and 90 meV. Again, this synthesis works both in a full 1-pot or a 2-pot fashion. These are record narrow PL features with relatively good PLQY for RoHS-compliant InAs-based QDs in the SWIR. They provide a strong material baseline for further development of QLED devices for consumer applications such as telecommunication, sensing and biological imaging. 

Next-generation III–V quantum dots (QDs) with enhanced optoelectronic properties and stability are expected to emerge from a complete understanding and control of their surface characteristics—specifically their three-dimensional (3D) atomic configuration, chemical composition, and bonding interactions. Although electron tomography is among the most powerful techniques for reconstructing the 3D atomic structure of nanomaterials, its application to III–V QDs remains challenging, as these systems are highly susceptible to structural degradation under prolonged electron-beam exposure. As a result, current 3D structural models of III–V QDs are typically inferred from 2D low-dose annular dark-field scanning transmission electron microscopy (ADF-STEM) projections through visual comparison and iterative manual adjustments.

To move beyond this qualitative and time-consuming approach, we developed a highly efficient AI-driven workflow that integrates quantitative transmission electron microscopy with molecular modeling. In this talk, we show how this combined experimental–theoretical protocol enables the generation of highly accurate and experimentally validated 3D models of novel InP QDs, including reliable reconstructions of their surface and interface atomic configurations.

One of the most recently emerging platforms for fabrication of single photon sources emitting in the telecom spectral range is a zincblende InAsP quantum dot (QD) embedded in an InP nanowire (NW) [1].They have great potential for perfectly vertically aligned multiple quantum dot molecules and the material system is not restricted via lattice mismatch with the substrate. The optimization of the QD’s properties is still complex and a high topic, mainly due to the difficulty of achieving precise control of their morphology, composition, and structural properties at the nanometer scale. These QDs typically measure only ~10 nm, making even small variations in shape, size, or stoichiometry highly impactful on their electronic structure and optical response [2-4].

To overcome such limitations, we propose the use of advanced scanning transmission electron microscopy (STEM) techniques to perform a comprehensive structural analysis of InAsP QDs grown in InP nanowires by Chemical Beam Epitaxy. High-Angle Annular Dark-Field (HAADF)-STEM, combined with geometric phase analysis (GPA) and high-resolution energy-dispersive X-ray spectroscopy (EDS), enables the correlation of atomic composition fluctuations with strain distribution at the nanometer-scale. This multimodal approach provides direct experimental access to key information with atomic resolution, which is essential for accurate modelling and epitaxial optimization

Preliminary results obtained by such advanced STEM techniques on InAsP QD reveal that the actual composition profiles and strain distributions obtained experimentally differ from theoretical growth expectations and consequently, from QD targeted emission wavelength. Therefore, the employment of STEM techniques will be very useful to determine the QD properties.

In the final work, we will present a set of InAsP QDs obtained using different growth strategies, with the aim of achieving a deeper understanding of how composition and the resulting strain influence the optical properties of investigated nanostructures. This work will allow refining QD growth protocols. A step that is crucial for an effective technological feedback of next-generation quantum emitters.

Colloidal quantum dots (QDs) based on III-V semiconductors offer solution-processable, size-tunable optical properties that comply with toxic heavy metal regulations in optoelectronic applications. While global research has primarily focused on InP and InAs QDs – spanning a spectral range from the mid-infrared to the visible – colloidal synthesis protocols now extend to InSb QDs for mid-wave infrared absorption, and molten-salt reactions have enabled access to Ga-based III-V compounds. Interestingly, the wavelength range accessible through size tuning often overlaps for In- and Ga-based semiconductors; for example, red-emitting QDs can be synthesized from both InP and GaAs. Such changes in composition and size alter material properties such as lattice parameters and band structure, enabling device performance optimization by tuning QD composition and size while maintaining a fixed operational wavelength. This raises the fundamental question of whether the field should converge on a single material system or continue exploring the compositional diversity of III-V QDs.

In this presentation, we apply density functional theory (DFT) and the Bloch orbital expansion as an unconventional computational approach to link QD geometry with electronic structure. By comparing the fuzzy band structure of QDs with their bulk band structures computed at the same theoretical level, we distinguish strongly confined, delocalized QD orbitals from those derived from bulk surface states, which deviate from the bulk bands. Notably, mid-gap surface states – most detrimental to optoelectronic device performance – can be readily identified as falling within the bulk bands. Additionally, the first delocalized QD orbitals can be identified via this approach, defining a trap band width for each material.

We first apply the method to a 3 nm InP QD model with chloride-passivated (100) and (111) facets, showing that its fuzzy bands exhibit a broad band of occupied surface states related to unpassivated (-111) facets exposing P dangling bonds. Remarkably, changing the composition to GaAs – a material with similar band gap energy – eliminates these mid-gap states. Extending our analysis across various III-V QD sizes and compositions, we observe that (1) indirect band gap materials exhibit larger trap band widths than direct band gap materials, (2) valence trap band width decreases significantly across the P>As>Sb series, with a similar trend for Al>In>Ga, and (3) larger QD models exhibit additional surface states due to extended crystal facets and associated defects. We conclude by relating our findings to previously published dangling bond energies.[1]

InP and InAs QDs are considered the most promising RoHS complient quantum dot materials for visible and short-wave infrared (SWIR) applications. However, compared to more traditional II-VI QDs they pose additional challenges: (1) InP and InAs are considerably more oxylophilic, so that their surfaces and core-shell interfaces are nearly always oxidized, (2) the high valence of the ions requires high surface coverage with typical 1- X-type ligands to maintain charge balence and (3) the best shell material is ZnSe, where the III-V/II-VI core shell interface is inherently charged, and the properties of teh core-shell QDs depend on subte atomistic details at the interface.

I will discuss recent experiments of our group on the fluorination and oxidation of InP, InAs and InP/ZnSe QDs. As synthesized InP have very low photoluminescence quantum yields (PLQYs), but these can be enhanced to near unity for InP and to ~20% for InAs QDs using mild etching via in situ HF generation[1] or direct addition of InF_3.[2] In both cases this results in the formation of InF₃ terminated surfaces and a drastic increase in PLQY. I will show that the same methods work on InAs QDs, and that this can be used to fabricate SWIR photodiodes with lower dark current and enhanced EQE.

Perhaps surprisingly, the above fluorination methods do not reduce the amount of oxygen on the surface. Using solid state NMR it can be shown that a significant amount of PO₄ is present at the interface of InP/ZnSe QDs, even for high PLQY samples. Isotope labeled ⁷⁷Se experiments demonstrate that the presence of abundant oxygen at the interface disrupts epitaxial shell growth.[3] In our experiments this is accompanied by a lower PLQY of the resulting samples, although other reports show that interfacial oxidation can be beneficial.[4]

Clearly the III-V/II-VI interface is complex understanding the atomistic composition and its effect on the QD properties remains an open challenge.

The growing demand for short-wavelength infrared (SWIR) imaging, particularly in the 1000–2000 nm range, is driven by its critical role in applications such as medical diagnostics, security surveillance, smart agriculture, automotive sensing, consumer electronics, and industrial inspection. Traditional SWIR sensors based on InGaAs, while effective, are hindered by high material costs and complex fabrication processes.

To address these limitations, colloidal quantum dots (CQDs) have emerged as a promising, cost-effective, solution-processable alternative compatible with wafer-scale integration. While lead-based materials like PbS have dominated the field, their incompatibility with the European Union’s Restriction of Hazardous Substances (RoHS) directive poses significant challenges. In this work, we present SWIR image sensors based on RoHS-compliant III-V CQDs, specifically InAs CQDs.

High-performance image sensors require photodiodes with high signal-to-noise ratio, achieved through high quantum efficiency (QE) and low leakage current, preferably at low bias to minimize power consumption. In this talk, we show how the choices of quantum dot ligands and charge transport materials shape the energy landscape of quantum dot photodiodes (QDPDs). Our optimized QDPDs exhibit a detectivity of 2.5 × 10¹¹ Jones at 1210 nm at -1 V. These QDPDs are monolithically integrated onto silicon readout integrated circuits (ROICs), enabling SWIR imaging for material discrimination, smoke penetration, and silicon wafer inspection.

Defect analysis reveals dominant deep trap states within the InAs CQD layer, being tail states of the conduction band that reach down to about 0.4 eV below the band edge, with a density at the order of 10¹⁶ cm^-3. This implies that defect reduction is essential for further QDPD performance improvement.

The ligands of indium phosphide (InP) quantum dots (QDs) were polymerized by energetic Ar ions generated by plasma, and the polymerized ligands enabled the formation of 3-μm patterns through photolithography. In the first step, the ligand capping the QDs was oleic acid (OA), and changes in the OA ligands with plasma bias voltage, source power, and time were monitored using Fourier transform infrared (FT-IR) spectroscopy. The energy range for OA polymerization was then determined by analyzing changes in the 3006 cm⁻¹ peak. In the second step, photoresist (PR) was coated on the cross-linked QD film, and a PR pattern was formed using conventional i-line UV lithography. Finally, the unmasked QD region is selectively removed by Ar sputter etching in plasma under optimized conditions of 150 W source power and 300 V bias voltage, forming a 3-μm scale QD pattern. This study utilized plasma-induced cross-linking to induce polymerization of QD ligands, ensuring compatibility with photolithography processes.

Colloidal quantum dots (QDs) have gained significant attention as promising emissive materials due to their outstanding optical properties, including tunable emission wavelengths, narrow spectral bandwidths, and excellent photoluminescence quantum efficiency (PLQE). QDs based on cadmium or lead, such as CdSe, CdS, PbS, and CsPbBr3, have been extensively studied, benefiting from mature synthetic protocols and well-established application techniques. However, concerns over their toxicity, environmental impact, regulatory constraints continue to limit their widespread commercialization., especially in consumer display applications. Consequently, indium phosphide (InP)-based QDs have emerged as an attractive, lower-toxicity alternative for visible-range emitters. Despite this promise, achieving high optical quality in InP QDs remains challenging due to their relatively high covalent bonding nature, which makes them more susceptible to oxidation and complicates to control of structural defects. These intrinsic characteristics have resulted in broader emission linewidths, lower PLQE, and reduced operational stability compared to CdSe-based QDs.

In this talk, I will introduce our advances in the development of InP-based QDs that exhibit nearly unity PLQE and remarkably high stability during both device fabrication and operation. Leveraging these superior optical properties, the InP QDs can be effectively utilized as color-conversion layers for multiple types of blue light sources, including OLEDs and micro-LEDs. In particular, the integration of red-emitting QDs with blue micro-LEDs presents a compelling solution to the long-standing issue of low external quantum efficiency in red micro-LEDs, especially at sub-50-um pixel sizes. This approach enables high-resolution displays with wide color gamut, low energy consumption, and improved manufacturability. Overall, these results highlight the strong potential of QDs to serve as a commercially viable, environmentally responsible, and highly efficient platform for future display technologies.

InAs colloidal quantum dots (CQDs) are promising for shortwave infrared (SWIR) optoelectronics, due to their size-tunable optical properties, compatibility with CMOS technology, and compliance with the RoHS directive. However, increasing CQD size to achieve extended SWIR (eSWIR) bandgaps and improving charge transport often compromises colloidal stability. Here, we report a growth strategy for ultra-long InAs colloidal quantum nanorods (CQNRs) that maintain quantum confinement while enhancing colloidal stability and charge transport. A key innovation is the precise chemical control through lithium bis(trimethylsilyl)amide (LiN(Si(CH₃)₃)₂) that directly controls their anisotropic growth, enabling the synthesis of nanorods up to ~200 nm in length, orders of magnitude longer than previously reported for colloidal InAs. Transitioning from spherical QDs to nanorods allows size extension without inducing aggregation or precipitation. The resulting CQNRs exhibit excellent colloidal stability and absorption up to 2000 nm in the eSWIR region. Photodiodes fabricated from these CQNRs exhibit very low dark current (6 μA cm^-2) and high external quantum efficiency (10.6%), attributed to reduced interparticle grain boundaries confirmed by four-dimensional scanning transmission electron microscopy. This work demonstrates the controlled growth of ultra-long, colloidally stable InAs CQNRs and provides a route to environmentally compliant large CQDs for next-generation high-performance eSWIR optoelectronic devices.

Short-wave infrared (SWIR, 900-1700 nm) light-sources are fundamental components of a variety of optoelectronic sensing systems, such as machine vision, and light detection and ranging (LIDAR).  So far, SWIR light-emitting diodes (LEDs) have been produced by exploiting single-crystal III-V semiconductors (predominantly In_1-xGa_xAs grown onto InP), whose multi-step epitaxial growth and processing limit deployment in consumer products. Alternative SWIR light-sources are colloidal quantum dots (QDs),¹ as they can be synthesized at a considerably lower price than that required for epitaxial crystals. Additionally, QDs are not grown on a substrate, thus they can be readily integrated with well-established and inexpensive complementary metal-oxide-semiconductor (CMOS) technologies. Despite the commercial success of visible QD displays, SWIR QD light-sources are not yet consumer-grade, given the difficulty in achieving high efficiency for emissions beyond 1100 nm in combination with compliance with the European Restriction of Hazardous Substances (RoHS) directives. In fact, state-of-the-art SWIR QD-LEDs are mainly based on toxic Pb- and Hg- chalcogenide QDs; given that progress on colloidal InAs-based QDs has been hindered by reactivity constraints of available As precursors (leading to low photoluminescence quantum yield), size-dispersion challenges, and electroluminescence limited to wavelengths below ≈1006 nm. In this talk, I will present our recent findings on the synthesis of InAs QDs via amino-As precursor,^2-4 and their application in LEDs.^{5, 6} In particular, I will focus on InAs core/shell QDs and respective LEDs delivering photoluminescence/electroluminescence beyond 1100 nm.

The synthesis of InP-based QDs has made great strides in recent years, with state-of-the-art core/shell strategies resulting in near-unity photoluminescence quantum yield (PLQY).[1] Ensuring reliability under working conditions is a shared challenge amongst emerging opto-electronic technologies, complicated by the fact that the fundamental chemical processes leading to performance deterioration remain poorly understood. In this work, we bridge the knowledge gap and identify a single process-of-failure that leads to photoluminescence (PL) quenching of InP-based QDs: InP/ZnSe/ZnS QDs and InP/ZnSe/Zn(Se, S)/ZnS QDs.

Using a home-built in situ PL setup,[2] we investigated the effect of different gas atmospheres and revealed that PL quenching is triggered under continuous illumination in an O₂-containing atmosphere, while straightforward oxidation of the QDs is ruled out by X-ray photoelectron spectroscopy (XPS). Instead, the PL quenching is directly correlated to the charging of the QDs, with femtosecond transient absorption spectroscopy (fs TAS) showing evidence of non-emissive trions after photoexcitation. Following illumination in air, the band-edge bleach decays more rapidly than after illumination in an inert atmosphere and is characterized by components with lifetimes of 133 ps and 5 ps, indicating a growing importance of non-radiative Auger processes. We sought to determine the radical species formed following the removal of the electron from the QD using electron paramagnetic resonance (EPR) spectroscopy, which confirmed the formation of superoxide and an alkoxyl-type radical. Gaining insight into this single process-of-failure is a necessary step to guide QD synthesis toward enhancing the reliability of devices using InP-based QDs for photoluminescent color conversion or electroluminescent light emission.

Colloidal I-III-VI quantum dots (QDs) including AgInS₂ are emerging as Restriction of Hazardous Substance (RoHS)-compliant emitters for next-generation optoelectronic technologies, offering compositional flexibility, tunable band gap, and strong chemical stability.¹ AgInS₂ feature a unique upper valence band structure with two energetically separated maxima at the Γ-point.² Here, we explore intrinsic exciton and biexciton dynamics in AgInS₂ QDs of different sizes (4-10 nm in diameter) by using ultrafast transient transmission spectroscopy. Although dominant nonradiative pathways and mid-gap donor-acceptor pair defects limit free-exciton emission in these QDs, we address this challenge by post-synthetic surface defect passivation at room temperature using dual ligands. As a result, AgInS₂ QDs show narrow emission with photoluminescence quantum yield up to 56%. Exciton formation is associated with inter-valence band hole relaxation which slows with smaller QDs due to confinement effects. Interestingly, the biexciton-induced absorption evolves on a similar timescale as hole relaxation, indicating exciton to biexciton transitions involves different excitons during the relaxation process. Fluence-dependent pump-probe measurements further reveal fast biexciton decay in smaller QDs due to exciton-exciton annihilation. Together, our results demonstrate that highly emissive AgInS₂ QDs can be achieved through dual-ligand passivation, and the exciton-biexciton dynamics is regulated by inter-valence-band hole relaxation, a feature distinctive to these QDs.

Colloidal nanocrystals of III/V composition have gained increasing interest for replacing heavy metal-dominated technologies in the long wavelength (near - to mid-infrared) spectrum today, such as photo-detectors (often still based on PbS) or light-emitting diodes (dominated by PbS and HgX). Here, I will present a suite of non-standard ultrafast spectroscopy tools suitable to explore the fastest events in these materials which still struggle to develop e.g. efficient stimulated emission of light. Using for example state-selective pump-probe, we can identify clear signatures of shallow trap states in close agreement with improved theoretical modeling. Next to this, I will present our recent efforts to implement continuum infrared spectroscopy, both as a toolbox to unravel ultrafast processes in III/V - but also many more - NCs, but also as a new platform to quanitfy intra-band transitions in these materials - a potentially new avenue for their future in NC-based opto-electronics.