Perovskite Light-Emitting Diodes (PeLEDs) represent a highly promising LED technology due to their exceptional color purity, tunable emission color, and low manufacturing cost. However, the current record external quantum efficiency (EQE) for PeLEDs is limited to 32\%, still below the 40\% achieved by organic LEDs (OLEDs). This limitation primarily stems from defects within the perovskite layer and at interfaces between different layers in the device. Effective passivation of these defects is essential for further advancing PeLED efficiency.

In this thesis, we established the first operational PeLEDs within the PVMD group, leveraging its perovskite solar cell production line. We developed the fabrication process from the ground up and characterized the resulting device performance.

The first part of this thesis addresses the stability of perovskite layers during optical testing in ambient air. We observed that carrier lifetime measurements depend heavily on the perovskite's exposure time to air and the presence of protective overlayers, rather than solely on its inherent optoelectronic properties. This instability arises from rapid perovskite degradation in air. To mitigate this, we employed spin coating to deposit a protective PMMA layer over the perovskite and optimized this coating process. Characterization confirmed that PMMA significantly slows degradation. Additionally, we identified and corrected alignment issues in the photoluminescence quantum yield (PLQY) measurement setup, which had introduced substantial uncertainty. We refined the PLQY testing procedure to enhance result reliability.

The second part focuses on developing a quasi-2D perovskite emissive layer (EML) with low bulk defect and superior optical properties. Based on quasi-2D perovskites (PEA2(FAPbBr3)n−1PbBr4) typically exhibit better emission characteristics than bulk counterpart (FAPbBr3) We first confirmed the phase composition of our synthesized perovskite, verifying the formation of quasi-2D perovskite with the targeted phase distribution (n = 3). We then introduced two additives: [2-(9H-Carbazol-9-yl)ethyl]phosphonic Acid (2PACz) and KBr to enhance the optoelectronic property of EML. Photoluminescence (PL) testing revealed that 2PACz significantly enhances PL intensity, while KBr showed no such effect. Subsequently, we applied different antisolvents to improve perovskite film morphology. Results demonstrated that ethyl acetate yielded the highest PLQY. Our champion quasi-2D perovskite sample achieved a PLQY of up to 49\%.

The third part details the development and characterization of carrier transport layers for PeLEDs. For the electron transport layer (ETL), we employed 1,3,5-Tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) and used simulations to study how its thickness affects optical performance. Simulations indicated negligible performance variation for TPBi thicknesses between 40 nm and 80 nm. For the hole transport layer (HTL), we fabricated a self-assembled monolayer (SAM) HTL using [2-(3,6-Dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic Acid (MeO-2PACz) and [4-(3,6-Dimethoxy-9H-carbazol-9-yl)butyl]phosphonic Acid (MeO-4PACz), which could reduce interfacial defect at HTL/ETL interface. However, devices with this SAM-HTL structure didn't emit light during voltage sweeps and exhibiting low turn-on voltages in J-V characteristic. We attribute this to electrical breakdown caused by electron tunneling through the extremely thin (1-2 nm) SAM layer. To suppress tunneling, we introduced an underlying NiO$_{x}$ layer. This modified structure demonstrated to be successfully prevented tunneling and enabled functional PeLEDs. To further optimize hole transport while minimizing thickness, we modeled the relationship between HTL thickness and electron tunneling probability. Calculations revealed that increasing the HTL thickness by approximately 3 nm effectively shields against tunneling. This optimized, ultra-thin HTL design paves the way for PeLEDs operating at low voltages with state-of-the-art optical performance.

The medical interest in targeted alpha therapy (TAT) has increased the demand for actinium-225 (225Ac), a promising isotope for cancer treatment. However, the production falls short. One potential route is the generation of 225Ac via proton irradiation of radium-226 (226Ra), introducing the challenge of separating these radionuclides. In this study, lanthanum and barium were used as chemical analogues for actinium and radium, respectively. This study investigates the production and characterisation of α-titanium phosphate (α-Ti(HPO4)2 · H2O, α-TiP) and its feasibility for the separation of lanthanum and barium using ion exchange.

Three synthesis methods were used with different titanium precursors: TiO2, Ti powder and TiOSO4. The resulting α-TiP samples were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), confirming phase purity but showing morphological differences.

The ion exchange behaviour of α-TiP was found to be closely linked to morphology and exchange site accessibility. Batch adsorption experiments demonstrated that α-TiP exhibits strong selectivity for trivalent lanthanum (La3+) over divalent barium (Ba2+) ions at acidic pH and relevant concentration ([La3+] = 2.5 μM and [Ba2+] = 1.0 mM).

The results support the potential of α-TiP as a viable material for lanthanum–barium separation. However, further studies are required to confirm radiation stability, reversibility of ion uptake and performance in column-based separation systems. Additionally, experiments should validate whether similar separation behaviour will be achieved for actinium and radium separation.

With the depletion of energy resources and escalating environmental issues, the development of new energy sources and advanced energy storage devices has become increasingly critical. Zinc-ion batteries have attracted significant attention due to their lower cost and safer chemistry. A major focus of zinc-ion battery research is the development of zinc anodes and electrolyte design. Zinc-free anodes have emerged as a promising strategy, offering higher zinc utilization compared to traditional zinc metal anodes (approximately 10%). Among many zinc-free anodes, Ti₃C₂Tx, a MXene (transition metal nitride/carbide layered material), stands out due to its lower lattice mismatch (~10%), higher conductivity, superior mechanical properties, and good hydrophilicity. However, the higher zinc utilization of zinc-free anodes presents challenges for the stable plating/stripping of zinc. Co-solvent engineering is a convenient and direct approach to improving the stability of zinc-free anodes.

In this study, we propose the use of PEG and IPA as co-solvents added to a 1M Zn(OTF)₂-H₂O electrolyte to enhance the stability of Ti₃C₂Tx zinc-free anodes. We found that the addition of PEG reduced the hydrogen evolution current by 0.42 mA (at -1.3 V vs. Ag wire), indicating suppression of the hydrogen evolution reaction. Furthermore, the addition of PEG in the electrolyte inhibits the 2D diffusion of zinc on the Ti₃C₂ surface and promotes zinc deposition along the (002) crystal direction, increasing the (002)/(001) ratio from 0.59 to 0.86, leading to more uniform zinc deposition. Consequently, the Ti₃C₂ zinc-free anode achieved a coulombic efficiency of 97.67% and a cycle life of 268 hours. Similarly, the addition of IPA reduced the hydrogen evolution current by 0.39 mA (at -1.3 V vs. Ag wire), indicating a weaker hydrogen evolution reaction. Moreover, the addition of IPA in the electrolyte inhibits 2D diffusion on the Ti₃C₂ surface and facilitates zinc deposition along the (002) crystal direction, increasing the (002)/(001) ratio from 0.59 to 0.87. The formation of an SEI containing ZnCO₃, ZnFx, and F-rich organics helps to homogenize the Zn ion gradient. Ultimately, the Ti₃C₂ zinc- free anode achieved a high coulombic efficiency of 98.95% and a cycle life of over 1200 hours in the IPA-containing electrolyte.

Holmium-166 is a promising radionuclide for therapeutic and imaging applications due to its advantageous decay characteristics. However, these applications require or would benefit from a higher specific activity of ¹⁶⁶Ho than that obtained via a ¹⁶⁵Ho(n,γ)¹⁶⁶Ho reaction by irradiating a pure ¹⁶⁵Ho target. The specific activity is limited, because only a minor fraction of the ¹⁶⁵Ho target nuclides is converted into ¹⁶⁶Ho during irradiation and these isotopes are inseparable using conventional chemical methods, since they are of the same element. The Szilard-Chalmers effect facilitates this separation by changing the chemical state of the produced radionuclide due to the recoil induced by neutron absorption. Nevertheless, currently applied target materials, mainly ligands, are unsuitable for commercial scale production with sufficient yield and specific activity, because of: radiolysis, isotopic interchange and recombination. It is proposed that these processes can be significantly reduced by exploiting zeolites, which are materials with interconnected cavities, to bind ¹⁶⁵Ho target nuclides in the closed cages prior to irradiation. The concept behind is, that upon recoil the ¹⁶⁶Ho nuclides relocate to the open cages, from which they are extracted after irradiation, while the ¹⁶⁵Ho target nuclides remain locked in the closed cages. This results in an increased specific activity. Therefore, the aim of this thesis is to examine the increase in the specific activity of ¹⁶⁶Ho produced via a (n,γ) reaction by applying the Szilard-Chalmers effect using zeolite A.

A procedure to achieve the optimal loading of holmium into the open cages (18.3 wt% Ho) and closed cages (93.3% of total holmium) of zeolite A was investigated, as well as the efficiency of its extraction from the open cages (between 39 and 55%). The obtained specific activity and yield were analysed upon irradiation of these zeolite A samples. Irradiating zeolite A with ¹⁶⁵Ho exclusively in the open cages resulted in only a slight increase of the specific activity (maximal 3.3 GBq/g), but a relatively good yield (maximal 53%). In contrast, irradiation of zeolite A with ¹⁶⁵Ho loaded in both the closed and the open cages, resulted in a considerably lower yield (maximal 14.4%), but a substantially increased specific activity (maximal 7.3 GBq/g), which is a factor 5.2 higher than without the Szilard-Chalmers effect. 
Nevertheless, further improvement should be considered as a higher specific activity is key to successful radionuclide therapy. This could potentially be achieved by increasing the extraction efficiency by exploring other types of zeolites, in search of more suitable functional characteristics.