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.

Lithium-ion batteries are the most widely used energy storage devices, and currently dominate the portable electronic device market and automotive industry, owing to their superior energy density and long cycle life. Currently, the market of lithium-ion batteries is dominated by graphite as a material for anode. This material has proven to be very stable and reliable. However, the capacity delivered by graphite is quite low (372 mAh.g−1). As a result, there is a need to explore alternative anode materials which can deliver a superior capacity, and thereby a higher energy density. A promising alternative to overcome this limited capacity issue is the use of silicon anodes, which can theoretically deliver a specific capacity of 3579 mAh.g−1. However, silicon is prone to volumetric change (almost 200-300% of its original volume) upon cycling. This leads to loss of active material due to pulverization and delamination, severely affecting its capacity retention and hence the battery cycle life. Of the several ways in which the capacity retention of silicon anodes can be improved, we have combined two approaches: alloying silicon with nitrogen and making this material porous. This work aims at investigating the influence of the chemical composition, porosity and mass loading of the SiNx anodes developed, on the electrochemical performance when used as an anode for lithiumion battery. The monolithic SiNx anodes used in this work were fabricated using Plasma Enhanced Chemical Vapor Deposition (PECVD) and were deposited directly on copper foil, which is the most widely used current collector material for batteries. By varying the relative flow rate of silane and ammonia (precursor gases), and by varying the deposition power, the composition of the anode, its porosity and mass loading can be varied. The resultant anodes were employed to assemble coin cell against lithium metal as the counter electrode. Compositional analysis revealed that the anodes deposited at different power and at a particular flow-rate ratio (flow of ammonia to the total flow of gas) lead to the same stoichiometry of SiNx. When tested as anode for lithium-ion battery, the material with composition SiN0.32 could deliver a specific capacity of 1567 mAh.g−1 at a current density of 75 mA.g−1, which compares to a C-rate of C/20. With an increased nitrogen content in SiNx a decrease in the specific capacity and better capacity retention was observed. Furthermore, this work directs that a good balance of porosity and areal mass loading of SiNx is crucial to achieve high performance lithium-ion battery anode.