Halide Perovskite and Perovskite-Inspired Nanocrystals for Optoelectronic Applications

Optoelectronic applications, such as photovoltaics (PVs) and light-emitting diodes (LEDs), play a key role in addressing the global energy crisis. Yet, they demand new semiconductors with high stability, low environmental impact, and low cost. One of the attractive ways of synthesizing semiconductor materials is their colloidal synthesis at the nanoscale, leading to nanocrystals (NCs). This thesis focuses on a promising family of NCs extensively investigated during the last decade, namely NCs based on halide perovskites and their derivatives. Halide perovskite nanocrystals (PNCs) display appealing optoelectronic properties due to high defect tolerance, tunable crystal structures and dimensions, and versatile synthesis. However, a comprehensive optimization of these PNCs synthesis to enhance their stability and optical properties is lacking. Furthermore, the understanding of the fundamental structure-property relationships in emerging PNCs is still very limited. At the same time, the toxicity of lead (Pb) present in the most efficient PNC compositions demands the development of eco-friendly lead-free PNCs for optoelectronic applications. In this dissertation, we have identified the relationships between the synthesis and the key properties of emerging or novel PNCs, starting from the popular CsPbI3 and then moving towards Pb-free compositions. In particular, we have (i) enhanced the phase stability of CsPbI3 PNCs by tailoring the reaction temperature, (ii) achieved highly luminescent CsMnCl3 PNCs by tailoring the synthesis of the emissive crystalline phase, and (iii) proposed the first-ever syntheses of Cs2TiX6 (X = Br and Cl) PNCs and phase-pure AgBiI4 perovskite-inspired NCs with enhanced stabilities for potential nonlinear optical applications. We believe that the results of this thesis will encourage other researchers and practitioners in the field to further investigate the promising perovskites and perovskite-inspired NCs that we have identified and eventually enable their usage in real-life optoelectronics applications

Triple A-Site Cation Mixing in 2D Perovskite-Inspired Antimony Halide Absorbers for Efficient Indoor Photovoltaics

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Structure-induced optoelectronic properties of phenothiazine-based materials

Phenothiazine (PTZ)-based materials have recently received considerable interest owing to their intriguing optoelectronic properties, low-cost, versatility of functionalization, and commercial availability. The advent of molecular engineering concepts in π-conjugated organic materials, such as the “donor-acceptor” approach, propelled the synthesis of a large number of PTZ-derivatives with tailored properties like low bandgap, tunable energy levels, and reversible redox properties. This resulted in the promising application of PTZs as electron donors or acceptors in organic solar cells or as hole-transporting materials in organic light-emitting diodes and perovskite solar cells. In this review, we discuss the recent and most appealing design strategies of PTZ-based materials for optoelectronics, with emphasis on the impact of the structural modifications on the fundamental physicochemical properties (absorption, emission, frontier energy levels, charge carrier mobility). We also highlight the key achievements in the development of solar cells, light-emitting diodes, and batteries employing PTZ core semiconductors. Our final goal is to underpin the reasons that still limit the performance of PTZ-based optoelectronics and to outline future research directions for the next-generation PTZ materials with ever enhanced properties.publishedVersionPeer reviewe