Low-dimensional perovskite nanoplatelet synthesis using in situ photophysical monitoring to establish controlled growth.

Perovskite nanoparticles have attracted the attention of research groups around the world for their impressive photophysical properties, facile synthesis and versatile surface chemistry. Here, we report a synthetic route that takes advantage of a suite of soluble precursors to generate CsPbBr3 perovskite nanoplatelets with fine control over size, thickness and optical properties. We demonstrate near unit cell precision, creating well characterized materials with sharp, narrow emission lines at 430, 460 and 490 nm corresponding to nanoplatelets that are 2, 4, and 6 unit cells thick, respectively. Nanoplatelets were characterized with optical spectroscopy, atomic force microscopy, scanning electron microscopy and transmission electron microscopy to explicitly correlate growth conditions, thickness and resulting photophysical properties. Detailed in situ photoluminescence spectroscopic studies were carried out to understand and optimize particle growth by correlating light emission with nanoplatelet growth across a range of synthetic conditions. It was found that nanoplatelet thickness and emission wavelength increase as the ratio of oleic acid to oleyl amine or the reaction temperature is increased. Using this information, we control the lateral size, width and corresponding emission wavelength of the desired nanoplatelets by modulating the temperature and ratios of the ligand

Proses Produksi Dan Pengemasan Yoghurtdicv. Cita Nasional Salatiga

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A Modular Approach to the Synthesis of Electron-Deficient Organic Semiconducting Materials

Utilizing extended pi conjugated structures, organic semiconducting materials can effectively transport charges and are imbued with properties unique from inorganic systems. The field of organic electronics has achieved preliminary success in applying these semiconducting small molecules and polymers to intriguing new applications, such as thin-film technology, biologically compatible electronics, flexible devices, and many other areas. Further advances in organic electronics require the discovery of new materials. For over two decades, fullerene based acceptors have been considered essential for high performance, slowing development of alternative electron deficient materials. Work undertaken in this dissertation focuses on advancing the next generation of non-fullerene acceptor materials. Robust and modular chemistry aids in the successful development of novel, high performance, electron acceptor materials with controllable physical and optoelectronic properties. This modular and robust synthesis is exemplified by the development of bay-annulated indigo (BAI). Using indigo as a precursor, this stable amide-based withdrawing unit has outstanding charge transport properties, showing one of the highest recorded ambipolar conductivities. In order to better control intermolecular interactions, a method to desymmetrize the BAI core has been developed. Using this new methodology, a donor-acceptor BAI adduct is synthesized which self-assembles into nanowires that are capable of transporting charge. The use of this self-assembling material as an additive for photovoltaic applications gives an improvement in solar cell efficiency of ~11% over the control P3HT/PC[60]BM device. To enhance the withdrawing character of existing conjugated systems, the 2-(1,3-dithiol-2-ylidene)malononitrile (DTM) group is proposed. Condensation of activated methylene compounds, such as malononitrile, with carbon disulfide produces a nucleophilic dithiolate salt that can participate in SNAr reactions. Incorporation of this withdrawing group is found to significantly alter the optoelectronic properties of 1,2,5-benzothiadiazole (BTD) acceptors. When monomers functionalized with the DTM group are polymerized, the resulting polymers have broadened light absorption, strong thermochromic and solvatochromic behavior, and improved crystallinity compared to a control fluorinated polymer analogue. When used as the active component in organic field effect transistors (OFETs) the DTM modified polymer is imbued with the ability to transport both electrons and holes, whereas the fluorinated polymer is a unipolar hole transport material. Finally, a wide band gap acceptor is developed with the goal of improving the open circuit voltage (VOC) in solar cells. Utilizing the flagship non-fullerene acceptor ITIC as a template, a new family of molecules are synthesized using weakly withdrawing thiobarbituric acid (TBTA) groups to raise the lowest unoccupied molecular orbital (LUMO) energy. Not only does this result in an increased VOC, but the material outperforms the parent ITIC acceptor. To understand the solid state properties of the TBTA based acceptor, a morphological study is undertaken. The withdrawing TBTA groups are functionalized with a range of solubilizing hydrocarbon chains to provide a meaningful comparison. When applied to solar cells the effect on performance is drastic. Grazing incidence wide angle x-ray scattering (GIWAXS) experiments are performed to examine the crystallinity and intermolecular interactions in this system. Using this information, clear relationships are drawn between molecular functionality and device performance. This underlies the importance of morphological studies and demonstrates a need to understand these complex relationships

Functional Organic Semiconductors Based on Bay-Annulated Indigo (BAI).

The advancement of organic electronics has been continually pushed by the need for stable and high performance acceptor materials. By utilizing inexpensive and stable indigo dye as a starting material, Bay-Annulated Indigo (BAI) provides a new motif for the development of semiconducting materials. Modular and straightforward synthesis makes BAI an outstanding platform for molecular design, while excellent stability, strong absorption, and high ambipolar mobility render BAI-based materials excellent candidates for organic electronics. BAI-based polymers and small molecules have taken advantage of these properties to show promising results in a variety of applications

Stepwise Bay Annulation of Indigo for the Synthesis of Desymmetrized Electron Acceptors and Donor-Acceptor Constructs.

A selective stepwise annulation of indigo has been demonstrated as a means of providing both monoannulated and differentially double-annulated indigo derivatives. Disparate substitution of the electron accepting bay-annulated indigo system allows for fine control over both the electronic properties as well as donor-acceptor structural architectures. Optical and electronic properties were characterized computationally as well as through UV-vis absorption spectroscopy and cyclic voltammetry. This straightforward method provides a modular approach for the design of indigo-based materials with tailored optoelectronic properties