Metal halide perovskites (simplified as perovskites as below), particularly those in nanocrystal forms, have recently emerged as highly efficient, bandgap tunable photonics materials that can be easily solution processed at low cost for display, lighting or other energy conversion applications. However, the quick degradation of perovskite nanocrystals under external stresses or upon colloidal aggregations has been a major challenge for most applications where high reliability is normally required. In this thesis, we have explored a polymer swelling-deswelling microencapsulation (SDM) process that enables the dispersion, in-situ crystallization and subsequent surface passivation of perovskite nanocrystals in polymer matrices, and leads to ultrastable metal halide perovskites - polymer composites (PPCs) with outstanding optical properties for various efficient and highly reliable photonics applications. In chapter two, we have proved the SDM concept by synthesizing green emitting CH3NH3PbBr3 PPCs with high photoluminescence (PL) efficiency and pure color emission, which can survive boiling water treatment for 30 min with less than 7% PL efficiency decay. In the third chapter, we extend the SDM principle to inorganic perovskites and synthesized CsPbBr3 nanorods in a polymer matrix (NRs-PM), which show polarized emission due to dielectric contrast and anisotropic shape. The NRs-PM can be aligned in macroscale through mechanical stretching at elevated temperature. In chapter four, we demonstrate that with ligand assisted SDM, PPCs of various emitting colors ranging from blue to near-infrared can be obtained, and high efficiency ( > 70%) can be achieved for PPCs of a wide range of optical density (0.05 to 0.78) without concentration quenching. The high efficiency, wide tunability and outstanding stability of these SDM-derived PPCs could enable a broad range of photonics applications. In chapter five, we propose to use a hybrid downconverter system comprising green PPC films and state-of-the-art red emitting downconverters for LCD backlight to realize wide color gamut. Beyond conventional displays, in chapter six, we introduce three novel applications that may be enabled by PPCs: 1) Tailored lighting that can provide delicate spectral control, 2) Highly transparent emissive projection display with high ambient contrast, low haze level and wide viewing angle, and 3) X-ray scintillators with high resolution and fast response.
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Doctor of Philosophy (Ph.D.)
College of Optics and Photonics
Optics and Photonics
Optics and Photonics
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
He, Juan, "Stable, Highly Luminescent Perovskite-Polymer Composites for Photonics Applications" (2019). Electronic Theses and Dissertations, 2004-2019. 6850.