Organic semiconductors have shown exceptional opportunities for manipulating energy in a range of structures in light-emitting diodes, lasers, transistors, transparent photovoltaics, etc. with the presence of excitons at room temperature that distinguishes them from traditional semiconductors. The control over the crystalline order, orientation, layer-coupling as well as defect formation are the key to the fabrication and optimization for improving the performance of organic electronics. In the first part of this thesis, we focus on understanding organic crystalline growth. Organic homoepitaxy growth mode is mapped as a function of vapor phase growth conditions on high quality organic crystalline substrates. Organic-organic hetero-quasiepitaxy is then studied to explore the design rules for ordered alternating organic growth similar to inorganic quantum well structure. A unique organic edge driven case is demonstrated providing new routes to controlling molecular orientation and multilayer ordering. These results could enable entirely new opportunities for enhancing unique excitonic tunability and could also be used as a platform to study organic exciton confinement and strong coupling.The second part of the thesis is focused on inorganic halide perovskite growth. Hybrid halide perovskites have attracted tremendous attention as an exceptional new class of semiconductors for solar harvesting, light emission, lasing, quantum dots, thin-film electronics, etc. However, the toxicity of lead devices and lead manufacturing combined with the instability of organic components have been two key barriers to widespread applications. In this work, we demonstrate the first single-domain epitaxial growth of halide perovskites. This in situ growth study is enabled by the study of homoepitaxy and mixed-homoepitaxy of metal halide crystals that demonstrates the capability of performing reflection high-energy electron diffraction (RHEED) on insulating surfaces. We then focus on tin-based inorganic halide perovskites, CsSnX3 (X = Cl, Br, and I), on lattice-matched metal halide crystals via reactive vapor growth route that leads to single-domain epitaxial films with excellent crystalline order lacking in solution processing. Exploiting this highly controllable epitaxial growth we demonstrate the first halide perovskite quantum wells that creates photoluminescent tunability with different well width. These demonstrations could spark the exploration of a full range of epitaxial halide perovskites and lead to novel applications for metal-halide-perovskite based single-crystal epitaxial optoelectronics.
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