Ajayan, Pulickel M.2019-05-172019-05-172018-052018-04-20May 2018Tsai, Hsinhan. "Hybrid Perovskite Materials for Stable Optoelectronics Applications." (2018) Diss., Rice University. <a href="https://hdl.handle.net/1911/105735">https://hdl.handle.net/1911/105735</a>.https://hdl.handle.net/1911/105735Organic-inorganic hybrid perovskites materials have grab enormous attention in the material research community. This is because of their exceptional semiconducting properties such as direct band gap, free carrier generation, broad absorption range, long diffusion length and carrier lifetime, which enable highly efficient photovoltaic device over 22%, surpassing other classical semiconductors in few years. However, one fundamental bottleneck remains in this system that mitigates such material from wide use that are reproducibility, photo- and chemical instability. These are found to be closely related to the structure of the material, such as the hydroscopic nature of the organic cation, symmetry of the crystal structure and degree of thin film crystallinity. Therefore, the focus of this thesis is to understand the basic mechanism in structure that dominate the stability of perovskites materials properties and design robust hybrid perovskite structures through organic cation engineering. Through synthetic approach, we found that the bulky organic molecules can be inserted to the perovskite lattice, forming a layered structure with quantum and dielectric confinement, called Ruddlesden-Popper (RP) perovskites. Employing our previously developed hot-casting method, we were able to obtain near single crystalline thin film with preferred orientation. With the protection of the bulky molecules, the stability of the perovskite layers is much extended. Beyond the photovoltaics, the oriented, highly crystalline thin film can facilitate the current injection in light-emitting diodes (LEDs) which had high radiance with 1 % EQE in device performance. The devices also had low turn-on voltage which can decrease the energy consumption and benefit to lighting applications. This thesis demonstrates the detail solutions for fundamental problems and the research results can help to promote technologies and push the limits in hybrid perovskites optoelectronics society.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.hybrid perovskitesLEDsphotovoltaicscrystal orientationThesis2019-05-17