Marciel, Amanda B2024-05-222024-05-222024-052024-04-18May 2024Samani, Mohammad Hossein Khalili. High-Purity 2D Perovskite Thin Films: Role of Solvent Interactions for Solution-Processed Optoelectronic Materials. (2024). PhD diss., Rice University. https://hdl.handle.net/1911/116208https://hdl.handle.net/1911/116208Perovskite solar cells have emerged as a hot topic in recent years with their promise of a cheaper and more efficient alternative to conventional silicon solar cells. While 3D perovskites have demonstrated impressive performance in solar cells, their long-term stability remains to be a challenge. This has led to exploration of 2D perovskites, which offer improved stability due to their unique atomic structure. In this thesis, we address several factors impacting stability, phase purity, and device performance of 2D perovskite systems. Firstly, we present a new synthetic route to produce single n–valued parent crys- tals. The phase selective method involves precrystallization of parent crystals with a single phase structure, that upon dissolution, yield memory seeds for a patterned growth and nucleation of thin films. Our analyses showed the parent crystals are 100% phase pure and resulting thin films have upwards of 90% phase purity with minor undesired n–phases. We monitored the seeds and growth process by dynamic light scattering and optical microscopy techniques, and fabricated devices with high stability and efficiencies (> 17%). Next, we probe the mechanism by which memory seeds interact with processing solvents of varying propertie, including polar, hydrogen bonding, van der Waals inter- actions to deepen our understanding of the dissolution process of phase-pure parent crystals. We leveraged dynamic light scattering, microscopy, and spectroscopy tech- niques to monitor different steps of film formation. Our study demonstrates that solvents exhibiting high propensity for hydrogen bonding and diminished dispersion forces promote the formation of thin films with superior phase purity and the tar- geted out-of-plane orientation. Conversely, solvents with dominant dispersion forces and a diminished capacity for hydrogen bonding lead to the formation of thin films exhibiting poor phase purity, diminished excitonic peak intensities, and an undesired in-plane orientation. Lastly, we increased device efficiency by employing lithium-doped nickel oxide (Li-doped NiOX) as the hole transport layer (HTL). This Li-doped HTL not only improves the physical characteristics of the 2D perovskite film structure, crystal formation, and alignment, but also optimizes the energy levels within the device, leading to efficient charge extraction. Furthermore, the resulting 2D perovskite solar cells with Li-doped NiOX demonstrate excellent stability under light exposure. In summary, this thesis presents works on improving stability, efficiency, and life-time of solar cell devices based on 2D metal halide perovskites. This goal has been achieved by engineering of different steps leading to the device fabrication, such as optimization of crystal synthesis, solvent-perovskite interactions, and transport layer engineering of the device module.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.PerovskitesSolvent EngineeringThin FilmsSolar CellsThesis2024-05-22