Polymer Dependent Optical Properties of Hybrid Perovskite Materials
Open Access
- Author:
- Jones, Lindsay
- Area of Honors:
- Materials Science and Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Robert John Hickey, III, Thesis Supervisor
Amy Carol Robinson, Thesis Honors Advisor - Keywords:
- perovskite
polymer
nanocrystals
photovoltaics - Abstract:
- Hybrid organic-inorganic perovskites are an exciting class of materials with applications in solar cells, flash photomemory, and light-emitting diodes (LEDs). These materials have the potential to contribute to the advancement of renewable energy and next-generation computing. With such a wide range of applications, there is a need to precisely tune the perovskite state (bulk versus nanocrystals) for specific application needs. Previous studies have used polymers as matrices for increased crystal stability and protection from degradation by water or heat. In addition, polymers have been shown to reduce the defects in the crystals, thus improving device performance. However, there are open questions regarding the role polymers play with respect to perovskite crystal growth. Tuning the size of the crystals is an exciting way to control the optical properties, which is critical for different applications. Therefore, it is proposed here that by choosing the appropriate polymers, they can act as "macroligands" that control the size of the crystal while also acting as a template for the perovskite synthesis, leading to highly tunable and stable organic-inorganic perovskite materials. We synthesized hybrid inorganic-organic perovskites materials composed of methylammonium lead bromide (MAPbBr3) and four different polymer matrices: poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), poly(styrene) (PS), and poly(vinylpyrrolidone) (PVP). Each polymer chosen exhibits a different chemical structure and composition, which directly affects the binding strength to the perovskite surface. The perovskite-polymer mixtures were studied as spin-coated films and in solution. Transmission electron microscopy (TEM) images and X-ray diffraction (XRD) data were used to confirm that nanocrystals form. Polar polymers that strongly interact with the perovskite materials, such as PVP, control crystal growth, resulting in nanocrystals. The formation of nanocrystals was further confirmed by samples exhibiting increased fluorescence and UV absorption in films versus solution. Knowing which polymers will yield bulk crystals and which will yield nanocrystals can lead to more informed decision-making when fabricating devices such as LEDs or solar cells, thus improving these devices’ performance.