Engineering halide perovskite nanoparticles using reverse micelle synthesis for enhanced stability, uniformity and use in optoelectronic devices

Abstract

In this thesis, we aimed to overcome the limitations of organo-metallic halide perovskites as materials for future optoelectronic applications. Despite having unique optical and electrical properties that make them attractive for various fields, such as energy conversion, photonics, and electronics, perovskites are known to be unstable in the presence of moisture, oxygen, and UV light. To tackle this issue, we employed a reverse micelle synthesis route using an amphiphilic diblock copolymer poly(styrene)-block-poly(2vinylpyridine) (PS-b-P2VP) as a nanoreactor, which was dissolved in a non-polar solvent. This approach allowed us to synthesize perovskite nanoparticles, with various A, B, and X site ions, with tunable emission wavelengths between 475 nm and 850 nm. Additionally, exploiting the properties of reverse micelle templating, novel properties were achieved including stable nanoparticles with two distinctly different emission spectra in a single solution, large induced Stokes shifts up to 660meV and high stability in ambient conditions over 200 days. To further improve the stability and electrical conductivity of perovskite nanoparticles, we created a core-shell structure by growing a suitable conductive shell around the perovskite nanoparticles using a three-step loading mechanism. For this, we opted for metal oxides with type-II band alignment with FAPbBr3, which allowed the separation of the exciton and improved the stability of the perovskite nanoparticles. We synthesized FAPbBr3-TiO2, FAPbBr3-NiO, and FAPbBr3-ZnO core-shell nanostructures with various shell thicknesses, which were able to withstand harsh conditions such as oxygen plasma etching. The incorporation of various nanoparticles as optical filters and as electrically active layers in organic solar cell devices resulted in an improvement in the overall performance. To apply the nanoparticles on sensitive surfaces, such as organic thin films, we also developed an indirect mechanical method using graphene transfer printing. This technique allowed us to successfully transfer perovskite and iron oxide nanoparticles without loss of properties.