Halide Perovskite and Perovskite-Inspired Light Emitters: Synthesis and Optical Spectroscopy

Abstract

Anthropogenic climate change needs urgent tackling to keep the global temperature rise below 2 °C above pre-industrial levels. Renewable energy use, energy efficiency, and other measures are necessary to achieve this goal. Lead halide perovskites have in the past decade shown themselves to be a promising, novel solar cell technology, with efficiencies beyond 25 %. Lead halide perovskites cannot only harvest but also emit light very efficiently and could thereby increase the efficiency of currently employed lighting technologies and reduce energy use for lighting, which accounts for 5 % of the world-wide greenhouse gas emissions. Despite their strong potential, perovskite light-emitting diodes face significant challenges to be introduced practically, specifically due to poor operating lifetime, a decrease in quantum efficiency at higher current densities, and poor efficiencies of blue devices compared to red and green counterparts. In addition, structural and resulting optical instabilities have yet prevented the fabrication of an electroluminescent, white light-emitting diode composed of a red-, green-, and blue-emitting lead halide perovskite layer. In this thesis, the fabrication and optical characterisation of a trichromatic (red, green, blue) all lead halide perovskite white-emitting layer is presented, which is not limited by structural and optical instabilities and acts as promising building block to make the first electroluminescent, trichromatic perovskite white light-emitting diode. Furthermore, this thesis presents the synthesis, characterisation, and photophysics of perovskite-inspired Cs2ZrX6 (X = Cl, Br) nanocrystals, which are amongst the strongest currently known emitters of this class of antifluorite materials and could be a true lead-free alternative in white light-emitting applications. Finally, this thesis highlights the differences in the emission properties of manganese-doped and undoped, blue-emitting lead halide perovskite nanomaterials, which show promise for implementation in more stable blue light-emitting diodes. Overall, this thesis presents fundamental studies on some strong light emitters that could enable more efficient and stable light-emitting applications.