Abstract

Perovskites are a material of emerging interest due to their unique optoelectronic properties, highly tunable bandgap and ease of synthesis which elevates their potential usage in LEDs and photovoltaics. Their discovery in the early 1800s has led to a surge of research which has been able to catch up to the leading solar cells in terms of efficiency despite their habit of degrading when exposed to air and moisture. This work describes two methods for reducing the environmental and health implications of lead halide perovskite degradation.
The first method involves protecting synthesized CsPbX3 (X = Br, Cl, I) nanocrystals, through the substitution of its parent capping groups (oleic acid and oleylamine) with fluorinated benzoic acid derivatives (3-fluorobenzoic acid, 2,4-difluorobenzoic acid, 2,6-bis(trifluoromethyl)benzoic acid, and 2,3,4,5-tetrafluorobenzoic acid). The fluorine moieties result in capping groups that are intrinsically hydrophobic. The effects of the bulkiness and/or the hydrophobic nature of the fluorinated capping groups are hereby explored.
Lead halide perovskites known for having low stability in ambient conditions, tend to degrade readily into CsBr and toxic lead compounds such as PbBr2 and PbCO3. The second method involves synthesizing a novel lead-free double perovskite nanocrystal that is composed of a “doubled” perovskite unit cell, Cs2NaYbCl6. Each of these syntheses are characterized using a mix of techniques such as photoluminescence, quantum yield, FT-IR, TEM, and NMR in hopes that these methods may bring about a route for further application of these materials. This thesis forms a series of fluorinated group capped CsPbBr3 nanocrystals and the synthesis of a novel lead-free double perovskite.