SEARCHING FOR Bi3+ PEROVSKITE OXYHALIDES: EXAMINING THE RELATIONSHIP BETWEEN STABILITY AND BISMUTH LONE PAIR HYBRIDIZATION
Date
2018-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Despite notable advancements in light-harvesting technology, the costs associated with refining silicon to the purity necessary for solar cell applications have prevented this technology from being made available to the poorest and most in-need communities.1 Over the past decade, research on a new light-harvesting structure, the hybrid organic-inorganic perovskite, has seen its single-junction power conversion efficiency jump from 3.8 % to over 22.1 % in little more than a decade.2,3 Meanwhile, silicon analog efficiencies have reached 26.3% after more than six decades of research and development.4
Compared to silicon solar cells, high-efficiency perovskites are easier to fabricate, cheaper to produce, less sensitive to chemical impurities, and highly tunable over wide ranges of band gap energies; making them suitable to a vast variety of applications for wavelengths up and down the electromagnetic spectrum.5 The most efficient perovskite structure published in the recent literature is methylammonium lead iodide (MAPbI3).3,6 Despite its high performance, the acute toxicity and low stability of the lead moiety of this compound has challenged researchers to synthesize chemical variants that are not only safer and more stable, but also possess photoelectric efficiencies on par with that of MAPbI3.7
The motivation for this work is to use the recent inception of perovskites in solar cell technology, along with bismuth- (lead’s nontoxic neighbor)- to produce a solar cell from common, inexpensive, and safe materials. The substitution of lead with bismuth requires a change in the metal atom’s valence state from +2 to +3, as well as the inclusion of a more easily-hybridized 6s lone pair.8 When hybridized, these electrons break the polyhedron backbone of the perovskite crystal, which could lead to layered Aurivillius crystal phases instead of the desired perovskite structure.9 This work therefore aims to synthesize a bismuth perovskite compound in which the bismuth lone pair does not hybridize and the perovskite symmetry is preserved.
Description
Keywords
chemical engineering, Biomolecular Engineering, bismuth, oxyhalides, lone pair hybridization