Abstract
Iron pyrite (fool's gold, FeS2) is a promising earth abundant and environmentally benign semiconductor material that shows promise as a strong and broad absorber for photovoltaics and high energy density cathode material for batteries. However, controlling FeS2 nanocrystal formation (composition, size, shape, stoichiometry, etc.) and defect mitigation still remains a challenge. These problems represent significant limitations in the ability to control electrical, optical and electrochemical properties to exploit pyrite's full potential for sustainable energy applications. Here, we report a symmetry-defying oriented attachment FeS2 nanocrystal growth by examining the nanostructure evolution and recrystallization to uncover how the shape, size and defects of FeS2 nanocrystals changes during growth. It is demonstrated that a well-controlled reaction temperature and annealing time results in polycrystal-to-monocrystal formation and defect annihilation, which correlates with the performance of photoresponse devices. This knowledge opens up a new tactic to address pyrite's known defect problems.
Highlights
Iron pyrite is a promising earth abundant and environmentally benign semiconductor material that shows promise as a strong and broad absorber for photovoltaics and high energy density cathode material for batteries
The initial step in synthesis of FeS2 nanocrystals consists of the creation of FeS2 quantum dot (QD) seeds
QD formations are realized by a rapid hot-injection of sulfur into an iron precursor solution, quickly creating QDs which show an average diameter of 2 nm with a narrow size distribution (Figure 1 and Supplementary Fig. S1) and create a transparent deep blue solution when dissolved in chloroform
Summary
Iron pyrite (fool’s gold, FeS2) is a promising earth abundant and environmentally benign semiconductor material that shows promise as a strong and broad absorber for photovoltaics and high energy density cathode material for batteries. The basics of the OA process are (1) primary nano-clusters or particles aggregate, (2) a rotational step to achieve collision of higher energy surfaces occurs, (3) removal of surfactants or absorbates, and (4) coherence is achieved by combination of the high surface energy facets into a single crystal that results in the reduction the overall surface energy of the particle This coherence, while thermodynamically favorable, may create line and plane defects and twining. The new process exhibits a combination of LaMer theory for the initial quantum dot seeds followed by OA growth to create the shape, size www.nature.com/scientificreports and crystallinity of the FeS2 nanocrystals. The performance of photodetector devices created out of FeS2 pyrite nanosheets will be presented and analyzed
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