Functional Nanomaterials: Functional Low-dimensional Materials (0D, 1D, 2D) Driving Innovations in Electronics, Energy, Sensors, and Environmental Engineering and Science 2021: Functional Nanomaterials
Sponsored by: TMS Functional Materials Division, TMS: Nanomaterials Committee
Program Organizers: Jiyoung Chang, University Of Utah; Michael Cai Wang, University of South Florida; Sarah Zhong, University of South Florida; Sun Choi, Korea Institute of Science and Technology; Pei Dong, George Mason University

Thursday 2:00 PM
March 18, 2021
Room: RM 45
Location: TMS2021 Virtual

Session Chair: Sarah Zhong, University of South Florida; Michael Wang, University of South Florida

2:00 PM  Invited
Direct Backbone Attachment of Polyesters on Grain Boundaries Enhances Chemical Stability and Suppressing Ion Migration in CH₃NH₃PbI₃ Hybrid Perovskite Solar Cells: Chang-Yong Nam¹; ¹Brookhaven National Laboratory
    Here, we have identified a new polar polymer, polycaprolactone (PCL), to passivate grain boundaries (GBs) of methylammonium lead triiodide (MAPbI₃) perovskites with only 1 – 2 polymer monolayers via direct backbone attachment. The solar cell with passivated MAPbI₃ exhibited improved power conversion efficiencies up to 20.1 %, with 90 % of the initial PCE being preserved after 400-h ambient storage, and 80 % even after 100-h, 85 C aging. The improved stability indicates critical roles of PCL GB passivation in retarding moisture-induced decomposition and suppressing ion migration within perovskites. Time-of-flight secondary ion mass spectrometry revealed that I^- ions could actively migrate into electrode, hole transport layer, and their interface in non-passivated device, even without externally applied electric field, while such migrations were significantly mitigated in PCL-passivated devices. This effective GB passivation by PCL suggests an important potential of polymer additives towards the development of stable high-performance perovskite solar cells.

2:25 PM
Antireflective Hybrid Nanocoatings Derived via Heated Liquid-phase Infiltration in Hierarchically Self-Assembled Block Copolymer Thin Film Templates: Ashwanth Subramanian¹; Nikhil Tiwale²; Gregory Doerk²; Kim Kisslinger²; Chang-Yong Nam²; ¹Stony Brook University; ²Brookhaven National Laboratory
    Here, we demonstrate a facile temperature-enhanced liquid-phase infiltration (LPI) method to control and drastically increase the quantity and kinetics of Pt infiltration into self-assembled block copolymer (BCP) thin films. By applying LPI at mildly elevated temperatures (40–80 °C), we showcase controllable optical functionality of hybrid BCP films along with conductive three-dimensional (3D) inorganic nanostructures. Quantitative analysis revealed enhanced metal loading into the BCP matrix at higher LPI temperatures. Combining temperature-enhanced LPI with hierarchical multilayer BCP self-assembly, we generated BCP-metal hybrid optical coatings featuring stack-layer-number-dependent antireflective properties as well as 3D Pt nanomesh structures displaying 3D percolating electrical conductance. This work not only enables tunability of organic-inorganic hybrid nanostructures and properties but also expands the library of materials that can be infiltration synthesized, paving a way for synthesizing BCP-templated, unique functional hybrid and inorganic nanostructures for applications in photochemical sensing, energy conversion, and storage.

2:45 PM
Giant Low-temperature Anharmonicity in Silicon Nanocrystals: Shuonan Chen¹; Devin Coleman¹; Douglas Abernathy²; Arnab Banerjee²; Luke Daemen²; Lorenzo Mangolini¹; Chen Li¹; ¹University of California, Riverside; ²Oak Ridge National Laboratory
    The phonon density of states of silicon nanocrystals with size between 4 and 7.5 nm was measured by inelastic neutron scattering in the 5~600 K temperature range. The narrow particle size distributions enable the study of size effects on phonon dynamics. Giant softening of phonon features below 30 meV, universal broadening of phonon features, and the disappearance of intermediate-energy phonons were observed with decreasing nanocrystals size. Such size effects are mostly attributed to the structure variations within the nanocrystals. The phonons below 30 meV in silicon nanocrystals show temperature dependence opposite to the bulk silicon, explained by the large anharmonicity of the under-constrained near-surface phonons. This is supported by the abnormal atomic mean-square-displacement, and low energy phonon population in small silicon nanocrystals. This work provides crucial information on the phonon dynamics in spatially confined materials.

3:05 PM  Invited
Nanomaterials for Multispectral Adaptive Radiative Heating and Cooling: Po-Chun Hsu¹; ¹Duke University
    Nanomaterials have been an essential component of thermal radiation heat management. By interrogating and controlling the structure-property relationship, innovative nanomaterials such as solar thermal plasmonic selective absorbers, rooftop radiative coolers, and wearable personal thermal management all resulted in extraordinary performance boosts in energy and sustainability applications. The next breakthroughs will lie in how to surpass the static and monofunctional nanomaterials and develop the nanomaterials and devices that can respond to ambient fluctuation at multiple wavelengths of thermal radiation, ranging from, visible, near-IR, to mid-IR. In this presentation, I will introduce several smart multispectral light- and heat-managing nanomaterials for building energy efficiency and personal digital therapeutics. The talk will encompass their fundamental scientific principles and engineering design criteria and demonstrate the scalability of these innovations.

3:30 PM  Invited
Silicon Carbide Biotechnology: Carbon-based Neural Interfaces: Chenyin Feng¹; Mohamad Beygi¹; Christopher Frewin¹; Md Rubayat-E Tanjil Rubayat-E Tanjil²; Ashok Kumar²; Michael Wang²; Stephen Saddow¹; ¹University of South Florida; ²USF ME
    Silicon carbide (SiC) is a semiconductor that displays ceramic-like properties. Long known for its hardness and resistance to chemical attack, numerous reports of SiC as a potential material for interfacing with the human body have been around for decades. However only recently has a comprehensive look into SiC for biomedical devices been undertaken. The USF SiC Group started to study the biocompatibility of various SiC single-crystalline forms, known as polytypes, in 2005 and our research was aimed at understanding the potential of SiC for biomedical applications. We have since developed SiC for several biomedical applications. In this talk we will focus on using carbon-based conductors to realize long-term, highly neural-compatible, interfaces and review progress to date on all-SiC interfaces which have shown the possibility of being MRI compatible.

3:55 PM
Substituent Effects on Electronic Properties of Cy5: Density Functional and Time-Dependent Density Functional Calculations: Austin Biaggne¹; Lan Li¹; Bernard Yurke¹; ¹Boise State University
    The electronic properties of the cyanine dye Cy5 were studied using density functional theory and time dependent density functional theory. The solvation energy and static dipole difference of Cy5 are of interest for their effects on the excitonic properties of cyanine aggregates. By modifying the ends of Cy5 to include substituent groups with varying electron donating and accepting strengths, the dye’s solvation energy and static dipole difference can be modified. We found that the inclusion of substituents decreases the solvation energy of Cy5, making it more hydrophilic. Dyes with two electron accepting substituents or accepting and donating substituents were found to have static dipole magnitudes up to 3 times that of pristine Cy5. It was also found that the trend of increasing static dipole difference is positively correlated to the increasing sum of the substituent’s Hammett constants, which quantify the electron donating or accepting strength of the substituents.