Showing papers by "Aram Amassian published in 2023"

Hybrid magnonics in hybrid perovskite antiferromagnets

Abstract: Hybrid magnonic systems are a newcomer for pursuing coherent information processing owing to their rich quantum engineering functionalities. One prototypical example is hybrid magnonics in antiferromagnets with an easy-plane anisotropy that resembles a quantum-mechanically mixed two-level spin system through the coupling of acoustic and optical magnons. Generally, the coupling between these orthogonal modes is forbidden due to their opposite parity. Here we show that the Dzyaloshinskii-Moriya-Interaction (DMI), a chiral antisymmetric interaction that occurs in magnetic systems with low symmetry, can lift this restriction. We report that layered hybrid perovskite antiferromagnets with an interlayer DMI can lead to a strong intrinsic magnon-magnon coupling strength up to 0.24 GHz, which is four times greater than the dissipation rates of the acoustic/optical modes. Our work shows that the DMI in these hybrid antiferromagnets holds promise for leveraging magnon-magnon coupling by harnessing symmetry breaking in a highly tunable, solution-processable layered magnetic platform.

Control of Phase Separation and Crystallization for <scp>High‐Efficiency</scp> and <scp>Mechanically Deformable</scp> Organic Solar Cells

Abstract: Stretchable organic solar cells (OSCs) have great potential as power sources for the next-generation wearable electronics. Although blending rigid photovoltaic components with soft insulating materials can easily endow the mechanical ductility of active layers, the photovoltaic efficiencies usually drops in the resulting OSCs. Herein, a high photovoltaic efficiency of 15.03% and a large crack-onset strain of 15.70% is simultaneously achieved based on a ternary blend consisting of polymer donor poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c']dithiophene-4,8-dione)] (PM6), non-fullerene accepter 2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2′′,3′′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl)bis (methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (Y6), and soft elastomer polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) through the control of phase separation and crystallization. By employing a high-boiling point solvent additive 1-chloronaphthalene (CN) with different solubilities for PM6 and Y6, the aggregation dynamics of PM6 and Y6 as well as the film solidification process are dramatically altered, allowing for the different molecular rearrangement and liquid–liquid phase separation evolution. Consequently, the ternary film with optimal CN content presents decreased SEBS domains and moderately improved molecular ordering of PM6 and Y6, enabling effective mechanical deformation and charge generation/transport. The revealed corrections between the film-formation process, film microstructure, and photovoltaic/mechanical characteristics in the ternary blend provide deep understanding of the morphology control toward high-performance stretchable OSCs.

Interactions between nonfullerene acceptors lead to unstable ternary organic photovoltaic cells.

Abstract: For organic photovoltaic (OPV) devices to achieve consistent performance and long operational lifetimes, organic semiconductors must be processed with precise control over their purity, composition, and structure. This is particularly important for high volume solar cell manufacturing where control of materials quality has a direct impact on yield and cost. Ternary-blend OPVs containing two acceptor-donor-acceptor (A-D-A)-type nonfullerene acceptors (NFAs) and a donor have proven to be an effective strategy to improve solar spectral coverage and reduce energy losses beyond that of binary-blend OPVs. Here, we show that the purity of such a ternary is compromised during blending to form a homogeneously mixed bulk heterojunction thin film. We find that the impurities originate from end-capping C=C/C=C exchange reactions of A-D-A-type NFAs, and that their presence influences both device reproducibility and long-term reliability. The end-capping exchange results in generation of up to four impurity constituents with strong dipolar character that interfere with the photoinduced charge transfer process, leading to reduced charge generation efficiency, morphological instabilities, and an increased vulnerability to photodegradation. As a consequence, the OPV efficiency falls to less than 65% of its initial value within 265 h when exposed to up to 10 suns intensity illumination. We propose potential molecular design strategies critical to enhancing the reproducibility as well as reliability of ternary OPVs by avoiding end-capping reactions.

Engineering ligand reactivity enables high-temperature operation of stable perovskite solar cells

Abstract: Perovskite solar cells (PSCs) consisting of interfacial two- and three-dimensional heterostructures that incorporate ammonium ligand intercalation have enabled rapid progress toward the goal of uniting performance with stability. However, as the field continues to seek ever-higher durability, additional tools that avoid progressive ligand intercalation are needed to minimize degradation at high temperatures. We used ammonium ligands that are nonreactive with the bulk of perovskites and investigated a library that varies ligand molecular structure systematically. We found that fluorinated aniliniums offer interfacial passivation and simultaneously minimize reactivity with perovskites. Using this approach, we report a certified quasi–steady-state power-conversion efficiency of 24.09% for inverted-structure PSCs. In an encapsulated device operating at 85°C and 50% relative humidity, we document a 1560-hour T85 at maximum power point under 1-sun illumination. Description Editor’s summary The thermal stability of three-dimensional perovskite solar cells can be improved by adding ammonium ligands that create a two-dimensional perovskite capping layers, but such ligands are prone to intercalation into the bulk. Park et al. showed that the smallest aromatic ligand, anilinium, had the lowest ligand reactivity with three-dimensional perovskites because of steric hindrance near the ammonium group, and a fluorinated derivative of this ligand created a robust interface structure. Encapsulated solar cells maintained 85% of their power conversion efficiency of about 20% at 85°C and 50% relative humidity after about 1600 hours of maximum power point operation. —PDS Suppressing ammonium ligand intercalation stabilizes the interface structure of perovskite solar cells at high temperatures.