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  1. A new generation of quantum material derived from intercalating zerovalent atoms such as Cu into the intrinsic van der Waals gap at the interface of atomically thin two-dimensional GeSe/SnS heterostructure is designed, and their optoelectronic features are explored for next-generation photovoltaic applications. Advanced ab initio modeling reveals that many-body effects induce intermediate band (IB) states, with subband gaps (~0.78 and 1.26 electron volts) ideal for next-generation solar devices, which promise efficiency greater than the Shockley-Queisser limit of ~32%. The charge carriers across the heterojunction are both energetically and spontaneously spatially confined, reducing nonradiative recombination and boosting quantum efficiency. Using this IB material in a solar cell prototype enhances absorption and carrier generation in the near-infrared to visible light range. Tuning the active layer’s thickness increases optical activity at wavelengths greater than 600 nm, achieving ~190% external quantum efficiency over a broad solar wavelength range, underscoring its potential in advanced photovoltaic technology.

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  2. Two-dimensional Cs3Bi2I9 (2D CBI) belongs to a family of soft nanomaterials and has been previously shown to host large electrophotonic responses and optically addressable valley degrees of freedom governed by flat bands, large carrier effective masses, and quantum confinement [Phys. Rev. Mater. 7, 2, 024002 (2023)]. Using advanced ab initio methods, we show the evolution of the excitonic features of 2D CBI with isoelectronic substitution of iodine with chlorine: Cs3Bi2I9-xClx (0 ≤ x ≤ 9). Our calculations reveal a significant increase in the excitonic behavior with exciton binding energy Eb as high as 3.0 ± 0.2 eV. Such Eb is significantly larger than those reported in any 2D materials. Our analysis shows notable deviation from established binding energy scaling laws for generic 2D materials. 
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  3. We report the mechanical properties of cubic boron nitride (c-BN) and diamond under the combined impact of dynamical pressure and temperature, calculated using ab initio molecular dynamics. Our study revealed a pronounced sensitivity of the mechanical properties of c-BN to applied pressure. Notably, c-BN undergoes a brittle-to-ductile transition at ∼220 GPa, consistent across various dynamical temperatures, while diamond exhibits no such transition. Furthermore, the Vickers hardness profile for c-BN closely mirrors that of diamond across a spectrum of temperature–pressure conditions, highlighting c-BN's significant mechanical robustness. These results underscore the superior resilience and adaptability of c-BN compared to diamond, suggesting its potential as an ideal candidate for applications in extreme environments.

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    Free, publicly-accessible full text available December 4, 2024
  4. Razeghi, Manijeh ; Jarrahi, Mona (Ed.)
    GeS and GeSe are 2D semiconductors with band gaps in the near infrared and predicted high carrier mobility. We find that excitation with 800 nm pulses results in long-lived free photocarriers, persisting for hundreds of picoseconds, in GeS and GeSe noribbons. We also demonstrate that zerovalent Cu intercalation is an effective tool for tuning the photoconductive response. Intercalation of ~ 3 atomic % of zerovalent Cu reduces the carrier lifetime in GeSe and GeS. In GeS, it also shortens the photoconductivity rise and improves carrier mobility. 
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  5. Free, publicly-accessible full text available August 1, 2024