Bulletin of the American Physical Society
2021 Annual Meeting of the APS Four Corners Section
Volume 66, Number 11
Friday–Saturday, October 8–9, 2021; Virtual; Mountain Daylight Time
Session E06: Physics of Solar Cell and Photovoltaic Materials |
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Chair: Markus Raschke, University of Colorado Boulder |
Friday, October 8, 2021 3:15PM - 3:27PM |
E06.00001: Structure-Property Correlations and Effect on Dynamics in intra-molecular Singlet Fission Moshe Chesler, Sumit Mazumdar Utilizing singlet fission (SF) in organic photovoltaics is a promising direction for overcoming fundamental efficiency limits in single-junction solar cells and thus may lead to development of more highly efficient next generation renewable energy technology. Attention in this area has recently shifted from intermolecular SF (xSF) between chromophores in a solid to intramolecular SF (iSF) between those in a dimer for which linked acene chains have presented as strong candidates for potential use in SF-based solar cells. We have performed high-order configuration interaction (CI) calculations on several candidate systems and found that the photophysics of such systems is highly dependent on various factors such as linkage between the chromophores and relative difference in chromophore size. While this sensitivity to structural changes makes developing a comprehensive theory and reliable set of design strategies for SF materials difficult, analyzing the electronic structure of the low-lying eigenstates of the SF process together with the ground state absorption spectrum for various molecules can provide a qualitative prediction for the dynamics of relevant systems and may ultimately help guide future materials characterization and design. [Preview Abstract] |
Friday, October 8, 2021 3:27PM - 3:39PM |
E06.00002: Dielectric spectroscopy on 2D and 3D metal halide perovskites using an interdigitated electrode geometry C. Emma McClure, Kameron Hansen, John Colton Metal halide perovskites are a class of 2D and 3D materials that are currently being used in solar energy and other applications. Fundamental characteristics such as exciton binding energy and complex permittivity are important to know in order to design better materials, but have proven challenging to accurately measure. We present experimental measurements of the capacitance of perovskite layers on interdigitated electrodes, along with a model to deduce the frequency dependence of dielectric constant, and we analyze different models which have been used by others for similar situations. [Preview Abstract] |
Friday, October 8, 2021 3:39PM - 3:51PM |
E06.00003: Simulating the Electroabsorption Spectrum of 2D Perovskite Multiple Quantum Wells Kameron Hansen, Emma McClure, John Colton, Luisa Whittaker-Brooks Electroabsorption, i.e. the difference in a material's absorption spectrum with and without an applied electric field, was the most significant technique to advance our understanding of excited states in GaAs-based multiple quantum wells in the 1980s. Today research efforts are focused on a new class of multiple quantum wells, namely 2D perovskite multiple quantum wells. However, in comparison to GaAs-based quantum wells, electroabsorption studies on 2D perovskites have been sparse and contradictory. This work aims to bridge the gap between 2D perovskite electroabsorption spectral features and our theoretical understanding of them by implementing the theory that was successful for GaAs-based multiple quantum wells, but in a regime suitable for 2D perovskites. We find a high level of agreement between theory and experiment which allow for a deepened understanding of the exciton's Stark shift and the continuum wavefunction leaking into the forbidden gap according to the high-field Franz-Keldysh effect. [Preview Abstract] |
Friday, October 8, 2021 3:51PM - 4:03PM |
E06.00004: Engineering Electronic and Magnetic Properties of $(A_{x}Ga_{1-x})_{2}O_{3}$ [A=In or Tl] Alloys Sharad Mahatara, Boris Kiefer Bandgap engineering aims at creating and controlling electronic states that can support specific technological applications. An example of bandgap engineering is the doping of $\beta$-$Ga_{2}O_{3}$ ($E_{g}$$\sim$4.8 eV), a wide gap insulator, that enables applications in UV sensing and in advanced power electronics. In this contribution, we use a Hubbard-U modified version of density-functional-theory (DFT) to study electronic effects of In and Tl dopants as well as vacancies on material properties of $\beta$-$Ga_{2}O_{3}$. We compare and contrast the electronic properties of little studied $(Tl_{x}Ga_{1-x})_{2}O_{3}$ with those of the much better characterized $(In_{x}Ga_{1-x})_{2}O_{3}$ alloys. Our calculations show that Tl-doping requires $\sim$4 times less doping to transverse the complete UV range as compared to In-doping, while showing comparable thermodynamic behavior. Spin-polarized calculations show that tetrahedral and octahedral Ga vacancies lead to spin-polarized ground states in both doped and undoped $\beta$-$Ga_{2}O_{3}$. Thus, $(Tl_{x}Ga_{1-x})_{2}O_{3}$ may not only be of interest for optoelectronics but also as a materials platform for spintronics applications [Preview Abstract] |
Friday, October 8, 2021 4:03PM - 4:15PM |
E06.00005: GaAs-Si Tandem Solar Cells Formed At T\textless 500K by Nano-Bonding via Surface Energy Engineering S. Jandhyala, P. Penmatcha, A. Gurijala, A. Chow, S. Khanna, S. Ram, M. Bertram, C. Cornejo, T. Diaz, W. Peng, T. Balasooriya, N. Gurijala, M. Sahal, R. J. Culbertson, K. L. Kavanagh, N. Herbots The theoretical Photo-Voltaic Efficiency (PVE) of GaAs/Si tandem solar cells (SC) is 44{\%}, but practically is only 33{\%} because current technology uses hetero-epitaxy or Direct Wafer Bonding at T \textgreater 700 K. Hence Nano-Bonding (NB) at T \textless 500K is used here instead to planarize GaAs and Si at the nano-, micro- and macro-scale via far-from-equilibrium surface phases via Surface Energy Engineering (SEE), then `nano-contacts' GaAs to Si via light mechanical compression 0- 70 kPa at T \textless 500 K to nano-bond. SEE reverses initial hydro-affinity (HA) of GaAs from hydrophobic to hydrophilic, and vice-versa for Si. HA and Surface Energy SE are measured by Three Liquid Contact Angle Analysis. High Resolution Ion Beam Analysis (HR-IBA to yield absolute Oxygen coverage. X-Ray Photoelectron Spectroscopy yields surface stoichiometry. The SE of GaAs increases via SEE from 30.4\textpm 1 mJ/m$^{2\, }$to 60\textpm 2 mJ/m$^{2}$, while IBA detects a 50{\%} decrease in Oxygen coverage from 7 ML to 3.5 ML. XPS shows that SEE decreases O-rich As$_{2}$O$_{5}$ on GaAs(100) decreases by at least 13.5{\%}, while As$_{2}$O$_{3}$ increases by at least 13.5{\%}. Next, nano-bonded GaAs/Si interfaces are then imaged via Surface Acoustic wave Microscopy (SAM) and Transmission Electron Microscopy. SAM shows than 98\textpm 1{\%} of GaAs nano- bonds successfully to Si at T \textless 500K [Preview Abstract] |
Friday, October 8, 2021 4:15PM - 4:27PM |
E06.00006: Enhanced and near-unidirectional thermal emission based on cascaded particle phonon-polaritons (PhPs) Stavroula Foteinopoulou, G. Chinna R. Devarapu Micron-scale objects made of semiconductors can support highly localized photonic modes in the reststrahlen band regime known as particle or Mie phonon-polaritons (PhPs). We will discuss how these particle PhPs can serve as building blocks to construct platforms with enhanced near-unidirectional thermal emission that is directed to the upper hemisphere only. These systems are highly relevant to current applications such as the development of long-wavelength infrared (LWIR) sources, thermal photovoltaics and passive radiative cooling. [Preview Abstract] |
Friday, October 8, 2021 4:27PM - 4:39PM |
E06.00007: Assessment of Material Properties of Carbon Nanotubes(CNTs) and C60 Fullerenes(C60HyFn) with PVC Derivatives as Potential Conductive Pipes Siena Lee This study represents a discovery of Carbon Nanotubes(CNTs) and C60 Fullerenes(C60HyFn) with polymers such as PVC derivatives. Electron donor–acceptor (D-A) energy transfer-based strategies were employed to construct functionalized conductive complexes using computer simulations. Upon interaction with P3HT, unique electrochemical properties were shown due to highly efficient D-A energy transfer from the polymers to the CNTs or C60. Polymers act as electron donors and hydrophobic CNTs or fullerenes act as an electron acceptor, enabling the production of applications in environmentally friendly electronic devices. This research performed the investigation of the interaction of CNTs and fullerenes with polymers to find their properties and efficiencies in conductivity. Fullerenes were studied as the conducting layer in an aqueous-processed conductive device and the relative angular orientation between the P3HT and PCBM was considered in finding the stability and the total energy of the complex. Molecular dynamics (MD) and quantum mechanics approaches such as the Density Functional Theory(DFT) were used to study the behavior. [Preview Abstract] |
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