Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session L20: Solar/Energy Conversion: Theory and Devices |
Hide Abstracts |
Sponsoring Units: GERA FIAP DPOLY Chair: Ernesto Marinero, Purdue University Room: LACC 308B |
Wednesday, March 7, 2018 11:15AM - 11:27AM |
L20.00001: Optical Properties of Zn2Mo3O8 : Combination of Theoretical and Experimental Study Tathagata Biswas, Pramod Ravindra, Eashwer Athresh, Rajeev Ranjan, Sushobhan Avasthi, Manish Jain We study the ground- and excited-state properties of Zn2Mo3O8 using first principles methods based on density functional theory and many body perturbation theory. We find that Zn2Mo3O8 is a indirect gap semiconductor, with a quasiparticle (optical) gap of 3.14 eV (2.34 eV). Our results are in good agreement with experimental data from UV-visible spectroscopy and spectroscopic ellipsometry. We show that the discrepancy between theoretical and experimental results can be attributed to finite temperature effects. The optical gap of this material makes it suitable for absorbing a significant fraction of solar radiation. This combined with piezoelectric response makes this material promising candidate for piezo-phototronics applications. |
Wednesday, March 7, 2018 11:27AM - 11:39AM |
L20.00002: First-principles study of Ti host doping effect to stabilize Si guest doping in Fe2O3 hematite. Ji Hui Seo, Hosik Lee, Keunsu Choi, Ki-Yong Yoon, Ji-Hyun Jang, Jun Hee Lee Si is well-known n-type dopant which enhances the photo-electrochemical (PEC) response of hematite electrodes, due to the improvement in conductivity by increased charge carrier concentrations. Owing to its limited doping ratio, many researchers focus on finding co-doping candidates to further increase Si doping ratio, and p-type dopants are generally proposed for the benefit of satisfying charge neutrality. However, using first-principle DFT calculations, we found that n-type host dopant Ti in hematite lowers the formation energy of n-type guest Si doping by around 1 eV, possibly increasing the Si doping ratio drastically. Although Ti is n-type dopant generating excess charge, it forms local holes in nearby Fe atoms, which stably host the additional n-type guest dopant, Si. For PEC enhancement, we suggest that n-type and n-type co-doping could be a better way both to stabilize the doping structure and increase the carrier concentrations than the conventional p-type and n-type co-doping. |
Wednesday, March 7, 2018 11:39AM - 11:51AM |
L20.00003: Seeing the Invisible Plasma with Transient Phonons in Cuprous Oxide: Deducing Phonon Dynamics using the Phonon-to-Exciton Induced Absorption Triggered by Electron-Hole Plasma Relaxation in Cuprous Oxide Laszlo Frazer, Richard Schaller, Kelvin Chang, Alexandr Chernatynskiy, Kenneth Poeppelmeier In cuprous oxide (Cu2O) there is no luminescence from electron-hole plasma. The emission of phonons from electron-hole plasma is the primary limit on the efficiency of photovoltaic devices operating above the bandgap. Therefore, we searched for optical phonons emitted by energetic charge carriers using phonon-to-exciton upconversion transitions. We found 14 meV phonons with a lifetime of 0.916 ± 0.008 ps and 79 meV phonons that are longer lived and overrepresented. It is surprising that the higher energy phonon has a longer lifetime. |
(Author Not Attending)
|
L20.00004: Modeling exciton diffusion in carbon nanotube-based solar cells Amirhossein Davoody, Alexander Gabourie, Irena Knezevic Carbon nanotubes (CNTs) are quasi-one-dimensional materials with a unique set of optical, electronic, and mechanical properties, which have drawn the attention of researchers for energy-harvesting applications. In order to maximize the efficiency of CNT-based solar cell devices, it is crucial to optimize the transport properties of excitons in CNT films. This is a formidable task due to the many factors involved in the exciton transport problem in CNT films. |
Wednesday, March 7, 2018 12:03PM - 12:15PM |
L20.00005: A thermodynamic cycle for the solar cell Robert Alicki, David Gelbwaser-Klimovsky, Alejandro Jenkins A solar cell is a heat engine, but textbook treatments are not quite satisfactory from a thermodynamic standpoint, since they present solar cells as directly converting the energy of light into electricity, and the current in the circuit as maintained by an electrostatic (or, in some cases, a chemical) potential. We propose a dynamic picture of a thermodynamic cycle in which the gas of electrons in the p phase serves as the working substance. The interface between the p and n phases acts as a self-oscillating piston, modulating the absorption of heat from the photons so that it may do net work during a complete cycle of its motion. We draw a simple hydrodynamical analogy between this model and the "putt-putt" engine of toy boats, in which the interface between the water’s liquid and gas phases serves as the piston. We point out some testable consequences of this model. |
Wednesday, March 7, 2018 12:15PM - 12:27PM |
L20.00006: A first principle investigation of the formation, stability and electronic properties of acanthite Cu2S with comparison to other Cu2S known phases toward a promising application in the field of photovoltaic. Sajib Barman, Muhammad Huda Cu2S is a well-known semiconductor in the field of renewable energy. As a solar absorber material, its application in thin film solar cell have been extensively studied over the years. It had shown nearly 10% efficiency in the past. However, excessive p-type doping resulted from spontaneous Cu vacancy formation makes the material unstable for proper usages in the field of photovoltaic. In this work, we have shown that a relatively new predicted phase of Cu2S known as acanthite phase is energetically as favorable as its well-known low chalcocite phase to form at 0K. We have used density functional theory as the framework for a systematic study to compare its formation, electronic and optical properties with other known Cu2S phases. Also, we have shown that Ag alloying with Cu2S can help to reduce Cu vacancy formation tendency in the crystal. Finally, we have compared this theoretically predicted acanthite phase with known minerals like AgCuS and Ag3CuS2 with regard to its application as a potential photovoltaic material. |
Wednesday, March 7, 2018 12:27PM - 12:39PM |
L20.00007: Greenhouse Effect to Enhance Photovoltaic Conversion Efficiency above the Detailed Balance Limit Andrei Sergeev, Kimberly Sablon, John Little We investigate the photovoltaic (PV) converter with potential efficiencies beyond the Shockley – Queisser limit. The device comprises a semiconductor n-p junction PV cell placed between a front surface “greenhouse” filter and a back surface mirror. The filter traps long wavelength photons and establishes the photonic bandgap above the semiconductor bandgap. Fast photoelectron relaxation due electron-holes energy transfer and effective trapping of long wavelength photons reduce the population of photoelectrons above the photonic bandgap and increase the population of photoelectrons accumulated above the semiconductor bandgap. This nonequilibrium operating regime is described by increased chemical potential of low energy photoelectrons and reduced chemical potential of high energy photoelectrons. In this way the device provides the reduced emission and enhanced conversion. We present the device design, material optimization, and PV characteristics. The device operation is also discussed in terms of endoreversible thermodynamics. |
Wednesday, March 7, 2018 12:39PM - 12:51PM |
L20.00008: Highly efficient, high speed vertical photodiodes based on few-layer MoS2 Jihan Chen, Zhen Li, Rohan Dhall, Steve Cronin Layered transition metal dichalcogenides, such as MoS2, have recently emerged as a promising material system for electronic and optoelectronic applications. Here, we report highly efficient photocurrent generation from vertical MoS2 devices fabricated using asymmetric metal contacts, exhibiting an external quantum efficiency of up to 7%. Compared to in-plane MoS2 devices, the vertical design of these devices has a much larger junction area, which is essential for achieving highly efficient photovoltaic devices. Photocurrent and photovoltage spectra are measured over the photon energy range from 1.25 to 2.5 eV, covering both the 1.8 eV direct K-point optical transition and the 1.3 eVΣ-point indirect transition in MoS2. Photocurrent peaks corresponding to both direct and indirect transitions are observed in the photocurrent spectra and exhibit different photovoltage–current characteristics. Compared to previous in-plane devices, a substantially shorter photoresponse time of 7.3 μs is achieved due to fast carrier sweeping in the vertical devices, which exhibit a−3 dB cutoff frequency of 48 kHz.1 |
Wednesday, March 7, 2018 12:51PM - 1:03PM |
L20.00009: Al-Intercalated Chevrel Phase Mo6S8 as a Janus Material for Energy Generation and Storage Michael Agiorgousis, Yi-Yang Sun, Damien West, Shengbai Zhang An approach to designing solar absorber materials based on intercalation-induced metal-to-semiconductor transition has been proposed. Using hybrid density functional calculation, Al-intercalated Chevrel phase Mo6S8 with end product Al4/3Mo6S8 is predicted to be a semiconductor with a 1.18 eV indirect band gap. Compared with GaAs and Si, Al4/3Mo6S8 shows significantly higher optical absorption over the solar spectrum as a result of the parallel bands across the band gap with direct transitions around 1.35 eV, nearly ideal for an absorber material in a solar cell. Chevrel phase Mo6S8 has recently been explored as a cathode material in rechargeable Al-ion batteries. Thus, Al4/3Mo6S8 is a potential dual-function (or Janus) material for both energy generation and storage. |
Wednesday, March 7, 2018 1:03PM - 1:15PM |
L20.00010: Local optoelectronic characterization of solvent annealed lead-free bismuth-based perovskite films Soumitra Satapathi, Jill Wenderott, Anubhav Raghav, Max Shtein, Peter Green Traditional organolead-halide perovskite-based devices have shown rapid improvements in their power conversion efficiency (PCE) in less than a decade, yet challenges remain for improving stability and film uniformity, as well as the elimination of lead to address toxicity issues. We fabricated lead-free methylammonium bismuth iodide (MBI) perovskite films and studied the effect of solvent annealing with dimethylformamide (DMF) on the local optoelectronic properties of the films as measured via (photo)conductive atomic force microscopy ((p)c-AFM)). We found solvent annealing to significantly increase electrical conductivity in the out-of-plane direction. Photoconductivity in both solvent-annealed and thermally-annealed MBI films was boosted in the grain interiors versus the grain boundaries (GBs). It was observed that DMF induced solvent annealing impacts charge transport through the film which can be a unique design parameter for optimizing local optoelectronic properties. By studying how solvent annealing changes the ways in which charge is transported through the film, we have developed a better understanding of how local optoelectronic properties are affected by DMF annealing. |
Wednesday, March 7, 2018 1:15PM - 1:27PM |
L20.00011: Morphological Characterization of PffBT4T-2OD-Based Ternary Organic Solar Cells I. AYHAN, Brooke Kuei, Enrique Gomez Ternary organic solar cells (TOSCs), consisting of one/two or two/one donor/acceptor, are a promising strategy for broadening the light absorption spectrum and enhancing the power conversion efficiency (PCE) of photovoltaic devices. In this study, the ternary blend system made use of PffBT4T-2OD (C62H88F2N2S5)n organic semiconductor as a donor (D) and PC70BM, N2200, and IDIC (C66H66N4O2S2) acceptors (A) and their photovoltaic properties were studied through optimizing processing parameters such as polymer concentration, D:A1:A2 ratio and annealing. The effect of these parameters on the structural, morphological, electrical and photovoltaic properties were systematically investigated by performing UV-Vis absorption, Grazing-Incidence Wide-Angle X-ray Scattering (GiWAXS) and energy-filtered transmission electron microscopy (EFTEM). This work shows a PffBT4T-2OD-based ternary system composed of morphologically compatible acceptors can achieve a remarkable PCE >8%, significant enhancement of short-circuit current and the fill factor. We attribute that the high morphology compatibility of the ternary system can benefit to optimize electron/hole mobility and diminish recombination. |
Wednesday, March 7, 2018 1:27PM - 1:39PM |
L20.00012: Adding to the Perovskite Universe: Inverse-Hybrid Perovskites Julian Gebhardt, Andrew Rappe Perovskites are a rich family of functional materials. Usually, they contain two cations on the A- and B-sites, surrounded by anions on the X-site, but compounds are also known that invert the ion types (inverse perovskites). Perovskites with one inorganic cation substituted by an organic molecule (hybrid perovskites) are currently intensively studied, due to the promise of CH3NH3PbI3 based solar-cells. We recently combined the concepts of inverse and hybrid perovskites, investigating the properties of inverse-hybrid perovskites by first-principles calculations, adding yet another structural variant to the perovskite universe. Our search discovered a variety of compounds that are computationally predicted to form either as stable perovskites or in a related corner- and edge-sharing phase. We observe materials with electronic properties ranging from metallic systems over small and intermediate band gaps to large band-gap semiconductors. The inverse structure could overcome stability problems of current hybrid perovskite photovoltaics. In addition, inverse-hybrid perovskites show inherent off-center displacement of ions, leading to polar phases. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700