Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session D36: Photovoltaics: Nanostructured Materials |
Hide Abstracts |
Sponsoring Units: GERA Chair: Steven Konezny, Yale University Room: C142 |
Monday, March 21, 2011 2:30PM - 2:42PM |
D36.00001: ABSTRACT WITHDRAWN |
Monday, March 21, 2011 2:42PM - 2:54PM |
D36.00002: Study of photo induced optical transparency of I/I3 redox couple in Dye Sensitized Solar Cells Josef Velten, Julia Bykova, Javier Carretero-Gonzalez, Elizabeth Castillo Martinez, Anvar Zakhidov Dye sensitized solar cells (DSCs) are an alternative to the standard silicon solar cell, consisting of a photoelectrochemical cell that has a light absorbing working electrode, a I-/I3- charge mediator and a counter electrode for reduction of I3- back to I-. Tradtionally, this counter electrode is composed of a few nanometer layer of platinum deposited onto transparent conductive oxide glass. Our work has focused on using structured carbon materials as a counter electrode. Earlier work focused on the use of carbon nanotubes, both single and multiwalled as a replacement for this platinum counter electrode material. Recent work has moved into using 2 dimensional carbon materials, such as graphene flakes and graphene ribbons. With the use of graphene ribbons we have discovered a unique effect that has not been reported for DSCs: under operating condition of AM 1.5 light, the charge mediating electrolyte undergoes a change in its absorption profile. We conclude that this phenomenon must arise from the structure of the graphene ribbons. This process has been demonstrated to be completely reversible, and shows no degradation to the DSC's operation. This presentation will also discuss the application of this phenomenon in the use of inverted DSCs and hybrid tandem cells. [Preview Abstract] |
Monday, March 21, 2011 2:54PM - 3:06PM |
D36.00003: Dye Sensitized Solar Cells with bilayer Multi/Single Carbon Nanotubes Zharkynay Kuanyshbekova, Anvar Zhakhidov In this presentation, we demonstrate the fabrication of dye sensitized solar cells using bilayers of MWCNT coated by SWCNT on top. Each DSC cell uses a typical titania photoelectrode deposited onto a transparent window electrode with photosensitive dye absorbed on the surface of the TiO$_{2. }$Adding SWCNT layer to MWCNT increased short circuit current from 10 to 14 mA/cm$^{2}$. Conventional DSC uses couterelectrode with Pt coated FTO, the Pt layers play role of catalyst for better charge transfer rate from electrolyte. In our bilayer electrode MWCNT sheet play a role a good conductor (similar to FTO), while SWCNT provide better catalytic properties for charge transfer (similar to Pt). The relatively high obtained efficiency of DSS ($\sim $7-8{\%}) cell is determined by the high generated photocurrent, which is comparable to the reference DSS made by same method using the standard PT catalyst. However, the fill-factor of the device is still low ($\sim $0.4-0.5). Therefore further improvement of electrical conductivity of these carbon based electrodes is under investrigation with CNT sheets to achieve high performance device. We acknowledge the help with transparent SWCNTs made in A.Nasibullin of Aolto University (Finland). [Preview Abstract] |
Monday, March 21, 2011 3:06PM - 3:18PM |
D36.00004: Equivalent Circuit Description of Non-compensated n-p Codoped TiO2 as Intermediate Band Solar Cells(IBSCs)1 Tian-Li Feng, Yi Xia, Guang-Wei Deng, Feng-Cheng Wu, Ping Cui, Haiping Lan, Zhenyu Zhang The novel concept of non-compensated n-p codoping has made it possible to create tunable intermediate bands in the intrinsic band gap of TiO2 [1] as a promising materials for developing IBSCs [2]. Here we investigate the quantum efficiency of such IBSCs with or without current extracted from the intermediate bands (IBs). Using the ideal equivalent circuit model, we find that the maximum efficiency of 57\% in the first case and 53\% in the second are both much higher than the Shockley-Queisser limit. We also obtain various key quantities of the circuits, allowing us to simplify the IBSCs into an ordinary cell with an intrinsic resistance, a useful step in realistic development of TiO2 based solar cells invoking device integration. These equivalent circuit results are also compared with the efficiencies obtained directly from consideration of electron transition between the energy bands, and both approaches reveal the intriguing existence of double peaks in the maximum efficiency as a function of the location of IBs.\\[4pt] [1] Zhu W. G., et al., Phys. Rev. Lett. 103, 226401 (2009).\\[0pt] [2] A. Luque, et al., J. Appl. Phys. 96, 1 (2004). [Preview Abstract] |
Monday, March 21, 2011 3:18PM - 3:30PM |
D36.00005: Fluctuation-Induced Tunneling Conductivity in TiO$_{2}$ Nanoparticle Thin Films Steven J. Konezny, Christiaan Richter, Robert C. Snoeberger III, Alexander R. Parent, Gary W. Brudvig, Charles A. Schmuttenmaer, Victor S. Batista We integrate temperature-dependent dark DC conductivity measurements and theoretical modeling to elucidate the mechanism of electron transport in nanoporous TiO$_{2}$, a common photoanode material for dye-sensitized solar cells (DSSCs) and solar photocatalysis. We show that fluctuation-induced tunneling conduction through contact junctions between sintered TiO$_{2}$ nanoparticles can account for the temperature dependence over the entire temperature range studied. We find quantitative agreement between experimental and calculated conductivities, which span over four orders of magnitude and change with decreasing temperature from thermally activated to temperature-independent. The reported results suggest that efforts to optimize charge transport in nanoporous TiO$_{2}$ thin films as a means of improving the overall efficiency of DSSCs and solar photocatalysis should focus on fabrication conditions that optimize the properties of the contact junctions between sintered TiO$_{2}$ nanoparticles. [Preview Abstract] |
Monday, March 21, 2011 3:30PM - 3:42PM |
D36.00006: ZnO Nanoparticles and Nanowire Arrays with Liquid Crystals for Photovoltaic Apprications Lourdes Salamanca-Riba, Nicholas Weadock, Luz Martinez-Miranda Liquid crystals are small monodisperse molecules with high mobilities and are easy and cheap to process. In addition, some of their phases exhibit molecular orientation that can provide a path for the electrons, or holes, to move from one electrode to the other. We have mixed a smectic A liquid crystal (8CB) with varying concentrations of ZnO nanoparticles of $\sim $5 nm in diameter and have observed a photovoltaic effect as a function of the concentration of ZnO. The liquid crystal is believed to enhance the alignment of the nanoparticles and aid in the diffusion of electrons through the particles to the collection electrode. We have also made PV cells of ZnO nanowire arrays grown on Au layers on Si substrates. The nanowire arrays are covered with 8CB liquid crystal for hole conduction. We compare the light absorption of the PV cells as a function of wavelength of the light for the ZnO nanoparticle and the ZnO nanowire cells. We present a detailed study of the structure of the two systems. [Preview Abstract] |
Monday, March 21, 2011 3:42PM - 3:54PM |
D36.00007: Intermediate Band Gap Solar Cells: The Effect of Resonant Tunneling on Delocalization Reid William, Doty Mathew, Shilpa Sanwli, Dan Gammon, Allan Bracker Quantum dots (QD's) have many unique properties, including tunable discrete energy levels, that make them suitable for a variety of next generation photovoltaic applications. One application is an intermediate band solar cell (IBSC); in which QD's are incorporated into the bulk material. The QD's are tuned to absorb low energy photons that would otherwise be wasted because their energy is less than the solar cell's bulk band gap. Current theory concludes that identical QD's should be arranged in a superlattice to form a completely delocalized intermediate band maximizing absorption of low energy photons while minimizing the decrease in the efficiency of the bulk material. We use a T-matrix model to assess the feasibility of forming a delocalized band given that real QD ensembles have an inhomogeneous distribution of energy levels. Our results suggest that formation of a band delocalized through a large QD superlattice is challenging; suggesting that the assumptions underlying present IBSC theory require reexamination. We use time-resolved photoluminescence of coupled QD's to probe the effect of delocalized states on the dynamics of absorption, energy transport, and nonradiative relaxation. These results will allow us to reexamine the theoretical assumptions and determine the degree of delocalization necessary to create an efficient quantum dot-based IBSC. [Preview Abstract] |
Monday, March 21, 2011 3:54PM - 4:06PM |
D36.00008: Development of High Efficient Flexible Dye-Sensitized Solar Cells Xiaojuan Fan We are developing a low cost and easy process to fabricate double-layer porous metal oxide thin films on flexible substrates for high performance dye-sensitized solar cells (DSSCs\textbf{). }The research addresses on the formulation of TiO$_{2}$ precursor to create smooth and continuous porous thin films on large size plastic or metal foil substrates enabling excellent adhesion, robust mechanics, and chemical stability. A second layer built on the underline porous nanocrystalline TiO$_{2}$ thin films are primarily used as bedding to receive more organic sensitizers. A variety of blending of polymer and Ti alkoxide precursors at different concentrations has been studied. After depositing the mixture on the substrates such as Al foils, samples are annealed to remove polymer residues leading to a porous nanocrystalline structure. Photo-electricity conversion efficiency of the fabricated solar cells will be tested under one sun illumination. [Preview Abstract] |
Monday, March 21, 2011 4:06PM - 4:18PM |
D36.00009: A novel nano-structured GaAs solar cell Dong Liang, Anjia Gu, Yijie Huo, Jingzhou Yan, Shuang Li, Erik Garnett, Evan Pickett, Yangsen Kang, Meiyueh Tan, Antonio Xavier Cerruto, Jia Zhu, Ching-Mei Hsu, Yan Yao, Majid Riaziat, Yi Cui, James S. Harris In this presentation, we will demonstrate a novel solar cell with nano-structured dense arrays of single crystal GaAs conformally grown on nanopillar templates with wafer-scale uniformity. The template is prepared via plasma enhanced etching with a monolayer of SiO$_{2}$ nanospheres as a mask followed by wet chemical etching. The GaAs p-n junction with an AlGaAs passivation window layer is grown via metal-organic chemical vapor deposition (MOCVD). The rectangular shape of the nano single crystal GaAs reveals anisotropic lateral growth rates of GaAs along (011) and (01\underline {1}) directions, which can be engineered by tuning the AsH$_{3}$ flow and temperature during growth. Optical absorption measurements show the outstanding light trapping properties of the nano-structured cell, which agree with the simulation results. I-V characteristics show an efficiency of 1.67{\%} for the nano GaAs solar cell, which is 15{\%} higher than its planar control cell with the same thickness of 200nm. The efficiency is the highest among all the large area GaAs nanowire core-shell solar cells reported in literature by 2010. [Preview Abstract] |
Monday, March 21, 2011 4:18PM - 4:30PM |
D36.00010: Highly Efficient Dye Sensitized Solar Cells based on Free-Standing Titania Nanotube Chaehyun Kim, Sungjin Kim, Alexander Cartwright, Hao Zeng Dye sensitized solar cells (DSSC) attract great attention due to their respectable efficiency with very low fabrication cost, good performance under diffuse light conditions and ability to be fabricated on flexible substrates. Its main efficiency limiting factor is the random hopping of electrons within the titania nanoparticle network, which causes carrier trapping and recombination. The charge transport and collection can be enhanced by employing ordered nanostructures such as nanowire or nanotube arrays. However, nanowire/nanotube based DSSCs with efficiencies higher than those of conventional DSSCs have yet to be demonstrated. In this work, we report the fabrication of DSSCs using highly crystalline free-standing titania nanotube arrays. The high crystallinity leads to high electron mobility and diffusion length, allowing thick nanotube films to be used for improving the long wavelength light absorption. This greatly enhances the photocurrent and power conversion efficiency as compared to that of nanotube DSSCs in earlier studies. [Preview Abstract] |
Monday, March 21, 2011 4:30PM - 4:42PM |
D36.00011: Nanowire electrodeposition for advanced photovoltaics Erik Menke, Justin Hujdic, Somnath Ghosh According to the Department of Energy's ``Basic Research Needs for Solar Energy Utilization'' report, there are a number of fundamental scientific issues that need to be addressed for nanostructure based solar cells, including: a. Control of nanoarchitecture b. Light harvesting c. Control of charge separation and recombination d. Control of charge carrier transport to the contacts Here, I will describe how lithographically patterned nanowire electrodeposition (LPNE) can address these issues by discussing the synthesis of high-density semiconductor nanowire arrays, as well as their optical and electronic properties. This talk consists of three parts. Part 1 presents a brief overview of how LPNE, essentially the combination of photolithography and electrodeposition, can be used as a general method to prepare high-density nanowire arrays. Part 2 demonstrates this method specifically for CIS/CdS core-shell nanowire arrays by discussing the electrodeposition of the nanowire arrays as well as the physical and chemical properties of the resulting nanowires. Finally, part 3 presents the optoelectronic properties of the resulting nanowire arrays and their potential application as solar cells. [Preview Abstract] |
Monday, March 21, 2011 4:42PM - 4:54PM |
D36.00012: Shedding Light on Solar Cells with Synchrotron Radiation Franz Himpsel, Peter Cook, Phillip Johnson, Xiaosong Liu, Wanli Yang, Angel Rubio, Juan-Maria Garc\'Ia-Lastra, Enrique Ortega, Celia Rogero, Ruben Gonzalez-Moreno, Eneko Azaceta, Ramon Tena-Zaera, Elena Guillen, Juan Anta X-ray absorption and photoelectron spectroscopy with synchrotron radiation are used to systematically determine the energy levels of molecules for dye-sensitized solar cells (including porphyrins and phthalocyanines [1-3]). N 1s absorption spectra combined with theoretical modeling provide the unoccupied molecular orbitals and the charge transfer between the central metal atom and the surrounding N atoms. Metal 2p-to-3d spectra provide the oxidation state of the metal. Fe and Mn, which occur frequently in biological analogs, easily change their oxidation between +3 and +2. Some dyes interact with the electronic states of nano-structured ZnO acceptor electrodes, causing a change in the electronic states of the ZnO or the dye.\\[4pt] [1] P. L. Cook, et al. J. Chem. Phys. 131, 194701 (2009). \newline [2] P. L. Cook, et al. J. Chem. Phys. 131, 214702 (2009). \newline [3] J.M. Garc\'{i}a-Lastra, et al., J. Chem Phys. 133, 151103 (2010). [Preview Abstract] |
Monday, March 21, 2011 4:54PM - 5:06PM |
D36.00013: Dye Sensitized Solar Cells Using Freestanding TiO2 Nanotube Arrays Xukai Xin, Jun Wang, Lei Zhao, Zhiqun Lin A TiO2 photoanode was prepared by depositing TiO$_{2}$ nanoparticle on the FTO glass followed by placing TiO$_{2}$ nanotube arrays on the top of TiO$_{2}$ nanoparticle film. The resulting TiO$_{2}$ nanotube/nanoparticle photoanode was sensitized with N719 dye after TiCl$_{4}$ treatment and exposure to O$_{2}$ plasma. The resulting dye sensitized solar cell (DSSC) showed that the highest DSSC power conversion efficiency of 8.02{\%} and 7.00{\%} were yielded when a 20 $\mu $m thick TiO$_{2}$ nanoparticle and a 13/7 $\mu $m TiO$_{2}$ nanoparticle/nanotube were used as photoanode, respectively. The I$\sim $V curve analysis suggested that the nanotubes had better electron transport pathway but lower electron generation. Future work will be focused on increasing the dye loading of nanotubes to improve the power conversion efficiency. [Preview Abstract] |
Monday, March 21, 2011 5:06PM - 5:18PM |
D36.00014: Dye-sensitized solar cells employing TiO2 nanotube arrays modified by hydrothermal process Meidan Ye, Changjian Lin, Zhiqun Lin Dye sensitized solar cells (DSSCs) based on TiO2 nanotube photoanode prepared by a facile combination of electrochemical anodization and hydrothermal process exhibited a remarkable performance. Well-ordered and smooth TiO2 nanotube arrays fabricated by a two-step anodic oxidation were subjected to hydrothermal process, thereby creating roughness on the surface of nanotubes and leading to increased dye loading. Subsequently, the resulting nanotubes were used to fabricate DSSC in backside illumination mode, yielding a significantly high power conversion efficiency of 7.12{\%} that was further increased to 7.75{\%} upon oxygen plasma treatment. [Preview Abstract] |
Monday, March 21, 2011 5:18PM - 5:30PM |
D36.00015: Nanostructured Thin Film Solar Cells: A Heterojunction of PbS Colloidal Quantum Dots and TiO2 Nanopillars Ho-Cheol Kim, Illan Kramer, John Bass, Teya Topuria, Leslie Krupp, Philip Rice, Ratan Debnath, Lukasz Brzozowski, Larissa Levina, Edward Sargent Colloidal quantum dot (CQD) has been recognized as a promising solar cell material that offers tunable band gap and inexpensive solution process. Recent report demonstrated the power conversion efficiency (PCE) of above 5{\%} (AM 1.5) using thin films of PbS CQDs and TiO$_{2}$ nanoparticles. This so-called depleted-heterojunction-CQD solar cells have overcome limitations of CQD Schottky devices and promised potential for further improvement of solar cell performance. In this paper, we report the effect of nanostructures of TiO$_{2}$ on the performance of heterojunction CQD solar cells. Well-defined nanopillars of TiO$_{2}$ were prepared on top of F:SnO$_{2}$ substrate using micro-transfer molding technique. TiO$_{2}$ nanopillars of 70 nm in diameter (half-width), 340 nm in height and 275 nm in center-to-center distance were used for subsequent layer-by-layer spin coating of PbS CQD. PCE of $>$5{\%} was measured for the nanopillar solar cells without extensive optimization. Detailed studies on the microstructure of materials, surface properties, optical and electrical properties and optimization will be discussed along with performance of flat TiO$_{2}$-PbS CQD solar cells. [Preview Abstract] |
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