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Publications (30)
Using two-photon tomography, carrier lifetimes are mapped in polycrystalline CdTe photovoltaic devices. These 3D maps probe subsurface carrier dynamics that are inaccessible with traditional optical techniques. They reveal that CdCl2 treatment of CdTe solar cells suppresses nonradiative recombination and enhances carrier lifetimes throughout the fi...
Atomic layer deposition (ALD) was used to grow subnanometer indium oxide recombination barriers in a solid-state dye-sensitized solar cell (DSSC) based on the spiro-OMeTAD hole-transport material (HTM) and the WN1 donor-pi-acceptor organic dye. While optimal device performance was achieved after 3-10 ALD cycles, 15 ALD cycles (similar to 2 angstrom...
The internal quantum efficiency (IQE) of solid-state dye sensitized solar cells (ssDSCs) is measured using a hybrid optical modeling plus absorptance measurement approach which takes into account the parasitic absorption of the hole transport material (HTM). Across device thicknesses of 1 to 4 microns, ssDSCs sensitized with Z907 and TT1 dyes displ...
Accurately measuring the bulk minority carrier lifetime is one of the greatest challenges in evaluating photoactive materials used in photovoltaic cells. One-photon time-resolved photoluminescence decay measurements are commonly used to measure lifetimes of direct bandgap materials. However, because the incident photons have energies higher than th...
Supplementary Information
High solubility is a requirement for energy relay dyes (ERDs) to absorb a large portion of incident light and significantly improve the efficiency of dye-sensitized solar cells (DSSCs). Two benzonitrile-soluble ERDs, BL302 and BL315, were synthesized, characterized, and resulted in a 65% increase in the efficiency of TT1-sensitized DSSCs. The high...
Introduction of a naphthalocyanine moiety to phthalocyanine allows for a gradual red shift of the absorption spectrum in the resulting chromophore. Using silicon as a core atom allows for the introduction of additional siloxane side chains which mitigate dye aggregation. A dye-sensitized solar cell with this hybrid sensitizer exhibits a broad and f...
Atomic layer deposition (ALD) was used to fabricate Al(2)O(3) recombination barriers in solid-state dye-sensitized solar cells (ss-DSSCs) employing an organic hole transport material (HTM) for the first time. Al(2)O(3) recombination barriers of varying thickness were incorporated into efficient ss-DSSCs utilizing the Z907 dye adsorbed onto a 2 μm-t...
Several recent major advances in the design of dyes and electrolytes for
dye-sensitized solar cells have led to record power-conversion
efficiencies. Donor-pi-acceptor dyes absorb much more strongly than
commonly employed ruthenium-based dyes, thereby allowing most of the
visible spectrum to be absorbed in thinner films. Light-trapping
strategies a...
Cosensitization of broadly absorbing ruthenium metal complex dyes with highly absorptive near-infrared (NIR) organic dyes is a clear pathway to increase near-infrared light harvesting in liquid-based dye-sensitized solar cells (DSCs). In cosensitized DSCs, dyes are intimately mixed, and intermolecular charge and energy transfer processes play an im...
Solution processed silver nanowire meshes (Ag NWs) were laminated on top of solid-state dye-sensitized solar cells (ss-DSCs) as a reflective counter electrode. Ag NWs were deposited in < 1 min and were less reflective compared to evaporated Ag controls; however, AgNW ss-DSC devices consistently had higher fill factors (0.6 versus 0.69), resulting i...
A detailed investigation of the effect of hole transport material (HTM) pore filling on the photovoltaic performance of solid-state dye-sensitized solar cells (ss-DSCs) and the specific mechanisms involved is reported. It is demonstrated that the efficiency and photovoltaic characteristics of ss-DSCs improve with the pore filling fraction (PFF) of...
Panchromatic response is essential to increase the light-harvesting efficiency in solar conversion systems. Herein we show increased light harvesting from using multiple energy relay dyes inside dye-sensitized solar cells. Additional photoresponse from 400-590 nm matching the optical window of the zinc phthalocyanine sensitizer was observed due to...
The full text of the corrigendum is available in the pdf provided.
Solar-energy conversion usually takes one of two forms: the 'quantum' approach, which uses the large per-photon energy of solar radiation to excite electrons, as in photovoltaic cells, or the 'thermal' approach, which uses concentrated sunlight as a thermal-energy source to indirectly produce electricity using a heat engine. Here we present a new c...
The energy relay dye, 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), was used with a near-infrared sensitizing dye, TT1, to increase the overall power conversion efficiency of a dye-sensitized solar cell (DSC) from 3.5% to 4.5%. The unattached DCM dyes exhibit an average excitation transfer efficiency (ETE) of 96% inside TT...
Energy transfer from phosphorescent ruthenium complex N877 dissolved in the liquid electrolyte to the squaraine sensitizer SQ1 anchored on the titanium oxide surface resulted in a four fold increase in external quantum efficiency in the blue part of the visible spectrum despite complete quenching of the luminescence of N877 by the iodine in the ele...
Photon Enhanced Thermionic Emission (PETE) is a newly proposed method of
solar energy harvesting which combines quantum and thermal processes
into a single electricity generating mechanism. The proposed PETE device
can be thought of as a synthesis of a photovoltaic (PV) cell and
thermionic converter, and the process is expected to overcome some of...
Förster resonant energy transfer can improve the spectral breadth, absorption and energy conversion efficiency of dye sensitized solar cells. In this design, unattached relay dyes absorb the high energy photons and transfer the excitation to sensitizing dye molecules by Förster resonant energy transfer. We use an analytic theory to calculate the ex...
Running relay: Incorporating an energy-relay dye (ERD) into the hole transporter of a dye-sensitized solar cell increased power-conversion efficiency by 29 % by extending light harvesting into the blue region. In the operating mechanism (see picture), absorption of red photons by the sensitizer transfers an electron into TiO2 and a hole into the el...
IntroductionBasic OperationGeneral Device Structure and Material ChoicesDevice StructuresPore FillingEffects of Pore Filling on Polymer Mobility and Exciton HarvestingOrganic Composite Photovoltaic ModelingFuture OutlookReferences
In this paper, the pore filling of spiro-OMeTAD (2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)9,9′-spirobifluorene) in mesoporous TiO2 films is quantified for the first time using XPS depth profiling and UV–Vis absorption spectroscopy. It is shown that spiro-OMeTAD can penetrate the entire depth of the film, and its concentration is constant thr...
In this paper, the pore filling of spiro-MeOTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9, 9'-spirobifluorene) in mesoporous TiO2 films is quantified for the first time using XPS depth profiling and UVVis absorption spectroscopy. We show that spiro-OMeTAD can penetrate the entire depth of the film, and its concentration is constant through...
Tandem architectures in which multiple energy gaps are combined in a series-connected stack of solar cells are seen as a promising approach to increasing the power conversion efficiency of organic solar cells to commercially relevant values. Even higher efficiencies can be obtained if the photocurrent-matching requirement of such tandem cells is re...
Conventional dye-sensitized solar cells have excellent charge collection efficiencies, high open-circuit voltages and good fill factors. However, dye-sensitized solar cells do not completely absorb all of the photons from the visible and near-infrared domain and consequently have lower short-circuit photocurrent densities than inorganic photovoltai...
By transitioning to semicrystalline polymers, the performance of polymer-based solar cells has recently increased to over 5% [W. Ma et al., Adv. Fund. Mater. 15, 1665 (2005); G. Li et al., Nat. Mater. 4, 864 (2005); M. Reyes-Reyes et al., Org. Lett. 7, 5749 (2005); J. Y. Kim et al., Adv. Mater. (Weinheim, Ger.) 18, 572 (2005); J. Peet et al., Nat....
A significant fraction of the cost of solar panels comes from the photoactive materials and sophisticated, energy-intensive processing technologies. Recently, it has been shown that the inorganic components can be replaced by semiconducting polymers capable of achieving reasonably high power conversion efficiencies. These polymers are inexpensive t...
Backside illuminated solar cells based on 6 µm long highly-ordered nanotube-array films sensitized by a self-assembled monolayer of bis(tetrabutylammonium)-cis-(dithiocyanato)-N ,N -bis(4-carboxylato-4 -carboxylic acid-2,2 -bipyridine)ruthenium(II) (commonly called 'N719') show a short-circuit current density of 8.79 mA cm −2 , 841 mV open circuit...