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Results for “Power conversion efficiency”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Modeling photovoltaic performance in periodic patterned colloidal quantum dot solar cells

Colloidal quantum dot (CQD) solar cells have attracted tremendous attention mostly due to their wide absorption spectrum window and potentially low processability cost. The ultimate efficiency of CQD solar cells is highly limited by their high trap state density. Here in this paper we show that the overall device power conversion efficiency could be improved by employing photonic structures that enhance both charge generation and collection efficiencies. By employing a two-dimensional numerical model, we have calculated the characteristics of patterned CQD solar cells based of a simple grating structure. Our calculation predicts a power conversion efficiency as high as 11.2%, with a short circuit current density of 35.2 mA/cm 2 , a value nearly 1.5 times larger than the conventional flat design, showing the great potential value of patterned quantum dot solar cells.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Low-temperature processed high-performance flexible perovskite solar cells via rationally optimized solvent washing treatments

High performance planar-heterojunction (PHJ) perovskite (CH3NH3PbI3) solar cells fabricated through lowtemperature annealing are demonstrated. Simple spin-coating with an optimized solvent washing process readily forms homogeneous and crystalline perovskite thin films. The perovskite films fabricated via this solvent washing process show a low dependence on annealing temperature in achieving high crystallinity and large grain size, prerequisites for high efficiency perovskite solar cells. The solar cell device fabricated by solvent washing and 100 C annealing exhibited a high power conversion efficiency (PCE) over 14% with high short circuit current density (JSC) of 19.3 mA cm 2 and fill factor (FF) of 0.80. More importantly, the device annealed at low temperature (<90 C) also yields high PCEs of over 12%. This enables us to fabricate flexible solar cells at low-temperatures with promising PCE as high as 9.43%. This study demonstrates that this optimized solvent washing process is highly relevant for low-cost rollto-roll (R-2-R) processing of high performance perovskite solar cells.

14 SOLAR ENERGY↗
DOE OSTI2024

Quantum limits of superconducting-photonic links and their extension to millimeter waves

Photonic addressing of superconducting circuits has been proposed to overcome wiring complexity and heat-load challenges. However, such superconducting-photonic links suffer from an efficiency-noise trade-off that limits scalability. This trade-off arises because increasing power conversion efficiency entails reducing optical power, which makes the converted signal susceptible to shot noise. We analyze this trade-off and find that the laser-driven qubit gate infidelity scales inversely with the number of photons used. While methods such as nonlinear detection or squeezed light could mitigate this effect, we consider generating higher-frequency electrical signals, such as millimeter waves (100 GHz), using laser light. At these higher frequencies, circuits have higher operating temperatures and cooling power budgets and alleviate constraints posed by the trade-off. Therefore, we demonstrate an optically driven cryogenic millimeter-wave source with a maximum power efficiency of 8 ×10 −5 that can generate a maximum of 0.7 μ⁢W of 80 GHz power, with a 1200-thermal-photon equivalent of added noise at 4K. Using this source, we perform frequency-domain spectroscopy of superconducting NbTiN resonators at 80–90 GHz. Our results show a promising approach to lessen the efficiency-noise constraints on superconducting-photonic links, while leveraging the benefits of photonic signal delivery. Further optimization of power efficiency and noise at high frequencies could make scalable photonic control of superconducting qubits viable at temperatures exceeding 1K.

Optoelectronics↗
DOE OSTI2024

Rapid advances enabling high-performance inverted perovskite solar cells

Perovskite solar cells (PSCs) that have a positive–intrinsic–negative (p–i–n, or often referred to as inverted) structure are becoming increasingly attractive for commercialization owing to their rapid increase in power conversion efficiency, easily scalable fabrication, reliable operation and compatibility with various perovskite-based tandem device configurations. In this report we review key material and device considerations for making highly efficient and stable p–i–n PSCs. First, we summarize key advances in charge transport materials, which were critical to the rapid power conversion efficiency progress. Second, we discuss promising perovskite compositions and fabrication methods. We highlight various additive engineering approaches to improve the perovskite layer as well as interface engineering strategies that target either the buried or top perovskite surface layer. Third, we review progress in tandem devices, focusing on optimization of the interconnection layer. Next, we summarize the status and strategies for improving p–i–n PSC stability, especially considering the challenges of outdoor applications. We also provide prospects for future research directions and challenges.

14 SOLAR ENERGY↗
DOE OSTI2016

Improved conversion efficiency of dye sensitized solar cell using Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposite

TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites were prepared by hydrothermal method for dye sensitized solar cell (DSSC) application. The structural and optical properties were investigated by X –ray diffraction (XRD) and UV-Visible spectroscopy respectively. XRD results revealed the formation of material in nano size. The average crystallite size is 22.32 nm, 17.41 nm and 6.31 nm for TiO{sub 2}, TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites respectively. The optical bandgap varies from 2.04 eV to 3.75 eV. Dye sensitized solar cells were fabricated using the prepared material. Pomegranate juice was used as a sensitizer and graphite coated conducting glass plate was used as counter electrode. The I – V characteristics were recorded to measure photo response of DSSC. Photovoltaic parameter like open circuit voltage, power conversion efficiency, and fill factor were evaluated for fabricated solar cell. The power conversion efficiency of DSSC fabricated with TiO{sub 2}, TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites were found 0.71%, 1.97% and 4.58% respectively.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Optical Characterization of Defects in High-Efficiency (Ag,Cu)(In,Ga)Se2

We applied time-resolved photoluminescence (TRPL) spectroscopy to study optimized chalcopyrite (Ag,Cu)(In,Ga)Se2 thin films. The device shows power conversion efficiency of 18.7%. The metastable defect VSe-VCu within ACIGS at EV+0.98 eV is detected in sub-bandgap TRPL excitation spectra. TRPL lifetime of 50 ns is limited by the density of mid-gap defects such as CuGa or CuIn. The similarity of TRPL dynamics before and after light soaking indicates the optimized ACIGS thin film is less metastable because the density of VCu-VSe defect is reduced to below 10^15 cm^-3. This study indicates that ACIGS has improved cell efficiency and reliability characteristics.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2022

Polymerized Small Molecular Acceptor with Branched Side Chains for All Polymer Solar Cells with Efficiency over 16.7%

The power conversion efficiencies (PCEs) of small molecule acceptor (SMA)-based organic solar cells have already exceeded 18%. However, the development of polymer acceptors still lags far behind their SMA counterparts mainly due to the lack of efficient polymer acceptors. In this work, a series of polymer acceptors named PY-X (with X being the branched alkyl chain) are designed and synthesized by employing the same central core with the SMA L8-BO but with different branched alkyl chains on the pyrrole motif. It is found that the molecular packing of SMA-HD featuring 2-hexyldecyl side chain used in the synthesis of PY-HD is similar to L8-BO, in which the branched alkyl chains lead to condensed and high-order molecular assembly in SMA-HD molecules. When combined with PM6, PY-HD-based all polymer solar cell (all-PSC) exhibits a high PCE of 16.41%, representing the highest efficiency for the binary all-PSCs. Moreover, the side-chain modification on the pyrrole site position further improves the performance of the all-PSCs, and the PY-DT-based device delivers a new record high efficiency of 16.76% (certified as 16.3%). The work provides new insights for understanding the structure–property relationship of polymer acceptors and paves a feasible avenue to develop efficient conjugated polymer acceptors.

14 SOLAR ENERGY↗
DOE OSTI2022

Phase stability and magnetic and electronic properties of a spark plasma sintered CoFe – P soft magnetic alloy

More efficient power conversion devices are able to transmit greater electrical power across larger distances to satisfy growing global electrical needs. A critical requirement to achieve more efficient power conversion are the soft magnetic materials used as core materials in transformers, inductors, and motors. To that effect it is well known that the use of non-equilibrium microstructures, which are, for example, nanocrystalline or consist of single phase solid solutions, can yield high saturation magnetic polarization and high electrical resistivity necessary for more efficient soft magnetic materials. In this work, we synthesized CoFe – P soft magnetic alloys containing nanocrystalline, single phase solid solution microstructures and studied the effect of a secondary intermetallic phase on the saturation magnetic polarization and electrical resistivity of the consolidated alloy. Single phase solid solution CoFe – P alloys were prepared through mechanically alloying metal powders and phase decomposition was observed after subsequent consolidation via spark plasma sintering (SPS) at various temperatures. The secondary intermetallic phase was identified as the orthorhombic (Co x Fe 1-x ) 2 P phase and the magnetic properties of the (Co x Fe 1-x ) 2 P intermetallic phase were found to be detrimental to the soft magnetic properties of the targeted CoFe – P alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Increasing photon absorption and stability of PbS quantum dot solar cells using a ZnO interlayer

We compared PbS quantum dot (QD) solar cells with different cathode interlayer materials, namely, LiF and ZnO nanoparticles, using the same device structure. Solar cells fabricated with the ZnO interlayer gave a power conversion efficiency of 4.8%, which is higher (above the experimental variation) than the 4.1% efficiency obtained with a LiF interlayer. We found that the ZnO interlayer alters the spatial distribution of the optical field, leading to an increase in external quantum efficiency in the visible range. Furthermore, devices with ZnO as interlayer showed more stable performance than the ones using LiF, with practically no power conversion efficiency degradation after 1 month inside a N{sub 2} glovebox.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Semiconductors: Interface Design Principles for High-Performance Organic Semiconductor Devices (Adv. Sci. 6/2015)

Organic solar cells (OSCs) are a promising cost-effective candidate in next generation photovoltaic technology. However, a critical bottleneck for OSCs is the electron/hole recombination loss through charge transfer state at the interface, which greatly limits the power conversion efficiency. In article number 1500024, W. Nie, A. Mohite, and co-workers demonstrate a simple strategy of suppressing the recombination rate by inserting a spacer layer at the donor-acceptor interface, resulting in a dramatic increase in power conversion efficiency.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Reliability of Small Molecule Organic Photovoltaics with Electron-Filtering Compound Buffer Layers

Electron-filtering compound buffer layers (EF-CBLs) improve charge extraction in organic photovoltaic cells (OPVs) by blending an electron-conducting fullerene with a wide energy gap exciton-blocking molecule. It is found that devices with EF-CBLs with high glass transition temperatures and a low crystallization rate produce highly stable morphologies and devices. The most stable OPVs employ 1:1 2,2',2"-(1,3,5-benzenetriyl tris-[1-phenyl-1H-benzimidazole] TPBi:C 70 buffers that lose <20% of their initial power conversion efficiency of 6.6 ± 0.6% after 2700 h under continuous simulated AM1.5G illumination, and show no significant degradation after 100 days of outdoor aging. When exposed to 100-sun (100 kW m -2 ) concentrated solar illumination for 5 h, their power conversion efficiencies decrease by <8%. Moreover, it is found that the reliability of the devices employing stable EF-CBLs has either reduced or no dependence on operating temperature up to 130 °C compared with BPhen:C 60 devices whose fill factors show thermally activated degradation. The robustness of TPBi:C 70 devices under extreme aging conditions including outdoor exposure, high temperature, and concentrated illumination is promising for the future of OPV as a stable solar cell technology.

14 SOLAR ENERGY↗
DOE OSTI2015

Exciton size and binding energy limitations in one-dimensional organic materials

In current organic photovoltaic devices, the loss in energy caused by the charge transfer step necessary for exciton dissociation leads to a low open circuit voltage, being one of the main reasons for rather low power conversion efficiencies. A possible approach to avoid these losses is to tune the exciton binding energy to a value of the order of thermal energy, which would lead to free charges upon absorption of a photon, and therefore increase the power conversion efficiency towards the Shockley-Queisser limit. We determine the size of the excitons for different organic molecules and polymers by time dependent density functional theory calculations. For optically relevant transitions, the exciton size saturates around 0.7 nm for one-dimensional molecules with a size longer than about 4 nm. For the ladder-type polymer poly(benzimidazobenzophenanthroline), we obtain an exciton binding energy of about 0.3 eV, serving as a lower limit of the exciton binding energy for the organic materials investigated. Furthermore, we show that charge transfer transitions increase the exciton size and thus identify possible routes towards a further decrease of the exciton binding energy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

High performance tandem organic solar cells via a strongly infrared-absorbing narrow bandgap acceptor

Tandem organic solar cells are based on the device structure monolithically connecting two solar cells to broaden overall absorption spectrum and utilize the photon energy more efficiently. Herein, we demonstrate a simple strategy of inserting a double bond between the central core and end groups of the small molecule acceptor Y6 to extend its conjugation length and absorption range. As a result, a new narrow bandgap acceptor BTPV-4F was synthesized with an optical bandgap of 1.21 eV. The single-junction devices based on BTPV-4F as acceptor achieved a power conversion efficiency of over 13.4% with a high short-circuit current density of 28.9 mA cm -2 . With adopting BTPV-4F as the rear cell acceptor material, the resulting tandem devices reached a high power conversion efficiency of over 16.4% with good photostability. The results indicate that BTPV-4F is an efficient infrared-absorbing narrow bandgap acceptor and has great potential to be applied into tandem organic solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Hexanary blends: a strategy towards thermally stable organic photovoltaics

Non-fullerene based organic solar cells display a high initial power conversion efficiency but continue to suffer from poor thermal stability, especially in case of devices with thick active layers. Mixing of five structurally similar acceptors with similar electron affinities, and blending with a donor polymer is explored, yielding devices with a power conversion efficiency of up to 17.6%. The hexanary device performance is unaffected by thermal annealing of the bulk-heterojunction active layer for at least 23 days at 130 °C in the dark and an inert atmosphere. Moreover, hexanary blends offer a high degree of thermal stability for an active layer thickness of up to 390 nm, which is advantageous for high-throughput processing of organic solar cells. Here, a generic strategy based on multi-component acceptor mixtures is presented that permits to considerably improve the thermal stability of non-fullerene based devices and thus paves the way for large-area organic solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Highly efficient dye-sensitized solar cell with GNS/MWCNT/PANI as a counter electrode

Highlights: • High-performance PANI/MWCNT-CE was incorporated in a Pt-CE in DSSCs. • GNS/MWCNT/PANI-CE exhibits a high power conversion efficiency (PCE) of 7.52%. • GNS/MWCNT/PANI composite has a high catalytic activity for the reduction of I{sub 3}{sup −}. • GNS/MWCNT/PANI composite has a low R{sub CT} on the electrolyte/CE interface. - Abstract: A graphene-based nanosheet composite/multiwalled carbon nanotube/polyaniline (GNS/MWCNT/PANI) was synthesized via an in situ polymerization technique and applied by the spin-coating method as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). The combination of the high catalytic activity of PANI and outstanding conductivity of GNS/MWCNT improved the photovoltaic performance of the hybrid CE. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed that the GNS/MWCNT/PANI composite has high catalytic activity for the reduction of triiodide to iodide and low charge-transfer resistance at the electrolyte/electrode interface. Transmission electron microscopy (TEM) images showed that the GNS/MWCNT/PANI-CE has a rough and porous structure and X-ray diffraction analysis confirmed the formation of PANI coating on the surface of the GNS/CNT. In particular, current–voltage measurements showed the superior power conversion efficiency (PCE) of 7.52% of the DSSC based on GNS/MWCNT/PANI-CE compared to the PCE of 6.69% of the DSSC based on Pt-CE.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Low-bandgap mixed tin–lead iodide perovskites with reduced methylammonium for simultaneous enhancement of solar cell efficiency and stability

High-performance perovskite/perovskite tandem solar cells require high-efficiency and stable low-bandgap perovskite subcells. State-of-the-art low-bandgap mixed tin–lead iodide perovskite solar cells exhibit either a high power-conversion efficiency or improved stability, but not both. In this article we report a two-step bilayer interdiffusion growth process to simultaneously meet both requirements for formamidinium-based low-bandgap mixed tin–lead iodide perovskite solar cells. The bilayer interdiffusion growth process allows for the formation of high-quality and large-grained perovskite films with only 10 mol% volatile methylammonium. Additionally, one-dimensional pyrrolidinium perovskite was applied to passivate the perovskite film and improve the junction quality, which resulted in a carrier lifetime of 1.1 µs and an open circuit voltage of 0.865 V for our perovskite film and device with a bandgap of 1.28 eV. Our strategies enabled a power-conversion efficiency of 20.4% for low-bandgap perovskite solar cells under AM 1.5G illumination. More importantly, an encapsulated device can retain 92% of its initial efficiency after 450 h of continuous 1 sun illumination.

14 SOLAR ENERGY↗
DOE OSTI2015

Screen printed silver top electrode for efficient inverted organic solar cells

Highlights: • Screen printing of silver pattern. • X-ray diffraction pattern confirmed the face centered cubic structure of silver. • Uniform surface morphology of silver pattern with sheet resistance of 0.06 Ω/sq. • The power conversion efficiency of fabricated solar cell is found to be 2.58%. - Abstract: The present work is mainly focused on replacement of the vacuum process for top electrode fabrication in organic solar cells. Silver top electrode deposited through solution based screen printing on pre-deposited polymeric thin film. The solution based printing technology provides uniform top electrode without damaging the underlying organic layers. The surface crystallinity and surface morphology of silver top electrode are examined through X-ray diffraction, field-emission scanning electron microscope and atomic force microscope. The purity of silver is examined through X-ray energy dispersive spectroscopy. The top electrode exhibits face centered cubic structure with homogeneous morphology. The sheet resistance of top electrode is found to be 0.06 Ω/sq and an average pattern thickness of ∼15 μm. The power conversion efficiency is 2.58%. Our work demonstrates that the solution based screen printing is a significant role in the replacement of vacuum process for the fabrication of top electrode in organic solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Rapid Development of Hybrid Perovskites and Novel Tandem Architectures

Multijunction solar cells based on epitaxially grown III-V materials hold the record for solar energy power conversion efficiency (PCE). However, due to the high cost of fabricating these devices, they are typically only used for concentrator cells and space applications. The overarching goal of this project was to develop low-cost printable hybrid perovskite (HP) materials appropriate and optimized for tandem solar cells with high power conversion efficiency under “1 Sun” illumination. Key results and findings over the course of the project we: Developed higher-performance high-bandgap (1.75 eV) perovskite materials and devices. In particular, we explored tens-of-thousands of compositions for high bandgap perovskites, achieving quasi-Fermi level splitting of 1.35 eV for a 1.75 eV bandgap material. We achieved World-record open circuit voltages from single junction p-i-n devices, 1.24 V from 1.75 eV bandgap material, which is what is preferable for tandems with a PCE of 14.3% using a guanidinium/formanadinium/ cesium alloyed lead iodobromide. We also developed a series of World-record efficiency devices at higher band-gaps based on 2D/3D perovskites using PEA. Developed higher-performance low-bandgap (1.35 eV) perovskite materials and devices. In particular, we developed a 1.35 eV bandgap perovskite of composition MAPb0.5Sn0.5(I0.8Br0.2)3 and showed its superiority to MAPb0.75Sn0.25I3. High efficiency solar cells were fabricated using PEDOT:PSS and doped-ICBA as HTL and ETL, respectively. Short circuit currents of 25.7 mA/cm2 and PCEs of 17.1% were obtained. Developed mechanically stacked 4-terminal CIGS-Perovskite tandems with PCE of 18.8% and monolithic 2-terminal CIGS-Perovskite tandems with PCE of 8.5%. The low efficiency of the monolithic device is a result of the high surface roughness of the solution processed CIGS bottom cells. This is not an intrinsic problem for CIGS-perovskite tandems, but does mean that smooth evaporated or sputtered CIGS films likely need to be used, unless a polishing step is employed. Developed monolithic 2-terminal Perovskite-Perovskite tandems with a stabilized PCE of 18.5%. This was the World-record perovskite-perovskite monolithic tandems for over a year in 2017-2018. Revealed that light is not an essential component of the so-called “light-induced” phase segregation. By using charge injection in the dark and electroluminescence, we showed that the presence of electrons in the conduction band and hole in the valence band is sufficient to drive the nearly ubiquitously observed phase segregation in high bandgap perovskites. Developed a new method to simultaneously measure absolute intensity photoluminescence and photoconductivity and use them to obtain simultaneous in-situ measurement of quasi-Fermi level splitting and diffusion length. This is important since it provides a proxy for device Voc and device Jsc. In addition, 67 papers were published with support from this award that detail many more advances in the field, including numerous publications in high impact journals such as Nature Photonics, Advanced Materials, ACS Energy Letters, and Energy and Environmental Science.

14 SOLAR ENERGY↗