Subscribe to our free daily newsletters
  Solar Energy News  




Subscribe to our free daily newsletters



SOLAR DAILY
Sustainable solvent platform for photon upconversion increases solar utilization efficiency
by Staff Writers
Tokyo, Japan (SPX) Dec 06, 2017


Deep eutectic solvents used as the medium of sensitizer and emitter chromophores (left) and the photon upconverter developed (right). The sample converts low-intensity (a few mW) green light into clear blue emission and demonstrates high thermal stability during exposure to a burner flame for 1 min.

The conversion of solar energy into electricity is currently restricted by a concept known as the Shockley-Quesser limit. This limitation allows only photons that have higher energies than those of the bandgap to be used, while those with lower energies are wasted. In an effort to obtain a solution to this problem and make solar energy conversion more efficient, the process of converting photons with lower energies into ones with higher energies, called photon upconversion, was developed.

In the past decade, a method of photon upconversion that uses triplet-triplet annihilation (TTA) of organic molecules has drawn attention because it is presently the only method applicable to weak light such as sunlight. In this method, two kinds of organic molecules or chromophores, a sensitizer and an emitter, are combined.

The sensitizer will absorb a photon and convert it to its excited triplet state. The excitation energy is then transferred to the emitter. When two emitters that have the excitation energy collide, one will convert to its lowest excited singlet state and release an upconverted photon that can be harvested for energy conversion.

While many studies into photon upconversion have been carried out in organic solvents, their practical use is limited due to the high vapor pressures, vapor toxicity, flammability, and lack of thermal stability of the solvent mixtures. Multiple approaches have been proposed so far to overcome these limitations, including the use of viscous fluidic media like ionic liquids that have low vapor pressures and high thermal stability. Ionic liquids are also limited in practicality, however, due to the relatively high costs of starting materials and synthetic processes, as well as their poor biodegradability.

To fundamentally resolve these previous problems, scientists at Tokyo Tech developed a TTA photon upconversion using a new class of liquids known as deep eutectic solvents (DESs). DESs are a potential alternative to ionic fluids, because they possess desirable properties similar to those of ionic fluids and can be created through a simple mixing of two substances, a hydrogen bond donor and a hydrogen bond acceptor, without the need for synthetic processes.

The starting substances for the generation of DESs are also generally much cheaper, safer, and more biodegradable than those needed for the creation of ionic liquids, making them an ideal alternative.

The photographs of the DESs used and photon upconverters developed are shown in Fig. 1. The prepared DES was optically transparent and colorless (left of Fig. 1) and used as the solvent for the sensitizer and emitter chromophores. The photographs of the photon upconverter developed are shown in the right of Fig. 1. The sample converts weak incident green light (wavelength: 532 nm; power: 2-3 mW) into blue emission (wavelength: ~440 nm). The expected high thermal stability was confirmed by the absence of ignition and fuming during exposure to a burner flame for 1 min.

Notably, the photon upconversion quantum yield of the samples reached 0.21 (where the maximum quantum yield is defined as 0.5; one higher-energy photon is created by using two lower-energy photons at maximum in photon upconversion). This corresponds to the upconversion quantum efficiency of 42 % (whose maximum is defined as 100%). This is a relatively high efficiency.

Overall, the scientists developed a novel material platform for TTA photon upconversion using cheaper, less toxic, and thermally stable DESs. This achievement is considered as an important landmark for the realization of practical application of photon upconversion technology.

Research paper

SOLAR DAILY
Windows of opportunity: Solar cell with improved transparency
Tokyo, Japan (SPX) Dec 04, 2017
Roof-mounted solar panels are an increasingly common sight in many places. As a source of cheap, clean electricity, their advantages are obvious. However, most solar panels are opaque, and therefore cannot be placed over windows. Now, researchers at The University of Tokyo's Institute of Industrial Science (IIS) have made developments in the design of transparent solar materials. Conventio ... read more

Related Links
Tokyo Institute of Technology
All About Solar Energy at SolarDaily.com


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

Comment using your Disqus, Facebook, Google or Twitter login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

SOLAR DAILY
Breakthrough process for directly converting methane to methanol

Convert methane to hydrogen without forming carbon dioxide at low-cost

Brazilian ethanol can replace 13 percent of global crude oil consumption

The water world of ancient photosynthetic organisms

SOLAR DAILY
Amazon brings Alexa from the home to the office in a new AI push

Robot learning improves student engagement

Lockheed Martin autonomous driving system tops 55,000M in extended test

With 'material robotics,' intelligent products won't even look like robots

SOLAR DAILY
U.S. wind turbines getting taller and more efficient

New wind farm in service off the British coast

End tax credits for wind energy, Tennessee Republican says

New York sets high bar for wind energy

SOLAR DAILY
GM recalling 1 million cars in China

Traffic-weary Chinese man fined for repainting road lines

GM sees 2019 launch for self-driving taxi fleet

SoftBank offer for Uber shares to cut valuation: reports

SOLAR DAILY
Musk's record-breaking battery officially launches in Australia

Batteries with better performance and improved safety

Activity descriptors for electrocatalysts in energy storage applications

Statoil: Batteries can address wind power variability

SOLAR DAILY
For Gabon's sickly uranium miners, a long quest for compensation

Belarus nuclear power plant stirs fears in Lithuania

Lightbridge and AREVA NP Sign Agreements to Immediately Advance Fuel Development

UK made grave errors over Hinkley nuclear project: MPs

SOLAR DAILY
Improving sensor accuracy to prevent electrical grid overload

Japan faces challenges in cutting CO2, Moody's finds

IEA: An electrified world would cost $31B per year to achieve

'Fuel-secure' steps in Washington counterintuitive, green group says

SOLAR DAILY
NASA Survey Technique Estimates Congo Forest's Carbon

Greenpeace slams Indonesia palm oil industry on deforestation

Amazon's recovery from forest losses limited by climate change

Poland says compliant with EU court order against ancient forest logging




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement