Researchers Find Simple, Cheap Way to Increase Solar Cell Efficiency

Posted on January 3, 2014 by Raj Shah

January 3, 2013 (Source: North Carolina State University) – Researchers from North Carolina State University and the Chinese Academy of Sciences have found an easy way to modify the molecular structure of a polymer commonly used in solar cells. Their modification can increase solar cell efficiency by more than 30 percent.

Polymer-based solar cells have two domains, consisting of an electron acceptor and an electron donor material. Excitons are the energy particles created by solar cells when light is absorbed. In order to be harnessed effectively as an energy source, excitons must be able to travel quickly to the interface of the donor and acceptor domains and retain as much of the light’s energy as possible.

One way to increase solar cell efficiency is to adjust the difference between the highest occupied molecular orbit (HOMO) of the acceptor and lowest unoccupied molecular orbit (LUMO) levels of the polymer so that the exciton can be harvested with minimal loss. One of the most common ways to accomplish this is by adding a fluorine atom to the polymer’s molecular backbone, a difficult, multi-step process that can increase the solar cell’s performance, but has considerable material fabrication costs.

A team of chemists led by Jianhui Hou from the Chinese Academy of Sciences created a polymer known as PBT-OP from two commercially available monomers and one easily synthesized monomer. Wei Ma, a post-doctoral physics researcher from NC State and corresponding author on a paper describing the research, conducted the X-ray analysis of the polymer’s structure and the donor: acceptor morphology.

PBT-OP was not only easier to make than other commonly used polymers, but a simple manipulation of its chemical structure gave it a lower HOMO level than had been seen in other polymers with the same molecular backbone. PBT-OP showed an open circuit voltage (the voltage available from a solar cell) value of 0.78 volts, a 36 percent increase over the ~ 0.6 volt average from similar polymers.

According to NC State physicist and co-author Harald Ade, the team’s approach has several advantages. “The possible drawback in changing the molecular structure of these materials is that you may enhance one aspect of the solar cell but inadvertently create unintended consequences in devices that defeat the initial intent,” he says. “In this case, we have found a chemically easy way to change the electronic structure and enhance device efficiency by capturing a lager fraction of the light’s energy, without changing the material’s ability to absorb, create and transport energy.”

The researchers’ findings appear in Advanced Materials. The research was funded by the U.S. Department of Energy and the Chinese Ministry of Science and Technology. Dr. Maojie Zhang synthesized the polymers; Xia Guo,Shaoqing Zhang and Lijun Huo from the Chinese Academy of Sciences also contributed to the work.

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Posted on January 3, 2014 by Raj Shah

January 3, 2013 (Source: National University of Singapore) – What started as a research project by the Solar Energy Research Institute of Singapore (SERIS) at NUS has culminated into a spin-off that helps light up rural communities.

With a grant from the Singapore-MIT Alliance for Research and Technology (SMART), the team initiated the concept of affordable solar-powered street lamps that can be used in areas not connected to an electricity grid. The development of the idea led to the formation of start-up Fosera Lighting Pte Ltd to commercialise the product.

The COMMLIGHT is a streetlight with an intelligent microprocessor and motion-sensor that automatically adjusts to the brightest level upon detection of activity. Otherwise, the lamp goes into dimmed mode when full lighting is not required to save energy. The integrated design with a built-in solar panel uses energy-saving LED lights and long-lasting Lithium-ion batteries to minimise maintenance.

By implementing the NUS-patented passive cooling concept for the battery and the microcontroller-driven power management algorithm with adaptive lighting, the system is highly efficient with an expected lifespan of up to 10 years. The electronics components housed in waterproof and durable aluminium ensure prolonged operation in tough climates. The lamp is easy to mount and uses theft-proven fixtures.

Typical applications are small streets, walkways, markets, small businesses, parking lots, bus stops, rural communities and places where the electric power grid is unavailable or a grid connection would be too expensive.

Last year, Fosera Lighting initiated the “Streetlights for Cambodia” campaign on Indiegogo.com. This campaign was a corporate social responsibility project to help improve the standard of living and safety of people in the Kampong Chhanang province of central Cambodia. “By this new way of raising money through crowd funding, we not only create an impact according to our vision, but also generate product volumes and visibility,” said Mr Robert Haendel, Founder and CEO of Fosera Lighting.

Conducted in partnership with Asian non-governmental organisations “Base of the Pyramid” Hub and the World Toilet Organisation, the campaign collected sufficient funds to install 16 COMMLIGHT lamps in the villages of Kraing Learve, Toek Laak and Trapaing Kravann.

Since starting operations in August this year, the young company has already sold its products to more than 18 countries globally.

“We will continue to develop further products with our own resources and in cooperation with SERIS,”said Mr Haendel. Currently, the firm is testing a wireless hotspot system integrated into the COMMLIGHT and focusing on cost reduction, he disclosed.

In recognition of its innovation, Fosera Lighting won first prize at the INSEAD Boot Camp Business competition and SMART business contest in 2012. It also clinched the title of the “Most Promising Start-up” in the engineering category at Techventure 2013, a networking platform for regional start-ups to present their ideas and projects to potential investors and develop business plans.

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S’pore Part of 3-Nation Solar Panel Project

Posted on January 3, 2014 by Raj Shah

January 3, 2013 (Source: Asia One) – SINGAPORE has embarked on an ambitious solar power project spanning three countries.

The aim is to test the power generation of solar panels in Singapore’s tropical climate, in a temperate zone in Japan and under Australian desert conditions.

Led by the Solar Energy Research Institute of Singapore (Seris) at the National University of Singapore, the project, which will take place in each of the countries simultaneously, will last until 2016 at least.

The findings will help researchers develop better models to predict the output of solar panels in different conditions such as varying temperatures and amount of sunlight.

Developers can then optimise solar power systems for different climate zones to enhance their performance over the systems’ lifespan, said Seris deputy chief executive Thomas Reindl. This will also reduce the price that the electricity generated has to be sold at to recoup costs, he explained.

In the past, solar panels had been mostly installed in moderate climates. That meant that standards to measure output and quality were also developed in those climates.

“In harsher climate zones such as the tropics with constant high temperatures and high humidity, the existing standard tests may not be sufficient,” the National Climate Change Secretariat and National Research Foundation (NRF) said in 2011.

Seris is partnering the Australian National University, the National Institute of Advanced Industrial Science and Technology in Japan, solar module manufacturers, certifying bodies and other organisations for its project, called True Power Alliance.

The first outdoor tests are expected to start early next year.

The research also involves monitoring the solar panel systems’ long-term performance, including the impact of dust accumulation and sand. Solar panel systems are expected to last 25 to 30 years with next to no degradation.

The project is funded by the Energy Innovation Research Programme. The researchers were among five teams that won $12 million in grants in total from the Government earlier this year in a grant call for energy innovations.