Researchers from the University of China have beaten the record for organic solar cell efficiency, reaching 17.3% compared with the previous maximum of 15%.
Results of the study were published in Science last week.
While traditional commercial solar cells are made from silicon, in recent years researchers have been increasingly turning to organic solar cells – known as organic photovoltaics (OPV) – as they have fewer engineering limitations than silicon. Typically made from carbon and plastic, OPVs are also usually cheaper to produce than traditional silicon cells.
The Chinese team members used a tandem cell system in the design of their OPV, meaning two solar cell devices were constructed within the same structure, working to target two wavelengths of light and thus increasing its yield and efficacy.
Study leader Dr Yongshen Chen said: “We have two layers of active materials; each layer can absorb different wavelengths of light. That means you can use sunlight in the wider wavelengths more efficiently, and this can generate more current.”
As well as being cheaper than silicon models, OPVs are flexible and can be made with compounds that are soluble in ink, allowing engineers to build semi-transparent solar cells into windows and bend them onto the sides and roofs of buildings.
OPVs have not been used in solar panel construction to date as they have typically been unable to compete with silicon PV’s efficacy of converting 18% – 22% of solar energy into electricity, with a world record of 27.3% reached in this summer in the UK. OPVs usually achieve only half of this rate.
However, the new Chinese design adds to a string of breakthroughs in OPV development. In April this year, a team from the University of Michigan broke records with an OPV cell with 15% efficacy, the first to be comparable to silicon cells.
Imperial College London professor Dr Artem Bakulin told the BBC: “The development of such new materials with previously unthinkable properties allowed them to achieve the reported record efficiency and, in general, makes OPV technology much more promising.”
Bringing OPVs into mainstream use is still hindered by the fact that silver is needed to manufacture the electrodes within them, a metal which is not abundant enough to create solar modules on a global scale.