by Staff Writers
Groningen, Netherlands (SPX) Jul 28, 2016
While investigating perovskite crystals, University of Groningen scientists made an observation that could make perovskite solar cells more efficient. It could also lead to new sensors for oxygen and water vapor. The results were published online by the journal Science Advances on 27 July.
Photovoltaic cells based on hybrid perovskites were first introduced in 2009, and they rapidly became as efficient as standard silicon solar cells. They now convert light into electricity at about 22 percent efficiency. 'And the theoretical limit is about 33 percent', says Maria Antonietta Loi, Professor of Photophysics and Optoelectronics at the University of Groningen.
However, part of the electric charge disappears into what are known as traps. This happens in both silicon and perovskite, and reduces the efficiency of photovoltaic cells. So it would be nice to know more about traps and how to avoid them. A serendipitous observation by University of Groningen scientists provided new insight into hybrid perovskite traps.
This laser light produces electronic charges in the crystal, which emit light when they recombine. In this instance the crystal should have emitted green light, but surprisingly, when the air was removed from around it, the green light disappeared too. Fang: 'But when we let the air in again, the light emission was restored.' So apparently, without air, most charges disappear into the traps.
Atmospheric gases somehow blocked the activity of the 'charge eaters' in the crystals, so Fang set out to investigate. He exposed crystals to different types of gas and discovered that oxygen and water vapor deactivated the traps, while gases such as nitrogen, carbon dioxide or argon had no effect. The next step was to localize the traps, which he did by using two different laser lights to excite either the surface or the interior of the crystals. He discovered that the traps were mainly on the surface.
If he succeeds, he will further enhance the efficiency of perovskite solar cells. 'The number of traps in the material that we used for these experiments was relatively low, but we estimate that by eliminating them, we could go from an efficiency of 22 percent to one equaling or surpassing that of crystalline silicon, which is 25 percent.'
There is another possible application for the findings. Loi: 'As the effect of oxygen and water vapor on perovskite is reversible, it would make a nice sensor.' Perovskite crystals inside sealed food packaging could detect the presence of harmful oxygen. 'Just shine a laser on the sensor, and if it lights up you know the seal has been broken.'
H.H. Fang, S. Adjokatse, H. Wei, J. Yang, G. R. Blake, J. Huang, J. Even, M. A. Loi, Ultrahigh sensitivity of methylammonium lead tribromide perovskite single crystals to environmental gases. Science Advances 2, e1600534 (2016).
University of Groningen
All About Solar Energy at SolarDaily.com
|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|