+44 (0)24 7671 8970
More publications     •     Advertise with us     •     Contact us
 
Loading...
{megaLeaderboard}
{normalLeaderboard}
News Article

Swiss engineers solve mystery of perovskite negative capacitance

News

Apparent capacitances are not stored charge but a slowly increasing current

Perovskite solar cells are highly efficient and low-cost but suffer from poor long-term stability. Related to this are various odd phenomena in perovskite materials and devices, where very slow microscopic processes produce a kind of memory effect.

Measuring the efficiency of a perovskite solar cell can depend on things like how long the device is illuminated prior to measurement or how the voltage was applied. A few years ago, this effect, known as current-voltage hysteresis, led to disputes on how to accurately determine the efficiency of perovskites. Another example of these obscure processes is a (partial) recovery of a previously degraded solar cell during day-night cycling.

Such effects are a concern when measuring the solar cells' performance as a function of frequency, which is a typical measurement for characterising these devices in more detail (impedance spectroscopy). They lead to large signals at low frequencies (Hz to mHz) and giant capacitance values for the (mF/cm2), including strange, 'unphysical' negative values that are still a puzzle to the research community.

Now, chemical engineers from the lab of Anders Hagfeldt at Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland have solved the mystery. Led by Wolfgang Tress, a scientist in Hagfeldt's lab, they found that the large perovskite capacitances are not classical capacitances in the sense of charge storage, but just appear as capacitances because of the cells' slow response time.

The researchers show this by measurements in the time domain and with different voltage scan rates. They find that the origin of the apparent capacitance is a slow modification of the current passing the contact of the solar cells, which is regulated by a slow accumulation of mobile ionic charge. A slowly increasing current appears like a negative capacitance in the impedance spectra.

The work sheds light onto the interaction between the photovoltaic effect in these devices and the ionic conductivity of perovskite materials. Gaining such in-depth understanding contributes to the endeavour to tailored, stable perovskite solar cells.

'Origin of apparent light-enhanced and negative capacitance in perovskite solar cells' by Firouzeh Ebadi et al; Nature Communications 05 April 2019

Schletter Group: 48 MWp Project in Italy
ENCAVIS Acquires Two More Solar Parks In Spain and Surpasses The Planned Expansion
Maximum profitability with KACO advanced technology for complex solar roofs
Enviromena wins contract to re-power three major solar farms ahead of the summer energy peak
New Swansea University Collaboration to Support Sustainable, Locally Manufactured Solar PV
New Swansea University Collaboration to Support Sustainable, Locally Manufactured Solar PV
Next2Sun Builds World's Largest Vertical PV Plant at Frankfurt Airport
DNV Publishes Bankability Study of Solcast Satellite Irradiance Data
Steel company SSAB switches to fossil-free energy in Italy with PV solution from Solnet
janom Investments enters the Croatian solar energy industry by investing in a 30 MW power plant project
Trina Solar Vertex S+ 505W n-type dual-glass modules enter mass production
BayWa r.e. and 3E sign partnership agreement for monitoring & analytics of global PV portfolio
Accelerating Spain's Energy Transformation: LONGi to supply Naturgy with 1 million modules in new deal
NTR announces corporate PPA with Almac Group to buy energy from Murley Wind Farm, Northern Ireland
Oxford PV sets new solar panel efficiency world record
Order Intake for the Construction of Wind Turbines in Turkey
Trilantic Europe acquires stake in AEROCOMPACT Group
Octopus Energy makes solar farm debut in Germany
Austria-based KOGA Energy, a solar EPC solutions provider, has kicked off.
Exus to acquire 625MW New Mexico solar portfolio
Capcora Accompanies SUSI Partners In Raising Senior Debt For a Polish Renewables Portfolio
Qualitas Energy acquires a 96 MW wind energy project pipeline in Germany
Nordex Group receives orders from the UK for approx. 150 MW
Trina Solar gains EPD certification from UL Solutions and EPDItaly for industry leading modules
Mandarin Oriental Hyde Park, London instals innovative solar tech to decarbonise heating
Efficiency First: The Road to Electrification
SCHLETTER Supplies Austria's Largest PV Roof System
E.ON partners with UK renewable heat innovator Naked Energy
Sonnedix signs innovative EUR500 million loan facility to finance construction of its renewable electricity pipeline in Europe and UK
Construction begins on Glennmont and Ørsted’s Borkum Riffgrund 3 offshore wind farm in Germany
ABB shores up reliable power supply at Southeast Asia’s largest floating solar plant
Sonnedix starts construction of 300MW UK solar PV portfolio

×
Search the news archive

To close this popup you can press escape or click the close icon.
Logo
×
Logo
×
Register - Step 1

You may choose to subscribe to the Solar + Power Magazine, the Solar + Power Newsletter, or both. You may also request additional information if required, before submitting your application.


Please subscribe me to:

 

You chose the industry type of "Other"

Please enter the industry that you work in:
Please enter the industry that you work in: