News

Black silicon photodetector breaks the 100% efficiency limit

The efficiency was so high that at first the researchers had a hard time believing the result. Now Aalto University spin-off company ElFys Inc. already supplies the record detectors for several industry sectors.
valoanturi
UV-light triggers electron multiplication in nanostructures. Figure: Wisa Förbom

Aalto University researchers have developed a black silicon photodetector that has reached above 130% efficiency. Thus, for the first time, a single photovoltaic device has exceeded the 100% external quantum efficiency limit at UV. This result opens new avenues for improving efficiencies beyond the famous Shockley-Queisser limit.

'When we saw the results, we could hardly believe our eyes. Straight away we wanted to verify the results by independent measurements', says Prof. Hele Savin, head of the Electron Physics research group at Aalto University.  

The independent measurements were carried out by the German National Metrology Institute, Physikalisch-Technische Bundesanstalt (PTB), which is known to provide the most accurate and reliable measurement services in Europe.

Head of the PTB Laboratory of Detector Radiometry, Dr Lutz Werner comments, 'After seeing the results, I instantly realised that this is a significant breakthrough - and at the same time, a much-welcomed step forward for us metrologists dreaming of higher sensitivities'. 

The secret behind the breakthrough: Unique nanostructures

The external quantum efficiency of a device is 100% when one incoming photon generates one electron to the external circuit. 130% efficiency means that one incoming photon generates approximately 1.3 electrons.

The researchers found out that the origin of the exceptionally high external quantum efficiency lies in the charge-carrier multiplication process inside silicon nanostructures that is triggered by high-energy photons. The phenomenon has not been observed earlier in actual devices since the presence of electrical and optical losses has reduced the number of collected electrons. 

'We can collect all multiplicated charge carriers without a need for separate external biasing as our nanostructured device is free of recombination and reflection losses', Prof. Savin explains.  

In practice, the record efficiency means that the performance of any device that is utilising light detection can be drastically improved. Light detection is already used widely in our everyday life, for example, in cars, mobile phones, smartwatches and medical devices.

'Our detectors are gaining a lot of attraction at the moment, especially in biotechnology and industrial process monitoring', says Dr Mikko Juntunen, CEO of Aalto University spin-off company, Elfys Inc. They are already manufacturing the record detectors for commercial use.

The results leading to the record efficiency have been accepted for publication in Physical Review Letters with a title "Black-silicon ultraviolet photodiodes achieve external quantum efficiency above 130%". 

More information:

Professor Hele Savin, Aalto University
ph. 050 541 0156
[email protected]

CEO Mikko Juntunen, ElFys Oy
ph. 040 860 9663
[email protected]

 

 

 

  • Published:
  • Updated:
Share
URL copied!

Related news

Aalto Töölön juhlasali
Campus, Press releases Published:

The renovation of the Aalto University Töölö building restored the spirit of the 1950s

The former main building of the School of Business in Runeberginkatu was renewed into a modern learning environment.
With the right guidance, certain bacteria can produce 3D objects made of nanocellulose
Press releases, Research & Art Published:

Scientists use bacteria as micro-3D printers

Technique creates highly customised structures that could be used in regenerative medicine
Amsterdamin konserttisali
Press releases Published:

Can you identify which concert hall this music is being played in? Test to see

Study shows music volume has a major impact on how the listener experiences the acoustics of a concert hall
Aikalava
Press releases Published:

Building European cities with wood would sequester and store half of cement industry’s current carbon emissions

Model shows that slowly increasing the use of wood in European construction could increase the carbon storage of buildings by 420 million CO2 tons over the next 20 years