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:

Read more news

image of a wooden pillar from little finlandia and the text time out
Research & Art Published:

Aalto University shakes up construction practices at the New European Bauhaus Festival in Brussels

The exhibition Time Out! will be on show in Brussels from 9 to 13 April 2024 as part of the NEB Festival.
Two of the awardees and their robotic arm all holding colorful mugs. Aalto Open Science Award, Honorary mention.
Awards and Recognition, Research & Art Published:

Aalto Open Science Award third place awardee 2023 – Intelligent Robotics Research Group with the Robotic Manipulation of Deformable Objects project

We interviewed the Intelligent Robotics Research Group with the Robotic Manipulation of Deformable Objects project, 3rd place awardees of the first Aalto Open Science Award.
Five Aalto University students around a table
Research & Art Published:

Read the Qual+ Newsletter

We are excited to welcome you to the second Qual+ Newsletter and continue bringing you new ways of looking at methods within management studies.
Picture of leaves in water.
Press releases Published:

Graduate Sustainability Competencies and Influence in the Workplace – Aalto University's Latest Research

Aalto University's Meeri Karvinen successfully defends her doctoral dissertation, February 2024.