Black silicon photodetector breaks the 100% efficiency limit
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
hele.savin@aalto.fi
CEO Mikko Juntunen, ElFys Oy
ph. 040 860 9663
mikko.juntunen@elfys.fi
Read more news
Researchers make micromanipulation more accessible
FilMBot aims to lower the barrier to high-precision work in education, research, and micro-assembly
Scientific conclusions depend on who performs the analysis
More than 450 independent researchers from around the world conducted over 500 re-analyses of datasets from one hundred previously published studies in the social and behavioural sciences. All analysts received the same data and the same central research question, but they were free to carry out the analysis based on their own expert judgment.
Positive communication and improvisation help build students’ communication skills to meet employer needs
The School of Business redesigned its mandatory first-year communication course