Periodic Reporting for period 1 - AMELI (A Metamaterial-based technology to create Electricity from Light)
Periodo di rendicontazione: 2023-11-01 al 2025-04-30
AMELI aims at developing a family of hot carrier devices that operate on a technology discovered by the PI during the course of his ERC-CoG project. This hot carrier technology does not rely on a P-N junction (or one of its many derivatives) to create electricity, giving access to a parameter space that is different from that of traditional solar cells. The goal of AMELI is to assess the potential for disruption of this approach and to propose a first proof of concept in photovoltaics (if we can reach a 10% energy conversion efficiency threshold) or a photodetector prototype at the end of the project.
We started our studies by further investigating and developing the device architecture from which we obtained our preliminary results. We quickly discovered that part of the basic physics eluded us, prompting us to launch a new round of fundamental research to elucidate the operating mechanisms. It turned out that we were wrong in the sign of one carrier temperature gradient at the basis of the photon-electricity conversion: the flow of electrical current from this gradient was opposite to what we initially thought. We were able to understand the physical reasons as to why this sign was opposite to what we expected. A practical consequence of this finding is that the flow of electrical current stemming from this gradient was actually opposite to that stemming from another gradient present in our devices: the carrier density gradient. In other words, the two gradients in these devices were actually countering one another, lowering the effective output electrical power.
This realization naturally prompted us to rethink our device architecture, so as to force the two gradients to act cooperatively rather than destructively. The new architecture changes by the geometry of the metasurfaces. We also invented a way to make the layer of CQDs even more efficient. All in all, the improvements allowed us to raise the open-circuit voltage to 20 µA/cm2 for a 40-nm thick device, representing a 100-fold enhancement compared to the original design presented in the proposal.
Even with this 100-fold enhancement, the efficiency of the device remained below 1% twelve months after the starting of the project, prompting us to focus on the development of photodetectors rather than solar cells during the last six months of the project. We identified a practical application for which our devices were uniquely fitted: photodetectors that can be integrated into places that are usually not compatible with conventional detectors.
The outcomes of the project are a better photovoltaic architecture (but still not satisfying in terms of measured efficiency) as well as a demonstrator of a near-infrared photodetector with unique integration capabilities.
This realization naturally prompted us to rethink our device architecture, so as to force the two gradients to act cooperatively rather than destructively. The new architecture changes by the geometry of the metasurfaces. We also invented a way to make the layer of CQDs even more efficient. All in all, the improvements allowed us to raise the open-circuit voltage to 20 µA/cm2 for a 40-nm thick device, representing a 100-fold enhancement compared to the original design presented in the proposal.
Even with this 100-fold enhancement, the efficiency of the device remained below 1% twelve months after the starting of the project, prompting us to focus on the development of photodetectors rather than solar cells during the last six months of the project. We identified a practical application for which our devices were uniquely fitted: photodetectors that can be integrated into places that are usually not compatible with conventional detectors.
The outcomes of the project are a better photovoltaic architecture (but still not satisfying in terms of measured efficiency) as well as a demonstrator of a near-infrared photodetector with unique integration capabilities.
For photovoltaics, further research is needed to improve the efficiency of the devices. For photodetectors with unique integration capabilities, the next step is filling for patent application and discussing with the industrial players that may be potentially interested.
Fundamental discoveries made during the project have not yet been published in any scientific journal since we are still in the process of protecting the intellectual property.
Fundamental discoveries made during the project have not yet been published in any scientific journal since we are still in the process of protecting the intellectual property.