It’s increasingly possible to stack technologies to produce smart systems.
By Jef Poortmans
It may sound strange, but striving to achieve smaller dimensions with Moore’s Law is an important enabler for producing increasingly better solar cells, with a more elaborate technology toolbox (including ALD, epitaxy, etc.)
Improved process steps are constantly being developed to achieve these small transistor dimensions (for growing material layers or to etch away structures), and we also can use some of them to produce the latest solar cells and batteries. For example, there’s atomic layer deposition (ALD), a technology that was developed with the switching of thermal oxides to high-k dielectrics in transistors.
The record efficiencies that we achieve with our nPERT cells are based on ALD layers of aluminum oxide, offering more efficient passivation than traditional thermal oxides. The same technology is used for thin-film PV cells, where they allow for better window layers. Another example is nanotexturing, which is used for producing the uppermost contacts of a solar cell and applying an antireflective coating. It will certainly be possible to use the knowledge of nano-imprint lithography in this area. Technologies such as ALD and molecular layer CVD are also very important for 3D thin-film batteries.
Moore’s Law has always been focused on increasing the functionality per surface area. This can be achieved by making transistors smaller. However, now that the complexity of the technology is becoming too great, researchers are looking for solutions in the third dimension. Yet thanks to 3D stacking, the functionality per surface area can still be increased without having to scale. This 3D approach has other benefits, too: it is becoming possible to stack other technologies compactly on top of one another to produce smart systems.
Sensors are a good example of this. And precisely these autonomous sensor systems will form the foundation of the future Internet of Power. Our current unidirectional power grid – from plant to consumer – will be replaced by a bidirectional system. Energy will be generated in a decentralized way (solar panels, wind turbines, biomass, etc.); houses and commercial businesses will have incoming and outgoing energy flows and increasingly be able to store energy. The situation is becoming complex and will be based on sensors, gathering data in the cloud, interpreting data and carrying out the right actions based on that data. This means that Moore’s Law is much more than an enabler for cheaper electronics. It also enables a greener future!
Dr. Jozef Poortmans is fellow and PV program director at Imec. He received his degree in electronic engineering from the Catholic University of Leuven, Belgium, in 1985. He joined the newly built Imec in Leuven where he worked on laser recrystallization of polysilicon and a-Si for SOI-applications and thin-film transistors. In 1988 he started his PhD study on strained SiGe-layers. Both the deposition and the use of these SiGe-alloys within the base of a heterojunction bipolar transistor were investigated in the frame of this study. He received his Ph.D. in June 1993. Afterwards he joined the photovoltaics group, where he became responsible for the group advanced solar cells. Within this frame he started up the activity about thin-film crystalline Si solar cells at Imec and he has been coordinating several European Projects in this domain during the 4th and 5th European Framework Program. In 2003, he became cluster coordinator of European projects in the latter domain. In 1998 he initiated the activity on organic solar cells at imec which was complemented with an activity on III-V solar cells started in 2000. Dr. Poortmans has authored or co-authored nearly 350 papers that have been published in Conference Proceedings and technical journals. He has written 4 book articles, two of which are dealing with the properties and applications of strained SiGe-alloys whereas the other two are in the field of photovoltaics.