The Salleo Group at Stanford University was founded by Prof. Alberto Salleo, associate professor of Materials Science & Engineering, in 2005. As of February 2013, Prof. Salleo has his tenure at Stanford. His group focuses on a wide range of projects under the Photovoltaics umbrella. Photovoltaics is the field where semiconductor materials are used to produce electricity from sunlight.
The Salleo Group is currently working on a number of projects including:
- Aggregation in Semicrystalline Organic Thin Films
- Lanthanide-based Upconverting Nanoparticles
- Nanostructured ZnO for Solution-based Transparent Electrodes
Before diving into these projects, let’s keep in mind that today’s biggest challenge in solar energy field is the associated cost. We are still far away from catching the ‘not so environment friendly’ sources in cost effectiveness. Unfortunately, this is true even with the government provided incentives that encourage households to utilize solar energy. That is why almost every science team in our research facilities and universities have projects to improve the cost effectiveness of solar energy modules. The Salleo Group, in these projects, is aiming to either replace expensive materials with cheaper yet efficient alternatives or improve the efficiency of currently available solutions to target the cost problem.
Aggregation in Semicrystalline Organic Thin Films
Even though the solar energy module market is dominated by Crystalline Silicon cells, one of the very promising techniques that may become a better alternative is Organic cells. However, Organic cell technologies are still a lot less reliable and a lot less efficient than Crystalline Silicon cells mainly because of these two materials’ natures. Compared to Silicone crystals where molecules are perfectly aligned and the application results are very predictable, Organic cells look like the famous ‘The Weeping Woman’ by Pablo Picasso.
Under the ‘Aggregation in Semicrystalline Organic Thin Films’ project, the Salleo Group is researching the nature of the Organic semiconductors in order to close the gap around the knowledge of these materials. Prof. Salleo’s team suggests not only focusing on the molecular structure of the material but also the ordered & disordered regions to have a better understanding of the behavior of organic semiconductors.
Lanthanide-based Upconverting Nanoparticles
Currently, the most efficient solar cells are multi-junction cells, with efficiencies up to 44%. Similarly, the cheaper and less efficient single-junction solar cells provide efficiencies as high as 29%. The reason Crystalline Silicon solar cells dominate the market with a lot less efficiency, commercial module average of about 18%, they are much more cost effective then single & multi junction cells. However, in applications where efficiency is significantly more important than the cost, like a spacecraft, these solutions are preferred over Crystalline Silicon. The solar cell efficiency graph below is from National Renewable Energy Laboratory (NREL) and the most recent version can be seen by clicking on this link.
The main limitation with single-junction cells is that the photons with lower energy than the band, the energy spectrum that results in electron movement / electrical current, are wasted without providing any benefit to the system. Prof.Salleo’s team is working on photon upconversion (UC), the technique where the photons with lower energy are absorbed and up-converted to energy levels that reside within the band. This way the lower energy photons will also be utilized, which may significantly improve the efficiency of single-junction solar cells.
This is one of the most exciting & promising approaches in Photovoltaics in our opinion and we will be closely following the Salleo Group’s progress. Lin Research Group at Georgia Institute of Technology also uses this technique. Click on this link to read about the Lin Research Group.
Nanostructured ZnO for Solution-based Transparent Electrodes
Indium Tin Oxide (ITO) is a widely used material in Photovoltaics. Unfortunately, its usage is not limited to Photovoltaics. Indium is one of the most utilized materials in LCD technology. With the great increase in LCD usage in TV, smart phones, and so on; the price of the material also greatly increased.
Prof.Salleo’s team, under the ‘Nanostructured ZnO for Solution-based Transparent Electrodes’ projects, is focusing on replacing Indium Tin Oxide (ITO) with Zinc Oxide (ZnO), a much less expensive material, to target the biggest challenge in solar energy field, the associated cost.
To read more about the Salleo Group, please visit the team’s website by clicking on this link.
Prof. Alberto Salleo
Professor Alberto Salleo’s first academic achievement was his undergraduate degree from University of Rome (Italy) in Physical Chemistry (thesis title “Oxidation of carbides at low oxygen fugacity”) and Ecole Polytechnique (France) in Applied Physics (thesis title “Role of external stresses on the oxidation of polycrystalline Nickel”) in 1994. Later, Prof. Salleo attended UC Berkeley and received his M.S. degree in Materials Science and Engineering in 1998 with the thesis “Ultra-violet laser damage in fused silica”. Following his M.S. degree, Prof. Salleo continued his education in UC Berkeley and earned a Ph.D degree in Materials Science and Engineering with his “High-intensity laser damage of fused silica” thesis in 2001.
After earning his Ph.D degree, Prof. Salleo worked as a post-doc in Palo Alto Research Center and a researcher at Electronic Materials Laboratory before joining Stanford University Materials Science and Engineering department in 2005. In February 2013, Prof. Salleo received tenure and the promotion to Associate Professor.
Even though we could not locate any video clips to share about Prof. Salleo’s work on Photovoltaics, there are short video clips that involve Prof. Salleo available online:
As you may have noticed, some of those video clips were from Prof. Salleo’s Youtube channel. He also has a LinkedIN and a Google+ profile.
To learn more about Prof.Salleo and his team, visit their website by clicking on this link.