Name: Marco Califano
Institution: University of Leeds
Research: Exploiting solar power using the NGS
To date efficient exploitation of solar energy, the only clean and sustainable energy that could realistically supply enough power to satisfy the needs of a modern society, has been hampered by the limited range of suitable materials for photovoltaics.
The recent development of semiconductor nanocrystals opens up new ways to tailor materials for solar energy conversion, and could lead to an 8-fold increase in the electric current generated in a solar cell, greatly improving the efficiency of the present devices, through the exploitation of a process called “carrier multiplication” (CM).
Nanocrystals are chemically synthesised semiconductor systems with characteristic dimensions of the order of few millionths of a millimeter whose properties, unlike those of any macroscopic object we are used to, depend on their size as well as on the material they are made of.
Unlike in conventional photovoltaic devices, where the absorption of a photon always creates one pair of oppositely charged particles, in CM-based solar cells multiple pairs can be generated upon the absorption of a single high-energy photon in a nanocrystal of a suitable material, their number depending only on the photon energy. This would allow a more efficient and complete conversion of solar energy into electric current and at the same time reduce the detrimental heat generation that accompanies conventional conversion.
Marcos work investigates CM theoretically (using state-of-the-art computational simulation tools) trying to identify the best materials, sizes and shapes of the nanocrystals that could lead to high-efficiency energy conversion in the next-generation solar cells.
Marco uses two different (non-open-source) parallel codes at the NGS Leeds site, one of which has fairly large memory requirements and can be used on up to 16 CPUs. The other has a good scalability with the number of processors up to about 128 CPUs, although he has only run it up to 32 CPUs at Leeds.
Running his parallel codes on the NGS allows Marco to use a larger number of nodes and larger memory, compared to his local cluster. He can therefore get faster results and run calculations which would be impossible on his small machine.
Marco explains that “The outcome of my research could help the UK develop alternative, renewable energy technologies that enhance the cleanliness and efficiency of energy production. This, in turn, will contribute to the Government's commitment to meet the greenhouse gas emission targets set in Kyoto. Non-polluting energy sources also reduce damage to crops and improve community health as well as making our industry less reliable on overseas energy supplies”.
Speaking of his experiences of using the NGS Marco expressed his thanks for assistance from local NGS staff, “I would like to praise the great support I received from locally based NGS staff that have helped me to overcome all the problems related to porting, compiling and running my codes on the NGS”.
Image - The square of the wave function of a hole state in a CdSe nanocrystal
Project funding - Royal Society
Project PI - Marco Califano
Project Title - Semiconductor nanocrystals: building blocks for high-performance photovoltaics and photonics
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