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Large Area Nanoparticle Deposition System

Periodic Reporting for period 1 - LANDS (Large Area Nanoparticle Deposition System)

Reporting period: 2015-08-12 to 2017-08-11

Newly emerging solar cell technologies such as organic photovoltaics and perovskite photovoltaics are widely expected to play an important role in providing society with significant amounts of inexpensive, environmentally friendly and renewable electricity in the years to come. These two promising solar cell technologies are in the “scale up” stage as they attempt to bridge the gap between academic research and commercial viability in the marketplace. Finding and understanding efficient ways to fabricate them over large areas is critically important to their survival and success today. Spray deposition holds great promise for providing the inexpensive and scalable fabrication method needed for producing certain layers for these cells, in particular for transparent electrodes. The main objective of the project here has been to build a state-of-the-art spray deposition platform/research tool to the Oxford University physics department building on the experience of the Fellow and train its members in its operation and exploitation in order to drive advancements in the research of next generation solar cells and eventually their successful introduction into the commercial market.
The project has funded the design and fabrication of a custom, computer controlled spray deposition machine compact enough to fit comfortably in a laboratory fume hood, LANDS (the Large Area Nanoparticle Deposition System). The fFellow has used this system to deposit thin films of nanoparticles such as silver nanowires and carbon nanotubes on a variety of substrates including glass, plastic and perovskite solar cells. A major drawback typical of these types of spray deposition systems has been eliminated, in that the fellow has successfully demonstrated the move from volatile solvent based deposition to that out of water. Additionally, the fFellow, in close collaboration with other Oxford University Physics Department researchers, has demonstrated that spray deposition of single walled carbon nanotubes for use as a hole transport material in perovskite solar cells provides a significant boost in power conversion efficiency when compared to other deposition methods such as spin coating. The fellow has passed on his expertise in spray deposition through the careful training of other researchers in the Oxford Physics department so that they will use the LANDS to further their research efforts going forward.
The work funded here has resulted in two significant breakthroughs. First, state of the art spray deposited transparent conductive layers for solar cells described in recent literature have relied on using large volumes of volatile solvents in their deposition. In our work here, we’ve discovered the keys to replacing these volatile solvents with water, without sacrificing electrode performance. This leads to a less expensive and more environmentally friendly deposition process. Second, we went beyond Ag nanowires, the previously used material and showed that single wall carbon nanotube hole transport layers may be crucial to improving the long-term stability and lifetime of perovskite solar cells. In our work here, we’ve shown that carbon nanotube films spray deposited from the LANDS boosts the power conversion efficiency of perovskite solar cells using these electrodes, from 13.5% to 16.5% over traditional deposition methods (spin coating). These breakthroughs are the sort that we as researchers must continue to have in order to bring organic photovoltaics and perovskite photovoltaics to the commercial market so that they can begin to fulfill their great potential to drive out the dirty electricity sources such as coal and fossil fuels from the energy production mix we use as a society.
picure of completed LANDS in fumehood in lab of Moritz Riede, Oxford physics dept