For a full list of our recent publications organized by category go here.
For the most up-to-date project list go here.
Photovoltaic Materials and Electronic Device Physics of Solar Photovoltaic Cells:
The unrestrained use of fossil fuels such as oil, natural gas and coal has contributed to global warming at a rate that seriously threatens the future of the world’s climate systems. Solar energy converted by photovoltaics is an ideal solution as an emission-free, infinitely renewable energy.
In addition to band gap engineering, PV device performance can be improved by engineering the microstructure of the material to increase the optical path length and provide light trapping. For this purpose, nano-columns are candidates for the ideal microstructure as it has been shown that when their diameters are optimized, resonant behavior is observed. Furthermore, nano-columns offer a reduction in strain and defect states, and can improve flexibility and wear characteristics on the macro scale.
The final stage of research will use the accumulated data and knowledge to determine the number of stacked layers and the relative concentrations of indium and gallium within each that maximizes light absorption and, more importantly, electricity generation.
Hydrogenated amorphous silicon (a-Si:H) based solar cells are less
expensive than traditional crystalline silicon based solar cells and
posses an excellent ecological balance sheet. The ecological and
economic promise of a-Si:H solar cells is currently incomplete because
of the light induced degradation of its electronic properties known as
the Staebler-Wronski Effect (SWE). Dr. Pearce's previous research
focused on the analysis of experimental evidence for a complex SWE
mechanism. From this work the contributions of non-D0 defects to the
SWE kinetics were identified and quantified for the first time by using
a combination of electron mobility-lifetime and subgap absorption on
films, and dark and light I-V characteristics on corresponding solar
cells. This was accomplished by overcoming the often-observed
discrepancies in the correlations of properties between materials and
devices. Utilizing this insight into the material properties allows for
the optimization of photovoltaic devices and a more thorough
understanding of their operation. This material research can be applied
to solar cells by the microstructural engineering of individual layers
of solar cells to characterize the carrier recombination within the
device. This work resulted in the separation, identification, and
quantification of contributions of the carrier recombination from the
p/i interface regions and the bulk to the dark current-voltage and
short-circuit current-open circuit voltage characteristics of
protocrystalline Si p-i-n and n-i-p solar cells. This has immediate
practical application in the optimization of commercial photovoltaic
Building on this work, one of the most promising methods of
overcoming SWE is incorporating a-Si:H into photovoltaic thermal hybrid
systems that operate at elevated temperatures that anneal SWE defects
out as the device is in operation. The group is currently working on
optimizing a-Si:H devices for this new application. A promising method
of doing this is by depositing a-Si:h directly on a metal such as steel
The OSOTF is a fully grid-connected test system, which continuously monitors the output of 95 photovoltaic modules and correlates their performance to a long list of highly accurate meteorological readings. The teamwork has resulted in one of the largest systems in the world for this detailed level of analysis, and can provide valuable information on the actual performance of photovoltaic modules in real-world conditions. Unlike many other projects, the OSOTF is organized under open source principles.
All data and analysis when completed will be made freely available to the entire photovoltaic community and the general public.
The first project for the OSOTF quantifies the losses due to snowfall of a solar photovoltaic system, generalizes these losses to any location with weather data and recommends best practices for system design in snowy climates. Future projects at the OSOTF are investigating novel systems layouts, low-level concentration, and the effects of spectral composition on solar cell performance. In addition the system will be used for technology and module comparisons and validations, as well as multiple specialized research programs going into the future.
This research investigates how the sharing of design processes, appropriate tools, and technical information enables more effective and rapid development of appropriate technologies for both industrialized and non-industrialized regions. This sharing will require the appropriate technology community to adopt open standards/licenses, document knowledge, and build on previous work. The group's work offers not only OSAT itself but also solutions in the form of platforms and software necessary on which to share and build knowledge about appropriate technologies. These solutions are open, easily accessible for those in need, have a low barrier to entry for both users and information creators, and must be vetted in order to utilized as a trustworthy source on critical information needs.
Open source 3-D printers, such as the RepRap, enable the use of designs in the public domain to fabricate open source appropriate technology (OSAT), which are easily and economically made from readily available resources by local communities to meet their needs. There is potential for open source 3-D printers to assist in driving sustainable development. This project is developing solar powered self-replicating open-source 3-D printers and waste plastic extruders - capable of making primary components of solar photovoltaic systems from recycled waste. The project has both technical components in actually designing and building the devices, but also concerns questions of life cycle analysis. - specifically - Does this approach make sense from an ecological footprint, emissions, and embodied energy perspectives?
We layed out the plan in: J. M Pearce, C. Morris Blair, K. J. Laciak, R. Andrews, A. Nosrat and I. Zelenika-Zovko, “3-D Printing of Open Source Appropriate Technologies for Self-Directed Sustainable Development”, Journal of Sustainable Development 3(4), pp. 17-29 (2010).
Now we are working on printing in metal and using recycled cans for feedstock. Gerald C. Anzalone, Chenlong Zhang, Bas Wijnen, Paul G. Sanders and Joshua M. Pearce, “Low-Cost Open-Source 3-D Metal Printing” IEEE Access, 1, pp.803-810, (2013). doi: 10.1109/ACCESS.2013.2293018 open access preprint
How would global society change if everyone had access to abundant low-cost renewable energy via solar electricity, open source 3D designs and an affordable kopen source 3-D printer like the RepRap?