Due to low efficiencies, the cost of electricity from current commercially available solar cells is five times greater than electricity from conventional sources. This research intends to help eliminate that cost difference by developing an ultra-high efficiency indium gallium nitride (InGaN) solar cell. The primary reason InGaN shows such incredible promise as a photovoltaic material is the ability to modify its band gap by adjusting the ratio of indium and gallium in the film. A multi-layered cell of InGaN can be made with band gaps ranging from 0.7eV (InN) to 3.4eV (GaN) which covers the entire range of the solar spectrum. Thus, a well-designed InGaN solar cell can absorb and convert a much higher fraction of the sun’s light energy into electricity. The first stage of research will focus on the characterization and understanding of InGaN as a semiconducting material.

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.

This project is aimed at  designing and fabricate plasmonic metamaterial ―perfect absorbers (plasmonic perfect meta-absorbers) to enhance the efficiency of hydrogenated amorphous silicon (a-Si:H) solar photovoltaic devices. Perfect meta-absorbers can be designed with broadband, polarization-independent, and wide-angle optical absorption features. These critical features, lacking in most optical enhancement schemes for solar cell designs, are ideally required to maximize the efficiency of solar cells. Wide-angle reception, for example, is particularly important to increase solar energy conversion efficiency for curved surfaces, and for maximized temporal and spatial response of the panels to solar light. In this project we will explore to what extent it is possible to manage the solar light efficiently using plasmonic metamaterial perfect absorbers integrated with a-Si:H-based solar photovoltaic devices.

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 products.

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 or aluminum.

The solar photovoltaic industry throughout the world is growing at an unprecedented rate, creating the jobs that underpin a green economy and a sustainable power grid. With this growth comes an increased demand from industry for high-quality research in solar systems design and optimization in realistic (and sometimes extreme) outdoor environments. To answer this need, a partnership has formed the Open Solar Outdoors Test Field (OSOTF). The OSOTF was originally developed with a strong partnership between Dr. Joshua Pearce, while he was at Queen’s University and the Sustainable Energy Applied Research Centre (SEARC) at St. Lawrence College headed by Adegboyega (Babs) Babasola. This collaboration has grown rapidly to include multiple industry partners and the OSOTF has been redesigned to provide critical data and research for the team.

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.

Open source appropriate technology (OSAT) refers to technologies that provide for sustainable development while being designed in the same fashion as free and open-source software. Facilitated by advances in information technology software and hardware, new ways to disseminate information such as wikis and Internet-enabled mobile phones, the global development of OSAT has emerged as a reality.

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.

The technological evolution of the 3-D printer (or rapid prototyper), widespread internet access and inexpensive computing has made a new means of open design capable of accelerating self-directed sustainable development.

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?