Energy Conversion

• As early as 1970, Prof. Karl Böer recognized the potential of thin film photovoltaic cells coupled with thermal collectors as a clean and inexpensive way to supply the energy needs of individual residences, reducing the dependency of the United States on foreign oil supplies. He converted this vision to a concrete proposal that was funded by the National Science Foundation and electric power utilities.

• Funding allowed Prof. Böer and the University of Delaware’s Board of Trustees to establish the Institute of Energy Conversion (IEC) in May of 1972, long before the first oil embargo and the formation of the U.S. Department of Energy. In 1972 the most advanced material system for thin film solar cells was copper sulfide/cadmium sulfide (Cu2S/CdS) which had efficiencies ranging from 3 to 5 percent, with a few reports of values as high as 7 percent. Early research at IEC focused on this cell, resulting in extensive modifications and a steady increase in conversion efficiency. The IEC was initially housed in a former factory at the edge of campus.

SOLAR ONE dedicated

• In 1973 SOLAR ONE – the first house to directly convert sunlight into both heat and electricity for domestic use – was dedicated. Built at the University of Delaware with support from the Delmarva Power and Light Co., SOLAR ONE was designed as an experimental structure to accumulate data from its solar harvesting system. In the following years many thousands of people would tour the building to see first-hand the possibilities of living in a solar powered house.

• In 1973 SOLAR ONE – the first house to directly convert sunlight into both heat and electricity for domestic use – was dedicated. Built at the University of Delaware with support from the Delmarva Power and Light Co., SOLAR ONE was designed as an experimental structure to accumulate data from its solar harvesting system. In the following years many thousands of people would tour the building to see first-hand the possibilities of living in a solar powered house.

• In 1975 Prof. Karl Böer stepped down as the Director of IEC to focus his efforts on SES, a company that was established to commercialize Cu2S/CdS solar cells, and to return to his academic interests. Dr. George Warfield became Acting Director of IEC for one year to allow for a national search for a new Director which selected Dr. Allen M. Barnett. The breadth of research activities was expanded when the Institute initiated the development of a wholly-new photovoltaic material, zinc phosphide (Zn3P2), and started an amorphous silicon (a-Si) program.

• In 1977 the Institute initiated a program to develop process designs for the commercial-scale manufacture of thin-film solar cells in cooperation with Dr. T.W. Fraser Russell of the Department of Chemical Engineering, University of Delaware. By 1980 this effort had attracted a three-year, $750,000 process development contract from Chevron Research Company for the research and development of an improved process for the continuous deposition of semiconductor on a continuously moving flexible web for which IEC was issued three patents.

• In 1979 Dr. Allen M. Barnett stepped down as Director to assume the position of Professor of Electrical Engineering at the University of Delaware, and to devote his efforts to developing silicon solar cells which led to a new commercial venture called AstroPower. Prof. T.W. Fraser Russell was appointed as the new Director by the University of Delaware.

• In 1980 IEC developed the first thin film solar cell to exceed 10 percent efficiency. It combined to low cost materials – Cu2S and (CdZn)S – in a heterojunction design and met the DOE’s national photovoltaic program goal for 1980. However, issues associated with the stability and encapsulation of this device led IEC to redirect efforts to more promising thin film solar technologies like a-Si and copper indium diselenide (CuInSe2).

• In 1982 the University of Delaware dedicated a new $2.5 million, 40,000 square foot laboratory on the University of Delaware campus as the new home of the Institute of Energy Conversion. In this new laboratory three systems to make a-Si were designed, built, and operated: Thermal chemical vapor deposition (CVD), photo CVD, and RF CVD reactors.

• IEC was one of the first organizations to propose multi-junction solar cells to increase the energy in sunlight converted to electricity. This originally focused on tandem cells utilizing different forms of a-Si. Later, IEC established a program to develop tandem solar cells based on CuInSe2 as the bottom cell with either a-Si or CdTe as the top. As a result, IEC developed the expertise to fabricate CdTe solar cells and this was done in both a physical vapor deposition system and a close spaced vapor transport system. This provided the foundation for IEC to eventually be the first and possibly only laboratory in the world to have fabricated solar cells with efficiencies greater than 10% utilizing four different absorbing semiconductors: a-Si, CdTe, CuInSe2, and Cu2S.

• Although the mid 1980s were lean years for photovoltaics, IEC continually supported the National Photovoltaic Program and maintained its research efforts in a-Si, CdTe, and CuInSe2. Three deposition systems for making CuInSe2 were developed and operated during this time. This versatility in methods of thin film fabrication has provided increased quantitative understanding of the fabrication process, and established IEC as a leader in the design and interpretation of experiments to provide the essential information for commercial scale design.

• In 1992 IEC was recognized by the United States Department of Energy and the National Renewable Energy Laboratory for its efforts in thin film photovoltaics, and was designated as a Center of Excellence for Photovoltaic Research and Education, thus acknowledging our contributions in both conducting research and training of students and professionals.

• Dr. Fraser Russell

Change in leadership and expansion

• In 1996 Professor T.W. Fraser Russell stepped down as Director (January) to return to teaching and research, and Prof. Robert W. Birkmire, a physicist who joined IEC in 1979, became its fourth director.
• During this time, IEC played a critical role as a member of a Department of Defense consortium of five companies by providing the technology to develop a CuInSe2 manufacturing facility based on our roll-to-roll deposition on flexible metal foils.
• In 1996 IEC started an internal program on thin polycrystalline Si film for photovoltaic application to expand its expertise into this emerging technology.
• Thoughout the 90’s IEC staff had leadership roles in the national Thin Film Partnership Teams managed by the US-DOE’s National Renewable Energy Lab. We participated in teams supporting the growing a-Si, CdTe and CuInGaSe2 industries. Numerous collaborations with industry and academic partners continued into the next decade.

• In 1996 Professor T.W. Fraser Russell stepped down as Director (January) to return to teaching and research, and Prof. Robert W. Birkmire, a physicist who joined IEC in 1979, became its fourth director.
• During this time, IEC played a critical role as a member of a Department of Defense consortium of five companies by providing the technology to develop a CuInSe2 manufacturing facility based on our roll-to-roll deposition on flexible metal foils.
• In 1996 IEC started an internal program on thin polycrystalline Si film for photovoltaic application to expand its expertise into this emerging technology.
• Thoughout the 90’s IEC staff had leadership roles in the national Thin Film Partnership Teams managed by the US-DOE’s National Renewable Energy Lab. We participated in teams supporting the growing a-Si, CdTe and CuInGaSe2 industries. Numerous collaborations with industry and academic partners continued into the next decade.

• In 2003 IEC acquired and installed a pilot-scale multi-chamber PECVD tool for developing advanced cell structures based on growing thin films of a-Si on crystalline Si wafers in partnership with US based solar manufacturer BP Solar.

• In 2007 IEC developed and demonstrated the first interdigitated back contact Si heterojunction solar cell, which many believed to be the ultimate high efficiency Si solar cell structure for future technology. Modeling and simulation of this is complex device provided guidance as to which parameters to focus on to improve the performance. This was conducted with funding from the US-DOE Solar America Initiative.

• Acquiring over $9 million dollars in US Dept of Energy Project Sunshot funding, IEC began several new and diverse projects, ranging from variations in CuInGaSe2 materials, laser processing and patterning for Si cells, and cell architectures to the development of novel light-trapping elements for PV cells. We also expanded staffing through recruitment of several new postdocs and graduate students.

• In 2016 IEC started an internal program to develop a manufacturable high throughput vapor deposition process of low-cost high efficiency Perovskite solar cell to circumvent and meet the challenges of wet chemical spin-coating processes.
• IEC was again awarded multiple contracts under the next phase of funding from US -DOE Sunshot program. Both projects extended and refined work started under the previous Sunshot awards and include partners from industry, national labs, and other universities. One project involved improving the manufacturability of CuInGaSe2 alloys and the other project sought to apply new laser and masking techniques to pattern the contacts of Si solar cells.

• IEC demonstrated one of the earliest successful incorporation Group 5 dopants in CdTe processed by an industrially-friendly manufacturing process. This development potentially allows a highly promising pathway to superior performance low cost CdTe solar modules. This preliminary work led to a successful DOE award in 2021.
• IEC developed a novel, but low cost and manufacturable sulfide-based passivation of silicon to improve solar cell performance and reliability. This work was supported through a DOE award.
• IEC demonstrated of very high performance low bandgap Cu(in,Ga)Se2 as a bottom cell partnered with a perovskite cell in a tandem device. The novel processing structure of the CIGS provides high cell voltage while maintaining ideal optical properties for tandem cell application.

• IEC opened a new laboratory designed to measure the performance and cybersecurity of grid-connected solar ‘smart’ inverters. As part of a team funded by US-DOE, the IEC is providing hardware to test communication, control and response to strengthen the grid reliability against cyber attacks.

• After decades of pioneering work on solar cells, IEC installed its first solar array for research and education. State-of-the-art bifacial modules were mounted on the ground outside the IEC building and connected to a smart energy hub inside which includes a back-up storage battery and electric vehicle charger. Research supported by the Delaware Department of Natural Resources and Environmental Control determined the benefits of different ground cover to enhance reflection onto the rear side of the modules.

• The University of Delaware’s Institute of Energy Conversion marks over 50 years of operation. It is the world’s oldest solar research facility, credited with significant advances in solar technology, developing new leaders in solar energy research and industry, and helping to expand renewable energy possibilities for the future.