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The Institute of Energy Conversion: The First Twenty-five Years: 1972-1997

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. This 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.

Thin Film Photovoltaics at IEC

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.

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 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 United States Department of Energy (DOE) was established, as well as the Solar Energy Research Institute (SERI) in Golden, Colorado with Dr. Paul Rappaport as the first director.

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.

By 1978 the Institute reported Cu2S/CdS cells with an efficiency of over 9 percent, which paved the way for future funding of thin film photovoltaics.

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. This Cu2S(CdZn)S 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 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.

In the early 1980s, IEC was one of the first organizations to propose multi-junction solar cells utilizing a-Si based cells in tandem. The Institute, in addition, 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 reactor and a close spaced vapor transport reactor. This provided the foundation for IEC to eventually be the 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 reactors for making CuInSe2 were developed and operated during this time. This versatility, in means 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.

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.

Today, IEC is a multi-disciplinary laboratory devoted to research and development of thin film photovoltaic cells and is one of the few laboratories in the world with expertise in Si, CdTe, and CuInSe2 based solar cells. Throughout its history, IEC has worked with over 50 companies – either formally on a contract basis, or informally on a researcher-to-researcher basis – in supporting their research efforts or transferring technology to start a new research program.

IEC has provided the technology as a member of a Department of Defense consortium of five companies to develop a CuInSe2 manufacturing facility.

In 1996 IEC started an internal program on thin polycrystalline Si film for photovoltaic application to expand its expertise into this emerging technology.

The Institute has established collaborative efforts with most University groups, both nationally and internationally, working on the development of thin film photovoltaics.

Probably one of the most important contributions IEC has made to the photovoltaic community is providing a training ground for people who have made important contributions to the photovoltaic technology. More than 105 students have received advanced degrees while performing their research at IEC, along with numerous post-doctoral fellows and visiting scholars.

Over the years, the Institute has had a parade of colorful and extremely talented people, all of whom cared very much about what they were doing and were truly committed to the research in, and improvement of, solar technology.