The Center for Autonomous Solar Power is engaged in several research areas.
Thin film solar cells.
A major goal of CASP is to conduct research that will lead to very low cost solar cells on flexible substrates. The Center is investigating earth abundant materials deposited on flexible glass and plastic that are compatible with a roll-to-roll process. Some of the materials currently used in solar technology include strategic materials such as indium, gallium, and tellurium that are either rare or trace elements in high demand for semiconductor technology. The Center is currently investigating three candidates for the absorber layer that offer abundance, optimal band gaps, and high optical absorption critical to thin film cells solar cells.
The three candidates include iron disulfide, zinc phosphide, and copper-zinc-tin-sulfide. These materials are deposited using a variety of techniques including, chemical vapor deposition, sputtering, pulsed laser deposition, and atomic layer deposition. All of the candidate films have been successfully synthesized and all are now fabricated in test cells. Additional active layers include zinc sulfide that forms the diode junction necessary for solar cell operation, and a transparent conductor. We have developed an aluminum doped zinc oxide layer that is an effective replacement for the indium doped tin oxide now in wide commercial use for solar cells and display devices.
Research in CASP focuses on the development of next generation supercapacitors in a solid-state design for efficient, long-lasting and high density electrical energy storage. Distinctly different from conventional, bulky supercapacitors, the CASP supercapacitors are configured in the multi-stacked flat as well as flexible configuration. Based on non-toxic materials, the supercapacitors use green process technology with a large area roll-to-roll production potential at a much lower cost. The supercapacitors act as energy buffers to enhance renewable electrical energy conversion systems and transportation making them maintenance free, energy efficient and reliable in delivering continuous power. Towards this vision for supercapacitors, we will focus on developing the electro-active material systems based on graphene and its nanocomposites with low cost transition metal oxides having multifunctional charge storage ability. For the electrolyte system in the solid-state form, we are developing the gels using room temperature ionic liquids (RTILs) and fully exploit their unique properties of non-volatility, chemical and thermal stability and the wide electrochemical potential window enabling high voltage operation of the supercapacitors.
Solar cells use only a fraction of the energy in sunlight. New devices under investigation in CASP are nanostructured materials designed to produce electricity from the infrared region of the spectrum. The research emphasis is on developing materials with a high electrical conductivity coupled with a low thermal conductivity to yield high temperature differences and high efficiency conversion of heat to electricity. The current focus is placed on random layers of heavy elements in silicon to reduce thermal conductivity.
The reliability of new devices and materials must be studied for integration into commercial devices. Individual layers and cells are characterized through repeated bending and stretching, through the range of temperatures and humidity expected in operation, and through moisture permeation of moisture through encapsulates and plastic or glass covers. Reliability studies in CASP are conducted in part using the facilities of the Integrated Electronics and Engineering Center at Binghamton University. The Integrated Electronics Engineering Center (IEEC) is well equipped with environmental chambers and test facilities for stress/strain studies of materials and devices.