IN A NUTSHELL: A new type of hyperbranched polymer (HBP)-polyhedral oligosilsesquioxane (POSS) hybrid material for use in space solar cells has been developed by Oxazogen, Inc. The space environment is extremely aggressive, and space solar cell components must retain their optical transparency and mechanical properties after exposure to UV, proton and electron radiation, atomic oxygen bombardment, and extremes of temperature over a period of years.  The range of wavelengths over which transparency is required is increasing, as new generations of multijunction solar cells are introduced.  HBP-POSS materials have a unique combination of high transmission, radiation resistance, crack resistance and dial-in physical properties that can create adhesives, flexible coatings or rigid coatings as desired.  Highly transparent and radiation-resistant materials of this type can be used as cover glass adhesives in rigid solar cells or as flexible protective coatings for the next generation of flexible solar cells. In additional they can be used as protective coatings or encapsulants for terrestrial photovoltaics, solar concentrators, electronics and OLEDs.  MMI’s HBP-POSS hybrid materials combine the easy application of organic systems with the robustness of inorganic systems that normally require specialty deposition processes.

THE PROBLEM: Once materials are in space they are inaccessible and cannot easily be replaced or maintained.  Hence the key attribute of any space material must be durability, and the ability to retain the properties which enable it to function.  The current generation of polydimethylsiloxane (PDMS)-based space solar cell adhesives is prone to radiation-induced darkening that reduces transmission, the amount of light reaching the solar cell, and the efficiency and life time of the solar cell.

THE STATE OF THE TECHNOLOGY: Right now, space solar cell adhesives are based on linear polydimethylsiloxanes (PDMS), or POSS-modified linear PDMS, polyimides or polymethacrylates.  Polyimides and polymethacrylates have inferior transmission (cut-off above 400 nm), and linear systems are prone to cracking, particularly when radiation-resistant phenyl or POSS functionality is introduced.

OUR NOVELTY: MMI has combined the unique properties of polyhedral oligosilsesquioxanes (radiation and atomic oxygen resistance) with the unique properties of its patented hyperbranched polymers (good adhesion, ease of application and crack-resistance across a wide temperature range) to develop price-competitive formulations with excellent transmission, radiation resistance, and physical properties and cure profiles that can be tailored to fit the needs and fabrication processes of the end-user.