Improving Solar Cell Protection and Efficiency with polymer downconverting coating

Solestial Inc (changed name from Regher Solar) proposes this SBIR project to improve the protection and conversion efficiency of ultrathin silicon (UT-Si) solar cell technology by adding the Layer of UV CONverting coating (LUVCON) developed by SSS Optical Technologies, that down-converts UV light to visible, therefore improving efficiency. At present UT-Si cells manufactured by Solestial have a 22% Beginning-of-Life efficiency, which is exactly in between Copper-Indium-Gallium-Selenide (CIGS) and Epitaxial Lift Off Inverted Metamorphic (ELO-IMM) thin film solar cells that are currently considered for making flexible solar blankets. However, the End-of-Life (EOL) efficiency of UT-Si cells drops minimally when exposed to space radiation making them more attractive for the use in space since radiation damage is mitigated. This was shown in our recently completed NASA SBIR Phase I project. By further improving the efficiency, UT-Si cells can achieve EOL efficiency significantly higher than ELO-IMM cells while being as inexpensive as CIGS cells making them an optimal choice for flexible solar arrays. Protection from low energy protons (<1MeV) is an additional benefit of LUVCON coating. It provides 4X reduction of proton displacement damage. Reduction of UV light damage to solar cells is expected to be >95%, while LUVCON coating remains stable under UV radiation. Solestial UT-Si solar cell demonstrated self-annealing capability of electron and proton radiation damage. This made them perfectly suitable for space missions in radiation-hard environment.The main proposed innovations include: (1) Development of polymer nanocomposite coatings impregnated with solar UV spectrum downconverting nanoparticles to improve the conversion efficiency of a solar cell; (2) Enabling the coating be radiation and UV light tolerant by optimizing its composition and thickness; (3) Development of a low-cost and reproducible process of coating to replace cover glass for space solar blankets and panels; and (4) Qualification testing of CICs and mini-blankets with the developed coating.Phase I will be focused on the development and demonstration of the LUVCON coating capability to significantly increase protection from UV light, low energy protons, and improving efficiency of Solestial silicon space solar cells as well as 3J IMM and 2J III-V cells . The demonstration of increased protection and stability of LUVCON against UV light, electron, and proton radiation environments, along with the increased efficiency of the PV cells, will serve as proof of the feasibility of Phase I project.Phase II will demonstrate feasibility of the proposed innovations at the scale of the blanket and conduct comprehensive electron and proton irradiation testing. We will collaborate with blanket manufacturers to package UT-Si solar cells in CICs and blankets and conduct complete qualification to be used in space power systems.