Pushing Radiation Hardness and Qualification of Ultrathin Silicon Solar Cells

Regher Solar proposes this SBIR project to mature ultrathin silicon (UT-Si) solar cell technology to achieve TRL 7 and quickly transition to TRL 8 followed by injection into both NASA and commercial missions.nbsp;At present UT-Si cells manufactured by Regher Solar have a 20% Beginning-of-Life (BOL) 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. With several practically attainable improvements UT-Si solar cells will reach 22% BOL efficiency in 2 years. However, the End-of-Life (EOL) efficiency of UT-Si cells drops substantially when exposed to space radiation making them less attractive for the use in space. If radiation damage is mitigated, UT-Si cells can achieve EOL efficiency of ELO-IMM cells while being as inexpensive as CIGS cells making them the optimum choice for flexible solar arraysnbsp;among all thin filmnbsp;technologies.nbsp;nbsp;This project will leverage an improved understanding of radiation-induced defects in c-Si that was developed in the last 3 years within the effort to fabricate more radiation hard Si detectors for the Large Hadron Collider. The main proposed innovations include: (1) using defect engineering to passivate radiation induced defects, (2) further reducing solar cell thickness from 20 to 10 microns to improve the effectiveness of passivation, and (3) utilizing active defect elimination methods that can be periodically applied to the solar cells in space.nbsp;Phase II of this project will demonstrate the feasibility ofnbsp;the proposed innovationsnbsp;and will conduct comprehensive electron and proton irradiation testing. We will collaborate with blanket manufacturers to package UT-Si solar cellsnbsp; in CICs and blankets and conduct complete qualification to achieve TRL 7. Phase II will also work with development partners to integrate UT-Si cells into ongoing missions and achieve TRL 8.