Thin Multijunction InP Solar Cells

The significance of the innovation in this Phase II SBIR is the development of a low cost, lightweight epitaxial liftoff (ELO) process for dual junction InP solar cells, which can provide a pathway towards the utilization of InP solar cells in practical space missions. This effort will advance InP solar cell development by decreasing the weight and increasing the flexibility of the solar cell while maintaining the efficiency performance. The innovation of this work is based upon the complete removal of the solar cell epitaxial layers from the entire InP substrate while maintaining the performance of the solar cell and the reuse of the InP substrate. The reusage of InP substrate provides for the first time a clear pathway towards the lowering of the cost of InP cells, which have been limited by the high cost of InP substrates. BENEFIT: The proposed Phase II work will focus on the improving the lift-off process of InP-based solar cells on 3-inch substrates and subsequently on 4-inch InP substrates. A significant cost reduction will be achieved through the unique process of epitaxial liftoff (ELO), which will allow the InP substrate to be reused. The majority of the cost of InP-based ELO solar cells will become the cost of the InP-based epitaxial materials and associated processing cost rather than the substrate. The proposed ELO technology platform therefore has the clear potential to reduce the cost of InP solar cells by a minimum of 50% in comparison to the current technology. As the ELO manufacturing process matures and the reliability of the ELO cells become proven, these solar cells can be universally applied to both space and terrestrial market.