Enabling Durable Bottom Cell for Multi-Junction Thin-Film Photovoltaics

Period of Performance: 10/30/2003 - 02/02/2006


Phase 2 SBIR

Recipient Firm

ITN Energy Systems, Inc.
8130 Shaffer Parkway Array
Littleton, CO 80127
Principal Investigator


ITN Energy Systems, Inc. (ITN) intends to meet the requirements (W/kg) for future high-altitude airship and spacecraft power by developing >20% efficient two-terminal monolithic tandem (multi-junction) photovoltaic (PV) cells using low-cost thin-films on lightweight flexible substrates. ITN will achieve this goal using thin-films of high-efficiency and radiation resistant copper indium diSelenide (CIS) and bandgap tunable CIS-alloys with Ga and/or Al. As an intermediate goal to this large endeavor, ITN is developing a "durable" bottom cell (low-bandgap), which would survive the harsh processing conditions of the monolithically deposited top cell. This new photovoltaic device will avoid traditional materials in high-efficiency CIGS devices, but that were found to be responsible for device degradation under top cell processing conditions. A prototype chamber will be built to allow for the large-area deposition of the enabling process. Consistent fabrication and optimization of the durable bottom cell devices, as well as initial tandem device fabrication, will be enabled. In addition, some promising alternative durable bottom cell materials and structures will be further developed. The achievement of a 10% efficient durable bottom cell would be enabling for the multi-junction device and allow for several promising thin-film technologies as the wide-bandgap top cell.