Title

CIGS2 Thin-Film Solar Cells on Flexible Foils for Space Power

Secondary Author(s)

Pandit, Mandar; Jahagirdar, Anant; Scheiman, David; Dhere, Neelkanth

Keywords

PV Modules; PV Cells

Abstract

Lightweight, flexible, thin-film solar cells have many promising applications in space and terrestrial photovoltaic power systems.1 Future space missions are likely to include very large satellites, such as solar power satellites and very small satellites. Long-term plans envisage swarms of distributed, autonomous, small satellites, termed microsats or even nanosats, to perform specific tasks. Some missions will use solar electric propulsion (SEP) instead of rockets. CIGS2 thin-film solar cells on flexible stainless steel (SS) may be able to increase the specific power by an order of magnitude from the current level of 65 Wkg 1. Thin- film technology could conservatively reduce the array-manufacturing cost of a medium-sized 5-kW satellite from the current level of $2000k to less than $500k.2 Weight benefits of higher-efficiency cells are decreased and high costs become less affordable in the case of flexible thin-film blanket arrays that can be easily rolled out. Non-rigid cells also have an advantage in stability. Because of the low initial velocities and steady acceleration, SEP satellites must spend long periods in intense regions of trapped radiation belts. CIGS solar cells are superior to the conventional silicon and gallium arsenide solar cells in the space radiation environment. The potential for improved radiation resistance of thin-film solar cells relative to single-crystal cells, could extend mission lifetimes substantially. Recent studies have shown that 12.6% efficient, thin-film cells would start to become cost-competitive in GEO and LEO missions.3 However, significant technological hurdles remain before thin-film technology could be implemented as the primary power source for spacecraft. There is a recent interest in the development of CIGS2 solar cells on flexible substrates. Several groups have reported fabrication of polycrystalline CuIn1 xGaxSe2 (CIGS) solar cells on flexible foils substrates.4 The CIGS cell with an efficiency exceeding 17% has been obtained using SS substrate.4 The objective of the present research is to develop ultra-lightweight, radiation-resistant, highly efficient, high-specific-power CuIn1 xGaxS2 (CIGS2) thin-film solar cells for space electric power. A small proportion of gallium is incorporated so as to obtain benefits of improved adhesion, slightly higher bandgap, and incorporation of a back-surface field, as has been done with CIGS cells. Initially, CIGS2 thin-film solar cells are being fabricated on 127-mm-thick SS substrates. A few CIGS2 cells have also been prepared on 20-mm-thick SS substrates. The main thrust is towards development of fundamental understanding and baseline processes rather than attaining the highest efficiencies.

Date Published

1-1-2002

Subjects

PV Cells; PV Modules

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