We compared the moisture sensitivity of a Cu(InGa)Se-2 (CIGS) photovoltaic cell protected by 55 nm thick Al2O3, grown by atomic layer deposition (ALD), with equivalent CIGS cells protected with a glass or a polyester lid. Aging studies for more than 1000 h at 85 degrees C/85% relative humidity with simulated solar illumination showed that the ALD Al2O3 thin-film barrier provided superior moisture protection for the CIGS cell, i.e. no reduction in open circuit voltage or fill factor occurred, compared to cells protected with a glass or plastic lid. We concluded that a moisture barrier grown by ALD could have broad applicability as a strategy for extending the lifetime of flexible CIGS cells. (C) 2010 Elsevier B.V. All rights reserved.