Promising alternatives to crystalline silicon as the basic building block of solar cells include copper-chalcopyrite thin films such as copper indium gallium diselenide, a class of thin films exhibiting bandgap-tunable semiconductor behavior, direct bandgaps and high absorption coefficients. These properties allow for the development of novel solar-energy conversion configurations like ultra-high efficiency multi-junction solar cells utilizing combinations of photovoltaic and photoelectrochemical junctions for hydrogen production. This paper discusses the current worldwide status as well as the development and optimization of copper-chalcopyrite thin films deposited onto various substrate types for different photovoltaic and photoelectrochemical applications at the Hawaii Natural Energy Institute. (C) 2009 Published by Elsevier B.V.