Abstract
Chalcopyrite Cu(In, Ga)Se2(CIGS) and related compounds belong to the semiconducting I-III-VI2 materials family and are most promising thin film solar cells which have demonstrated up to 20% cell efficiencies and over 15% module efficiencies to date. Many CIGS companies in EU, US, and Japan have started several ten MW/year scale commercial production and have announced to increase their production capacities further within a couple of years. In this review, recent developments in highly efficient CIGS module technologies and issues to be solved for further development are discussed. Recent progress in the development of reliable alkali incorporation control techniques which is required to demonstrate high cell efficiencies from flexible CIGS cells fabricated on alkali-free substrates is also introduced. The mechanism behind the beneficial effects of alkali doping into CIGS absorber layers is also discussed.
