@article {jackson2016effects, title = {Effects of heavy alkali elements in Cu (In, Ga) Se2 solar cells with efficiencies up to 22.6\%}, journal = {physica status solidi (RRL){\textendash}Rapid Research Letters}, volume = {10}, year = {2016}, pages = {583{\textendash}586}, author = {Jackson, Philip and Wuerz, Roland and Hariskos, Dimitrios and Lotter, Erwin and Witte, Wolfram and Powalla, Michael} } @article {powalla2013high, title = {High-efficiency Cu(In,Ga)Se2 cells and modules}, journal = {Solar energy materials and solar cells}, volume = {119}, year = {2013}, pages = {51{\textendash}58}, author = {Powalla, Michael and Jackson, Philip and Witte, Wolfram and Hariskos, Dimitrios and Paetel, Stefan and Tschamber, Carsten and Wischmann, Wiltraud} }