@article {powalla2013high,
	title = {High-efficiency Cu(In,Ga)Se<sub>2</sub> 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}
}
