Charlotte Platzer-Björkman1, Nicolas Barreau2, Marcus Bär3,4,5,6, Leo Choubrac7, Louis Grenet8,9, Jaeyeong Heo10, Tomas Kubart1, Alberto Mittiga11, Yudania Sanchez12, Jonathan Scragg1, Soumyadeep Sinha10and Matteo Valentin "Back and front contacts in kesterite solar cells: state-of-the-art and open questions" Journal of Physics Energy 1, 4, pp. 44005 - 2019