Researchers from the University of Milano-Bicocca, Polytechnic University of Catalonia (UPC), Istituto di Struttura della Materia (CNR), University of Rome “Tor Vergata” and New Energies have demonstrated solution-processed perovskite/kesterite tandem solar cells that surpass 22% power conversion efficiency in a 4‐terminal architecture on rigid substrates and exceed 20% on flexible devices. Their work focuses on kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) absorbers, which are based on earth-abundant, n