Efficient Flexible Monolithic Perovskite–CIGS Tandem Solar Cell on Conductive Steel Substrate

Here we report for the first time a monolithic perovskite–CIGS tandem (CIGS = Cu(In,Ga)Se2) solar cell on a flexible conductive steel substrate with an efficiency of 18.1%, the highest for a flexible perovskite–CIGS tandem to date, representing an important step toward flexible perovskite-based tandem photovoltaics.