The paper PSCs were developed with a low - temperature Paper / Au / SnO2 / meso - TiO2 / CH3NH3PbI3 / Spiro - OMeTAD / MoOx / Au / MoOx architecture utilizing a Au / SnO2 and MoOx / Au / MoOx stack as electron - and hole - extracting electrodes respectively, delivering state of
the art power conversion efficiency of 2.7 % for solar cells prepared directly on the opaque paper substrate.