Improved Stability of Inverted and Flexible Perovskite Solar Cells with Carbon Electrode

We demonstrate highly efficient, stable, and flexible perovskite solar cells of large areas, utilizing a carbon back-contact electrode in a p-i-n cell configuration. We enabled good electronic contact at the interface with carbon by inserting an ultrathin buffer layer before the carbon coating. Solar cells of such structure reach a power conversion efficiency of 15.18% on PET foil (device area of 1 cm(2)). We performed impedance spectroscopy and transient decay measurements to understand the electron transport characteristics. Furthermore, we demonstrate excellent operational (maximum power point) and thermal (85 degrees C) stability of these devices over 1000 h of aging.