Enhanced performance of organic and perovskite solar cells using simple linear polyethyleneimine with reduced chemical reactivity

Interface engineering based on amine-containing polyelectrolytes has been proven to be useful for highperformance organic and perovskite solar cells by improving charge collection at the interfaces. Here, we demonstrate efficient organic and perovskite solar cells by introducing non-conjugated polyelectrolyte, linear polyethyleneimine (LPEI), as a cathode interfacial layer (CIL). Notably, such a polyelectrolyte contains secondary amine groups in its molecular structure, which could provide chemical stability with most of the state-of-the-art non-fullerene acceptors (NFAs), and concurrently form dipole layer to endow underlying materials with work function tunability. As a result of favorable interfacial contact, organic solar cells with LPEI CIL exhibited a high power conversion efficiency (PCE) of 14.8%. Furthermore, it was found that the LPEI is compatible with conventional metal oxides such as zinc oxide (ZnO) and tin oxide (SnO2) as a bilayer configuration, leading to an increase of PCE from 14.7% to 16% for organic solar cells and from 17.5% to 20% for perovskite solar cells, respectively.