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 high-performance 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.