BDT-Th-modified naphthalimide cathode interlayer material for binary organic solar cells with 20.01% efficiency

We design and synthesize two naphthalimide (NI)-based cathode interface materials, 2NIN and 4NIN, with 4,8-di(thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene (BDT-Th) as the central core, bearing two and four amine-functionalized NI groups, respectively. Compared with the previously reported triphenylamine- and benzotrithiophene-based tridentate cathode interface materials (NTA and 3PNIN), both 2NIN and 4NIN molecules obtain higher electron mobilities and better film-forming capacities. Meanwhile, 4NIN exhibits a more twisted molecular structure, a larger dipole, stronger electrode modification ability, and more ordered and tighter molecular packing relative to 2NIN. The D18/L8-BO-based binary organic solar cells (OSCs) with 4NIN interlayer exhibit power conversion efficiencies of 20.01% (0.052 cm2) and 18.87% (1 cm2), respectively, significantly higher than those of 2NIN modified devices (18.01% and 14.63%). Moreover, 4NIN modified OSCs demonstrate superior light and thermal stabilities relative to 2NIN- and reference PDINN-based cells.