Enhanced Performance and Stability of TiO 2 ‐Nanoparticles‐Based Perovskite Solar Cells Employing a Cheap Polymeric Surface Modifier

Interface engineering of TiO 2 nanoparticles (NPs)‐based perovskite solar cells (PVSCs) is often necessary to facilitate the extraction and transport of charge carriers. In this work, poly[{9,9‐bis[3′‐( N , N ‐dimethyl)propyl]‐2,7‐fluorene}‐ alt ‐2,7‐(9,9‐dioctylfluorene)] (PFN) and polystyrene (PS) are demonstrated to be effective surface modifiers of the TiO 2 NPs electron‐transporting layer in n‐i‐p PVSCs. The low‐cost insulating polymer PS performs better than the PFN conjugated polymer owing to its high film quality, low surface energy and insulating characteristics. A peak power conversion efficiency (PCE) of 15.09 % with an open‐circuit voltage ( V OC ) of 1.05 V and a PCE of 17.13 % with an ultrahigh V OC of 1.18 V is achieved with TiO 2 NPs/PS‐based PVSCs using poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) and spiro‐OMeTAD, respectively, as the hole‐transporting material.