Water-Soluble Cationic Copolyacrylamides Modifying NiO_x for High-Performance Inverted Perovskite Solar Cells

A series of poly(acrylamide-[2-(methacryloyloxy)ethyl]trimethylammonium chloride) (CPAM: PAM, PMD25, and PMD50) with varying quaternary ammonium chloride contents were synthesized and employed as interfacial modification layers between nickel oxide (NiO X ) and methylammonium lead iodide (MAPbI 3 ) layers in inverted perovskite solar cells (PVSCs). The incorporation of amide and quaternary ammonium units in CPAM played a crucial role in enhancing the crystallinity of the MAPbI 3 layer. Surface modification with CPAM improved interface contact, crystal growth promotion, and passivation of interface and crystal defects. This led to denser packing, larger crystal grain sizes, and higher crystal quality of the MAPbI 3 layer, particularly with the PMD25 modifier. The enhanced crystal quality further facilitated the hole mobility within the MAPbI 3 layer. Photoluminescence (PL) and time-resolved PL measurements confirmed accelerated charge separation and hole transport from NiO X to the MAPbI 3 layer, indicating improved interfacial contact and energy-level alignment at the NiO X /MAPbI 3 interface. Consequently, the PVSCs fabricated using CPAM-modified NiO X layers exhibited significantly enhanced short-circuit current ( J SC ) and photoconversion efficiency (PCE) compared to those of the pristine sample. Among the CPAM variants, PMD25 demonstrated the best photovoltaic (PV) performance, with a PCE of 19.42%, open-circuit voltage of 1.07 V, J SC of 25.44 mA/cm 2, and fill factor of 72.1%. The incorporation of CPAM as an interfacial modification layer in the NiO X /MAPbI 3 system effectively enhanced the PV performance and the storage stability of inverted PVSCs.