Synergistic crystallization modulation and defect passivation via dual-additive antisolvent strategy for efficient wide-bandgap perovskite solar cells

Wide-bandgap (WBG) perovskite solar cells (PSCs) are essential for high-efficiency tandem photovoltaics, yet they suffer from significant open-circuit voltage ( V oc ) and operational instability driven by photo-induced phase segregation. Herein, we demonstrate a synergistic dual-additive antisolvent strategy (DAS) utilizing a pseudo-polypeptide polymer, poly(2-ethyl-2-oxazoline) (PEOz), and a cyclic small molecule, piperidinium iodide (PipI), to modulate crystallization and passivate defects in WBG perovskite films. In this orthogonal mechanism, PEOz acts as a macromolecular scaffold at grain boundaries to retard rapid nucleation and physically seal structural voids, while the sterically unhindered PipI directly coordinates with the underlying lattice to induce a highly preferred (100) and (110) orientation and passivate deep-level defects. This combined approach effectively suppresses non-radiative recombination and locks the crystal framework against light-induced halide segregation, yielding compact, pinhole-free films with enlarged grains. Consequently, the champion inverted perovskite solar cell with a bandgap of 1.68 eV achieves an outstanding power conversion efficiency (PCE) of 23.56%, accompanied by a high V oc (1.24 V) and an enhanced fill factor (84.63%). Furthermore, unencapsulated devices exhibit enhanced stability under continuous illumination, retaining over 87% of their initial efficiency after 243 hours of continuous illumination test. This work provides a robust and generic pathway toward highly efficient and stable WBG perovskite photovoltaics.