Carboxyl-functionalized heterocyclic cations solidify grain boundaries of wide-bandgap perovskite toward high-performance perovskite/silicon tandem solar cell

Developing high-quality wide-bandgap (WBG) perovskites is crucial to construct efficient perovskite/silicon tandem solar cells (TSCs). However, the high defect density and halide segregation hinder the improvement of power conversion efficiency (PCE) and stability for WBG perovskite solar cells (PSCs). Herein, one carboxyl-functionalized imidazolium cation modulation strategy is reported to heal the multiple defects within WBG perovskite films by multifarious chemical bonding modes. After incorporating the additive imidazole-4-acetic acid hydrochloride (ImAcHCl), the trap-assisted nonradiative recombination at grain boundaries is suppressed, the halide segregation is mitigated, and the stability of perovskite films is improved. Moreover, this method is effective in defect passivation for different bandgaps of perovskites. Ultimately, the ImAcHCl-modified 1.68 eV WBG PSCs achieve a PCE of 24.54% ranking among the highest PCEs realized for 1.66–1.70 eV PSCs, and retain 90% of their initial PCE after 883 h of continuous maximum power point tracking. Integration with crystalline silicon subcells further enabled the construction of a perovskite/Si tandem device with a PCE of 33.06%. This work provides valuable insights into overcoming the instability challenges of the WBG perovskite film via functional group functionalization method toward high-performance WBG PSCs and perovskite/silicon TSCs.