Elimination of buried interface defects for highly efficient and stable wide-bandgap perovskite solar cells

As one of the important components of high-effi-ciency perovskite/silicon series devices, widebandgap (WBG) perovskite solar cells (PSCs) have been suffering from serious carrier transport barriers and huge open-circuit voltage deficit derived from non-radiative recombination, especially at the buried interface that are often overlooked. Herein, we combined cationic and anion passivation strategies via ammonium tetra-n-butyl tetrafluoroborate (TBABF₄) pre-treating the buried interface. Theoretical calculation predicts that the tetrabutylammonium (TBA⁺) organic cations and (tetrafluoroborate) BF₄⁻ anions can easily interact with charged interfacial defect. Characterizations further confirm the enhancement of carrier transport performance and decrease in defect density upon TBABF4 pre-treatment. Consequently, a power conversion efficiency of 21.35% with an ultrahigh filling factor of 84.12% is obtained for 1.68 eV-WBG inverted PSCs. In addition, the device with TBABF4 pretreatment demonstrates excellent shelf, thermal, and operational stability.