Fig. 1. (Color online) (a) Chemical structure of PLL. (b) FTIR spectra of the PbI₂, PLL, and PLL + PbI₂. (c) Schematic of the interaction force between PLL and perovskite. (d) Schematic diagram of the mechanism of PLL inhibition of ion migration.

Fig. 2. (Color online) (a) X-ray diffraction (XRD) patterns, (b) 110 peak intensities and full width at half maxima (FWHM) values, (c) UV−vis absorption spectra and (d) PL spectra of the pristine and PLL perovskite films.

Fig. 3. (Color online) (a) and (d) Colloidal particle size distribution of perovskite precursors measured by DLS. (b), (e) Top-view SEM images and (c), (f) grain size statistics of the pristine and PLL perovskite films.

Fig. 4. (Color online) (a) J−V curves of the PLL perovskite devices with different concentrations (0.01, 0.03, and 0.05 mg∙mL⁻¹). (b) J−V curves of pristine and PLL perovskite devices and schematic of the corresponding PSCs device structures. (c) IPCE spectra and (d) Nyquist plots at V = −1.0 V of the pristine and PLL perovskite devices.

Fig. 5. (Color online) (a) PCE distribution, (b) V_oc distribution, (c) J_sc distribution and (d) FF distribution of the pristine and PLL perovskite devices.

Fig. 6. (Color online) (a) Water contact angles of the pristine and PLL perovskite films. Normalized (b) PCE, (c) J_sc, (d) V_oc, and (e) FF variation curves of the unsealed pristine and PLL perovskite devices aged under 45 ± 5% RH.

Fig. 7. (Color online) UV−vis absorption spectra aging at 85 °C of the (a) pristine and (b) PLL perovskite films. (c) Images of the pristine and PLL perovskite films before and after aging at 85 °C. Normalized (d) PCE, (e) J_sc, (f) V_oc and (g) FF variation curves of the unsealed pristine and PLL PSCs aging at 85 °C.