Thermotropic Liquid Crystals Enable Efficient and Stable Perovskite Solar Cells and Modules

Perovskite solar cells (PSCs) have seen impressive progress in performance and stability, yet maintaining power conversion efficiencies (PCEs) when scaling areas remains a challenge. Here we find that the additives used to passivate large-area perovskite films often co-crystallize near-simultaneously with perovskites or tend to aggregate at the surface/interface, which contributes to defects and to spatial inhomogeneity. We therefore introduce a thermotropic liquid crystal (TLC) additive with heightened diffusion ability at the perovskite annealing temperature to enable uniform, low-defects, and stable large-area perovskite films. We document as a result small-area PSCs achieving a PCE of 25.6% and modules having a certified PCE of 21.6% at an aperture area of 31 cm². These retain performance under the damp-heat test (ISOS-D-3, 85% relative humidity, 85°C) with T₈₆ of 1200 hours, and show high resistance to reverse bias with (ISOS-V-1, negative <i>V</i>_mpp) and without bypass diodes.