Van der Waals Force-Assisted Heat-Transfer Engineering for Overcoming Limited Efficiency of Flexible Perovskite Solar Cells

Flexible perovskite solar cells (f-PSCs) have attracted increasing attention for a variety of applications because of their desirable form factor and improved durability. However, the f-PSC fabrication process has not been optimized, resulting in their uneven efficiency. We report a van der Waals stacking (vdWS) process that yields uniform and highly crystalline perovskite films on flexible substrates by uniform heat transfer during the perovskite annealing process. In addition, the surface and grain boundary defects on the perovskite film were effectively minimized with the vacuum-assisted passivation post-treatment; accordingly, the environmental and mechanical stabilities of f-PSCs were enhanced. Also, the best f-PSC with an active area of 0.14 cm(2) achieved power conversion efficiencies (PCEs) of 41.23% and 22.54% under 1000 1x and 1 sun illuminations, respectively. Furthermore, the vdWS process showed scalable uniformity through flexible perovskite solar minimodules with a certified PCE of 18.35% in an active area of 48.90 cm(2).