Millimeter-Sized Clusters of Triple Cation Perovskite Enables Highly Efficient and Reproducible Roll-to-Roll Fabricated Inverted Perovskite Solar Cells

The high-power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) on lab-scale devices trigger the need to develop scalable manufacturing processes to accelerate their commercialization transition. A roll-to-roll (R2R) vacuum-free printing on flexible substrates allows for high-volume and low-cost manufacturing which is especially well-suited for PSCs due to its solution processibility and low-temperature annealing requirements. Herein, a facile hot deposition technique is reported to fabricate triple-cation (Cs(0.07)FA(0.79)MA(0.14)Pb(I0.83Br0.17)(3)) perovskite films in an ambient environment using a R2R slot-die coating method. This perovskite composition, whilst being most studied in lab devices due to its high efficiency and stability, has not been applied in R2R fabrication thus far. The demonstrated R2R slot-die coated flexible PSCs achieve stabilized PCE reaching 12% at maximum power point in inverted "p-i-n" architectures, the highest efficiency reported to date for R2R inverted PSCs. To achieve this, the underlying hole transport layer (poly(3,4-ethylenedioxythiophene):polystyrene sulfonate) is modified with guanidinium iodide additive which leads to the formation of large millimeter-sized perovskite clusters, improved perovskite crystallinity, and enhanced charge-transfer efficiency. This study highlights the potential of the facile hot-deposition method while providing critical insights into the role of interfacial engineering in eliminating performance losses and fabricating efficient printed flexible PSCs.