Self-assembled 2D perovskite layers for efficient printable solar cells

2D organic–inorganic hybrid Ruddlesden–Popper perovskites have emerged recently as candidates for the light-absorbing layer in solar cell technology due largely to their impressive operational stability compared with their 3D-perovskite counterparts. The methods reported to date for the preparation of efficient 2D perovksite layers for solar cells involve a nonscalable spin-coating step. In this work, a facile, spin-coating-free, directly scalable drop-cast method is reported for depositing precursor solutions that self-assemble into highly oriented, uniform 2D-perovskite films in air, yielding perovskite solar cells with power conversion efficiencies (PCE) of up to 14.9% (certified PCE of 14.33% ± 0.34 at 0.078 cm²). This is the highest PCE to date for a solar cell with 2D-perovskite layers fabricated by nonspin-coating method. The PCEs of the cells display no evidence of degradation after storage in a nitrogen glovebox for more than 5 months. 2D-perovskite layer deposition using a slot-die process is also investigated for the first time. Perovskite solar cells fabricated using batch slot-die coating on a glass substrate or R2R slot-die coating on a flexible substrate produced PCEs of 12.5% and 8.0%, respectively.