Light Makes Right: Laser Polishing for Surface Modification of Perovskite Solar Cells

Interface engineering is a common strategy for passivatingsurfacedefects to attain open circuit voltages (V (oc)) in perovskite solar cells (PSCs). In this work, we introduce theconcept of polishing a perovskite thin-film surface using a nanosecond(ns) pulsed ultraviolet laser to reduce surface defects, such as danglingbonds, undesirable phases, and suboptimal stoichiometry. A carefulcontrol of laser energy and scanning speed improves the photophysicalproperties of the surface without compromising the thickness. Usinglaser polishing, a V (oc) of 1.21 V is achievedfor planar PSCs with a triple cation composition, showing an improvedperovskite/hole transport interface by mitigating surface recombinationlosses. We measure an efficiency boost from 18.0% to 19.3% with improvedstability of up to 1000 h. The results open the door to a new classof surface modification using lasers for interface passivation inwell-controllable, automated, scalable, and solvent-free surface treatments.