Ultrasonic spray deposition of a passivating agent for spray‐coated, methylammonium‐free perovskite solar cells

Defect management in perovskite solar cells (PSCs) via surface passivation has become a cornerstone in maximizing both stability and solar-to-electrical power conversion efficiency (PCE) of devices by reducing defect densities and/or improving energetic alignment between the perovskite and charge-transporting layers. Despite this, few reports explore the use of roll-to-roll compatible technologies to deposit such interfacial treatments, limiting the applicability of passivation in real-world contexts. In this work, iso-butylammonium bromide (i-BABr) is spray-coated onto a Cs0.15FA0.85PbI2.85Cl0.15 perovskite surface which is deposited using gas-assisted ultrasonic spray coating. It is found that i-BABr treatments result in the formation of a quasi-2D perovskite layer. The spray-coated surface treatment results in an impressive 80 mV improvement in the median open-circuit voltage with respect to untreated devices. Importantly, the spray-coated passivation results in very similar positive benefits to the application of spin-coated treatments demonstrating the promise of the spray-passivation methodology. It is shown that devices created in this manner demonstrate PCEs of up to 21.0% (19.4% stabilized), representing the highest reported efficiency for one-step, spray-coated methylammonium-free PSCs. This work represents the first demonstration of a spray-coated surface passivation treatment that is compatible with high-throughput, roll-to-roll processing