Enhanced Particle‐to‐Particle Interaction of Tin Oxide Electron Transporter Layer for Scalable Flexible Perovskite Solar Cells

Perovskite solar cells (PSCs) have exceeded 26% efficiency. One attribute of PSCs is their printability at relatively low temperatures, particularly advantageous for flexible solar cells. However, developing efficient, fully printable flexible PSCs on rough and soft plastic substrates remains a challenge. Herein, efficient flexible PSCs fabricated by only scalable methods in ambient conditions are reported. First, the source of the issue in fabricating flexible PSCs—the presence of charge carrier shorting pathways within electron‐transport layer (ETL) due to incomplete coverage of surface of flexible substrates—is identified. To address this challenge, the ETL deposition ink is modified with a phase‐transfer catalyst, often used in synthetic organic chemistry. Dynamic light scattering and nuclear‐magnetic resonance studies show that the catalyst enhances ETL particle‐to‐particle interaction in the ink, eventually leading to conformal coverage of rough flexible substrates. As a result, a power conversion efficiency of 17.6% for all‐scalable flexible n–i–p ‐structured PSCs based on methylammonium lead iodide (MAPbI 3 ) is demonstrated, among the highest reported to date for fully scalable flexible PSCs, all fabricated in ambient air.