Enhanced Efficiency and Stability of Carbon‐Based Perovskite Solar Cells by Eva Interface Engineering

Abstract Nanocrystalline tin (IV) oxide (SnO 2 ) as an electron‐transport layer (ETL) has unique advantages in realizing highly efficient and stable planar perovskite solar cells (PSCs), especially showing great potential in the low‐temperature preparation of large‐area flexible carbon‐based PSCs (C‐PSCs). However, the high trap density on the surface of SnO 2 tends to cause serious nonradiative recombination losses, thereby reducing photoelectric performance. In this work, an inexpensive and easily obtained polymer poly(ethylene‐co‐vinyl acetate) (Eva) is used as a interfacial modifier to reduce the interfacial defects and nonradiative recombination losses at the SnO 2 /perovskite interface. As a result, the crystallinity and conductivity of the perovskite layer are significantly increased, and the charge lifetime and stability are effectively improved. The Eva modified SnO 2 ‐based C‐PSCs obtain an optimal power conversion efficiency (PCE) of 12.29%, which is 25.7% higher than that of 9.78% for the unmodified C‐PSCs. Furthermore, the unencapsulated devices maintain 88.6% and 91.9% of the initial PCE over 1 month in ambient air for the unmodified and Eva‐modified C‐PSCs, respectively. The study provides valuable experience for the development of highly efficient and stable C‐PSCs using common polymers for interface modification engineering.