Minimizing Buried Interface Energy Losses via Urea Phosphate Derivatives Enable High‐Efficiency Carbon‐Based Mesoscopic Perovskite Solar Cells

Abstract Carbon‐based mesoscopic perovskite solar cells (C‐MPSCs) have attracted widespread attention owing to the advantages of printable fabrication and excellent stability. However, the nonradiative recombination loss at buried interfaces hinders further efficiency improvements of C‐MPSCs. In the study, urea phosphate derivative is utilized as a modifier for the buried interfaces of C‐MPSCs. In the mesoporous titanium dioxide (m‐TiO 2 ) layer, guanylurea phosphate (GUP) can interact with TiO 2 , anchoring to the surface of m‐TiO 2 and forming a molecular bridge at the perovskite/m‐TiO 2 interface. The molecular bridge facilitates the extraction of charge carriers and minimizes nonradiative recombination losses, while GUP can passivate the dangling Pb 2+ and I − vacancy defects in the perovskite, respectively. Furthermore, GUP helps slow down the perovskite crystallization, promotes pore filling, reduces residual stress in the device, and optimizes energy level alignment. Consequently, the power conversion efficiency of C‐MPSCs with GUP increases to 19.78%, from 18.22% of the control devices. C‐MPSCs with GUP exhibit excellent stability in air storage, thermal aging, and damp heat stability tests. The study provides a novel approach to eliminate nonradiative recombination losses at the buried interfaces of C‐MPSCs.