Robust molecular-dipole-induced surface functionalization of inorganic perovskites for efficient solar cells

Abstract

CsPbI₃ inorganic perovskite shows high potential for single-junction or tandem solar cells due to its suitable bandgap energy (E_g = ∼1.7 eV), but defect-assisted nonradiative recombination and unmatched interfacial band alignment within the inorganic perovskite solar cells (PSCs) to a large extent affect its photovoltaic performance. Herein, the derivatives of cinnamic acid (CA) are applied for the surface functionalization of inorganic perovskites for efficient and stable PSCs. Extensive theoretical calculations and experimental studies reveal that the molecular structure of CA-based molecules significantly affects the surface functionalization of perovskites, therefore determining the photovoltaic performance of PSCs. Benefiting from the surface defects passivation of perovskites and instrumental interfacial dipole within the PSCs induced by the surface functionalization of perovskites using 4-aminocinnamic acid (CA-NH₂) molecules, the charge carrier recombination was substantially suppressed, resulting in PSCs with a power conversion efficiency of up to 19.03%. Moreover, after the surface functionalization, PSCs also show good stability. Extensive theoretical calculations were performed to fundamentally understand the surface functionalization using CA-NH₂ molecules on the surface properties of inorganic perovskites and electronic interactions between CA-NH₂ molecules and perovskites.