Multidentate ligand-decorated indium tin oxide electrodes for efficient and durable perovskite solar cells

As commercial electron transport materials for perovskite solar cells (PSCs), pre-synthesized tin oxide (SnO₂) nanoparticles suffer from colloidal agglomeration and inhomogeneous size distribution in aqueous solutions. The formed micro-size SnO₂ aggregates on the planar indium tin oxide (ITO) substrate not only create energy disorder to impair interfacial charge transfer but also hampers the growth of perovskite crystals, deteriorating the photovoltaic performance and device lifespan of PSCs. Here, a multidentate ligand of 1,2-cyclohexanedinitrilotetraacetic acid (CDTA) is developed to modify the surface chemistry of ITO substrates, facilitating the formation of pinhole-free and uniform SnO₂ electron transport layers for the crystallization of high-quality perovskite films. Moreover, the surface CDTA ligands lift the work function of ITO from 4.68 to 4.12 eV, enabling interfacial band alignment modification to improve the electron extraction from the ITO/SnO₂ interface. As a result, the CDTA-modified PSCs exhibit a significantly enhanced PCE of 24.67% and much prolonged device lifespan, retaining 91.3% and 92.8% of the initial PCEs under 2,000 h dark storage and after 500 h under one-sun illumination in nitrogen, respectively. This work demonstrates a simple yet efficient interfacial engineering strategy for the design of efficient and durable PSCs.