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Surface Ligands for Methylammonium Lead Iodide Films: Surface Coverage, Energetics, and Photovoltaic Performance
摘要： Surface ligand treatment provides a promising approach to passivate defect states, improve material and device stability, manipulate interfacial energetics, and increase the performance of perovskite solar cells (PSCs). To facilitate targeted selection and design of surface ligands for PSCs, it is necessary to establish relationships between ligand structure and perovskite surface properties. Herein, surface ligands with different binding groups are investigated to determine their extent of surface coverage, whether they form a surface monolayer or penetrate the perovskite, how they influence material energetics and photoluminescence, and how this combination of factors affects PSC performance. Ultraviolet and inverse photoelectron spectroscopy measurements show that surface ligands can significantly shift the ionization energy and electron affinity. These changes in surface energetics substantially impact PSC performance, with the performance decreasing for ligands that create less favorable energy landscapes for electron transfer from MAPbI3 to the electron transport layer, C60.
关键词： defect passivation,perovskite solar cells,interfacial energetics,surface ligands,photovoltaic performance
更新于2025-09-19 17:13:59
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Influence of Surface Ligands on Energetics at FASnI <sub/>3</sub> /C <sub/>60</sub> Interfaces and Their Impact on Photovoltaic Performance
摘要： Interfacial chemistry and energetics significantly impact the performance of photovoltaic devices. In the case of Pb-containing organic metal halide perovskites, photoelectron spectroscopy has been used to determine the energetic alignment of frontier electronic energy levels at various interfaces present in the photovoltaic device. For the Sn-containing analogues, which are less toxic, no such measurements have been made. Through a combination of inverse, and X-ray photoelectron spectroscopy ultraviolet, (UPS, IPES, and XPS, respectively) measurements taken at varying thickness increments during stepwise deposition of C60 on FASnI3, we present the first direct measurements of the frontier electronic energy levels across the FASnI3/C60 interface. The results show band bending in both materials and transport gap widening in FASnI3 at the interface with C60. The XPS results show that iodide diffuses into C60 and results in n-doping of C60. This iodide diffusion out of FASnI3 impacts the valence and conduction band energies of FASnI3 more than the core levels, with the core level shifts displaying a different trend than the valence and conduction bands. Surface treatment of FASnI3 with carboxylic acids and bulky ammonium substituted surface ligands results in slight alterations in the interfacial energetics, and all surface ligands result in similar or improved PV performance relative to the untreated devices. The greatest PV stability results from treatment with a fluorinated carboxylic acid derivative; however, iodide diffusion is still observed to occur with this surface ligand.
关键词： perovskite solar cell,formamidinium tin iodide,interfacial energetics,inverse photoelectron spectroscopy,surface modification,photoelectron spectroscopy,ion diffusion
更新于2025-09-12 10:27:22