Interfacial band alignment at indium-gallium-tin-oxide/copper iodide heterojunction by X-ray photoelectron spectroscopy

초록

Metal halides have evolved as promising p-type materials owing to their superior optoelectronic properties. However, it is highly demanded to understand the band offsets and charge transport dynamics at the interface for implementing high-performance photodetector applications. Here, we demonstrate the interfacial band analysis at the indium-gallium-tin-oxide (IGTO)/gamma-copper iodide (gamma-CuI) heterojunction and study charge transport dynamics across the interface. The surface properties and Raman features of IGTO and gamma-CuI are investigated, and their X-ray photoelectron spectroscopy (XPS) spectra, including core level and valence band, are systematically studied. The band alignment at the IGTO/gamma-CuI heterointerface is experimentally determined using highresolution XPS and ultraviolet photoelectron spectroscopy. The staggered band alignment (type II) is determined, exhibiting band offset values of 1.28 +/- 0.02 eV for the valence band and 0.94 +/- 0.02 eV for the conduction band. This band configuration is further analyzed by Anderson's affinity rule, confirming its suitability for efficient charge separation and carrier transport. The favorable type-II alignment facilitates suppressed carrier recombination and enhanced photogenerated charge extraction, which are critical for photodetector performance. Thus, this work highlights the importance of interfacial band-offset engineering and establishes IGTO/ gamma-CuI heterojunctions as promising candidates for next-generation optoelectronic and photodetector applications.

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