Room-temperature-grown CsAg2I3 single-crystal microrods for high-performance heterostructured UV photodetection and imaging

Abstract

Lead-free metal halide perovskites, especially with low-dimensional structures, show great potential in fabricating high-performance optoelectronic devices due to their nontoxicity and extraordinary photophysical properties. In this work, centimeter-sized one-dimensional lead-free CsAg2I3 single-crystal (SC) microrods with high quality were grown using the antisolvent vapor-assisted crystallization method. The CsAg2I3 SC microrods had a wide bandgap of 3.51 eV, proved by both the Tauc plot and density functional theory calculations. Theoretical calculations also indicated that the iodine vacancies (VI) exhibited the lowest formation energy and a pronounced band redshift, suggesting VI was likely to be the dominant point defect that could effectively tune the absorption edge of CsAg2I3, rather than silver vacancies (VAg), iodine interstitials (Ii), or silver interstitials (Agi). Photodetectors (PDs) were fabricated based on the CsAg2I3 SC microrod/PEDOT:PSS heterojunction and showed good photoelectric performance under 254 nm ultraviolet-C (UVC) light, with responsivity and specific detectivity of 0.08 mA/W and 6.43 × 108 Jones, respectively, under a bias voltage of 5 V. In addition, a home-made imaging system constructed based on the as-fabricated PD exhibited stable and good imaging capability for the 254 nm UVC light even with an ultralow intensity of 19.5 μW/cm2. Our work provides a valuable demonstration of inorganic–organic heterojunction for the low-dimensional lead-free perovskite CsAg2I3 in multifunctional optoelectronic applications.