Lead halide perovskites have gained extensive attention in the photodetectors (PDs) field, but the problems of intrinsic toxicity and poor stability still hamper their practical applications. Furthermore, ultraviolet (UV) PDs have rarely been explored due to challenges, including the lack of suitable materials and the costly and complicated fabrication processes. In order to solve the above problems, herein it is reported a novel all-inorganic lead-free halide CsAg 2 I 3 single crystal (SC) with pure phase and high quality. This CsAg 2 I 3 SC shows ultra-stable crystal structure, steady chemical properties, and good optical properties, and it can be stable up to 893 K. Its 1D crystal structure and soft crystal lattice support the formation of self-trapped excitons, leading to a broadband emission at 610 nm with a large Stokes shift of 315 nm (2.23 eV). The strong absorption for UV light combined with direct bandgap, large Stokes shift, and ultra-high stability promises an environment-friendly, low-cost, and high-performance UV PD based on the 1D all-inorganic silver (I) halides.
Low-dimensional ternary silver halide (CsAg 2 I 3 ), an emerging inorganic lead-free perovskite, has garnered significant scientific attention due to its strong quantum confinement effects, wide bandgaps, non-toxicity, and others. However, the photophysical properties and optoelectronic performance of CsAg 2 I 3 materials and devices are significantly compromised by crystal quality and defects arising from liquid-phase preparation. Herein, 1D CsAg 2 I 3 single crystals newly grown by the chemical vapor deposition method are reported. These crystals display exceptional quality and stability over a 3-month period despite exposure to air and moisture. The high in-plane anisotropic structure, phonon vibrations, and refractive index of CsAg 2 I 3 crystals are also experimentally elucidated. Polarization-sensitive ultraviolet photodetector based on the CsAg 2 I 3 monocrystal features a responsivity of 139 mA W −1 , a specific detectivity of 1.05 × 10 11 cm Hz 1/2 W −1 , an ultra-fast photoresponse speed of 48.2/69.1 µs, and a dichroic ratio of 2.66 upon 360 nm irradiation at −5.0 V bias. The photodetector excels amongst its competitors, moving toward the potential application of rapid optical anti-counterfeiting identification. This work, which leverages grown high-crystalline and highly stable CsAg 2 I 3 monocrystals, holds promises for advancing this functional material into a robust next-generation optoelectronic devices capable of probing sensitive optical sensing and specific azimuth recognition.
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