  Borophene has recently attracted significant attention as an emerging
two-dimensional monoelemental material for refractive index sensing because of
its ultra-high surface-to-volume ratio and outstanding surface sensitivity.
However, current research mainly focuses on designing borophene-based sensors
with single-peak absorption, which lacks reliability compared to the
performance of multi-peak sensors. In this paper, high-performance borophene
refractive index sensors with multiple nearly perfect absorption peaks are
proposed. The geometric parameters of the metadevices are optimized using
finite-difference time-domain (FDTD) simulations to obtain three strong
absorption peaks in the near-infrared (near-IR) regime with intensities of
99.72%, 99.18%, and 98.13%. Further calculations show that the sensitivities of
the three strong peaks reach 339.1 nm shift per refractive index units
(nm/RIU), 410.1 nm/RIU, and 738.1 nm/RIU, and their corresponding figure of
merits (FOMs) reach up to 15.41/RIU, 14.65/RIU and 10.85/RIU, respectively,
exhibiting great potential for near-IR refractive index sensing. Moreover, the
three absorption peaks can be easily tuned by adjusting the carrier density of
borophene, which can be realized by applying different external electric bias
voltages. These results can provide theoretical guidance for the development of
multi-peak near-IR dynamic integrated photonic devices
