  Terahertz absorbers are crucial to the cutting-edge techniques in the
next-generation wireless communications, imaging, sensing, and radar stealth,
as they fundamentally determine the performance of detectors and cloaking
capabilities. It has long been a pressing task to find absorbers with
customizable performance that can adapt to various environments with low cost
and great flexibility. Here, we demonstrate perfect absorption empowered by
bound states in the continuum (BICs) allowing for the tailoring of absorption
coefficient, bandwidth, and field of view. The one-port absorbers are
interpreted using temporal coupled-mode theory highlighting the dominant role
of BICs in the far-field radiation properties. Through a thorough investigation
of BICs from the perspective of lattice symmetry, we unravel the radiation
features of three BIC modes using both multipolar and topological analysis. The
versatile radiation capabilities of BICs provide ample freedom to meet specific
requirements of absorbers, including tunable bandwidth, stable performance in a
large field of view, and multi-band absorption using a thin and flexible film
without extreme geometric demands. Our findings offer a systematic approach to
developing optoelectronic devices and demonstrate the significant potential of
BICs for optical and photonic applications which will stimulate further studies
on terahertz photonics and metasurfaces.
