Mono- and Bilayer MoS₂ Photodetectors: High-Performance Broadband AC Readout With Color-Selective Noise Suppression

Low-frequency (1/f) noise is a primary limiter in visible photodetectors, producing baseline drift and obscuring weak signals. We engineer a broadband alternating-current (AC) photodetection platform by integrating partially overlapped mono- and bilayer molybdenum disulfide (MoS₂), grown via chemical vapor deposition and transferred on interdigitated electrodes. The AC readout decouples modulated photocurrent from slow drifts across a wide temperature range (243–323 K). Correlative structural and optical characterization confirms heterogeneous mono- and bilayer MoS₂ structure with a strong ∼1.85 eV excitonic transition. Operating at 0 V bias, the device achieves ultrahigh responsivity (6.60 × 10⁵ A W⁻¹), specific detectivity (2.76 × 10¹⁵ Jones), bandwidth-integrated specific detectivity (1.64 × 10¹⁴ Jones), external quantum efficiency (2.04 × 10⁸%), and a response time of ∼3.1 ms at 405 nm (298 K, 100 Hz). Comparable performance persists at 532 and 635 nm and remains stable from 20 Hz to 1 kHz. Moreover, wavelength-dependent kinetics reveal two-step, trap-assisted transients at 405 and 532 nm vs. a single-step response at 635 nm, consistent with resonant excitonic absorption. Notably, noise spectra steepen from (Formula presented.) to (Formula presented.) at 532 nm, attributed to trap-mediated mid-gap states resulting in charge accumulation. Together, these results demonstrate a low-noise, high-gain, fast AC photodetector.