Understanding how different stacking sequences in layered semiconductors respond to external stimuli is crucial for elucidating their optoelectronic behavior and for guiding the design of advanced devices. Here, we report a distinct and anomalous pressure-dependent photoresponse in 2H-${\mathrm{SnS}}_2$ and clarify its fundamental contrast with the 4H polytype. The photocurrent of 2H-${\mathrm{SnS}}_2$ increases by nearly 30-fold up to 2.8 GPa and then decreases at higher pressures, in contrast to the monotonically increasing photocurrent observed in 4H-${\mathrm{SnS}}_2$ over the entire pressure range, indicating that the pressure response is strongly dependent on the stacking sequence. Concurrently, the resistance of 2H-${\mathrm{SnS}}_2$ decreases by more than two orders of magnitude at 9.5 GPa, accompanied by an increase in the carrier density from $6.9\times {10}^{14}$ to $1.8\times {10}^{17}{\mathrm{cm}}^{-3}$. Combined high-pressure measurements indicate that the photocurrent evolution is dictated by the competition between pressure-induced bandgap narrowing and defect-assisted recombination. These findings provide insight into the underlying carrier dynamics in layered semiconductors and highlight the stacking structure as a key determinant of the pressure-driven evolution of their photoelectric behavior.

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• Photocurrent
• Layered crystals
• Pressure techniques