Photoconductivity, pyroconductivity, and pyroelectricity effects in photodetection of layer-structured CuInP₂S₆/MoS₂ heterojunction

Layer-structured ferroelectric material-modulated heterojunctions are promising for use as photodetectors. However, the mechanism behind their photodetection performance, including photoconductivity, pyroconductivity, and pyroelectricity effects, has not yet been fully studied. Herein, we present a CuInP₂S₆/MoS₂ heterojunction with a layered structure, in which the narrow bandgap of MoS₂ extends the detection wavelength range with a specific detectivity (D^*) of 10⁸-10¹⁰ Jones. The pyroelectric effect, dominated by polarization, introduces significant current peaks and valleys when the light is turned on and off. A competitive mechanism is discovered among the photoconductivity, pyroconductivity, and pyroelectricity effects. At low optical power intensities, the pyroconductivity effect is dominant under 405 nm light, while the pyroelectricity effect dominates under 808 nm light. However, at high optical power intensities, both the photoconductivity and pyroconductivity effects become dominant, regardless of the light wavelength. The responsivity (R), external quantum efficiency (EQE), and D^* of the CuInP₂S₆/MoS₂ heterojunction are two orders of magnitude for 405 nm light compared to 808 nm light. These results not only demonstrate the coupling effect among the photoconductivity, pyroconductivity, and pyroelectricity effects in the photodetection of layer-structured CuInP₂S₆/MoS₂ heterojunctions but also highlight the potential applications of these heterojunctions in multifunctional devices, provided that these effects can be clearly distinguished.