Narrowband photodetectors are employed in optical communication, where designated wavelengths are used to transmit data, and in environmental sensing to identify specific gases that absorb distinct wavelengths of light. In this study, we developed a novel polyoxometalate compound for application as a near-infrared (NIR) photodetector. Li6 [α-P2W18O62]-.28H2O compound was synthesized successfully and was characterized using 31P NMR, FT-IR, UV–Vis, C–V, SEM, TEM, and AFM. We used Li6 [α-P2W18O62]-.28H2O compound as interlayer in Schottky type photodetector structure. Photodiode and photodetector measurements were performed under various solar intensities (20, 40, 60, 80, and 100 mW), ultraviolet, visible, and near-infrared wavelengths ranging from 351 to 1600 nm. Notably, the device exhibited an excellent responsivity, external quantum efficiency, and detectivity under near-infrared wavelengths. It showed 64.17 mA/W responsivity, 4.34 × 1010 Jones detectivity and 7.96 % external quantum efficiency at 1000 nm and 0 bias voltage. Moreover, the device demonstrated 4.736 A/W responsivity and 8.57 × 1011 Jones detectivity under solar light. Furthermore, this research introduces a novel compound for developing narrowband photodetectors utilizing polyoxometalate.