This study aims to achieve a filterless, narrow-band, near-infrared photodiode based on a p+-Cu2S/p-Si isotype heterojunction device. The device is developed by depositing 60 nm thick Cu2S thin film on Si substrates from Copper Sulfide pieces via the Thermionic Vacuum Arc technique (TVA). The molecular structure of the thin film is analyzed by utilizing Raman and X-Ray photoelectron spectroscopy (XPS) and confirmed to be in the Cu2S phase. Moreover, the high hole concentration in Cu2S is correlated with XPS results. The photodiode exhibits a response climax centered at 1049 nm and a full-width at half-maximum (FWHM) value of 104 nm. An outstanding responsivity value of 375 mA/W (at 0 V bias) is obtained at a peak wavelength of 1049 nm, which surpasses most filterless, narrow-band photodiodes. Furthermore, while operating at 0 V bias, the photodiode showed an excellent specific detectivity value of 4.17 × 1011 Jones with a 1.7 × 103 on/off ratio (at 1049 nm, 11.47 mW/cm2), in addition to its high photocurrent stability and response speed (under 0.8 s). In light of these findings, this proof-of-concept device is a great candidate as a filterless, narrow-band, NIR self-powered photodiode.