This study investigates the synthesis, characterization, and application of Al/NaSrEr(BO3)2/n-Si and Al/NaSrEr(BO3)2/p-Si photodiodes (PDs). The NaSrEr(BO3)2 compounds were synthesized and deposited onto n-type and p-type Si wafers via spin coating, followed by the formation of aluminum electrodes using thermal evaporation. Comprehensive characterization was conducted using FT-IR, powder X-ray diffraction (P-XRD), ICP-MS, thermogravimetric/differential thermal analysis (TGA/DTA), and SEM–EDS to investigate the structural, compositional, and morphological properties of the orthoborate films. FT-IR spectra confirmed the vibrational modes of the borate structure, while P-XRD analysis revealed crystalline phase formation. ICP-MS results verified elemental ratios consistent with theoretical predictions, and SEM–EDS provided insight into surface topography and elemental distribution. The optical and electrical behavior of the fabricated photodiodes was assessed through Current–Voltage (I–V) and Current–Time (I–t) measurements. Device performance metrics such as ideality factor, barrier height, responsivity, and specific detectivity were derived. Under an illumination intensity of 100 mW/cm2, the NaSrEr(BO3)2/n-Si device exhibited a responsivity of 1.28 A/W and a detectivity of 5.91 × 1010 Jones. In contrast, the NaSrEr(BO3)2/p-Si photodiode delivered enhanced performance, with a responsivity of 2.38 A/W and detectivity of 7.82 × 1010 Jones. This research highlights the potential of NaSrEr(BO3)2-based materials for enhancing the performance of photodiodes and sensor systems, while also laying the groundwork for future advancements in borate-based optoelectronic devices.