In this work, boron doped graphene nanoparticles (NPs) were synthesized by the hydrothermal route with different boron tribromide concentrations such as 52, 104, and 156 μL. The structural, morphological and optical properties of the prepared NPs were studied using different characterization techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscopy (AFM), UV–vis spectroscopy and photoluminescence spectroscopy (PL). The XRD pattern reveals the hexagonal crystal structure. The SEM image showed textured sheet-like layers which got agglomerated to form fluffy structures. The TEM images recorded single-crystalline nature and also confirms the particle size was reduced upon increasing boron tribromide solution concentration with recognizable particle shape. The topographic properties of the synthesized B-doped graphene NPs were also studied through AFM images. The UV visible absorbance characteristics peaks 243 and 372 nm were observed correspond to π – π* in C–C bands and n- π* transition. After that as grown NPs were used to fabricate diode junctions on p-Si substrates (p-Si/n-B-doped graphene). The electrical performance of each p-Si/n-B-doped graphene diodes junction was examined using I–V characteristics and electrical parameters of diode junction such as ideality factor, barrier height and reverse saturation current were found 2.9–4.3, 0.75–0.83 eV and 4.88 × 10−6-7.26 × 10−6 A. The calculated ideality factor values of the p-Si/n-B-doped graphene diodes are decreased with increase in boron tribromide solution concentration.