Diphenylacetylene (DPAC) is a promising organic scintillator material for fast neutron detection. Solubility measurement was carried with two different solvents such as toluene and methanol. Stilbene mixed diphenylacetylene (DPACS) was successfully harvested from toluene with the dimensions of 42 × 12 × 8 mm3. X-ray diffraction confirms the monoclinic crystal structure with the obtained lattice parameters. The vibrational characteristic functional group was identified by FTIR studies. UV–Vis spectral analysis of the grown DPACS crystal reveals good optical transparency in visible and near IR region. The thermal behaviour and melting point of the sample was analysed by TGA-DSC. Chemical etching analysis was carried out on the crystal surface at an ambient temperature to see the dislocations and growth pattern of the crystal. Fluorescence broad emission peak was observed and the prompt and delayed fluorescence lifetimes of the DPACS were calculated. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.