Dopant-induced optical enhancements in methylene blue-doped bibenzyl single crystals for neutron detector applications

High-quality methylene blue-doped bibenzyl (MB-BB) single crystals were successfully grown using a solution growth technique. Dopant addition induces the colour alteration in the crystal from colourless to light blue. Doped bibenzyl crystals were analysed using powder X-ray diffraction, FTIR, Raman, and fluorescence spectra analysis and compared with pure bibenzyl single crystals. Powder XRD indicated altered diffraction peak intensities due to guest molecule inclusion. High-resolution X-ray diffraction revealed a narrow rocking curve with FWHM of around 64 arcsecs, signifying the excellent quality and suitability of MB-BB crystals for device fabrication. The optical absorption study confirmed a Stokes’ shift in MB-BB crystals. Notably, the grown crystals exhibited prompt and delayed decay times of 0.45 and 2.26 ns, respectively, significantly faster than conventional organic single crystals.