Concerted Photoluminescence of Electrochemically Self-Assembled CuSCN/Stilbazolium Dye Hybrid Thin Films

Hybrid thin films of crystalline CuSCN and 4-(N,N-dimethylamino)-4'-(N'-methyl)stilbazolium (DAS) in three distinctively different nanostructures were obtained by electrochemical self-assembly from a single pot containing all the chemical ingredients. Their optical properties for UV-vis-NIR absorption, photoluminescence (PL), and PL excitation spectra were examined between 77 and 298 K, in comparison with solution and solid powder of DAS tosylate (DAST). Unlike all other dyes we tested before, PL of DAS was not quenched but rather enhanced when hybridized with CuSCN. DAST exhibited a strong exciton-phonon coupling to weaken, broaden, and red shift PL at room temperature, so that it inversely is strongly enhanced, sharpened, and blue-shifted at 77 K. The PL of the same dye in the hybrid thin film, however, shows a slight red shift and only a moderate enhancement at reduced temperatures due to strong exciton stabilization in dielectric environment of CuSCN and concerted PL by energy transfer from CuSCN to DAS luminophore, making it a unique nearly temperature-independent luminescent material.