Photoluminescence and Boosting Electron-Phonon Coupling in CdS Nanowires with Variable Sn(IV) Dopant Concentration

High-quality Sn(IV)-doped CdS nanowires were synthesized by a thermal evaporation route. Both XRD and Raman scattering spectrum confirmed the doping effect. The room temperature photoluminescence (PL) demonstrated that both near bandgap emission and discrete trapped-state emission appeared simultaneously and significantly, which were attributed to the strong exciton trapping by impurities and electron-phonon coupling during the light transportation. The PL intensity ratio of near bandgap emission to trapped-state emission could be tune via doped Sn(IV) concentration in the CdS nanowires. It is interesting that the trapped-state emission shows well separated peaks with the assistance of 1LO, 2LO, 4LO phonons, demonstrating the boosting electron-phonon coupling in these doped CdS nanowires. The influence of Sn(IV) dopant is further revealed by PL lifetime decay profile. The optical micro-cavity also plays an important role on this emission process. Our results will be helpful to the understanding of doping modulated carrier interaction, trapping and recombination in one-dimensional (1D) nanostructures.