Forster resonance energy transfer assisted white light generation and luminescence tuning in a colloidal graphene quantum dot-dye system.

The development of white light-emitting LED (WLED) is now one of the important demands of present society due to its energy saving feature. However, in this work, an ingenious strategy has been employed to develop Forster resonance energy transfer (FRET) based and rare-earth material free luminescent duo (LD) for the generation of white light. A colloidal LD, consisting of nitrogen-doped graphene quantum dots (N-GQDs) and DCM dye (DCM@N-GQDs), is employed for demonstrating the FRET. The band-gap is engineered by nitrogen (N) doping in GQDs, and an energy transfer efficiency of ~30% for white light generation is attained. The widely tunable PL emission from blue to the red region has been obtained by changing the D-A ratio. Therefore, the present work has provided an alternate approach to widen the light emission band of a conventional laser dye, which is otherwise restricted within a limited region of the visible spectrum. FRET-based WLED (F-WLEDs) with colour rendering index of 70 and correlated colour temperature of 4690 K have also been fabricated. The F-WLED exhibits an emission overlapping of 56% with the solar spectrum (AM 1.5) in visible region, which is doubled in compared to that of a commercial WLED. The present report of rapid synthesis of highly luminescent N doped GQDs and the strategy used here for generation of FRET based colloidal DCM-GQDs luminescent duo may also be extended further with other suitable laser dyes for further widening as well as tuning the spectral range of light emissions of different commercially available laser dyes and GQDs for their different photonic applications.