Highly transparent and colour-tunable composite films with increased quantum dot loading

Transparent films incorporated with quantum dots are promising light conversion materials for many cutting-edge technologies including light-emitting diodes and luminescent solar concentrators. In this work, we demonstrated that a combination of water soluble quantum dots and ultrathin cellulose nanofibers is an advantageous strategy to fabricate highly emissive thin films of tens of micrometers. By varying the composition of quantum dots, these thin films exhibit tunable photoluminescence emissions, ranging from blue to red as well as white light. Because of the inherent nanoscale phase separation of cellulose nanofibers, the loading content of quantum dots can be increased up to 50 wt%, which results in a significant increase of the refractive index. The combination of high refractive index (∼1.56), colour-tunable emissions (450-650 nm) and high transparency (∼80%, at a wavelength longer than the absorption band of quantum dots) makes them promising candidates for photonic and optoelectronic devices.