Controlling the spatial distribution of quantum dots in nanofiber for light-harvesting devices

The ability to control inter-dot or inter-molecule spacing of functional moieties in solid-state devices has long been studied for both fundamental and technological reasons. In this study, we present a new strategy for controlling the distance between quantum dots (QDs) based on one-dimensional spatial confinement in a polymer nanofiber template. This reliable technique allows for the isolation of QDs at a sufficient distance in a thin film and retains their monomeric character, with distinct spectra from aggregates (~30-nm shift) and monoexponential photoluminescence decay, indicating the suppression of inter-dot interactions. We successfully developed light-harvesting devices by incorporating QDs in nanofibers as an auxiliary light harvester, improving the performance of these devices from 5.9 to 7.4%. This strategy offers a viable path of controlling the arrangements of various functional moieties in solid-state devices. By packing quantum dots evenly in polymer nanofibres, a Korean team has found a way to boost the performance of artificial light harvesters. The high-intensity optical properties of quantum dots make them ideal for devices such as lasers and photosensors, but such effects are lost when the tiny dots aggregate together. To prevent unwanted clustering, Dongho Kim from Yonsei University in Seoul and co-workers used electrospinning techniques to embed quantum dots into poly(methyl methacrylate) nanofibres. Electron microscopy images and spectroscopic measurements showed this approach isolated the dots retaining their monomeric characteristics and that their separations were determined by the nanofibre diameter— a result that supports using this strategy to manipulate other moieties into useful spatial arrangements. Incorporating the hybrid material in a dye-sensitized solar cell revealed that the dots raised the light-harvesting efficiency from 5.9% to 7.4%. Confining quantum dots (QDs) into one-dimensional polymer nanostructures, we develop an inter-dot spacing control technique by which we can effectively isolate QDs in the solid-state film. The resultant isolated QDs in this nanostructure have clear monomeric features caused by attenuation of several problematic interactions, such as self-quenching. By incorporating isolated QD as an auxiliary light harvester, we can improve the performance of light-harvesting devices due to its additional absorption and efficient energy transfer. This study provides a general strategy that could be potentially useful for the spatial control of other functional moieties in various devices.