Research On The Enhancement Of Light Utilization Efficiency Based On Colloidal Assemblies

Light is the source of life. As a vital topic in the science and technology field, toimprove the light utilization efficiency of each optical process has very importantacademic value and practical significance. In this dissertation, the two types of colloidalassemblies (photonic crystals and plasmonic materials) have been employed toinvestigate the light utilization efficiency enhancement in the three typical processes ofdye-sensitized solar cells (DSSCs), fluorescence and Raman respectively. The mainresearch contents and conclusions are as follows:Firstly, the application of photonic crystals in enhancing the solar cell efficiencywas studied. A new kind of double inverse opals (DIO) structure photonic crystal(introducing a scattering sphere in each lattice pore of traditional inverse opals) wasused to couple traditional DSSCs to form a back reflector mirror structure. Due to thephotonic bandgap property of photonic crystals, such structure greatly enhanced opticalabsorption efficiency of dye. The theoretical calculation shows that a single DIOstructure layer can make photo-current efficiency improving47%, while double DIOlayers can improve the absorption of dye in full visible spectrum, and enhancementfactor can reach80%, compared to the traditional DSSC.Then the metal colloidal assembly plasmonic material was constructed, andthe application of their surface plasmons in Raman signal enhancement wasresearched. A facile method was created to form Au colloidal assemblies with1nm uniform gap between two particles, by using cucurbituril as a molecularlinker. Cucurbituril as the Surface Enhanced Raman Scattering (SERS)"hotspot" container can realize the SERS of "inertial" molecules by supramolecularhost-guest recognization. The hot-spot enhancement factor can reach up to109.In addition, the system eliminating chemical enhancement effect can be used astheoretical research platform of SERS electromagnetic enhancementmechanism.Finally photonic crystals were coupled to surface plasmons of metalcolloids, in order to study the application of this composite structure influorescence enhancement. This proposed new strategy can realize all of three enhancement factors, excitation enhancement, quantum efficiency enhancementand light extraction efficiency enhancement. We have theoretically proved themechanism by Finite Difference Time Domain simulation and show an exampleto demonstrate experimentally (Rhodamine B is taken as the modal molecule).The enhancement factor of coupling system is much larger than the plus of thetwo effects an up to260folds has been achieved.Different strategies were utilized in above three optical processes toachieve the great enhancement of output "signals", and improve the utilizationefficiency of incident light. These strategies have important guide value for theresearch on light efficiency enhancement not only for the physical processessuch as photovoltaics, photoluminescence, and light scattering, but also for thephotocatalysis and photochemical reaction processes.