Medium Effect On Low Power Upconversion Mechanism And Structure Activity Relationship

Triplet-triplet annihilation up-conversion(TTA-UC) shows many advantages, such as strong ability of absorption, high up-conversion efficiency, tunable wavelength and so on, so that it can realize some practical approaches for the solar utility. TTA-UC can be carried out by the excitation as low as less than 100 mW/cm-2. The optical density of excitation is closed to the energy of solar, so that it is useful to the application of solar energy.There are many problems on the application of low-powered up-conversion. The biggest one is how to improve the up-conversion efficiency. General researches focus on how to synthesize different kinds of new acceptors and sensitizers to get high efficiency. But the organic synthesis is complex, and it is not conform to the spirit of environmental protection. In this paper, we firstly use metal-porphyrin derivatives and anthracene derivatives to study the structure effect, solvent effect and medium effect of β-cyclodextrin on the up-conversion efficiency and we also discussed the applications of up-conversion.The specific content of this paper is as follows: firstly, we study the environment effect on the efficiency of up-conversion. In this part, we research the effect on the up-conversion spectrums and efficiencies with the protic and aprotic solvent medium of the systems. We found the different influences of protic and aprotic medium on the up-conversion. With the increase of polarity of the aprotic solvents, the efficiency of up-conversion is also increased. On the contrary, with the increase of polarity of the protic solvents, the efficiency of up-conversion is decreases. The fundamental reason of this phenomenon is that the viscosity of solvent increased with the increase of polarity of the protic solvents. In that case, the life of sensitizer becomes longer. So the up-conversion efficiency can be improved.Finally, we explored the effect on the spectrum and efficiency of up-conversion with the present of β-CD molecule which containing hydroxyl. We found both in protic solvent and in aprotic solvents, β-CD can well improve the up-conversion efficiency. It is because that they can constitute a super-molecule. The super-molecule is only located in the hydrophilic equatorial region of solvents. The ternary super-molecular structure is stable and useful. So that β-CD can improve the up-conversion efficiency eventually.