Studies On The Composite Of Rare-earth Upconversion With Gold Nanoparticles Enhancing The Efficiency Of Dye-sensitized Solar Cells

Even the most successful sensitizers of dye-sensitized solar cells (DSSCs) such as N3, N-719, and N-749 can absorb light with wavelengths in a range between 300 and 800 nm. Meanwhile, most of the solar infrared(IR) and near-infrared (NIR) regions, which collect almost half of the energy of the sun's radiation, have not been utilized by these sensitizers. The upconversion material can absorb NIR light and radiatevisible upconverted emission, which can be absorbed by the sensitizers and more photoinduced electrons can be produced to increasethe efficiency of DSSCs. At the same time it can also play a role of reflection, promoting further the absorption of spectrum. In this paper, we report a new strategy to improve the efficiency of dye-sensitized solar cells by using external NIR light harvesting and light-reflecting bifunctional layers consisting of upconversion nanoparticles combined with gold particles.The upconversion materals can absorb NIR light and radiate visible upconverted emission, which can be absorbed by the N719 dye and more photoinduced electrons can be produced to increase the efficiency of DSSCs. Gold particles can function as a back reflector for the upconverted visible photons emitted from the upconversion materals bouncing back into the DSSC. The DSSC with a composite of rare-earth upconversion with gold nanoparticles shows a conversion efficiency increase of 21.0% compared to the cell without a rear reflector.This paper is divided into three parts:1. Firstly,the paper reviewed the emitting mechanism and method of rare-earth upconversion material and its application in solar cells.2. Three different morphologies of ?-NaYF4:Yb3+, Er3+ nanoparticles were synthesized by hydrothermal.They are nanodisk, nanotubes and nanorods.The ?-NaYFF4:Yb3+, Er3+ nanorods became the candidate as the Conversion layer for the highest fluorescence intensity. Based on these concepts,we fabricated the composite of rare-earth upconversion with gold nanoparticles.Firstly, the upconversion materials were coated on the rear side of the counter electrode of DSSCs.then, the gold nanoparticles were sputtered on the surface of upconversion layer.3. Fabrication of DSSCs. The DSSC with a composite of rare-earth upconversion with gold nanoparticles shows a conversion efficiency increase of 21.0% compared to the cell without a rear reflector. It was found that the efficiency is on the rise with the thickness of gold nanoparticles increasing.