Using upconversion nanoparticles to improve photovoltaic properties of poly(3-hexylthiophene)-TiO2 heterojunction solar cell

We develop an approach to improve the photovoltaic properties of polymer solar cells, by incorporating a function of light upconversion into the solar cell. We synthesize hydrophilic rhombic lanthanide-doped LiYF4 at the average length of 100 nm and breadth of 40 nm. The synthesized nanoparticles which are capable of converting long-wavelength photons into shorter ones are introduced into the poly(3-hexylthiophene)-TiO2 heterojunction solar cell. The results of the upconversion fluorescence spectra demonstrate the energy transfer from the upconversion nanoparticles to poly(3-hexylthiophene). It is revealed by using monochromatic illumination that the upconversion nanoparticles enable the devices to utilize the long-wavelength photons which are beyond the absorption of poly (3-hexylthiophene), and thus, the photovoltaic performance is enhanced.