Performance Study Of Rare Earth Luminescent Materials In Dye-sensitized Solar Cells

Solar energy is a clean source of energy that can be used,it has a wide range and abundant reserves,so it has a great development potentiality.Facing the crisis of exhaustion of fossil fuels,photovoltaics–the conversion of sunlight to electrical power–arises the researchers’interest as the best method of utilizing sunlight.The dye-sensitized solar cell（DSSC）was first proposed by Gr?tzel M.and his group in 1991,in which dye molecules can sensitize metal oxides semiconductor,achieving the conversion from sunlight to electricity.With their low cost raw materials,simple preparation process and environmentally-friendly production process,DSSC is considered to be a promising replacement for Silicon-based solar cells and their application prospect is brilliant.The spectral distribution of sunlight at AM1.5G consists of photons with wide wavelengths ranging from ultraviolet（UV）to infrared（IR）（200–2500nm）.Because the band gap of photo-anode limits its absorbance range and ruthenium-based sensitizers only utilize visible light,which means the most of the solar infrared irradiation is not utilized.Besides,UV light can mitigate dye degradation which results in an reducment of the devices’long-term stability.Thus,how to find a UC or DC luminescence materials which can convert IR or UV light into visible light is distinctly important for enhancing the DSSC’s photoelectron conversion efficiency（PCE）and long-term stability.But few researchers’modified compact layers by rare-earth ions,they always doped them in photoanode.The kinetic study shows that the recombination rate between conductive substrate（such as FTO）and I₃^-is very fast and the rate is fast than that of TiO₂ and I₃^-,thus it is important to reduce the recombination rate between FTO and I₃^-in order to improve the performance of DSSC.Besides,reserchers have applied some specific morphology and size luminescence materials in DSSCs as their scattering layer for enhanced scattering ability and incresed light path.The specific works of this paper are as follows:（1）In Part One,multifunctional and ultrathin SnO₂ compact single layer（CSL）is modified by europium ion doped ytterbium fluoride(YbF₃:Eu³⁺),which is designed and fabricated by a facile spin-coating method for the DSSC.The device with SnO₂/YbF₃:Eu³⁺CSL exhibits enhanced long-term stability and PCE compared to those of the device without CSL.The enhanced long-term stability is due to the SnO₂/YbF₃:Eu³⁺CSL can transform UV light into visible light to mitigate dye degradation.The enhanced PCE is associated with the reduced recombination rate of electrons,the enhanced short-wavelength light response and the high transparency of the CSL.（2）In order to enhance the PCE of DSSC,we overlay SnO₂/YbF₃:Er³⁺（SYEr）onto SnO₂/YbF₃:Eu³⁺（SYEu）to construct a multifunctional SnO₂/YbF₃:Eu³⁺//SnO₂/YbF₃:Er³⁺compact bilayer（SYEu/SYEr CBL）.In the same way,this CBL can reduce the recombination rate of electrons.Moreover,DSSC with the luminescence system can reach an enhanced PCE further,which contain the matrix SnO₂ and the conversioner YbF₃:Eu³⁺（YEu）and YbF₃:Er³⁺（YEr）.Furthermore,these findings offer potential applications for photovoltaic device with a wide range response of sunlight via the variation in rare-earth species and cell structures.（3）The core-shell-coated and Ag-NPs decorated YF₃:Yb³⁺,Er³⁺/Ag@SiO₂（YFYE/Ag@SiO₂）were prepared by TEOS hydrolysis and incorporated into the photoanodes of DSSCs.The influences of different coating layers and decorated Ag NPs on the upconversion of YFYE and the performance of DSSCs were comparatively investigated.The SiO₂ coated can reduce the quenching betweeb YFYE grains and the Au-NPs can enhance the intensity of upconversion luminous emission.Besides,the enhanced performance attributed to the possible enhanced scattering from the big size grains.