Preparation Of Rare Earth Doped Upconversion Luminescence Materials And Their Applications In Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSCs), as a new type of solar cells developed over the past decade, are regarded as the low-cost and high-efficiency photovoltaic cells. The photo-anode is an important part of the DSSCs, plays an important role in cell's performances and its function is to load sensitizers and collect and transport electrons. TiO2 as a kind of extremely stable semiconductor matrial which can only absorb the ultraviolet of wavelength less than 387nm, so the photoelectric conversion efficiency is very low. In order to improve the photoelectric conversion efficiency and increase the spectral range of sensitization, one important method is to sensitize the broadband gap TiO2 by chemically bonded or physical adsorption. however, even the best dyes (N719, N749) only absorb visible light in the wavelength range 300-800 nm, and most of the solar infrared and ultraviolet irradiation are not utilized. If the infrared and ultraviolet irradiation can be transferred to visible light by an up and down conversion luminescence process, and is reabsorbed by the dye in the DSSC, more solar irradiation can be utilized, and the photocurrent of the DSSC will be effectively enhanced.In this paper, up and down conversion luminescence powders with different kinds of rare earth as photoluminescent centers were synthesized by precipitation method and Gd2O3 and Lu2O3 were used as host material. The conversion luminescence powders were added in TiO2 films for used in DSSC. The influence of the flurescence powders on the photoelectronic properties of the cells were investigated by XRD,F-4500,Ⅰ-Ⅴcurve of the solar cell and so on. The conversion luminescence powders as luminescence medium and p-type dopant, are introduced into the DSSC to improve its photocurrent, photovoltage and solar conversion efficiency. The test results are as follows:(1) Gd2O3:Eu3+ nanophosphor was prepared using the homogeneous precipitation technique, The solar conversion efficiency for a DSSC with Gd2O3:Eu3+ doping (6:100) reached 7.01%, which enhances 17.4% compared to that of a DSSC without Gd2O3:Eu3+ doping. Under the ultraviolet irradiation of 24 mW·cm-2 a DSSC doped Gd2O3:Eu3+(6:100) achieves a light-to-electric energy conversion efficiency of 1.90%, and lacking the rare-earth ions doping possesses the photovoltaic conversion efficiency only 1.47%.(2) Lu1.976Ybo.o2Tmo.oo403 nanopowder was prepared by the co-precipitation method, The solar conversion efficiency for a DSSC with Lu2O3:Tm3+,Yb3+ doping (4:100) reached 6.63%, which enhances 11.1% compared to that of a DSSC without Lu2O3:Tm3+,Yb3+ doping. Under the infrared irradiation of 60mW·cn-2 a DSSC doped Lu2O3:Tm3+,Yb3+(4:100) achieves a light-to-electric energy conversion efficiency of 0.194%, and lacking the rare-earth ions doping possesses the photovoltaic conversion efficiency only 0.119%.(3) Gd2O3:Sm3+ nanoparticle was prepared using carbonate coprecipitation method, The solar conversion efficiency for a DSSC with Gd2O3:Sm3+ doping (6:100) reached 6.72%, which enhances 12.6% compared to that of a DSSC without Gd2O3:Sm3+ doping. Under the ultraviolet irradiation of 24 mW·cm-2 a DSSC doped Gd2O3:Sm3+ (6:100) achieves a light-to-electric energy conversion efficiency of 1.87%, and lacking the rare-earth ions doping possesses the photovoltaic conversion efficiency only 1.47%.