Study Of The Photovoltaic Performance Of Perovskite Solar Cells Based On Er And Er-Yb Co-doped Ti0₂ Nanorods

With the increasing of energy crisis and environmental pollution,people's demand for renewable energy is also growing.Solar energy is one of the fastest developing technology in the field of energy and new energy,which is inexhaustible,inexhaustible.At present,silicon solar cells and compound semiconductor solar cells have achieved good photoelectric conversion efficiency.However,both the solar cell material and the preparation technology need highcost.In recent years,people pay more attention to the organic metal halide perovskite solar cell,as it has the advantages of high absorption coefficient,absorption range and diffusion length,and inexpensive solution preparation.In just a few years,the conversion efficiency of perovskite solar cells has exceeded 22%.The standard AM1.5G solar spectral range is 280~2500 nm,and it is it is only a small part(280-800 nm)absorbed by the solar cells,thus most of the incident light energy losses.One way to solve this problem is to convert the near infrared light into a visible light that can be absorbed by the solar cells,which can generate additional photocurrent and improving the efficiency of the solar cells.Due to the high conversion efficiency of upconversion luminescence material of Na YF4:Yb/Er,it is widely used in dye-sensitized solar cells.However,the separation distance between the dye and the upconversion material limits the charge transport.People try to use rare earth elements directly dop Ti O2 and apply it to solar cells.So far,rare earth element doped Ti O2 has been rarely reported in the perovskite solar cells.Based on the above analysis,in this thesis,rare earth elements Er and Er/Yb were used to dop Ti O2 nanorods.Er-doped and Er-Yb co-doped Ti O2 can transfer near-infrared to visible light which can be absorbed by the the perovskite cells.The aim of this experinment is to expand near-infrared absorption and improve the conversion efficiency of the perovskite cells.This thesis contains into two parts:Firstly,we prepared rare earth Er doped Ti O2(Er-Ti O2)nanorod arrays as the mesoporous layer of perovskite solar cell by the hydrothermal method.Perovskite solar cells with a structure of FTO/c-Ti O2/Er-Ti O2/MAPb I3-x Clx/Spiro-OMe TAD/Au were prepared,in which Ti O2 was used a electron transfer layer,MAPb I3-x Clx as a absorption layer,and Spiro-OMe TAD as a hole transporting layer.The morphology and properties of Er doped Ti O2 nanorod arrays were characterized by X ray diffraction(XRD)and scanning electron microscopy(SEM),such as diameter and length.The results indicate that the diameter of Er doped Ti O2 nanorod becomes larger.The UV-Vis absorption spectra and Tauc curve demonstrated that the band gap of Er doped Ti O2 becomes narrow,which could be one to the reasons for the larger open circuit voltage.We measured steady state photoluminescence of FTO/MAPb I3-x Clx,FTO/Ti O2/MAPb I3-x Clx,FTO/13%Er-Ti O2/MAPb I3-x Clx.The emission intensity of FTO/13%Er-Ti O2/MAPb I3-x Clx was the weakest in three samples.This proved that the electronic extraction rate is faster in the solar cell based on Er-Ti O2 mesoporous layer.Current density-voltage curve and the table of photovoltaic parameter visually presented the contrast of the solar cells based on 13%Er-Ti O2 and Ti O2 mesoporous layer.The photocurrent density of Er-Ti O2 compared with the solar cell based on undoped-Ti O2 from 20.7 m A / cm2 increased to 21.51 m A / cm2,the open circuit voltage of solar cell increased from 0.83 V to 0.85 V,efficiency improved from 11.04 % to 12.08 %.Secondly,rare earth doped Ti O2 can give rise to upconversion.Based on the Er-Ti O2 of the first part,we synthesized Er-Yb co-doped Ti O2 nanorods with ytterbium(Yb)as a sensitizer.Perovskite solar cells with a structure of FTO/c-Ti O2/Er-Yb-Ti O2/MAPb I3-x Clx/Spiro-OMe TAD/ Au were prepared,in which Er-Yb co-doped Ti O2 was used an electron transfer layer.The XPS and XRD indicated Er and Yb were successfully incorporated into Ti O2.The steady state photoluminescence of Er-Yb-Ti O2 evidenced the upconversion could convert the infrared light to visible light,so that the perovskite can absorb more photons,then the photocurrent density of solar cell increased.The ultraviolet visible absorption spectra and Tauc curve proved the band gap of Er-Yb Ti O2 becomes narrow.This is conducive to the transfer of electrons from perovskite to titanium dioxide electronic capture layer.SEM images show that the Er-Yb-Ti O2 rods than Ti O2 shorter and thicker,pores are relatively well filled by the spiro-Me OTAD for the shorter nanorod film compared with the longer nanorod films.The EIS and steady state photoluminescence of samples demonstrated carrier transmission faster in the solar cell based on Er-Yb-Ti O2.The short circuit voltage of perovskite solar cell based on Er-Yb co-doping titanium dioxide increased from 0.83 V to 0.90 V.The photocurrent density increased from 20.7 m A/cm2 to 21.83 m A/cm2,and PCE from 11.04 % to 13.41 %.