| Solar energy comes from solar radiation,which is inexhaustible compared with human civilization.It is an energy source without any environmental pollution and an effective way to help mankind alleviate energy problems.Solar cells are one of the main methods of using solar energy.Perovskite solar cells are one of the most concerned solar cells in recent years.Perovskite solar cells have been able to rise rapidly because of the dye sensitized solar cell research results.Dye-sensitized solar cells use dyes,the device preparation cost is high,but the final conversion efficiency is not satisfactory,and perovskite material optical performance is not inferior to the dyes,and the cost is lower,the manufacturing method is simple.The electron transport layer in perovskite solar cells is usually made of wideband gap material,and ZnO has a wide band gap of 3.37 e V.In the preparation of perovskite solar cells,ZnO as the electron transport layer will make the solar cells have a large space potential,and the improvement of space potential is more conducive to the transfer of electron-hole pair to both ends of the battery.ZnO also has a much larger exciton binding energy（60 me V）than the thermal ionization energy（25 me V）at room temperature,so excitons can be stable at room temperature.The highly vertical ordered ZnO nanowire arrays can increase the scattering of photons,thereby increasing the absorption of light by solar cells,greatly reducing the transmission path of charges in the electron transport layer,and facilitating the transport and separation of electron-hole pairs.In this paper,one-dimensional ZnO nanowire arrays are used as an electron transport layer in perovskite solar cells.The main research contents are as follows:（1）ZnO nanowire arrays were synthesized by microwave-assisted hydrothermal method,and the effects of different conditions of annealing on the structure and defects of the ZnO nanowire arrays were studied.The prepared samples were characterized by field emission scanning electron microscope,X-ray diffraction and photoluminescence spectra.The results show that the ZnO nanowire arrays grow vertically with the F-doped Tin Oxide conductive substrate,and the sample morphology remain unchanged after different annealing times.The X-ray diffraction pattern shows that the samples crystallized best when annealed at 400℃for 2 h.The photoluminescence spectra shows that the emission intensity of near-band edge increased with the increase of annealing time,but the emission intensity related to defects decreased with the decrease of annealing time.（2）Based on the ZnO nanowire arrays that have been prepared,the application of ZnO nanowire arrays as electron transport layer in perovskite solar cells under different conditions（spinning times of ZnO nanowire seed layers,ZnO nanowire growth time,Ga ion doping concentration,and the growth position of ZnO nanowires in the beaker）is studied.The X-ray diffraction image shows that the prepared ZnO nanowires are hexagonal wurtzite structure.Scanning electron microscope result shows that the length of ZnO nanowires increased linearly with growth time.The current density-voltage characteristic curve shows the performance of perovskite solar cells prepared under different conditions.The conclusion is:perovskite solar cells with power conversion efficiency of 3.61%,open-circuit voltage of 0.655 V,short-circuit current density of 11.64 m A/cm2 and filling factor of47.34%could be prepared by spinning the ZnO seed layer for five times and growing the ZnO nanowires doped with 7%Ga ions（i.e.,the molar ratio of Ga（NO3）3·x H2O and Zn（CH3COO）2·2H2O was 1:13.29）at the bottom of the beaker for 10 min.（3）A layer of polytetrafluoroethylene was deposited on the ZnO nanowire array by vapor deposition method.The ZnO nanowire arrays with PTFE low surface energy coating have high contact Angle and very low water rolling Angle.The modified ZnO nanowire arrays largely satisfy the conditions of high surface roughness and low surface energy of superhydrophobic,the contact angle of the formed superhydrophobic ZnO nanowires changed from 5°to 160°.The superhydrophobic layer deposited on the ZnO nanowires acts as a passivation,weakens the proton transfer reaction at the ZnO/CH3NH3Pb I3 interface,reduces the decomposition of the perovskite film,and effectively improves the stability of the solar cell. |
