Preparation And Properties On Electron Transporting Layer For Perovskite Solar Cells

The material and morphology of electron transport layers has a significant impact on the device architecture and electronic processes of mesoscopic perovskite solar cells（PSCs）.In this thesis,the preparation and characterization of two electron transport layers,CeO₂:Eu³⁺-TiO₂ and TiO₂-NR arrays,and their effects on the perovskite solar cell（PSCs）of photoelectric performance and stability under UV irradiation were studied.The details are as follows:（1）Enhanced photovoltaic performance and light stability of perovskite solar cells（PSCs）was achieved by applying down conversion（DC）CeO₂:Eu³⁺-TiO₂ composite electrodes and the related mechanism are reported.High-yield CeO₂:Eu³⁺nanocrystals were synthesized by a simple hydrothermal method with combinational use of trisodium phosphate dodecahydrate and sodium hydroxide.Uniform and efficient CeO₂:Eu³⁺nanophosphors were prepared at an optimized reaction time.The optimal CeO₂:Eu³⁺nanophosphors were 70 nm in size,with octahedral and mirror-like facets that provided excellent DC luminescence.The CeO₂:Eu³⁺nanophosphors grown at the optimal conditions were incorporated into mesoporous TiO₂ layers of PSC devices.The PSC device with the CeO₂:Eu³⁺composite electrode exhibited an energy conversion efficiency of 10.8%,which improved efficiency by6.8%relative to the referenced one with undoped CeO₂ nanocrystals.PSC devices added with undoped and doped CeO₂ nanocrystals exhibited significantly better stability toward UV light compared to the bare TiO₂ based PSC cell.（2）Ultrathin MgO is coated on the surface of compact TiO₂（c-TiO₂）.The MgO coated c-TiO₂ is first used as seeds to hydrothermally grow one-dimensional（1D）TiO₂ nanorod（NR）arrays for PSC devices.Rutile nanorod arrays are fabricated via a facile solvothermal method using tetrabutyl titanate（TBT）as the Ti precursor.The microstructures and morphologies,including nanorod diameter,length,and areal density,of the TiO₂ NR arrays are varied by controlling the concentration of TBT from 0.3 M to 0.7 M.Furthermore,the profound effects of the MgO modification and titania nanorod morphology on the pore-filling of perovskite CH₃NH₃PbI₃,charge separation and recombination at the perovskite/titania nanorod interface are investigated.Our results reveal that the Ti precursor concentration strongly affects the open-circuit voltage(V_oc),short-circuit current density(J_sc),and fill factor（FF）of the 1D TiO₂ NR array-based device.Under optimized conditions with MgO coating and at 0.4 M TBT,our champion cell with 1D TiO₂ NRs demonstrates a power conversion efficiency（PCE）of 17.03%with J_sc=22.01 mA cm^-2,V_oc=1.06 V,and FF=0.73.Under the same fabrication conditions,MgO modification enhances the average PCE to 16.24%for the PSCs with the MgO coating from 13.38%for the PSCs without the MgO coating.The devices show an approximately 18%improvement in performance,which mainly results from the open-circuit voltage and fill factor enhancements.Moreover,advantageously,the MgO modification is found to reduce the current density-voltage（J-V）hysteresis with respect to the scan direction and improve the UV stability of the non-encapsulated cells.