Study On Modification And Photovoltaic Devices Of Lead Halide Perovskite

Due to super-long carrier diffusion length,high absorption coefficient,tunable bandgap,ionic property of crystal,etc,lead-based halide perovskite has been a research hotspot of photovoltaic materials in recent years.One limitation of perovskite photovoltaic devices is the defects at the perovskite grain boundaries and surfaces,which are always electronic trap states to induce the nonradiative recombination of photogenerated carriers and the easiest degradation sites due to their high activity and ionic diffusivity.On this basis,this work mainly focuses on the modification of lead-based halide perovskite and improves the stability and power conversion efficiency（PCE）of its carbon-based fully-printable photovoltaic device via Mn ion doping and hydrophobic ligand coordination.Firstly,the first step is to prepare the carbon-based fully printable mesoscopic scaffold（CPMS）,which includes TiO₂/ZrO₂/C triple-layers and is screen-printed onto a FTO glass substrate.The TiO₂layer and carbon layer of CPMS are equivalent to the photoanode and electrode of dye-sensitized solar cells,respectively.The insulated ZrO₂ is used as skeleton to support the entire structure.Secondly,we proposed a halide exchange-driven cation exchange（HEDCE）reaction for the synthesis of Mn doped CsPbCl₃（Mn:CsPbCl₃）perovskite nanocrystals（NCs）.The key point of HEDCE is the simultaneous substitution of cation and anion of impurity molecules of MnCl₂ and PbBr₆^4-sub-lattice structure of perovskite at the same time and site.The photoluminescence quantum yield（PLQY）of obtained Mn:CsPbCl₃ NCs is 56%.Thirdly,we integrated self-powered ultraviolet photodetectors（PDs）via filling Mn:CsPbCl₃NCs in CPMS.By doping Mn in CsPbCl₃ NCs,the fast exciton-to-Mn energy transfer（^ps）and slow radiative recombination of Mn from ⁴T₁ to ⁶A₁（^μs）can be built in the interface of NCs and TiO₂,which can work as electron storage center to further suppress the charge recombination induced by defects.The photocurrent of PDs has nearly twice enhancement from 0.08 mA cm^-2 to0.14 mA cm^-2 and a high responsivity of 7.3 mA W^-1 is achieved at 340 nm.Meanwhile,the photocurrent is stable due to surface ligand protection of NCs.Finally,a post-healing method of defects at the perovskite grain boundaries and surfaces was developed via hydrophobic ligand coordination for carbon-based,fully printable mesoscopic solar cells.The perovskite is organic-inorganic MAPbI₃.The defects are post-healed via O atoms of trioctylphosphine oxide（TOPO）coordinating to halide-deficient sites,leading to an enhancement of PCE from 11.0%to 12.8%.Moreover,due to the hydrophobicity of three long chain alkyls in TOPO,the humidity stability of device has been improved simultaneously.