Research On The Solar Cells And Light-emitting Solar Cells Based On All-inorganic Cesium Lead Halide Perovskite

Perovskite is one of the newfashioned optoelectronic materials attracting much attention at present.High-efficiency organic-inorganic perovskite solar cells have thermal instability due to organic components,while all-inorganic perovskites are more stable at high temperature.In this paper,CsPbIBr₂ solar cells and CsPbBr₃ quantum dot light-emitting solar cells are taken as the research objects,focusing on the improvement of device efficiency and stability.The morphology,crystal structure,carrier transport and recombination of inorganic perovskite films were optimized by additive engineering,interface engineering and ligand post-treatment,so as to improve device efficiency and long-term stability.The main results are as follows:（1）The properties of CsPbIBr₂ films and solar cells were optimized by Gua SCN additive engineering.Guanidine thiocyanate（Gua SCN）was used as an additive and added into the precursor solution of CsPbIBr₂.The obtained perovskite films have a compact and smooth surface with few grain boundaries,and the（100）crystal planes perpendicular to the substrate are the dominant growth orientation,which is conducive to carrier transport,promote charge transfer and inhibite the carrier recombination.In addition,Gua SCN escapes from the perovskite film after annealing at 280°C,maintaining the pure perovskite component and not introducing impurities into the perovskite film to bring additional defects.When the molar ratio of Gua SCN to perovskite is 3%,the photoelectric conversion efficiency（PCE）increases from 8.86%to 10.90%,and the device has high reproducibility,low hysteresis and excellent long-term stability.The unencapsulated device retains 95%of its initial PCE after 600 h storaged in air.（2）The performance of CsPbIBr₂ solar cells were improved by interfacial layer of nanofibrillar conjugated polymer.The conjugated polymer was used as the interface layer between the CsPbIBr₂ perovskite layer and the Spiro-OMe TAD hole transport layer.Owing to the lamellar stacking and theπ-πstacking of the conjugated polymer backbone,the polymer film shows nanofibrillar crystals.The strong electron-withdrawing group interacts with the uncoordinated Pb²⁺and halogen vacancy of perovskite,which passivates the surface defects of perovskite,optimizes the energy level structure of the device,and accelerates the hole transport and extraction by upward bending of the band edge.The optimal concentration of conjugated polymer is 0.5 mg/m L,and 11.05%high PCE is obtained,while the control device without conjugated polymer interfacial layer is only 8.92%PCE.Meanwhile,the conjugated polymer interface layer significantly increases the hydrophobicity of the perovskite film and improves the long-term stability of the device.The unencapsulated device based on 0.5 CP still maintains 91%of the initial efficiency after nearly 900 h in air.（3）The performance of CsPbBr₃ quantum dot light-emitting solar cells was improved by post-treating CsPbBr₃ quantum dot films based on aromatic carboxylic acid ligand.The long-chain insulating ligands on the surface of CsPbBr₃ quantum dots hinder the charge transfer between quantum dots.The aromatic carboxylic acid-benzoic acid（BA）was dissolved in methyl acetate for the post-treatment of CsPbBr₃ quantum dot films to further exchange the long-chain ligands.The surface morphology of CsPbBr₃ quantum dot film after BA ligand treatment is optimized.The surface becomes smoother.Light absorption of the quantum dot films and charge transfer between quantum dots are enhanced.At the same time,the surface defects of quantum dots are effectively passivated,thus the non-radiative recombination is reduced.The device based on BA ligand post-treatment achieves 5.46%PCE,which is the highest efficiency of CsPbBr₃ quantum dot solar cells at present.The device can also emit bright green light at a voltage of 4.4 V,with a maximum brightness of 584 cd/m²,and a dual-function CsPbBr₃ quantum dot light-emitting solar cell is obtained.