Research On Fabrication Of Flexible And Large-area Perovskite Light-emitting Diodes

With the advent of big data and cloud computing,information interaction has undergone dramatic changes.The Internet of Thing is pushing people to pursue high-quality life and advanced emissive materials.Apart from the high efficiency and wide gamut,low cost and resilient features also make perovskite materials feasible for the fabrication of flexible perovskite light-emitting diodes（Pe LEDs）.They can potentially provide diverse applications,such as wearable electronics,foldable displays,and bio-integrated devices.In addition,the characteristics of solution preparation,eco-friendly and compatible with roll-to-roll production endow perovskite with commercial applications.Nevertheless,in contrast to the extensive efforts to improve the overall performance and understand the photophysical mechanism of the Pe LEDs,flexible Pe LEDs and large-area Pe LEDs have received comparatively less attention.On the one hand,the current studies on flexible Pe LEDs mainly focus on the modulation of interfacial contacts between charge transport layers and perovskite emitters,and the use of flexible electrodes or substrates.The intrinsic flexibility of active perovskite emitters has been rarely investigated,making it intractable to fabricate high-performance flexible Pe LEDs.On the other hand,the external quantum efficiency（EQE）of blade-coated and inkjet-printed large-area Pe LEDs still lags behind the spin-coated ones.The modulation of the crystallization kinetics is vital to realize high-efficiency large-area Pe LEDs.Based on the above analysis,this thesis mainly focuses on improving the efficiency of flexible Pe LEDs by constructing a flexible silica network and fabricating high-performance large-area Pe LEDs via modulation of crystallization process of perovskite films.The specific research content of this paper is as follows:1.Firstly,we found that silane molecules could effectively suppress the nonradiative recombination defects in the perovskite emitters by passivating the uncoordinated Pb²⁺ions.The trifluoropropyl groups could also effectively improve the hydrophobicity of perovskite films.Finally,we fabricated highly efficient green Pe LEDs with a maximum EQE of 19.2%,as well as excellent environmental stability.2.We found that abundant hydrogen bonds between hydroxyl groups and halogen ions endow perovskite film with superior flexibility without sacrificing optoelectronic properties.Density functional theory（DFT）simulation indicated that the trifluoropropyl groups could be anchored on the surface of perovskite,thereby passivating the halide vacancies at grain boundaries.The synergistic influence of the hydrogen bonding and the interaction between trifluoropropyl groups and perovskite contributed to insignificant optoelectrical performance degradation and outstanding self-healing ability.In this way,efficient flexible Pe LEDs with a maximum EQE of 16.2%could be achieved,which showed a less noticeable efficiency degradation even after 1000 bending cycles.3.Finally,to fabricate high-efficiency large-area Pe LEDs,we supposed that inserting a Li F insulating layer could endow perovskite with good hydrophilicity.In addition,the introduction of sulfurous acid could regulate the crystallization kinetics of perovskites,avoiding the formation of low-dimensional phases.The bifunctional molecule can passivate the deep energy level defects in perovskites and improve the photoluminescence quantum yield（PLQY）of perovskite thin films.In the end,we achieved a maximum EQE of 20.9%based on a large-area device of 2500 mm².