Controlled Synthesis And Emission Properties Of Two-dimensional Ruddlesden-popper Perovskite Materials

Metal halide perovskite is highly appreciated in display lighting,solar cells,lasers,photodetectors and other fields because of its excellent photoelectric properties.Compared with three-dimensional perovskites,two-dimensional Ruddlesden-Popper perovskites(2D-RPPs)have some superiorities,including stability,composition tunability and diversity of photoelectronic properties.In addition,on account of the low defect density and strong quantum confinement effect of 2D-RPPs,we can foresee its broad prospect in display lighting.Nevertheless,except for some 2D-RPPs single crystals,most 2D-RPPs films show poor luminescence efficiency,which severely hinders the construction of efficient 2D-RPPs based light emitting diodes(LEDs).To address this problem,this paper focuses on the doping of2D-RPPs and the phase regulation of quasi-2D-RPPs.The main research contents are summarized as follows:Pure PEA₂PbBr₄ films and Mn²⁺doped Mn:PEA₂PbBr₄ films were successfully prepared by one-step method.The doping amount of Mn²⁺can be changed by adjusting Mn/Pb ratio.Mn²⁺doping not only results in the decrease of the interlayer spacing but also enhances the crystallinity of 2D-RPPs.The maximum bandedge and Mn²⁺emissions are hardly affected by varying Mn²⁺doping amount due to limited doping concentration,and bandedge emission is dominant in these Mn:PEA₂PbBr₄ films.In the mean time,the rigidity of the structure is improved and electron-phonon coupling is weakened after Mn²⁺doping.Thanks to improved crystallinity and structural rigidity,the PL quantum yield(PLQY)of Mn:PEA₂PbBr₄ films is promoted compared with PEA₂PbBr₄ films.The PLQY of PEA₂PbBr₄films is about 8.58%,and the PLQY of Mn:PEA₂PbBr₄ films increases with the rise of the doping amount of Mn²⁺.The PLQY of Mn:PEA₂PbBr₄ films with higher doping amount can be up to 42%,which is nearly 4 times higher than that of PEA₂PbBr₄ films.The phase regulation of quasi-2D-RPPs PEA₂Cs_n-1Pb_nBr_3n+1 was carried out by changing the solvent evaporation temperature,anti-solvent type,organic cation dosage and other experimental conditions.We noticed that the quasi-2D-RPPs films with mainly low-n phase can be prepared by increasing the proportion of PEABr.In this way,blue emission of the quasi-2D-RPPs films at 440 nm and 470 nm were achieved.The effect of temperature on the exciton emission in different phase was explored.It was found that the heat quenching for exciton emission is obvious in all n phases,and the heat quenching in high-n phase is more significant.Therefore,there are more non-radiative energy loss processes in the high-n phase of the quasi-2D-RPPs prepared by this method.