Abstract：The quasi-2D Ruddlesden-Popper（R-P） halide perovskite has been widely used in solar cells， light-emitting diodes， lasers and other optoelectronic devices due to its excellent photoelectric properties. However， the exciton-phonon interaction， which seriously affects the relaxation and transport characteristics of carriers， has not been fully revealed. Compared with the widely studied 3D perovskite structure， quasi 2D perovskite has a naturally formed quantum well structure with greater exciton binding energy and more obvious exciton effect. However， the exciton-phonon interaction of quasi 2D perovskite is still less studied. Therefore， a quasi-2D R-P perovskite film （PEA）2Csn-1PbnBr3n+1 has been prepared by solution method with a gain coefficient of ~1 090.62 cm-1 and an amplified spontaneous emission of low threshold （~12.48 μJ/cm2）. Based on this， we studied the luminescence properties of （PEA）2Csn-1PbnBr3n+1 film with temperature variation by using variable temperature fluorescence spectroscopy（77-300 K） and transient absorption spectroscopy， in order to elaborate the influence of exciton-phonon interaction on its luminescence properties. It was found that in the low temperature domain （77-120 K）， The bandgap change caused by exciton-phonon interaction is relatively weak， and the lattice thermal expansion is dominant. With the increase of temperature， the exciton-phonon interaction has a great influence on the change of bandgap. On the other hand， the exciton-phonon interaction causes the line width of the luminescence spectrum to widen， but we observed the abnormal line width narrowing in the temperature range of 77-120 K， which is attributed to an energy transfer mechanism in the multi-quantum well caused by the localization effect. Until above 120 K， the line widening caused by the exciton-phonon interaction is sufficient to reverse this trend. In this paper， the exciton-phonon interaction of quasi 2D perovskite is of guiding value for improving the optical properties and luminescence applications of quasi 2D perovskite.
Abstract：Metal halide perovskite solar cells have been able to achieve certified photovoltaic conversion efficiencies of 25.7%， approaching the maximum certified efficiency of 26.7% for crystalline silicon solar cells. It is well known that the component engineering of the crystal structure of ABX3 perovskite materials plays a key role in achieving efficient and stable devices， especially the component engineering of the X-site halide anion， which has received much attention from researchers in recent years. Recently， researchers have carried out several studies on the introduction of pseudo-halide anions as doping components， precursor additives， thin film post-treatment materials， charge transport materials， interfacial passivation， and modifiers for perovskite crystals， and the results demonstrate that pseudo-halide ion modification is an important strategy to improve device efficiency and stability. This review provides a detailed comparison and summary of the various types of pseudo-halide ions currently available for use in perovskite solar cells and provides an in-depth summary of the mechanisms and nature of their effects on perovskite crystal film morphology， photovoltaic properties， carrier migration properties， and device photovoltaic characteristics and stability. At the same time， this paper also provides an outlook and analysis of the currently unexplored pseudo-halide ions to effectively contribute to the enhancement of the photovoltaic properties of perovskite solar cells in future research.
Keywords：Pseudo-halide ions;Component engineering;perovskite solar cells;Defect passivation
Abstract：A series of Na3Sc2（1-x）（BO3）3∶xTb3+ phosphors were prepared by high-temperature solid-state method. We investigated the crystal structure， surface morphology， elemental composition， and luminescence properties through X-Ray diffraction（XRD）， scanning electron microscope（SEM）， photoluminescence（PL） spectrum， vacuum ultra violet（VUV） fluorescence spectrum， high temperature fluorescence spectrum and fluorescence decay lifetime. The results indicate that the Na3Sc2（1-x）（BO3）3∶xTb3+ phosphors can emit bright green light（~553 nm） under 242 nm UV excitation. The PL intensity of Na3Sc2（1-x）（BO3）3∶xTb3+ reaches the maximum when x=0.025. Vacuum UV fluorescence spectra show that these phosphors could be also excited by 187 nm deep ultraviolet light. And when the ambient temperature starts to rise from room temperature， the Na3Sc1.95（BO3）3∶0.025Tb3+ exhibits an anti-thermal-quenching phenomenon. When the temperature reaches 473 K， the luminescence intensity of the sample reached the highest， 109.3% of that at room temperature （298 K）. The strong emission and high thermal stability of these new green phosphors indicate the certain potential application in lighting and display fields.
Keywords：phosphor;Tb3+ doped;anti-thermal-quenching;lighting and display
Abstract：A series of Tb3+/Eu3+ single-doped， co-doped Ca0.3Sr0.7（MoO4）2 phosphors with a tunable color were synthesized by the conventional co-precipitation method. The crystal structure and morphology of phosphors were characterized by X-ray diffraction and field emission scanning electron microscopy. The results showed that a small amount of Tb3+ and Eu3+ doped into the sample has no effect on the crystal structure of the sample， and there are no impurity peaks. We researched the luminescence properties and temperature sensing properties. The energy transfer from Tb3+ to Eu3+ in Sr0.3Ca0.7（MoO4）2∶Tb3+，Eu3+ phosphors was confirmed in the luminescence characteristics of the samples. The temperature-dependent emission spectra suggested that the as-prepared samples possessed good thermal stability. The absolute sensitivity and relative sensitivity of samples were calculated， and the maximum relativity sensitivity of Sr0.3Ca0.625（MoO4）2∶0.05Tb3+，0.025 Eu3+ sample was 0.861%·K-1 at 514 K. In addition， under near-ultraviolet light by adjusting the doping concentration of Eu3+， the Sr0.3Ca0.7（MoO4）2∶Tb3+，Eu3+ phosphors realized tunability of emission color.
Keywords：Photoluminescence properties;energy transfer;phosphors;Optical temperature sensing