Temperature-dependent luminescence spectra of Ruddlesden-Popper quasi-2D perovskites

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 ~1090.62 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 (77-300K) 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 (<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 K-120 K, which is attributed to an energy transfer mechanism in the multi-quantum well caused by the localization effect, until after 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.