Ruddlesden-Popper型准二维钙钛矿温度依赖发光光谱研究

Temperature-dependent Luminescence Spectra of Ruddlesden-Popper Quasi-2D Perovskites

准二维Ruddlesden-Popper(R-P)卤化物钙钛矿具有优越的光电特性,在太阳能电池、发光二极管、激光器等光电器件中受到广泛关注,但严重影响载流子的弛豫和传输特性的激子-声子之间的相互作用还未得到充分揭示。与广泛研究的三维钙钛矿结构相比,准二维钙钛矿存在天然形成的量子阱结构,具有更大的激子结合能,激子效应更加明显,但对其激子-声子相互作用的研究仍然较少。因此,我们通过溶液法制备了准二维R-P型钙钛矿(PEA)_(2)Cs_(n-1)Pb_(n)Br_(3n+1)薄膜,其增益系数高达~1090.62 cm^(-1),获得了低阈值(~12.48μJ/cm^(2))的放大自发辐射。基于此,我们通过变温荧光光谱(77~300 K)和瞬态吸收光谱技术研究了(PEA)_(2)Cs_(n-1)Pb_(n)Br_(3n+1)薄膜随温度变化的发光特性,以阐述其内部的激子-声子相互作用对其发光性能的影响。发现在低温域内(77~120 K),由激子-声子相互作用引起的带隙变化相对较弱,晶格热膨胀占主导地位;随着温度升高,激子-声子相互作用对带隙变化产生较大影响。另一方面,激子-声子相互作用会促使发光光谱线宽加宽,但我们在77~120 K的温度范围内观察到了反常线宽变窄现象,这归因于由局域化效应引起的多量子阱中的能量转移机制;直到120 K之后,激子-声子相互作用引起的谱线加宽才足以逆转这一趋势。本文对准二维钙钛矿的激子-声子相互作用的研究对于提高准二维钙钛矿光学性能及其发光应用具有指导价值。

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)_(2)Cs_(n-1)Pb_(n)Br_(3n+1) has been prepared by solution method with a gain coefficient of~1090.62 cm^(-1) and an amplified spontaneous emission of low threshold(~12.48μJ/cm^(2)).Based on this,we studied the luminescence properties of(PEA)_(2)Cs_(n-1)Pb_(n)Br_(3n+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.