Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL, 60439, USA.
Department of Chemistry and Biochemistry, Northern Illinois University, 1425 W. Lincoln Hwy., DeKalb, IL, 60115, USA.
Nat Commun. 2019 Jan 29;10(1):482. doi: 10.1038/s41467-019-08363-2.
Organic-inorganic hybrid perovskites such as methylammonium lead iodide (CHNHPbI) are game-changing semiconductors for solar cells and light-emitting devices owing to their defect tolerance and exceptionally long carrier lifetimes and diffusion lengths. Determining whether the dynamically disordered organic cations with large dipole moment benefit the optoelectronic properties of CHNHPbI has been an outstanding challenge. Herein, via transient absorption measurements employing an infrared pump pulse tuned to a methylammonium vibration, we observe slow, nanosecond-long thermal dissipation from the selectively excited organic mode to the inorganic sublattice. The resulting transient electronic signatures, during the period of thermal-nonequilibrium when the induced thermal motions are mostly concentrated on the organic sublattice, reveal that the induced atomic motions of the organic cations do not alter the absorption or the photoluminescence response of CHNHPbI, beyond thermal effects. Our results suggest that the attractive optoelectronic properties of CHNHPbI mainly derive from the inorganic lead-halide framework.
有机-无机杂化钙钛矿，如碘化甲基铵（CHNHPbI），因其对缺陷的容忍度和超长的载流子寿命和扩散长度，是改变游戏规则的太阳能电池和发光器件半导体。确定具有大偶极矩的动态无序有机阳离子是否有利于 CHNHPbI 的光电性能，一直是一个突出的挑战。在此，通过瞬态吸收测量，利用调谐到甲基铵振动的红外泵浦脉冲，我们观察到从选择性激发的有机模式到无机亚晶格的缓慢、纳秒级长的热耗散。在热不平衡期间的瞬态电子特征，当诱导的热运动主要集中在有机亚晶格上时，表明有机阳离子的诱导原子运动除了热效应之外，并没有改变 CHNHPbI 的吸收或光致发光响应。我们的结果表明，CHNHPbI 的吸引人的光电性能主要源于无机铅卤化物框架。
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