Department of Chemistry and ‡Argonne-Northwestern Solar Energy Research Center, Northwestern University , Evanston, Illinois 60208, United States.
Nano Lett. 2018 Feb 14;18(2):1044-1048. doi: 10.1021/acs.nanolett.7b04520. Epub 2018 Jan 11.
Understanding carrier relaxation in lead halide perovskites at the nanoscale is critical for advancing their device physics. Here, we directly image carrier cooling in polycrystalline CHNHPbI films with nanometer spatial resolution. We observe that upon photon absorption, highly energetic carriers rapidly thermalize with the lattice at different rates across the film. The initial carrier temperatures vary by many multiples of the lattice temperature across hundreds of nanometers, a factor that cannot be accounted for by excess photon energy above the bandgap alone or in variations of the initial carrier density. Electron microscopy suggests that morphology plays a critical role in determining the initial carrier temperature and that carriers in small crystal domains decay slower than those in large crystal domains. Our results demonstrate that local disorder dominates the observed carrier behavior, highlighting the importance of making local rather than averaged measurements in these materials.
理解纳米尺度下卤铅钙钛矿中的载流子弛豫对于推进其器件物理至关重要。在这里，我们直接以纳米空间分辨率成像多晶 CHNHPbI 薄膜中的载流子冷却。我们观察到，在吸收光子后，高能载流子以不同的速率在整个薄膜中迅速与晶格热化。初始载流子温度在数百纳米范围内变化了晶格温度的许多倍数，这一因素不能仅用带隙以上的过量光子能量或初始载流子密度的变化来解释。电子显微镜表明，形态在确定初始载流子温度方面起着关键作用，并且小晶畴中的载流子衰减速度比大晶畴中的载流子慢。我们的结果表明，局部无序主导了观察到的载流子行为，突出了在这些材料中进行局部而不是平均测量的重要性。
