Penzo Erika, Loiudice Anna, Barnard Edward S, Borys Nicholas J, Jurow Matthew J, Lorenzon Monica, Rajzbaum Igor, Wong Edward K, Liu Yi, Schwartzberg Adam M, Cabrini Stefano, Whitelam Stephen, Buonsanti Raffaella, Weber-Bargioni Alexander
The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Institute of Chemical Sciences and Engineering of the École Polytechnique Fédérale de Lausanne, Lausanne CH 1015, Switzerland.
ACS Nano. 2020 Jun 23;14(6):6999-7007. doi: 10.1021/acsnano.0c01536. Epub 2020 Jun 2.
Förster resonant energy transfer (FRET)-mediated exciton diffusion through artificial nanoscale building block assemblies could be used as an optoelectronic design element to transport energy. However, so far, nanocrystal (NC) systems supported only diffusion lengths of 30 nm, which are too small to be useful in devices. Here, we demonstrate a FRET-mediated exciton diffusion length of 200 nm with 0.5 cm/s diffusivity through an ordered, two-dimensional assembly of cesium lead bromide perovskite nanocrystals (CsPbBr PNCs). Exciton diffusion was directly measured steady-state and time-resolved photoluminescence (PL) microscopy, with physical modeling providing deeper insight into the transport process. This exceptionally efficient exciton transport is facilitated by PNCs' high PL quantum yield, large absorption cross section, and high polarizability, together with minimal energetic and geometric disorder of the assembly. This FRET-mediated exciton diffusion length matches perovskites' optical absorption depth, thus enabling the design of device architectures with improved performances and providing insight into the high conversion efficiencies of PNC-based optoelectronic devices.
通过人工纳米级构建块组件进行的Förster共振能量转移（FRET）介导的激子扩散可作为一种光电子设计元件来传输能量。然而，到目前为止，纳米晶体（NC）系统的扩散长度仅为30纳米，这对于器件应用来说太小了。在此，我们展示了通过有序的二维溴化铯铅钙钛矿纳米晶体（CsPbBr PNCs）组件实现的FRET介导的激子扩散长度为200纳米，扩散率为0.5厘米/秒。通过稳态和时间分辨光致发光（PL）显微镜直接测量激子扩散，并通过物理建模对传输过程有更深入的了解。这种异常高效的激子传输得益于PNCs的高光致发光量子产率、大吸收截面和高极化率，以及组件最小的能量和几何无序。这种FRET介导的激子扩散长度与钙钛矿的光吸收深度相匹配，从而能够设计出性能改进的器件架构，并深入了解基于PNC的光电器件的高转换效率。
