The outstanding optoelectronic performance of lead halide perovskites lies in their exceptional carrier diffusion properties. As the perovskite material dimensionality is reduced to exploit the quantum confinement effects, the disruption to the perovskite lattice, often with insulating organic ligands, raises new questions on the charge diffusion properties. Herein, we report direct imaging of >1 μm exciton diffusion lengths in CH₃NH₃PbBr₃ perovskite nanocrystal (PNC) films. Surprisingly, the resulting exciton mobilities in these PNC films can reach 10 ± 2 cm² V⁻¹ s⁻¹, which is counterintuitively several times higher than the carrier mobility in 3D perovskite films. We show that this ultralong exciton diffusion originates from both efficient inter-NC exciton hopping (via Förster energy transfer) and the photon recycling process with a smaller yet significant contribution. Importantly, our study not only sheds new light on the highly debated origins of the excellent exciton diffusion in PNC films but also highlights the potential of PNCs for optoelectronic applications.

卤化钙钛矿的出色光电性能在于其出色的载流子扩散性能。由于降低了钙钛矿材料的尺寸以利用量子约束效应，通常利用绝缘的有机配体对钙钛矿晶格的破坏提出了关于电荷扩散性质的新问​​题。本文中，我们报道了CH ₃ NH ₃ PbBr ₃钙钛矿纳米晶体（PNC）膜中> 1μm激子扩散长度的直接成像。令人惊讶地，这些PNC膜中产生的激子迁移率可以达到10±2 cm ²  V ^-1  s ^-1直觉上比3D钙钛矿薄膜中的载流子迁移率高出几倍。我们表明，这种超长的激子扩散源于有效的NC间激子跳跃（通过Förster能量转移）和光子回收过程，而两者的贡献却较小。重要的是，我们的研究不仅为在PNC膜中出色的激子扩散引起了广泛争议的起源提供了新的观点，而且还强调了PNC在光电应用中的潜力。