Designing next-generation light-harvesting devices requires a detailed understanding of the transport of photoexcited charge carriers. The record-breaking efficiencies of metal halide perovskite solar cells have been linked to effective charge-carrier diffusion, yet the exact nature of charge-carrier out-of-plane transport remains notoriously difficult to explain. The characteristic spatial inhomogeneity of perovskite films with nanograins and crystallographic disorder calls for the simultaneous and hitherto elusive in situ resolution of the chemical composition, the structural phase and the ultrafast dynamics of the local out-of-plane transport. Here we simultaneously probe the intrinsic out-of-plane charge-carrier diffusion and the nanoscale morphology by pushing depth-sensitive terahertz near-field nanospectroscopy to extreme subcycle timescales. In films of the organic–inorganic metal halide perovskite FA_0.83Cs_0.17Pb(I_1−xCl_x)₃ (where FA is formamidinium), domains of the cubic α-phase are clearly distinguished from the trigonal δ-phase and PbI₂ nano-islands. By analysing deep-subcycle time shifts of the scattered terahertz waveform after photoexcitation, we access the vertical charge-carrier dynamics within single grains. At all of the measured locations, despite topographic irregularities, diffusion is surprisingly homogeneous on the 100 nm scale, although it varies between mesoscopic regions. Linking in situ carrier transport with nanoscale morphology and chemical composition could introduce a paradigm shift for the analysis and optimization of next-generation optoelectronics that are based on nanocrystalline materials.

设计下一代光捕获设备需要详细了解光激发电荷载流子的传输。金属卤化物钙钛矿太阳能电池破纪录的效率与有效的载流子扩散有关，但载流子面外传输的确切性质仍然很难解释。具有纳米晶粒和晶体无序的钙钛矿薄膜的空间不均匀性特征要求同时且迄今为止难以实现的化学成分、结构相和局部面外传输的超快动力学的原位分辨率。在这里，我们通过将深度敏感的太赫兹近场纳米光谱推向极端的子周期时间尺度，同时探测固有的面外电荷载流子扩散和纳米级形态。在有机-无机金属卤化物钙钛矿 FA _0.83 Cs _0.17 Pb(I _{1− x} Cl _x ) ₃ （其中 FA 为甲脒）薄膜中，立方 α 相的区域与三角 δ 相和 PbI ₂明显不同纳米岛。通过分析光激发后散射太赫兹波形的深子周期时移，我们获得了单晶粒内的垂直载流子动力学。在所有测量的位置，尽管地形不规则，但扩散在 100 nm 尺度上令人惊讶地均匀，尽管它在介观区域之间有所不同。将原位载流子传输与纳米级形态和化学成分联系起来可以为基于纳米晶体材料的下一代光电子学的分析和优化带来范式转变。