Unravelling ultrafast charge recombination and transport dynamics in hybrid perovskites.

混合钙钛矿的光致发光（PL）效率对于多晶半导体来说是非常高的。我是第一个报告这一点的人，以垂直腔结构中的激光为例，我继续证明强辐射发射是钙钛矿在太阳能电池（报告的功率转换效率>20%）和发光二极管（我们实验室中的外部量子效率现在>18%）中表现出色的关键。未来的收益将需要了解和控制的非辐射损失在散装和电极。我们最初的结果表明，PL来自自由电荷的复合，但现在需要新的物理概念来理解这个过程如何能够提供如此出乎意料的高辐射产额，同时保持低的非辐射损失。与典型的高发射III-V量子阱系统相比，所报道的长寿命带来了更长的长度尺度。材料的不均匀性是一个核心参数，因为电子和空穴在复合之前会进行大量采样，这可能会改变它们的物理特性和相互作用。由于在短时间尺度上记录本地信号的挑战，最先进的PL研究记录了时间分辨率约为100 ps的空间平均信息。然而，我们已经发现载流子相互作用已经在亚皮秒时间，这可能会影响更长时间尺度的复合。在这些快速的时间尺度上探测PL，现在将深入了解一个新的物理机制。为此，我们的新技术将联合收割机超快光谱分辨PL与空间显微镜相结合，这将使时间和空间分辨率的最新技术水平提高一个数量级，达到亚皮秒和亚微米的水平。我们将使用这种新的设置来研究载流子在由本征性质（由载流子-载流子相互作用控制）主导的制度中的复合和扩散，这将使我们能够解开非本征效应（由材料性质（如捕获）控制）。同时，局部探测将解决材料形态对重组和定位的影响。我们的研究将为混合钙钛矿的光物理学提供前所未有的见解，这些混合钙钛矿在以前无法进入，但高度相关的时间和空间制度中。我们的研究结果将建立一个新的物理和材料来源的图片，使异常有效的辐射复合在混合钙钛矿，这将是至关重要的解锁增益器件性能。

The photoluminescence (PL) efficiency of the hybrid perovskites are exceptionally high for a poly-crystalline semiconductor. I was the first to report this, as exemplified by lasing in vertical cavity structure, and I have gone on to demonstrate that the strong radiative emission is key for the perovskites' exceptional performance in solar cells (power conversion efficiency >20% reported) and light-emitting diodes (external quantum efficiency now >18% in our labs). Future gains will require understanding and control of the non-radiative losses both in the bulk and at the electrodes. Our initial results showed that the PL arises from the recombination of free charges, but new physical concepts are now required to understand how this process can give such unexpectedly high radiative yields, while maintaining low non-radiative losses. The reported long lifetimes bring much longer length scales into play, compared to typical high-emission III-V quantum-well systems. Material inhomogeneity is a central parameter, since electrons and holes sample large volumes before recombination, which potentially changes their physical properties and interactions. State-of-the art PL studies recorded spatially-averaged information with time-resolution around 100 ps, due to challenges in recording local signals on short timescales. Yet, we have found carrier interactions already on sub-picosecond times, which are likely to affect recombination at longer time scales. Probing PL at these fast timescales, will now give insights into a new physical regime. For this, our new technique will combine ultrafast spectrally-resolved PL with spatial microscopy, which will advance the state-of-the art in temporal and spatial resolution by an order of magnitude to sub-picosecond and sub-micrometre regimes. We will use this new setup to study carrier recombination and diffusion in a regime dominated by intrinsic properties (controlled by the carrier-carrier interactions), which will allow us to untangle extrinsic effects (controlled by material properties such as trapping). Simultaneously, local probing will resolve the impact of material morphology on recombination and localisation. Our study will give unprecedented insights into the photo-physics of hybrid perovskites in previously inaccessible, yet highly relevant, temporal and spatial regimes. Our findings will establish a new picture on the physical and material origin enabling the exceptionally-efficient radiative recombination in hybrid perovskites, which will be crucial for unlocking gains in device performance.