Materials displaying electron photoemission under visible-light excitation are of great interest for applications in photochemistry, photocathodes, advanced electron beam sources and electron microscopy. We demonstrate that in manganese-doped CdSe colloidal quantum dots (CQDs), two-step Auger up-conversion enables highly efficient electron photoemission under excitation with visible-light pulses. This effect is enabled by extremely fast, subpicosecond Auger-type energy transfer from excited manganese ions to an intrinsic CQD exciton. Since the rate of this process outpaces that of intraband cooling, the high-energy ‘hot’ electron produced by the first Auger-excitation step can be efficiently promoted further into the external ‘vacuum’ state via one more manganese-to-CQD energy-transfer step. This CQD ionization pathway exploits exceptionally large uphill energy gain rates associated with the spin-exchange Auger process and leads to photoemission efficiencies of more than 3%, orders of magnitude greater than in the case of undoped CQDs. We demonstrate that using this phenomenon, we can achieve high-yield production of solvated electrons (>3% internal quantum efficiency), which makes it of considerable utility in visible-light-driven reduction photochemistry.

在可见光激发下显示电子光发射的材料在光化学、光阴极、先进电子束源和电子显微镜中的应用具有重要意义。我们证明，在锰掺杂的 CdSe 胶体量子点 (CQD) 中，两步俄歇上转换可在可见光脉冲的激发下实现高效的电子光发射。这种效应是通过从激发的锰离子到本征 CQD 激子的极快的亚皮秒俄歇式能量转移实现的。由于该过程的速率超过了带内冷却的速率，因此由第一个俄歇激发步骤产生的高能“热”电子可以通过更多的锰到 CQD 能量有效地进一步进入外部“真空”状态-转移步骤。这种 CQD 电离途径利用了与自旋交换俄歇过程相关的异常大的上坡能量增益率，并导致超过 3% 的光电发射效率，比未掺杂 CQD 的情况高几个数量级。我们证明，使用这种现象，我们可以实现溶剂化电子的高产率（>3% 的内部量子效率），这使得它在可见光驱动的还原光化学中具有相当大的用途。