Two-dimensional (2D) semiconductors have attracted intense interest for their unique photophysical properties, including large exciton binding energies and strong gate tunability, which arise from their reduced dimensionality^1,2,3,4,5. Despite considerable efforts, a disconnect persists between the fundamental photophysics in pristine 2D semiconductors and the practical device performances, which are often plagued by many extrinsic factors, including chemical disorder at the semiconductor–contact interface. Here, by using van der Waals contacts with minimal interfacial disorder, we suppress contact-induced Shockley–Read–Hall recombination and realize nearly intrinsic photophysics-dictated device performance in 2D semiconductor diodes. Using an electrostatic field in a split-gate geometry to independently modulate electron and hole doping in tungsten diselenide diodes, we discover an unusual peak in the short-circuit photocurrent at low charge densities. Time-resolved photoluminescence reveals a substantial decrease of the exciton lifetime from around 800 picoseconds in the charge-neutral regime to around 50 picoseconds at high doping densities owing to increased exciton–charge Auger recombination. Taken together, we show that an exciton-diffusion-limited model well explains the charge-density-dependent short-circuit photocurrent, a result further confirmed by scanning photocurrent microscopy. We thus demonstrate the fundamental role of exciton diffusion and two-body exciton–charge Auger recombination in 2D devices and highlight that the intrinsic photophysics of 2D semiconductors can be used to create more efficient optoelectronic devices.

二维 (2D) 半导体因其独特的光物理特性而引起了极大的兴趣，包括大的激子结合能和强的栅极可调性，这源于它们的降维^1,2,3,4,5. 尽管付出了相当大的努力，但原始二维半导体中的基本光物理学与实际器件性能之间仍然存在脱节，这通常受到许多外在因素的困扰，包括半导体接触界面处的化学无序。在这里，通过使用具有最小界面无序的范德华接触，我们抑制了接触诱导的 Shockley-Read-Hall 复合，并在 2D 半导体二极管中实现了近乎固有的光物理决定的器件性能。使用分裂栅几何结构中的静电场来独立调制二硒化钨二极管中的电子和空穴掺杂，我们发现在低电荷密度下的短路光电流中有一个不寻常的峰值。时间分辨光致发光显示，由于激子-电荷俄歇复合增加，激子寿命从电荷中性状态下的约 800 皮秒降至高掺杂密度下的约 50 皮秒。总之，我们表明激子扩散限制模型很好地解释了电荷密度相关的短路光电流，扫描光电流显微镜进一步证实了这一结果。因此，我们展示了激子扩散和两体激子-电荷俄歇复合在二维器件中的基本作用，并强调二维半导体的本征光物理学可用于制造更高效的光电器件。我们表明激子扩散限制模型很好地解释了电荷密度相关的短路光电流，扫描光电流显微镜进一步证实了这一结果。因此，我们证明了激子扩散和两体激子-电荷俄歇复合在二维器件中的基本作用，并强调二维半导体的本征光物理学可用于制造更高效的光电器件。我们表明激子扩散限制模型很好地解释了电荷密度相关的短路光电流，扫描光电流显微镜进一步证实了这一结果。因此，我们证明了激子扩散和两体激子-电荷俄歇复合在二维器件中的基本作用，并强调二维半导体的本征光物理学可用于制造更高效的光电器件。