Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA 94720, USA.
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, Berkeley, CA 94720, USA.
Science. 2019 May 3;364(6439):468-471. doi: 10.1126/science.aaw8053.
Defects in conventional semiconductors substantially lower the photoluminescence (PL) quantum yield (QY), a key metric of optoelectronic performance that directly dictates the maximum device efficiency. Two-dimensional transition-metal dichalcogenides (TMDCs), such as monolayer MoS, often exhibit low PL QY for as-processed samples, which has typically been attributed to a large native defect density. We show that the PL QY of as-processed MoS and WS monolayers reaches near-unity when they are made intrinsic through electrostatic doping, without any chemical passivation. Surprisingly, neutral exciton recombination is entirely radiative even in the presence of a high native defect density. This finding enables TMDC monolayers for optoelectronic device applications as the stringent requirement of low defect density is eased.
传统半导体中的缺陷会显著降低光致发光（PL）量子产率（QY），这是光电性能的一个关键衡量标准，直接决定了器件的最大效率。二维过渡金属二卤化物（TMDCs），如单层 MoS2，通常表现出低 PLQY 的原始样品，这通常归因于大的本征缺陷密度。我们表明，当通过静电掺杂使 MoS 和 WS 单层本征化时，其 PLQY 达到近 1，而无需任何化学钝化。令人惊讶的是，即使存在高本征缺陷密度，中性激子复合也是完全辐射的。这一发现使 TMDC 单层材料适用于光电设备应用，因为降低缺陷密度的严格要求变得宽松了。
