Most optoelectronic devices operate at high photocarrier densities, where all semiconductors suffer from enhanced nonradiative recombination. Nonradiative processes proportionately reduce photoluminescence (PL) quantum yield (QY), a performance metric that directly dictates the maximum device efficiency. Although transition metal dichalcogenide (TMDC) monolayers exhibit near-unity PL QY at low exciton densities, nonradiative exciton-exciton annihilation (EEA) enhanced by van-Hove singularity (VHS) rapidly degrades their PL QY at high exciton densities and limits their utility in practical applications. Here, by applying small mechanical strain (less than 1%), we circumvented VHS resonance and markedly suppressed EEA in monolayer TMDCs, resulting in near-unity PL QY at all exciton densities despite the presence of a high native defect density. Our findings can enable light-emitting devices that retain high efficiency at all brightness levels.

大多数光电器件在高光载流子密度下运行，其中所有半导体都遭受增强的非辐射复合。非辐射过程会按比例降低光致发光 (PL) 量子产率 (QY)，这是直接决定最大器件效率的性能指标。尽管过渡金属二硫属化物 (TMDC) 单层在低激子密度下表现出接近统一的 PL QY，但范霍夫奇点 (VHS) 增强的非辐射激子 - 激子湮灭 (EEA) 在高激子密度下迅速降低了它们的 PL QY，并限制了它们在实际应用。在这里，通过施加小机械应变（小于 1%），我们绕过了 VHS 共振并显着抑制了单层 TMDC 中的 EEA，尽管存在高本征缺陷密度，但在所有激子密度下仍能获得接近统一的 PL QY。