Inhibited nonradiative decay at all exciton densities in monolayer semiconductors

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 low exciton exciton-exciton annihilation (EEA) by van-Hove singularity (VHS) rapidly degrades their densities and limits utility in practical applications. Here, applying small mechanical strain (< 1%), we circumvent VHS resonance drastically suppress EEA monolayer TMDCs, resulting despite presence of native defect density. Our findings can enable light-emitting retain efficiency brightnesses.