Engineering Exciton Recombination Pathways in Bilayer WSe2for Bright Luminescence

Shiekh Zia Uddin, Naoki Higashitarumizu, Hyungjin Kim, Eran Rabani, Ali Javey

Research output: Contribution to journalArticlepeer-review

Abstract

Exciton-exciton annihilation (EEA) in counterdoped monolayer transition metal dichalcogenides (TMDCs) can be suppressed by favorably changing the band structure with strain. The photoluminescence (PL) quantum yield (QY) monotonically approaches unity with strain at all generation rates. In contrast, here in bilayers (2L) of tungsten diselenide (WSe2) we observe a nonmonotonic change in EEA rate at high generation rates accompanied by a drastic enhancement in their PL QY at low generation rates. EEA is suppressed at both 0% and 1% strain, but activated at intermediate strains. We explain our observation through the indirect to direct transition in 2L WSe2 under uniaxial tensile strain. By strain and electrostatic counterdoping, we attain ∼50% PL QY at all generation rates in 2L WSe2, originally an indirect semiconductor. We demonstrate transient electroluminescence from 2L WSe2 with ∼1.5% internal quantum efficiency for a broad range of carrier densities by applying strain, which is ∼50 times higher than without strain. The present results elucidate the complete optoelectronic photophysics where indirect and direct excitons are simultaneously present and expedite exciton engineering in a TMDC multilayer beyond indirect-direct bandgap transition.

Original languageEnglish
Pages (from-to)1339-1345
Number of pages7
JournalACS Nano
Volume16
Issue number1
DOIs
StatePublished - 25 Jan 2022

Keywords

  • bilayer WSe
  • electroluminescence
  • exciton-exciton annihilation
  • quantum yield
  • strain

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