Modulation of carrier lifetime in MoS2 monolayer by uniaxial strain**Project supported by the Natural Science Foundation of Beijing, China (Grant No. JQ19004), the Excellent Talents Training Support Fund of Beijing, China (Grant No. 2017000026833ZK11), the National Natural Science Foundation of China (Grant Nos. 51991340 and 51991342), the National Key Research and Development Program of China (Grant Nos. 2016YFA0300903 and 2016YFA0300804),

Abstract

Carrier lifetime is one of the most fundamental physical parameters that characterizes the average time of carrier recombination in any material. The control of carrier lifetime is the key to optimizing the device function by tuning the electro–optical conversion quantum yield, carrier diffusion length, carrier collection process, etc. Till now, the prevailing modulation methods are mainly by defect engineering and temperature control, which have limitations in the modulation direction and amplitude of the carrier lifetime. Here, we report an effective modulation on the ultrafast dynamics of photoexcited carriers in two-dimensional (2D) MoS2 monolayer by uniaxial tensile strain. The combination of optical ultrafast pump–probe technique and time-resolved photoluminescence (PL) spectroscopy reveals that the carrier dynamics through Auger scattering, carrier–phonon scattering, and radiative recombination keep immune to the strain. But strikingly, the uniaxial tensile strain weakens the trapping of photoexcited carriers by defects and therefore prolongs the corresponding carrier lifetime up to 440% per percent applied strain. Our results open a new avenue to enlarge the carrier lifetime of 2D MoS2, which will facilitate its applications in high-efficient optoelectronic and photovoltaic devices.