Acoustic phonon recycling for photocarrier generation in graphene-WS2 heterostructures

Ke Wei,Xin Zheng,Tian Jiang,Jie You,Hao Ouyang,Yizhen Sui,Xiangai Cheng,Zhongjie Xu,Yating Ma,Yuxiang Tang,Yan Kang,Han Li

doi:10.1038/s41467-020-17728-x

Ke Wei, Xin Zheng + Show 10 more

Open Access

https://doi.org/10.1038/s41467-020-17728-x

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Abstract

Electron-phonon scattering is the key process limiting the efficiency of modern nanoelectronic and optoelectronic devices, in which most of the incident energy is converted to lattice heat and finally dissipates into the environment. Here, we report an acoustic phonon recycling process in graphene-WS2 heterostructures, which couples the heat generated in graphene back into the carrier distribution in WS2. This recycling process is experimentally recorded by spectrally resolved transient absorption microscopy under a wide range of pumping energies from 1.77 to 0.48 eV and is also theoretically described using an interfacial thermal transport model. The acoustic phonon recycling process has a relatively slow characteristic time (>100 ps), which is beneficial for carrier extraction and distinct from the commonly found ultrafast hot carrier transfer (~1 ps) in graphene-WS2 heterostructures. The combination of phonon recycling and carrier transfer makes graphene-based heterostructures highly attractive for broadband high-efficiency electronic and optoelectronic applications.

Highlights

Electron-phonon scattering is the key process limiting the efficiency of modern nanoelectronic and optoelectronic devices, in which most of the incident energy is converted to lattice heat and dissipates into the environment
This technique consists of two femtosecond pulses (~100 fs, 800 nm) with different intensities, with the stronger one being sent to an optical parametric amplifier (OPA) to change the photon energy, which can vary from 470 to 2600 nm, serving as the pump pulse
To simulate the relaxation of ΔTLÀWS2, we develop an interfacial thermal transport model based on the electron and phonon relaxation pathways

Summary

Introduction

Electron-phonon scattering is the key process limiting the efficiency of modern nanoelectronic and optoelectronic devices, in which most of the incident energy is converted to lattice heat and dissipates into the environment. Graphene (G), an atomically thin carbon layer with a gapless band structure[2], a flat absorption feature[3], a high thermal conductivity and a low heat capacity[4], is considered a highly promising material for relieving this heat production[5,6,7,8,9,10,11] in the fields of light conversion and detection[12,13,14,15,16,17,18,19,20] In recent years, both theoretical[21,22] and experimental[23,24] works have shown that carrier–carrier scattering in graphene is efficient enough to prevail over the electron-optical-phonon coupling, leading to highly efficient multiple hot-carrier generation originating from the primary photoexcited electron-hole pair. Graphene, an excellent phonon transport material, has never been reported to show a phonon recycling property far

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