Negative Differential Photoconductance as a Signature of Nonradiative Energy Transfer in van der Waals Heterojunction

Medha Dandu; Garima Gupta; Kausik Majumdar

doi:10.1021/acsnano.1c05844

Negative Differential Photoconductance as a Signature of Nonradiative Energy Transfer in van der Waals Heterojunction

ACS Nano. 2021 Oct 26;15(10):16432-16441. doi: 10.1021/acsnano.1c05844. Epub 2021 Oct 13.

Authors

Medha Dandu¹, Garima Gupta¹, Kausik Majumdar¹

Affiliation

¹ Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India.

PMID: 34644047
DOI: 10.1021/acsnano.1c05844

Abstract

The physical proximity of layered materials in their van der Waals heterostructures (vdWhs) aids interfacial phenomena such as charge transfer (CT) and energy transfer (ET). Besides providing fundamental insights, CT and ET also offer routes to engineer optoelectronic properties of vdWhs. For example, harnessing ET in vdWhs can help to overcome the limitations of optical absorption imposed by the ultra-thin nature of layered materials and thus provide an opportunity for in situ enhancement of quantum efficiency for light-harvesting and sensing applications. While several spectroscopic studies on vdWhs probed the dynamics of CT and ET, the possible contribution of ET in the photocurrent generation remains largely unexplored. In this work, we investigate the role of nonradiative energy transfer (NRET) in the photocurrent through a vertical vdWh of SnSe₂/MoS₂/TaSe₂. We observe an unusual negative differential photoconductance (NDPC) arising from the existence of NRET across the SnSe₂/MoS₂ junction. Modulation of the NRET-driven NDPC characteristics with optical power results in a striking transition of the photocurrent's power law from a sublinear to a superlinear regime. Our observations reveal the nontrivial influence of ET on the photoresponse of vdWhs, which offer insights to harness ET in synergy with CT for vdWh based next-generation optoelectronics.

Keywords: charge transfer; negative differential photoconductance; nonradiative energy transfer; photoluminescence; superlinear photocurrent; van der Waals heterojunctions.