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

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.

Highly Nonlinear Biexcitonic Photocurrent from Ultrafast Interlayer Charge Transfer

“…A superlinear photodetector, where the output electrical signal varies in a superlinear manner with the input light intensity, is attractive for several functional optoelectronic applications, such as a higher harmonics generator, square-law detector, compensator for sublinearity, optical implementation of neural circuits, and several other analog applications. However, there are very few reports to date − demonstrating a nonlinear photocurrent, and the reported degree of nonlinearity is often weak and highly dependent on the design/device parameter. A nonlinear photocurrent generation from the intrinsic nonlinear absorption of the active material will thus be highly attractive.…”

Long-Range Energy Transfer in Strongly Coupled Donor–Acceptor Phototransistors

“…Here, we used the photoresponsivity of the MoS 2 monolayer (donor) as a selective tool to study the phenomena. The effect of charge and energy transfer on the photoresponse has been extensively studied in 2D TMDs–quantum dot/organic/inorganic van der Waals heterostructures. ,− In this paper, a clear energy transfer is observed in photoresponsivity measurements for the noncavity system if there is no spacer layer between the donor and the acceptor molecules. Similar to conventional systems, energy transfer disappears if the D-A pair is separated above the Förster zone, whereas energy can be transferred to a larger distance through the polaritonic states .…”

Highly nonlinear biexcitonic photocurrent from ultrafast inter-layer charge transfer

“…However, there are very few reports to date [1][2][3][4] demonstrating a nonlinear photocurrent, and the reported degree of nonlinearity is often weak and highly dependent on the design/device parameter. A nonlinear photocurrent generation from the intrinsic nonlinear absorption of the active material will thus be highly attractive.…”