Key Takeaways & Executive Findings
- •• • Achieved ultrahigh light on-off ratio exceeding 10^6, enabling high-contrast detection in low-light conditions, critical for sensitive imaging and communication systems. • • Demonstrated gate-tunable photoresponse with responsivity up to 1.2 A/W and specific detectivity of 10^12 Jones, allowing dynamic sensitivity adjustment for varying illumination. • • Exhibited polarization-sensitive detection with a linear dichroism ratio of 2.1 at 532 nm, enabling discrimination of light polarization for applications in ellipsometry and secure communications. • • Self-powered operation with fast response times (rise/fall < 100 μs) and broad spectral range (400-1000 nm), reducing power consumption and enabling high-speed, broadband photodetection.
Abstract
Polarization-sensitive photodetection is critical for advanced optical communication and imaging systems, yet conventional photodetectors suffer from low on-off ratios and limited polarization discrimination. Here, we report gate-tunable PdSe2/WSe2 van der Waals heterostructures that achieve ultrahigh light on-off ratio and polarization-sensitive photodetection. The heterostructure forms a type-II band alignment, enabling efficient charge separation and self-powered operation. By applying a gate voltage, the photoresponse can be modulated, achieving an on-off ratio exceeding 10^6 under illumination. The device exhibits a high responsivity of 1.2 A/W and a specific detectivity of 10^12 Jones at room temperature. Polarization-sensitive measurements reveal a linear dichroism ratio of 2.1 at 532 nm, attributed to the anisotropic crystal structure of PdSe2. The photodetector operates over a broad spectral range from visible to near-infrared (400-1000 nm) with fast response times (rise/fall < 100 μs). The gate-tunable capability allows dynamic control of the photocurrent, enabling adaptive sensing applications. These results demonstrate that PdSe2/WSe2 heterostructures are promising candidates for high-performance, polarization-sensitive photodetectors, offering a pathway for next-generation optoelectronic devices.
1. Introduction
Conventional photodetectors based on silicon or III-V compounds face fundamental limitations in polarization sensitivity and on-off ratio, hindering their use in advanced optical systems. Silicon photodiodes, while mature, exhibit low polarization discrimination and require complex fabrication to achieve high on-off ratios. Two-dimensional materials, such as transition metal dichalcogenides (TMDs), offer unique anisotropic properties and tunable bandgaps, but their photodetectors often suffer from low responsivity and slow response times due to poor carrier mobility and trapping effects.
This work addresses these bottlenecks by constructing PdSe2/WSe2 van der Waals heterostructures, which combine the high mobility of WSe2 with the strong in-plane anisotropy of PdSe2. The type-II band alignment facilitates efficient charge separation, while the gate-tunable nature allows dynamic control of the photocurrent. The resulting device achieves an ultrahigh on-off ratio exceeding 10^6 and a polarization sensitivity ratio of 2.1, surpassing many existing 2D material photodetectors. This approach provides a scalable route to high-performance, polarization-sensitive photodetection for next-generation optical communication and imaging technologies.
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Taiman Luo, Jiabao Che, Jiajun Xu, Junjie Huang, Huaqiang Pang, Wei Gao, Zhaoqiang Zheng, Zuxin Chen, Mengmeng Yang (2026). Gate-Tunable PdSe2/WSe2 van der Waals Heterostructures for Ultrahigh Light On–Off Ratio Polarization-Sensitive Photodetection. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4360-7
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Frequently Asked Questions
What is the maximum on-off ratio achieved and under what bias conditions?
The device achieves an ultrahigh light on-off ratio exceeding 10^6 under illumination, with gate voltage modulation. The exact bias conditions are not specified in the provided text, but the on-off ratio is measured at room temperature.
How does the gate voltage affect the photoresponse and what is the tuning range?
The gate voltage modulates the photocurrent, allowing dynamic control of the responsivity. The device exhibits a responsivity of 1.2 A/W and detectivity of 10^12 Jones, with the gate enabling adjustment of the photocurrent magnitude. The tuning range is not explicitly quantified, but the gate-tunable capability is demonstrated.
What is the polarization sensitivity mechanism and how is the linear dichroism ratio measured?
The polarization sensitivity arises from the anisotropic crystal structure of PdSe2, which absorbs light differently along different crystallographic axes. The linear dichroism ratio of 2.1 at 532 nm is measured by comparing photocurrents under orthogonal polarization states.
What is the device's spectral response range and response speed?
The photodetector operates over a broad spectral range from 400 to 1000 nm (visible to near-infrared). The response times are fast, with rise and fall times both less than 100 μs, enabling high-speed operation.
How does the device achieve self-powered operation and what is the open-circuit voltage?
The device operates in self-powered mode due to the built-in electric field at the heterojunction, which separates photogenerated carriers without external bias. The open-circuit voltage is not specified in the provided text, but the self-powered capability is confirmed.
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