UV-Vis-NIR broadband self-powered Bi2O2Se-based semi-vertical heterojunction photodetector with high performance
image: N-type Bi2O2Se nanosheets exhibiting high carrier mobility were synthesized via chemical vapor deposition (CVD), and Bi2O2Se/InSe semi-vertical heterojunction photodetectors were subsequently fabricated. Leveraging the synergistic effects of a single-sided depletion region, type-II band alignment, and high-mobility graphene electrodes, the device successfully achieves high sensitivity and ultrafast response, thereby enabling excellent self-powered broadband photodetection.
Credit: Nano Research, Tsinghua University Press
High-performance photodetectors are crucial for advancing broadband communications, multispectral imaging, and environmental monitoring. Two-dimensional bismuth selenide (Bi2O2Se) nanosheets, as an emerging ternary layered semiconductor, demonstrate significant potential in photodetection due to their moderate bandgap, high carrier mobility, and excellent environmental stability. However, their inherently high carrier concentration typically results in elevated dark currents and limited response speed, hindering further performance enhancement. To synergistically optimize response speed and sensitivity, the research group led by Professor Zhonghuai Wu designed and fabricated a self-powered broadband photodetector based on a Bi2O2Se/InSe semi-vertical heterojunction. By incorporating a structure combining a unilateral depletion region with graphene electrodes, this device effectively promotes efficient separation and rapid extraction of photo-generated carriers. This enables high-sensitivity detection while maintaining ultrafast response characteristics.
The team published their research in Nano Research on February 2, 2026.
A Bi2O2Se/InSe semi-vertical heterojunction photodetector was designed in this study. The heterojunction is formed by integrating 2D InSe, which is renowned for its strong light-matter interaction and high optical absorption coefficient, with Bi2O2Se, which exhibit exceptionally high carrier mobility. This configuration enables self-powered broadband photodetection across the full UV-Vis-NIR spectrum. Within the device structure, n-type Bi2O2Se is stacked directly atop a graphene bottom electrode, and n-type InSe is subsequently layered above the n-Bi2O2Se. This vertical stacking induces a single-sided depletion region within Bi2O2Se and a corresponding carrier accumulation region in the InSe. Such a unilateral depletion profile effectively suppresses the recombination of photogenerated carriers, thereby enhancing both responsivity and external quantum efficiency. Simultaneously, the graphene electrode promotes the formation of an extended lateral depletion region within the heterostructure. Under the influence of the built-in electric field, photogenerated carriers are rapidly separated along the vertical transport channel, thereby significantly reducing both migration distance and transit time. This accelerated carrier extraction decouples optical gain from response speed—a longstanding challenge in photodetector design—simultaneously enables high gain without compromising speed. Moreover, graphene exhibits high carrier mobility, which reduce contact resistance and form an excellent ohmic contact with the materials. This minimizes series resistance and shortens carrier transit time. When employed as an electrode, graphene further suppresses recombination of photogenerated carrier while enabling rapid device response.
Therefore, under zero bias conditions, the device exhibits outstanding performance: a high optical switching ratio of 104, a responsivity (R) of 0.47 A/W, a D* of 3.21 × 1012 Jones, an external quantum efficiency (EQE) as high as 166.09%, and rise/fall times of 48.5/41.7 μs. It exhibits broadband optical response spanning ultraviolet to near-infrared (300~1050 nm), achieving high sensitivity while maintaining excellent fast response capability.
"In this work, we successfully addressed the inherent trade-off between high sensitivity and response speed commonly through the co-design of a Bi2O2Se/InSe semi-vertical heterojunction and a graphene electrode," stated the corresponding author, Professor Zhonghuai Wu from Beijing Institute of Technology.
"The device exhibits excellent self-powered detection capability across the entire ultraviolet-visible-near-infrared spectrum. The simultaneous achievement of both high sensitivity and fast response characteristics provides a promising technical pathway for the development of next-generation broadband, low-power photodetection systems," said Zhonghuai Wu.
Other contributors include Ying Li, Fan Zhang, Shiqiang Wang, Dapeng Li, Ying Sun, Zhen Gao and Dezhi Zheng from Beijing Institute of Technology.
This work was supported by the Beijing Outstanding Young Scientist Program (JWZ020240101014).
DOI Link:
https://doi.org/10.26599/NR.2026.94908400
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 8,000 articles. In 2025 InCites Journal Citation Reports, its 2025 IF is 9.4 (8.3, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.