Surface/interface engineering for high‑resolution micro‑/nano‑photodetectors

As artificial intelligence and miniaturized electronics surge forward, conventional photodetectors struggle to deliver the resolution, speed and energy efficiency required for next-generation imaging, sensing and human–machine interaction. Now, a team led by Professor Wei Chen at Tsinghua University has published a comprehensive roadmap on surface/interface engineering that turns micro-/nano-scale photodetectors into ultra-sharp “electronic eyes”. The work appeared in Nano-Micro Letters.

Why Surface/Interface Engineering Matters
• Defect Healing: Atomic-level passivation and functional-group grafting suppress interfacial traps, slashing dark current and boosting signal-to-noise ratio.
• Band-gap Sculpting: van-der-Waals heterojunctions, quantum wells and strain gradients tailor the spectral window from deep-UV to long-wave infrared without extra filters.
• Light-management: Elliptical gratings, pyramidal textures and plasmonic nano-cavities extend the optical path, enabling >90 % absorption in films thinner than 50 nm.
• Mechanical Bridging: Hydrophobic–hydrophilic patterning and buffer layers reconcile soft organics with rigid inorganics, giving flexible devices a bending radius <1 mm while maintaining pixel pitch down to 1 µm.

Innovative Design and Features
• Material Menu: 2D black phosphorus with strain-tunable bandgap, perovskite nanowire arrays for full-colour imaging, TMDC/graphene heterostacks for picosecond response, and lead-free CsSnBr_x inks for green manufacturing.
• Processing Toolkit: ALD-grown 1-nm Al₂O₃ passivation shells, EHD printing of 1 µm pixels, plasma-enhanced CVD for wafer-scale TMDCs, and self-assembled monolayers that lower interfacial traps by an order of magnitude.
• Architecture Gallery: 1D nanonail forests, 2D lateral p–n heterojunctions, 3D pyramid-on-pyramid textures, and resonant cavities that fold a 1550 nm beam into a 300 nm active layer.

Applications and Future Outlook
• Thermal Imaging: Passivated InGaAs/AlGaN pixel arrays resolve 20 mK temperature differences at 1 kHz frame rates for night-vision and medical diagnostics.
• Flexible Wearables: Transfer-printed single-crystal perovskite sheets wrapped around a robotic finger provide 317 ppi imaging during grasping tasks.
• Bio-inspired Vision: A hemispherical 1 µm-pitch nanowire retina coupled to liquid-metal nerves mimics human-eye resolution and is implantable for vision restoration.
• Catalytic Sensing: TiO₂/BaTiO₃ core–shell nanorods double photoelectrochemical water-splitting efficiency while acting as self-powered UV monitors.

Challenges and Opportunities
The review pinpoints reproducibility of sub-10 nm interfaces, long-term stability under moist bio-environments, and CMOS-compatible pitch scaling below 200 nm as the next grand challenges. Future research will marry machine-learning-guided multi-parameter optimization with roll-to-roll nano-imprint lithography to deliver wafer-scale, defect-free electronic eyes for intelligent systems.

This comprehensive roadmap offers device engineers, materials scientists and circuit designers a unified vocabulary for transforming any photodetector—old or new—into a high-resolution, low-power, spectrum-agile imaging engine.