Bin Sun

Short-wave infrared (SWIR) sensing at 1500 nm is essential for eye-safe LiDAR and night vision. Conventional detectors fail in photon-starved environments due to systemic readout noise. Realizing photomultiplicative gain without amplifying noise or sacrificing response speed remains a bottleneck for colloidal quantum dot (CQD) detectors. Here, we report an asymmetric n-i-n CQD architecture that breaks this trade-off via interfacial band engineering. Integrating a C60 molecular interlayer establishes an energetically asymmetric junction that suppresses dark leakage while localizing accumulation of photogenerated holes. This accumulation acts as a dynamic gate, enhancing the local electric field and narrowing the electron-injection barrier to enable tunneling-mediated photomultiplication. The devices achieved a maximum external quantum efficiency (EQE) of over 1400% under -3.2 V and 300% at 1520 nm under -1.6 V, with a response time of 33 µs, and a dark-current density of 8×10-4 mA cm–2 at -0.5 V. Crucially, we monolithically integrated this architecture with a CMOS readout integrated circuit to demonstrate a 640×512-pixel focal-plane imaging under low-light conditions. These findings establish interfacial tunneling engineering as a promising strategy for combining high photomultiplicative gain, fast response, and CMOS-compatible integration in next-generation SWIR imaging systems.

Multifunctional photoelectrochemical systems that combine solar energy conversion and chemical sensing are gaining interest, but their performance is often limited by poor interfacial charge separation and uncontrolled charge-carrier pathways. Herein, CuO_x modified TiO₂ hollow spheres (CuO_x/TiO₂ HSs) were engineered to construct a built-in p-n heterojunction that actively regulates interfacial charge transfer. Combined characterization and DFT calculations indicate that the successful construction of the p-n heterojunction enables efficient separation of photogenerated electrons and holes. This not only allows electrons to migrate to the TiO₂ surface enhancing the hydrogen evolution reaction rate, but also directs holes to the CuO_x surface, where they participating in oxidation reactions to improve sensing performance. Consequently, the optimized CuO_x/TiO₂ HSs achieve a hydrogen evolution rate of 1.43 mmol g^-1 h^-1 under simulated sunlight with excellent cycling stability (88% retention after 16 h). In addition, the material exhibits a wide linear range of 60-12,000 μM and a low detection limit of 3.37 μM for glucose sensing. This work provides an experimental approach for the design of p-n TiO₂ heterojunctions.

Shortwave infrared (SWIR) detection is pivotal for diverse applications, ranging from depth imaging and autonomous driving to biological sensing. Among various semiconductor candidates, PbS colloidal quantum dots (CQDs) stand out due to their tunable bandgap and solution processability, offering immense potential for integration into next-generation optoelectronic circuits. However, PbS CQD photodetectors with an inverted structure, which is crucial for integration with silicon or organic electronics, still remain underexplored, largely restricted by their poor quantum efficiency, particularly at around 1350 nm. Herein, we demonstrate a high-performance inverted SWIR photodetector with a device configuration of ITO/NiO_x/PbS-EDT/PbS-I^–/ZnO/Al, achieving smooth band alignment and efficient carrier transport. Furthermore, via a two-step passivation process, large-scale and low-defect PbS CQDs were obtained. Consequently, in devices, a high quantum efficiency exceeding 40% at 1350 nm was successfully achieved, accompanied by a high specific detectivity of 1.05 × 10¹³ Jones and a fast response of 470 μs, which demonstrates potential for high-resolution and high-speed SWIR sensing. As a result, the proof of concept in SWIR imaging and fire detection confirms that the constructed PbS CQD detector meets the requirements for practical sensing application.

Large-sized lead sulfide (PbS) colloidal quantum dots (CQDs) face significant stability challenges in near-infrared applications due to increased surface active sites. While traditional halogen ligands achieve preliminary passivation, they are prone to dissociation under high-temperature operating conditions, leading to rapid device performance degradation. This study proposes an aromatic bidentate ligand passivation strategy based on 2-picolinic acid (2-PCA). The device demonstrates an external quantum efficiency (EQE) of 35% at 1650 nm wavelength, with responsivity and normalized detectivity reaching 0.46 A/W and 3.58 × 10¹¹ jones, respectively representing a 2.33-fold improvement over conventional halogen-passivated devices. Under thermal stress at 180 °C for 2 h, devices with 2-PCA ligands retain approximately 90% of their initial normalized EQE, marking a 15-fold improvement in stability compared to devices using halogen ligands (PbX₂, X = Br^-, I^-), which undergo nearly complete failure. This aromatic bidentate ligand passivation strategy provides a new pathway for developing high-performance infrared photodetectors with enhanced thermal stability.

The performance of lead sulfide colloidal quantum dot (PbS-CQD) solar cells has long been hindered by interface defects in the transport layer. Traditionally, 1,2-ethanedithiol (EDT), used in solid-state ligand exchange, has been a common choice as the hole transport layer (HTL) in many PbS-CQD solar cells. However, the rapid reaction rate and chain length mismatch (shorter-chain EDT versus longer-chain oleic acid) during the ligand exchange process often introduce crack defects in the HTL film, resulting in an unexpected low performance. In this work, ethyl acetate (EA) was introduced into acetonitrile (ACN) solution to slow down the ligand exchange rate. With EA's assistance, a high-quality HTL film with fewer cracks was achieved, leading to a reduced trap density from 2.26 × 10¹⁶ cm^-3 to 1.85 × 10¹⁶ cm^-3. Consequently, this led to an improved V_OC by 27.5 mV and an increased power conversion efficiency (PCE) from 11.01% to 12.16%.

Single crystal copper halide perovskites (CsCu₂I₃) have gained extensive interest due to their nontoxic composition and superior ultraviolet (UV) photodetecting abilities.