The 1550-nanometre band occupies a particularly valuable position in the near-infrared spectrum. Light at this wavelength is widely used in optical communications, while also offering practical advantages for sensing systems that must operate around people, vehicles and other sensitive environments. Compared with shorter-wavelength lidar sources, 1550-nanometre systems can be designed to meet eye-safety requirements at higher transmitted energies under appropriate operating conditions. Greater permissible pulse energy can translate into stronger returning signals, longer useful sensing distances or improved performance when atmospheric conditions weaken the reflected light. Yet detecting this wavelength efficiently and selectively remains a demanding engineering problem, especially when lidar hardware must become smaller, cheaper and more power-conscious.

The central idea in the new work is to use colloidal quantum dots as the light-absorbing material in a tandem photodiode. Colloidal quantum dots are semiconductor nanocrystals whose optical and electronic properties can be tuned by controlling their composition, size and surface chemistry. Unlike many conventional semiconductor detector materials, they can be deposited from inks and processed over relatively large areas using techniques compatible with low-temperature fabrication. Their absorption can also be adjusted across the visible and infrared spectrum, making them attractive for sensors that must be tailored to a specific wavelength. In a tandem device, multiple quantum-dot photodiodes are placed in a vertical stack, allowing the structure to interact with incoming light in a controlled, wavelength-dependent manner.

Spectral selectivity is essential because a lidar detector does not receive only the signal sent by its laser. Sunlight, artificial lighting, reflections from nearby objects and electronic noise can all contribute unwanted background. If a detector responds broadly across the spectrum, the desired return pulse may be buried beneath those competing signals. A spectrally selective detector instead acts like an optical and electronic gate: it preferentially responds to the target wavelength while suppressing light outside the sensing band. By integrating two photodiode sections rather than relying on a single absorbing layer, the tandem architecture gives researchers additional freedom to shape how different wavelengths are absorbed, transmitted or converted into electrical signals.

In operation, a lidar transmitter emits light toward a target, and the reflected photons travel back to the receiver. The detector converts those photons into an electrical response, while timing electronics determine the interval between transmission and return. Because light travels at a fixed speed, even a very short delay contains information about distance. The challenge becomes more severe as targets grow darker, farther away or partially obscured by haze, because fewer photons return to the detector. A detector designed specifically for 1550 nanometres can improve the ratio between the useful lidar signal and the surrounding optical background. The tandem quantum-dot structure is therefore not simply a new material choice; it is an attempt to unite wavelength control, photodetection and lidar-specific signal processing in one integrated platform.

The use of colloidal quantum dots could also change how future lidar receivers are manufactured. Traditional infrared photodiodes often depend on specialized semiconductor growth, high-temperature processing or costly substrates. Quantum-dot layers, by contrast, can potentially be deposited on diverse surfaces and incorporated into thin, lightweight devices. That flexibility is especially relevant for emerging lidar systems in robotics, drones, industrial monitoring and vehicles, where bulky optical assemblies can limit design options. A detector that is compact and spectrally targeted could help reduce the burden placed on filtering optics, cooling systems and downstream computation. It may also open routes toward detector arrays capable of combining distance information with wavelength-sensitive imaging.

The concept is significant because lidar is moving from laboratories and high-end surveying equipment into everyday machines. Autonomous vehicles need to distinguish road users, barriers and road geometry under changing illumination. Robots must navigate warehouses, factories and homes filled with reflective and irregular surfaces. Atmospheric and environmental instruments use laser ranging to study aerosols, vegetation and changing landscapes. In each of these applications, the receiver must separate a deliberately generated optical signal from a complex background. Spectral selectivity can provide an additional layer of discrimination before the data reaches software, potentially reducing the amount of information that must be filtered digitally and improving the reliability of measurements made in bright or optically cluttered environments.

The reported platform also highlights a broader shift in photonics: the effort to build sophisticated optical functions directly into thin-film semiconductor devices. Instead of treating the detector as a passive endpoint connected to a separate collection of filters and optical components, researchers are increasingly designing the material stack itself to perform part of the signal-selection task. Tandem quantum-dot photodiodes fit this philosophy because their individual layers can be engineered to absorb different portions of the spectrum and to work together electrically. Such control may eventually support receivers that are not only sensitive at 1550 nanometres but can also distinguish multiple bands, identify atmospheric interference or combine ranging with chemical and material recognition.

Important questions remain before the technology can become a commercial lidar component. Practical systems must maintain stable performance over temperature changes, prolonged illumination and repeated electrical operation. Quantum-dot surfaces require careful chemical treatment because defects and imperfect interfaces can trap charge, slow the detector response or increase noise. A lidar receiver must also balance sensitivity against speed: detecting very weak signals is useful only if the device can respond quickly enough for high-rate ranging. Manufacturing uniform tandem stacks over large areas, protecting them from moisture and oxygen, and integrating them with readout electronics are additional challenges. The new study places spectral-selective quantum-dot detection into a lidar context, but the wider path to deployment will depend on how the devices perform under the demanding conditions of field operation.

Even with those challenges, the research points toward a future in which lidar receivers are designed around the physics of the signal they need to measure. The 1550-nanometre wavelength is already central to optical communications and advanced ranging, but its full potential depends on detectors that can recognize it efficiently amid a flood of unwanted light. By combining tunable colloidal quantum dots with a tandem photodiode structure, the researchers offer a route to make that recognition more precise and potentially more manufacturable. If the approach can be refined for speed, durability and scalable production, it could contribute to a new generation of selective lidar systems—devices that see farther not merely by transmitting more light, but by becoming smarter about which photons count.

Subject of Research: Spectral-selective 1550-nanometre light detection and ranging using tandem colloidal quantum dot photodiodes.

Article Title: Spectral-selective light detection and ranging at 1550 nm using tandem colloidal quantum dot photodiodes.

Article References: Yang, J., Liu, J., Deng, C. et al. “Spectral-selective light detection and ranging at 1550 nm using tandem colloidal quantum dot photodiodes.” Light Science & Applications 15, 355 (2026). https://doi.org/10.1038/s41377-026-02244-2

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41377-026-02244-2

Keywords: lidar, light detection and ranging, 1550 nm, colloidal quantum dots, tandem photodiodes, spectral-selective detection, near-infrared photodetectors, optical sensing, photonics, autonomous systems.

Near-infrared (NIR) photodetection has long been a critical area of research due to its vital role in fields such as biomedical imaging, environmental monitoring, and telecommunications. However, traditional detectors often face challenges concerning sensitivity, operational stability, and scalability. The recent development reported by Zhan, Li, Chen, et al., presents a transformative approach by integrating colloidal quantum dots into phototransistor architectures, thereby significantly enhancing the responsivity to NIR wavelengths while minimizing power consumption.

Colloidal quantum dots (CQDs) are semiconductor nanocrystals renowned for their size-tunable bandgaps and exceptional photophysical characteristics. Their solution-processability enables cost-effective, large-area device fabrication, contrasting sharply with the intricate manufacturing requirements of conventional semiconductor photodetectors. The research team exploited these advantages to engineer phototransistors capable of detecting extremely low photon fluxes, a capability essential for reducing harmful radiation exposure in medical diagnostics and improving detection in dimly lit environments.

The heart of this innovation lies in the delicate balance between the photoconductive gain and the noise characteristics within the CQD phototransistor. By carefully tailoring the surface chemistry and interface engineering of the quantum dots, the researchers achieved efficient charge separation and transport, which are pivotal for high photodetection sensitivity. These modifications suppressed recombination losses and enhanced carrier mobility, resulting in a device that maintains a high signal-to-noise ratio even at minimal incident light intensities.

Moreover, the device design integrates a strategic layering of CQDs with complementary semiconductor materials to facilitate charge transfer and amplify photocurrent generation. This heterojunction configuration not only optimizes the absorption spectrum extent into the near-infrared but also stabilizes the operational environment against ambient oxygen and moisture, factors commonly detrimental to quantum dot performance over time. The resulting phototransistor exhibits remarkable device stability, a critical parameter for real-world deployment.

The capability to operate efficiently under low-dose NIR illumination presents profound implications for medical imaging technologies. Minimizing exposure to potentially harmful radiation without compromising image clarity can significantly advance non-invasive diagnostic procedures. These CQD phototransistors can be integrated into flexible, wearable devices, revolutionizing patient monitoring where continuous and sensitive detection of physiological signals in the near-infrared regime is paramount.

In addition to biomedical applications, the breakthrough extends to image communication systems. Near-infrared light is increasingly used in secure communication due to its penetration abilities and low ambient interference. Phototransistors developed in this study offer enhanced responsivity that can support higher data transmission rates with improved signal integrity, propelling advances in optical wireless communication protocols and encryption technologies.

Technically, the research delineates a robust fabrication protocol where CQDs were synthesized with controlled size distribution, ensuring spectral uniformity crucial for reproducible device performance. Advanced ligand-exchange processes rendered the quantum dot surfaces with high electronic coupling, facilitating efficient charge transport networks. Detailed spectral analysis confirmed the phototransistors’ peak sensitivity aligning with target NIR wavelengths, thus validating their practical applicability.

Extensive characterization of the devices revealed a responsivity exceeding current benchmarks by a significant margin, with detectivity metrics indicative of profound sensitivity enhancements. The rise and fall times of the phototransistors proved shorter than comparable devices, suggesting potential for rapid modulation and real-time signal processing capabilities essential in dynamic imaging and communication scenarios.

The interdisciplinary collaboration driving this research combined expertise in nanomaterials chemistry, semiconductor physics, and device engineering. This synergy enabled the exploration of complex interfacial phenomena governing carrier dynamics within CQD films, yielding insights instrumental for fine-tuning phototransistor architectures. Computational modeling supplemented experimental findings, providing predictive capabilities to optimize device parameters further.

Moreover, the scalable nature of the fabrication technique underscores the potential for commercialization. Solution-based processing paves the way for cost-effective manufacturing on flexible substrates, allowing integration into wearable electronics, portable sensors, and large-area imaging panels. This flexibility meets the growing demand for adaptable, high-performance photodetectors in next-generation technological landscapes.

Looking forward, the research team anticipates expanding the spectral sensitivity range by engineering CQDs with different compositions, aiming to tailor devices for diverse spectral regimes beyond near-infrared. Additionally, efforts to enhance the environmental robustness and long-term operational reliability remain focal points to ensure applicability in varied climatic and usage conditions.

This breakthrough heralds a new era where colloidal quantum dot phototransistors deliver both the sensitivity and adaptability required for cutting-edge near-infrared photodetection and communication. As the scientific community continues to unravel quantum dot materials’ full potential, such innovative devices are poised to become foundational components in the evolving ecosystem of photonic technologies.

The innovative approach combining materials science and device engineering in this study exemplifies the progress toward harnessing nanoscale phenomena for macroscopic technological impact. It also exemplifies how emerging nanotechnologies can intersect with practical application domains, offering solutions that are both sophisticated and accessible.

In conclusion, the development of high-responsivity colloidal quantum dot phototransistors represents a significant leap forward in the field of near-infrared detection. These devices promise to enhance the sensitivity and efficiency of photodetection systems used across multiple industries, stimulating further research and potential commercialization in a rapidly evolving photonic landscape.

Article Title:
High responsivity colloidal quantum dots phototransistors for low-dose near-infrared photodetection and image communication

Article References:
Zhan, S., Li, B., Chen, T. et al. High responsivity colloidal quantum dots phototransistors for low-dose near-infrared photodetection and image communication. Light Sci Appl 14, 201 (2025). https://doi.org/10.1038/s41377-025-01853-7

Image Credits:
AI Generated

DOI:
https://doi.org/10.1038/s41377-025-01853-7