Colloidal PbS quantum dot (QD)/graphene hybrid photodetectors are emerging QD technologies for affordable infrared light detectors. By interfacing the QDs with graphene, the photosignal of these detectors is amplified, leading to high responsivity values. While these detectors have been mainly operated at room temperature, low-temperature operation is required for extending their spectral sensitivity beyond a wavelength of 3 µm. Here, we unveil the temperature-dependent response of PbS QD/graphene photodetectors by performing steady-state and time-dependent measurements over a large temperature range of 80-300 K. We find that the temperature dependence of photo-induced charge carrier transfer from the QD layer to graphene is (i) not impeded by freezeout of the (Schottky-like) potential barrier at low temperatures, (ii) tremendously sensitive to QD surface states (surface oxidation), and (iii) minimally affected by the ligand exposure time and QD layer thickness. Moreover, the specific detectivity of our detectors increases with cooling, with a maximum measured specific detectivity of at least 10 10 Jones at a wavelength of 1280 nm and temperature of 80 K, which is an order of magnitude larger compared to the corresponding room temperature value. The temperature-and gate-voltage-dependent characterization presented here constitute an important step in expanding our knowledge of charge transfer at interfaces of low dimensional materials and towards the realization of next-generation optoelectronic devices.

Extreme miniaturization of infrared spectrometers is critical for their integration into next-generation consumer electronics, wearables and ultrasmall satellites. In the infrared, there is a necessary compromise between high spectral bandwidth and high spectral resolution when miniaturizing dispersive elements, narrow band-pass filters and reconstructive spectrometers. Fourier-transform spectrometers are known for their large bandwidth and high spectral resolution in the infrared; however, they have not been fully miniaturized. Waveguide-based Fourier-transform spectrometers offer a low device footprint, but rely on an external imaging sensor such as bulky and expensive InGaAs cameras. Here we demonstrate a proof-of-concept miniaturized Fourier-transform waveguide spectrometer that incorporates a subwavelength and complementary-metal–oxide–semiconductor-compatible colloidal quantum dot photodetector as a light sensor. The resulting spectrometer exhibits a large spectral bandwidth and moderate spectral resolution of 50 cm−1 at a total active spectrometer volume below 100 μm × 100 μm × 100 μm. This ultracompact spectrometer design allows the integration of optical/analytical measurement instruments into consumer electronics and space devices.

Infrared light detection enables diverse technologies ranging from night vision to gas analysis. Emerging technologies such as low‐cost cameras for self‐driving cars require highly sensitive, low‐cost photodetector cameras with spectral sensitivities up to wavelengths of 10 µm. For this purpose, colloidal quantum dot (QD) graphene phototransistors offer a viable alternative to traditional technologies owing to inexpensive synthesis and processing of QDs. However, the spectral range of QD/graphene phototransistors is thus far limited to 1.6 µm. Here, HgTe QD/graphene phototransistors with spectral sensitivity up to 3 µm are presented, with specific detectivities of 6 × 108 Jones at a wavelength of 2.5 µm and a temperature of 80 K. Even at kHz light modulation frequencies, specific detectivities exceed 108 Jones making them suitable for fast video imaging. The simple device architecture and QD film patterning in combination with a broad spectral sensitivity manifest an important step toward low‐cost, multi‐color infrared cameras.

The rapid evolution of the neuromorphic computing stimulates the search for novel brain-inspired electronic devices. Synaptic transistors are three-terminal devices that can mimic the chemical synapses while consuming low power, whereby an insulating dielectric layer physically separates output and input signals from each other. Appropriate choice of the dielectric is crucial in achieving a wide range of operation frequencies in these devices. Here we report synaptic transistors with printed aluminum oxide dielectrics, improving the operation frequency of solution-processed synaptic transistors by almost two orders of magnitude to 50 kHz. Fabricated devices, yielding synaptic response for all audio frequencies (20 Hz to 20 kHz), are employed in an acoustic response system to show the potential for future research in neuro-acoustic signal processing with printed oxide electronics.

Near (NIR) to shortwave (SWIR) infrared optical imaging, in particular, is used to assess the oxygen arterial saturation by quantifying the ratio of oxyhemoglobin to deoxyhemoglobin. The benefit of reduced tissue absorption in this spectral range (biological window: 700-1400 nm) [4] enables non-invasive direct probing. [1,5] First, flexible but flat detector concepts reveal the potential of an improved adaption to the skin and are based on organic [6] or hybrid graphene-colloidal PbS quantum dots (QDs) [7] materials. E-textiles based on smart fibers further improve interfacing the skin by reducing the structure dimension (from 2D flat substrate to 1D fibers) [8] and demonstrate their potential for energy harvesting and storage, light emission, as well as sensing applications. [9][10][11][12][13][14] Optimally, an e-textile allows for the integration of a diverse set of functionalities to, for instance, assess different vital signs as predictors of the overall health status of an individual. This requires the integration of multiple functions to a single fiber and poses a distinct need for new technological approaches. Methods to integrate IR detectors locally and on curved surfaces are, thus, highly desired. The combination of low-dimensional nanomaterials, such as Hybrid graphene-colloidal PbS quantum dots (QDs) phototransistors are promising to overcome the geometrical restrictions of photodetectors to flat substrates. While compatible with conformal manufacturing, the experimental demonstration of their application to curved surfaces remains elusive. This work demonstrates the seamless integration of an infrared (IR) photodetector to a polymer optical fiber (POF) by wrapping graphene around the POF of 1 mm in diameter and, subsequently, inkjet printing of PbS QDs onto the curved surface. The device acts as a functional coating and detects infrared light propagating through the POF without interrupting the waveguide. The formulated α-terpineol and hexane co-solvent ink supports drop-on-demand placement with a resolution of 50 µm and is colloidally stable over 7 months. A responsivity map over gate voltage and temperature (300 to 80 K) of a device, fabricated on a common flat substrate, reveals a responsivity of R ≈ 1 × 10 3 AW −1 (irradiance ≈1 µW cm −2 ) and a detectivity of D* ≈ 1 × 10 10 Jones at 1.6 µm wavelength. This work brings the integration of this cost-effective and adaptable hybrid detector approach closer to multifunctional e-textiles and will, notably, help to improve the interfacing of the skin as desired for wearable and non-invasive healthcare applications.