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Sulphur-doped graphene quantum dots (S-GQDs) were prepared in this work by a novel and facile method using the co-combustion (T-X-J method) of a liquid mixture of paraffin oil and carbon disulphide (CS2). Ultra-high performance (R: 307 A W−1; D*: 1.5 × 1014 Jones) ultraviolet photodetectors based on S-GQDs were fabricated under ambient conditions, shedding light on the fabrication of graphene based high-performance optoelectronic devices.

Solution processable high-performance, large-area, low-cost infrared organic photodetectors (OPDs) have been receiving more and more attention for their important applications both in scientific and technological fields. The search for a simple method to upgrade device performance for OPDs becomes increasingly important. Here, the performance of an OPD in the near-infrared (NIR) region is tremendously improved by doping iodine into the device's active layer (P3HT:PCBM:I2), 2.7 wt% iodine doping may increase the absorption by 31.3% for the active film and result in a ∼11 000-fold increase in responsivity for the detector. A high detectivity (D*) of ∼1.6 × 1012 cm Hz1/2 W−1, a good specific responsivity (R) of ∼80 A W−1 and a large EQE (external quantum efficiency) of 120% are achieved under illumination (λ = 850 nm) at room temperature. Systematic characterizations reveal that iodine-doping can introduce acceptor states in the energy band gap for the polymer layer, and thus increase the harvesting to long wavelength photons. A small dose of iodine doping can significantly induce improvement in device performance. This work demonstrates a simple but feasible method to enhance an NIR optoelectronics device.

Integration of organic/inorganic hybrid perovskites with metallic or semiconducting phases of 2D MoS2 nanosheets via solution processing is demonstrated. The results show that the collection of charge carriers is strongly dependent on the electronic properties of the 2D MoS2 with metallic MoS2 showing high responsivity and the semiconducting phase exhibiting high on/off ratios.

Herein, we report an effective and simple method for producing Tellurium Quantum dots (TeQDs), zero-dimensional nanomaterials with great prospects for biomedical applications. Their preparation is based on the ultrasonic exfoliation of Te powder dispersed in 1-methyl-2-pyrrolidone. Sonication causes the van der Waals forces between the structural hexagons of Te to break so that the relatively coarse powder breaks down into nanoscale particles. The TeQDs have an average size of about 4 nm. UV-Vis absorption spectra of the TeQDs showed an absorption peak at 288 nm. Photoluminescence excitation (PLE) and photoluminescence (PL) are used to study the optical properties of TeQDs. Both the PLE and PL peaks revealed a linear relationship against the emission and excitation energies, respectively. TeQDs have important potential applications in biological imaging and catalysis as well as optoelectronics.

Graphene oxide (GO) was synthesized by a hydrothermal method using glucose solution as the sole reagent. The wavelength-dependent photoresponse of GO was investigated by fabricating metal–GO–metal photodetectors. The devices demonstrated a broadband photoresponse from 290 to 1610 nm covering deep ultraviolet (UV) to near-infrared (NIR), which is the broadest spectral range yet demonstrated on GO. The response times of the photodetectors in the UV and visible range are about 100 ms, which are at least one order of magnitude faster than photodetectors based solely on GO reported previously. The responsivity of the photodetector can be as high as 23.6 mA W−1 in the visible range. The wavelength-dependent photoresponse is closely related to the absorption characteristics of GO. Potential for a self-powered GO based photodetector is first demonstrated, and the device shows a prominent photoresponse at zero bias. The GO based photodetectors pave the way for developing low-cost, broadband, self-powered as well as spectrally tuneable photodetectors.

Integration of organic/inorganic hybrid perovskites with metallic or semiconducting phases of 2D MoS

Polyaniline-functionalized graphene quantum dots (PANI-GQD) and pristine graphene quantum dots (GQDs) were utilized for optoelectronic devices. The PANI-GQD based photodetector exhibited higher responsivity which is about an order of magnitude at 405 nm and 7 folds at 532 nm as compared to GQD-based photodetectors. The improved photoresponse is attributed to the enhanced interconnection of GQD by island-like polymer matrices, which facilitate carrier transport within the polymer matrices. The optically tunable current–voltage (I–V) hysteresis of PANI-GQD was also demonstrated. The hysteresis magnifies progressively with light intensity at a scan range of ±1 V. Both GQD and PANI-GQD devices change from positive to negative photocurrent when the bias reaches 4 V. Photogenerated carriers are excited to the trapping states in GQDs with increased bias. The trapped charges interact with charges injected from the electrodes which results in a net decrease of free charge carriers and a negative photocurrent. The photocurrent switching phenomenon in GQD and PANI-GQD devices may open up novel applications in optoelectronics.

Graphene has attracted much attention at various research fields due to its unique optical, electronic and mechanical properties. Up to now, graphene has not been widely used in optoelectronic fields due to the lack of large-area uniform doped graphene (n-doped and p-doped) with smooth surface. Therefore, it is rather desired to develop some effective doping methods to extend graphene to optoelectronics. Here we developed a novel doping method to prepare large-area (> centimeter scale) uniform doped graphene film with a nanoscale roughness(RMS roughness ∼1.4 nm), the method (nano-metal film doping method) is simple but effective. Using this method electron doping (electron-injection) may be easily realized by the simple thermal deposition of Ag nano-film on a transferred CVD graphene. The doping effectiveness has been proved by Raman spectroscopy and spectroscopic ellipsometry. Importantly, our method sheds light on some potential applications of graphene in optoelectronic devices such as photodetectors, LEDs, phototransistors, solar cells, lasers etc.

An interesting class of low-dimensional nanomaterials, namely, selenium quantum dots (SeQDs), which are composed of nano-sized selenium particles, is reported in this study. The SeQDs possess a hexagonal crystal structure. They can be synthesized in large quantity by ultrasound liquid-phase exfoliation using NbSe2 powders as the source material and N-Methyl-2-pyrrolidone (NMP) as the dispersant. During sonication, the Nb-Se bonds dissociate; the SeQDs are formed, while niobium is separated by centrifugation. The SeQDs have a narrow diameter distribution from 1.9 to 4.6 nm and can be dispersed with high stability in NMP without the need for passivating agents. They exhibit photoluminescence properties that are expected to find useful applications in bioimaging, optoelectronics, as well as nanocomposites.

Doping with hetero-atoms is an effective way to tune the properties of graphene quantum dots (GQDs). Here, potassium-doped GQDs (K-GQDs) are synthesized by a one-pot hydrothermal treatment of sucrose and potassium hydroxide solution. Optical properties of the GQDs are altered as a result of K-doping. The absorption peaks exhibit a blue shift. Multiple photoluminescence (PL) peaks are observed as the excitation wavelength is varied from 380 nm to 620 nm. New energy levels are introduced into the K-GQDs and provide alternative electron transition pathways. The maximum PL intensity of the K-GQDs is obtained at an excitation wavelength of 480 nm which is distinct from the undoped GQDs (375 nm). The strong PL of the K-GQDs at the longer emission wavelengths is expected to make K-GQDs more suitable for bioimaging and optoelectronic applications.

The giant anisotropic Raman response of encapsulated ultrathin black phosphorus (BP) is reported by uniaxial strain. A modified bending technique is employed to apply precise uniaxial tensile strain along the zigzag or armchair direction of the ultrathin BP encapsulated by a layer of polymethyl methacrylate. The Raman shift rates of the A 1 g, B 2g, and A 2 g modes are significantly distinct for strain applied along different directions. For the strain applied along zigzag direction, the Raman shift rate of the B 2g mode can reach a remarkable value of ≈−11 cm−1/% strain. In addition, the Gruneisen parameter is as high as ≈2.5, which is the largest among all the reported common 2D materials. Density functional perturbation theory calculations are performed to understand the exceptional anisotropic strain response discovering that not only the bond lengths but also the bond angels are changed in the strained ultrathin BP, which lead to the giant anisotropic Raman response. Furthermore, an alternative method based entirely on the strained ultrathin BP and nonpolarized Raman spectroscopy is demonstrated to determine the crystallographic orientations of ultrathin BP. This work paves a way to study the strain-induced anisotropic electrical conductance and magnetotransport properties of BP.

Ultraviolet (UV) photodetector is a kind of important optoelectronic device which can be widely used in scientific and engineering fields including astronomical research, environmental monitoring, forest-fire prevention, medical analysis, and missile approach warning etc. The development of UV detector is hindered by the acquirement of stable p-type materials, which makes it difficult to realize large array, low-power consumption UV focal plane array (FPA) detector. Here, we provide a novel structure (Al/Poly(9,9-di-n-octylfuorenyl-2,7-diyl)(PFO)/ZnO/ITO) to demonstrate the UV photovoltaic (PV) response. A rather smooth surface (RMS roughness: 0.28 nm) may be reached by solution process, which sheds light on the development of large-array, light-weight and low-cost UV FPA detectors.