Colloidal quantum dots can be stabilized in either a polar solvent or a nonpolar solvent depending on their surface chemistry. The former is typically achieved by charge stabilization while the latter by steric hindrance. This allows reversible tuning of their surface polarity for targeted application by engineering their ligand profile. Here we developed a hybrid stabilization approach that leveraged a combination of steric hindrance and charge stabilization simultaneously. We demonstrated this mechanism in a phase transfer process where hexane dispersed and hydrophobic CdSe/CdS core/shell quantum dots were exchanged into the hydrophilic dimethylformamide (DMF) phase. This was achieved by employing both Z-type cadmium acetate and X-type halide ligands. The results suggested only by using this hybrid stabilization strategy were we able to achieve good colloidal stability while preserving their photoluminescence quantum yield. This hybrid ligand strategy may promise new opportunities for the application of QDs in optoelectronic areas.

Hybrid perovskite solar cells (PSCs) are promising candidates in exploring high performance flexible photovoltaics, where a low-temperature-processed metal oxide electron transfer layer (ETL) is highly preferable. In this work, we demonstrate perovskite solar cells based on inorganic cadmium-sulfide (CdS) as the electron transfer layer, fabricated using low-temperature chemical bath deposition (CBD) at <85 °C. We show that natural Cd-doping has been achieved in the perovskite fabricated via a physical–chemical vapor deposition (P-CVD), which under properly controlled reaction and post-growth annealing leads to a high power conversion efficiency of 14.68% for the CdS-PSCs on glass substrate. Then, flexible perovskite solar cells with CdS as the ETL are fabricated for the first time and demonstrate a high PCE of 9.9%. These results highlight the exciting potential of a low-temperature-processed and readily scalable CdS-based PSC structure in the development of high performance flexible solar cells.

Organometal halide perovskite materials are outstanding candidates not only for solar cells but also for photo-detection. In this work, we develop a well-controlled lower temperature (<120 °C) and fast chemical vapor deposition process (LFCVD) to fabricate photovoltaic detectors with a high speed response (τrise/τfall ∼ 460 ns/940 ns) and a 3 dB-bandwidth above 0.9 MHz, which are the highest among those with a large active area (>0.1 cm2) without external power supply. Remarkably, the perovskite photovoltaic detectors demonstrate an excellent air-exposure stability for more than two months without particular encapsulation. These excellent performances are attributed to a well-controlled expansive gas–solid reaction and formation of perovskite crystallites that collide and pinch off the pinhole leakage paths at the grain boundaries. More importantly, the accumulated strain at the colliding grain boundaries leads to a selective evaporation of MAI during post-growth annealing, and thus passivate the local defects by the remnant PbI2 layer. These results highlight the potential of LFCVD perovskite materials in developing ultra-fast and self-driven photovoltaic detectors with outstanding stability and scalability.

Designing Prussian blue with optimally exposed crystal planes and confining it in a conductive matrix are critical issues for improving its sodium storage performance, and will result in much improved sodium ion adsorption and diffusion, together with improved electron mobility. Here, we firstly illustrate through DFT simulations that the {100} lattice planes and [100] direction of the KxFeFe(CN)6 crystal are the preferred occupation sites and diffusion route for sodium ions. In addition, through coupling with RGO, KxFeFe(CN)6 electrodes exhibit better electronic conductivity. Accordingly, {100} plane-capped cubic K0.33FeFe(CN)6 wrapped in RGO was fabricated using a facile CTAB-assisted method. Due to the highly robust framework, higher specific surface area, greatly reduced number of lattice water defects and conductive RGO coating, K0.33FeFe(CN)6/RGO exhibits superior electrochemical performance in sodium-ion batteries. As a cathode, the RGO-coated K0.33FeFe(CN)6 yields an initial discharge–charge capacity of 160 mA h g−1 at a rate of 0.5C, and an excellent capacity retention of 92.2% at 0.5C and 90.1% at 10C after 1000 and 500 cycles. Furthermore, XRD, DFT simulation, XANES and EXAFS verified that the structural changes during the Na-ion insertion–extraction processes are highly reversible. All these results suggest that {100} plane-capped K0.33FeFe(CN)6/RGO has excellent potential as a cathode for sodium-ion batteries.

MoS2, the classical representative of layered structure transition metal dichalcogenides (TMDCs), has been widely used as an ideal n-type semiconductor, offering an interesting opportunity to construct heterostructures with other 2D layered or 3D bulk materials for ultrafast optoelectronic applications. In this work, we report the synthesis of ultrathin MoS2 nanopetals via a solution-processable route, and the solution assembly of a 2D MoS2 nanopetal/GaAs n–n homotype heterojunction using graphene as the carrier collector. The fabricated devices have excellent photoresponse characteristics including a good detectivity of ∼2.28 × 1011 Jones, a noise current approaching 0.015 pA Hz−1/2 at zero bias and notably a very fast response speed, up to ∼1.87/3.53 μs with a broad photoresponse range. More interestingly, the device could respond to fast pulsed illumination up to 1 MHz, far exceeding the performance of many current congeneric 2D nanostructured and solution-processable photodetectors reported. These results suggest that our devices, together with the solution assembly methodology of the device described herein, can be utilized to give large-scale integration of low-cost, high-performance photodetectors, thus opening up new possibilities for 2D layered material-based photovoltaic and optoelectronic applications in the future.

Herein, we demonstrate a facile and less costly approach to deliberately modulate the composition of CsPbX3 (X = Cl, Br, I) NCs. Taking advantage of the highly ionic nature of perovskite structures, complete anion-exchange could be realized on the basis of directly synthesized CsPbBr3 employing zinc halogenide salts as anion source, which embraces the advantages of remarkably short exchange time and room-temperature reaction environment while maintaining the cubic phase for all CsPbX3 NCs, as well as accessing superior perovskite NC qualities with high stability and narrow full width at half maximum peak widths of 18 nm to 38 nm. By controlling the relative concentration of halide anions in a CsPbX3 NC-dispersed solution, their photoluminescence spectra can be finely tuned with ease covering the entire visible spectral region of 410–700 nm.

•Aqueous CdZnTe QDs with high photoluminescence were synthesized.•CdZnTe QDs were incorporated in CaCO3 matrix via a co-precipitation method.•CdZnTe QDs/CaCO3 composites show higher photostability and processability.•A WLED with a high color rendering index of 92.7 was fabricated.A facile synthesis of aqueous CdZnTe quantum dots (QDs) incorporated in CaCO3 matrix is demonstrated, providing a new type of solid-state light conversion material. Highly luminescent CdZnTe QDs were firstly synthesized using CdCl2, ZnCl2 and Te as precursors and 3-Mercaptopropionic acid (MPA) as ligand. Then CdZnTe QDs were incorporated into CaCO3 matrix through a co-precipitation method. Due to the protection of the tight matrix, the resulting CdZnTe QDs/CaCO3 composites exhibit good photostability and processability as well as high photoluminescence properties. A white light-emitting diode (WLED) applying the composites as a red color conversion layer was also fabricated, which showed excellent performance including a Commission Internationale de I'eclairage (CIE) color coordinate of (0.3662, 0.3396), a high color rendering index (Ra) of 92.7 and a low correlated color temperature (Tc) of 4146 K under 20 mA forward-bias current, suggesting the promising application of the composites in solid-state lighting systems.

•The PbI2 is dissolved completely at the room temperature and shows a high crystallization morphology with the NH4Cl inclusion.•The ligand matrix offers activated surface for the perovskite deposition and effectively reduces the deposition time.•The Cl− was introduced into the perovskite film to form the CH3NH3PbI3 and CH3NH3PbI3-xClx, reducing the hysteresis effect.•The perovskite solar cell exhibits a high PCE of 16.42% with the NH4Cl:PbI2 ratio of 0.75.An improved vapor-phase deposition that leveraged the use of surface activation of PbI2 film has been developed for modifying perovskite crystallization process. This was achieved by loading Cl− ligands on closely-packed PbI2 particle film—a scaffold that allowed in situ formation of perovskite active layer. The introducing of Cl− ligands served the Cl-capped and thus electrostatically-charged PbI2 nanoparticles showed improved colloidal stability in DMF, which facilitated the preparation of PbI2 film. More importantly, during the process of CH3NH3I (MAI) deposition i.e. the growth of perovskite materials, the presence of three-dimensional Cl− ligand matrix favored the formation of dense perovskite film. Moreover, a desired release of chloride was also achieved, thus promote the rearrangement of the perovskite during the volume expansion process. This finally led to a PCE of PSCs exceeding 16.42% under AM 1.5 irradiation. Therefore, surface-activation with Cl-ligand matrix could provide guidelines for the morphology optimization and the perovskite devices performance enhancement.The NH4Cl was introduced as additive to realize Cl− ligands on closely-packed PbI2 particle film, and favor the formation of dense perovskite film in subsequence chemical vapor deposition. An impressive power conversion efficiency of 16.42% was obtained with the NH4Cl:PbI2 ratio of 0.75. The results showed that the release of chloride promotes the rearrangement of the perovskite during the volume expansion process, meanwhile the chloride was also introduced into the perovskite crystal structure to form the CH3NH3PbI3 and CH3NH3PbI3-xClx phase, reducing the hysteresis effect in the devices. Therefore, surface-activation with Cl-ligand matrix could provide guidelines for the morphology optimization and also a promising method for the perovskite devices performance enhancement.Download high-res image (198KB)Download full-size image

An easy sol–gel method was devised to synthesize the carbon-wrapped Na0.67Ni0.17Ti0.67Co0.17O2 nanoparticles (NNTC/C), which served as anode material in the new type of sodium-ion batteries. Functioned as the sodium storage medium, the NNTC/C exhibited initial discharge/charge capacities of 122/110 mA h g−1 at the rate of 0.2 C in the voltage range of 0.2–2.5 V with capacity retention of almost 82% of its initial capacity after 500 cycles. It is indicated that among the component metals, redox association only exists between the Ti4+/Ti3+ couple and the Na+ insertion and extraction during the charge/discharge process. In addition, ex situ X-ray diffraction analysis illustrated a small fluctuation of cell volume in the cycling, suggesting a high level of reversible structural changeability and stability of the NNTC/C. The characterization results demonstrate that the NNTC/C is an ideal candidate as anode material for high-performance sodium-ion batteries.

Herein, we report a facile method of direct photodissociation of toluene molecules to photoluminescent carbon dots (CDs) under pulsed laser irradiation in the absence of surfactants or catalysts. The as-synthesized CDs with diameters 1.3–4.0 nm present regular emission peaks and the crystallographic structure of these species has been identified as graphite 2H from the analysis of high resolution transmission electron microscope (HRTEM) images, X-ray photoelectron spectroscopy (XPS) and Raman spectrum. In addition, First-Principle calculations were performed to discuss the photon-induced excitation in the photodissociation process. The results demonstrate that electrons can be transited from Highest Occupied Molecular Orbital (HOMO) to Lowest Unoccupied Molecular Orbital (LUMO) in toluene molecule by 248 nm single photon excitation process and the Stark effect plays a crucial role in the photodissociation process. These CDs exhibit excellent stable emission due to the stability of crystal structure, which could be considered for promising luminescent applications.

Advances in the photocurrent conversion of two-dimensional (2D) transition metal dichalcogenides have enabled the realization and application of ultrasensitive and broad-spectral photodetectors. The requirements of previous devices constantly drive for complex technological implementation, resulting in limits in scale and complexity. Furthermore, the development of large-area and low-cost photodetectors would be beneficial for applications. Therefore, we demonstrate a novel design of a heterojunction photodetector based on solution-processed ultrathin MoSe2 nanosheets to satisfy the requirements of its application. The photodetector exhibits a high sensitivity to visible–near infrared light, with a linear dynamic range over 124 decibels (dB), a detectivity of ~1.2 × 1012 Jones, and noise current approaching 0.1 pA·Hz–1/2 at zero bias. Significantly, the device shows an ultra-high response speed up to 30 ns with a 3-dB predicted bandwidth over 32 MHz, which is far better than that of most of the 2D nanostructured and solution-processable photodetectors reported thus far and is comparable to that of commercial Si photodetectors. Combining our results with material-preparation methods, together with the methodology of device fabrication presented herein, can provide a pathway for the large-area integration of low-cost, high-speed photodetectors.

Highly uniform NaV6O15 nanorods were obtained via a facile and low-cost PVP-modulated hydrothermal process. It is largely accepted that such a unique feature is favorable for rapid diffusion for sodium ions according to the intrinsic crystal structure. As the cathode, the as-prepared NaV6O15 nanorods are capable of delivering a high initial capacity of approximately 157 mA h g−1 at 20 mA g−1 for potentials ranging from 1.5 to 3.8 V and yielding 121 mA h g−1 at a high current density of 200 mA g−1. EIS analysis results demonstrated that the diffusion coefficients DNa as high as 2.71 × 10−12 cm2 s−1 at room temperature. In addition, it could be clearly observed that the NaV6O15 exhibited metallic behavior from the electron density of states, providing excellent electron conductivity. All these results suggest that NaV6O15 nanorods can be a very promising cathode for sodium batteries.

A green and efficient synthesis of aqueous CdTe quantum dots (QDs) embedded in inorganic salt enabled by co-precipitation is demonstrated, providing a new type of solid-state conversion material with emission colors covering green to red spectral regions. CdTe QDs were synthesized in the water phase, followed by incorporation into inorganic salt with the assistance of ethanol. Due to the protection of the tight matrix, the resulting composites exhibit good stability and processability as well as high photoluminescence properties. A white light emitting diode (WLED) applying the composites as a red color conversion layer with good luminescence properties is also fabricated, suggesting the promising application of the composites in solid-state lighting systems.

The incorporation of colloidal CdTe quantum dots into an inorganic matrix, BaSO4, through a handy and rapid co-precipitation method is demonstrated for the first time. Owing to the protection of the BaSO4 matrix, the resulting composites show stronger luminescence, longer fluorescent lifetime, and higher photo- and thermal stability as well as being more anti-acid compared to the parental CdTe QDs. Moreover, the composites hold several advantages for industrial applications. White light-emitting diodes (WLEDs) utilizing the composites as a red color conversion layer are fabricated, and produce bright white light with high color-rendering properties including a CIE coordinate of (0.34, 0.33), an Ra of 88, and a Tc of 5112 K at 20 mA, suggesting their great potential application in a solid-state lighting system with high color-rendering properties.

Depleted heterojunction (DH) solar cells have shown great potential in power conversion. A 3-D DH structure was first designed and fabricated through a layer-by-layer spin-coating technique to increase the interfacial contact of p-type PbS quantum dots (QDs) and n-type CdS nanorod arrays. As a result, a decent power conversion efficiency of 4.78% in this structure was achieved, which is five times the efficiency of a planar heterojunction structure of a similar thickness. In the 3-D DH structure, n-type CdS nanorod arrays (NRs) were grown vertically as electron acceptors, on which p-type PbS quantum dots were deposited as absorbing materials in a layer-by-layer spin-coating fashion. The results are discussed in view of effective transportation of electrons through CdS NRs than the hopping transportation in large nanoparticle-based CdS film, the enlarged interfacial area, and shortened carrier diffusion distance.Keywords: CdS nanorod arrays; depleted heterojunction; PbS quantum dots; power conversion efficiency; solar cells

•MoSe2 nanoplates were first synthesized through pyrolysis process.•MoSe2 demonstrates the first discharge and charge capacities of 513 and 440 mAh g−1.•The sodium batteries exhibited good cycling stability and rate performance.•The Na ion diffusion properties were investigated by first-principles calculation.•The surface and interlayer diffusion barrier of Na ions are 1.36 and 0.344 eV.The development of novel sodium-ion batteries has been hindered by the lack of ideal anode materials. Herein, we report both experimental and theoretical assessment of layered MoSe2 nanoplates as the anode materials. The MoSe2 nanoplates are successfully synthesized by a facile thermal-decomposition process. As the anode, the MoSe2 nanoplates are capable of delivering the initial discharge and charge capacities of 513 and 440 mAh g−1 at the current of 0.1C in a voltage of 0.1–3 V, respectively. The analysis of Ex-situ XRD patterns reveals that there is no slippage between layers and the change of coordination of molybdenum when the MoSe2 electrode is discharged to 0.6 V and conversion reactions during the following discharge/charge process are also demonstrated. In addition, the electronic structure, Na ions transport and conductivity are investigated by first-principles calculation. A quasi-2D energy favorable trajectory is proposed to illustrate the sodium ion vacancy-hopping migration mechanism form octahedron to tetrahedron in MoSe2 lattice. The results suggest great potential of MoSe2 as an anode material for Na ion batteries.

•CdS with optimized thickness was used as the electron acceptor materials.•An inverted FTO/CdS/PbS QDs/MoO3/Ag heterojunction structure was built.•Low-temperature deposition demonstrates potential large-scale production process.•The CdS/PbS QDs solar cells deliver an efficiency of 5.22%.Colloidal quantum-dot (QD) solar cells have emerged as one of the most promising photovoltaic techniques. Herein, we report an inverted PbS QD solar cells employing solution-processed CdS as the electron acceptor materials. Chemical bath deposition – one featuring ease of fabrication and compatibility with a low-temperature process – was employed to prepare CdS film on FTO glass, followed by deposition of PbS QDs as absorbing layer in a layer-by-layer fashion, thereby forming a depleted heterojunction structure. The results suggested that the thickness of CdS layer can be a key factor for determining the photovoltaic performance. After systematical optimization, an inverted FTO/CdS/PbS QDs/MoO3/Ag structure with an ultra-thin CdS film of 40 nm delivered a decent power conversion efficiency of 5.22%. The maximum temperature is ~85 °C via device fabrication demonstrates potential large-scale production process.

The real applications of Na3V2(PO4)3 cathode material for sodium batteries have been hindered by low-cost and facile synthesis method. Herein, we report a facile self-combustion method to synthesize Na3V2(PO4)3 nanoparticles coated with carbon shell (NVP/C). Using as the cathode, the NVP/C is capable of delivering the initial discharge and charge capacities of 100.72 and 111.3 mAh g−1 at the current of 0.1 C in a voltage of 2.5–3.8 V, and the capacity retention of the sample is approximately 95% of its initial specific capacity after 50th cycles. The first-principles simulation results show that the Na ions migration route prefers between two adjacent tetrahedral sites with the vacancy-hopping mechanism in a curved way, with the lowest activation energy of 0.292 eV. The diffusion coefficients DNa+ at room temperature was also calculated as higher as 2.38 × 10−9 cm2 s−1. The results suggest great potential of self-combustion synthesized NVP/C as cathode materials for Na-ion batteries.

The real application of lithium-ion batteries in electric vehicles lacks the ideal anode materials. Herein, we report both experimental and theoretical study of MoSe2 nanocrystals as the anode materials. MoSe2 nanocrystals are successfully synthesized via a facile thermal-decomposition process. As the anode, the nanocrystalline MoSe2 yields the initial discharge and charge capacities of 782 and 600 mA h g–1 at the current of 0.1 C in a voltage of 0.1–3 V. First-principles simulation demonstrates that, during the initial discharge process, there is a Li atoms induced phase transition from 2H-MoSe2 to the O-MoSe2 phase at 0.9 V, and then Mo cluster occurs as more Li atoms intercalated into the MoSe2 lattice, which is associated with the formation of Mo and Li2Se. And the following charge/discharge processes are related to the conversion reaction between Mo and Li2Se. Meanwhile, the Li ion vacancy-hopping diffusion mechanism from octahedron to tetrahedron in MoSe2 lattice is proposed based on a quasi-2D energy favorable trajectory and the calculated diffusion constant is 1.31 × 10–13 cm2 s–1. For comparison, the amorphous MoSe2 demonstrates the same phase transition process after the initial charge/discharge cycle. The results show that the nanocrystalline MoSe2 can be the very promising novel anode materials for high performance Li-ion batteries.

Vertically aligned nanowire arrays (NWAs) of semiconductor materials, combined with the merits of the large surface-to-volume ratio and low reflectance induced by light scattering and trapping, have attracted growing interests in the fabrication of high-performance optoelectronic nano-devices due to their exceptional geometrical structure and device architecture. However, an inexpensive synthesis of II–VI group semiconductor NWAs, e.g. CdS, CdSe NWAs, especially their heterostructures, is still a great challenge, and the devices (photodetector, field emitter, etc.) based on these NWA heterostructures have therefore been rarely studied. Here, we report a new method of synthesizing high-quality vertical CdS NWAs which heteroepitaxially grow on CdSe single-crystalline sheets (SCSs). The CdS NWA/CdSe SCS heterostructures as a whole are designed and fabricated into novel photodetectors via E-beam lithography. The obtained photodetectors exhibit excellent performance with high photosensitivity, responsivity, and external quantum efficiency, alongside fast response speed, and wide range response spectrum. Additionally, field-emission data of these vertically tapered CdS NWAs on CdSe SCS show enhanced properties with low turn-on field, high enhancement factor, and good stability. The results indicate that the synthesized CdS NWA/CdSe SCS heterostructure is a good candidate for broadband (ultraviolet-visible) photodetectors and field-emitters.

A low-intensity ultraviolet photodetector (PD), with a gain as high as ∼2.4 × 106, has been successfully constructed based on gallium (Ga) doped zinc sulfide (ZnS) nanoribbons (NRs). The device exhibits excellent photoconductive properties upon a bias voltage as low as ∼0.01 V in terms of high sensitivity to UV light with an intensity of 1 μW cm−2 (corresponding to an incident power of 10−14 W), relatively fast response times of ∼3.2 ms, and an extremely high detectivity of ∼1.3 × 1019 cm Hz1/2 W−1. The high gain and fast response time are attributed to the excellent ohmic contact obtained by using a high quality ITO electrode and having a carrier mobility as high as 130 cm2 V−1 s−1, which was confirmed from the back-gate field effect transistors. These results show that the single-crystalline n-type ZnS:Ga NRs will have potential applications in future high-performance low-intensity ultraviolet photodetectors.

Sb-doped p-type ZnTe nanoribbons (NRs) and Ga-doped n-type CdSe NRs were synthesized via a co-thermal evaporation method in a horizontal tube furnace, respectively. Crossbar heterojunction diode (HD) devices were constructed from p-ZnTe:Sb NRs and n-CdSe NRs by a convenient route. The p-ZnTe/n-CdSe NR HD device exhibits a significant rectification characteristic with a rectification ratio up to 103 within ±5 V and a low turn-on voltage of 2.6 V. Photoresponse analysis reveals that such HD devices were highly sensitive to light illumination with excellent stability, reproducibility and fast response speeds of 37/118 μs at reverse bias voltage. It is expected that such HD devices will have great potential applications in electronic and optoelectronic devices in the future.

This communication explored a novel approach – one that incorporates postsynthetic annealing treatment – in tailoring the shape of Ag nanostructures, by which Ag nanocubes and nanorods were achieved using a coalescence-growth process.

•This work demonstrates that the excitation energy cannot be transferred from Sb3+ to Eu3+ in YBO3.•White luminescence is tuned up by taking the isolated emission of Sb3+ and Eu3+ simultaneously in YBO3.•The strong electron–lattice interaction between Sb3+ and YBO3 results in a much larger Stokes shift of Sb3+ than Bi3+.•The spin–orbit interaction of the small Sb3+ is stronger than that of Bi3+.•There is no matchable energy levels for the energy transfer from Sb3+ to Eu3+.The phosphors of Sb3+ and Eu3+ activated YBO3 were synthesized via solid-state reaction. The crystal structure was investigated using X-ray diffraction analysis. The luminescence and energy transfer were investigated on the synchrotron radiation instrument, by exciting with different wavelengths at room temperature or as low temperature as 14 K. The electron–lattice interaction between the activator Sb3+ and the host of YBO3 combined with the spin–orbit interaction of Sb3+ result in a large Stokes shift in Sb3+ emission, giving rise to no matchable energy levels for the energy transfer from Sb3+ to Eu3+. Nevertheless, the excitation energy could transfer from Bi3+ to Eu3+, which has the same ns2 electronic configuration as Sb3+. Taking advantage of the simultaneous isolated luminescence of Sb3+ and Eu3+, finally, the white luminescence from a single phosphor was tuned up by tailoring Sb3+ and Eu3+ concentrations in the YBO3 host, which shows potential application in deep ultraviolet light-emitting diodes (LEDs).

A new structure nonvolatile memory, with large conductance switching (on/off ratio > 106), has been constructed from a p-ZnS nanoribbon (NR)/n-Si heterojunction. The p-type ZnS NRs were obtained using cuprous sulfide (Cu2S) as the Cu dopant. Excellent Ohmic contact to p-type ZnS NRs was achieved by using a Cu/Au bilayer electrode, which contributed to the formation of the thin Cu2S interfacial layer between the electrode and the NR, as confirmed from the combined X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analysis. These devices exhibit a stable and reproducible hysteresis and excellent memory characteristics with a long retention time of 1 × 105 s and good endurance >6 months at room temperature. The electrical switching behavior could be attributed to the charge trapping and detrapping in interface states at the junction. The approach could potentially provide a viable way to create new advanced nonvolatile memory devices with simple structure and to fabricate large conductance switching and large-capacity data storage.

Ag-doped p-type ZnS nanoribbons (NRs) with a high hole concentration of 5.1 × 1018 cm−3 and high carrier mobility of 154.0 cm2 V−2 s−1 were synthesized by using silver sulfide (Ag2S) as the Ag source. Excellent ohmic contact to p-ZnS NR with specific contact resistivity as low as 5.6 × 10−7 Ω cm2 was achieved by using bilayer Cu (4 nm)–Au electrode, which according to the depth profiling X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analysis can help to form a thin Cu2S interfacial layer between the electrode. Based on the high quality ZnS NRs and achievement on ohmic contact, p–n photodiodes have been constructed from the p-ZnS nanoribbon (NR)–n-Si heterojunction with a response speed as high as ∼48 μs (rise time). Furthermore, the device also exhibits stable optoelectrical properties with high sensitivity to UV-visible-NIR light and an enhancement of responsivities of 1.1 × 103 AW−1 for 254 nm under a reverse bias of 0.5 V. These generality of the above results shows that the p-ZnS NR–n-Si heterojunction will have potential applications in future high-performance photodetectors.

Self-powered photodetectors based on CdS:Ga nanoribbons (NR)/Au Schottky barrier diodes (SBDs) were fabricated. The as-fabricated SBDs exhibit an excellent rectification characteristic with a rectification ratio up to 106 within ±1 V in the dark and a distinctive photovoltaic (PV) behavior under light illumination. Photoconductive analysis reveals that the SBDs were highly sensitive to light illumination with very good stability, reproducibility and fast response speeds at zero bias voltage. The corresponding rise/fall times of 95/290 μs represent the best values obtained for CdS based nano-photodetectors. It is expected that such self-powered high performance SBD photodetectors will have great potential applications in optoelectronic devices in the future.

Sb-doped ZnTe nanoribbons (NRs) with enhanced p-type conductivity were successfully synthesized by a simple thermal co-evaporation method. Nanodevices, including nano-field-effect transistors (FETs) and nano-photodetectors (nanoPDs), were constructed based on the ZnTe:Sb NRs and their structure dependent device performances were systemically investigated. It is found that the transport properties of the ZnTe nanostructures as well as the device structures play a critical role in determining the device performances. In contrast to the nano-metal-oxide-semiconductor FETs (nanoMOSFETs) with back-gate structure, the top-gate nano-metal-insulator-semiconductor FETs (nanoMISFETs) show much enhanced performances in all aspects. On the other hand, owing to the appropriate p-type doping, nano-photodetectors (nanoPDs) based on the ZnTe:Sb NRs exhibit excellent device performances, such as high responsivity and photoconductive gain, fast response speed, large detectivity and so on. Moreover, the response time could be effectively shortened by using nano-heterojunction photodetectors (nanoHPDs). It is expected that knowledge gained from this work could be readily extended to nanodevices based on other nanostructures.

High-quality CuInSe2 nanoparticles were successfully synthesized through a green, simple, low-cost route using environmentally friendly N-oleoylmorpholine as a new solvent of Se powder and oleylamine as capping ligand. The as-synthesized nanoparticles were characterized by X-ray diffraction, TEM, HRTEM, and energy dispersive X-ray spectroscopy. The experimental results revealed that the as-prepared CuInSe2 nanoparticles with chalcopyrite tetragonal structure have an average size about 8 nm. The facile and green synthesis strategy was also used to synthesize hexagonal shaped CuInSe2 nanorings by altering the synthesis parameters. Possible shape evolution and crystals growth mechanisms have been suggested for the formation of spherical shaped CuInSe2 nanoparticles and hexagonal shaped CuInSe2 nanorings, respectively.

Efficient n-type doping of ZnS nanoribbons (NRs) were accomplished by using chlorine (Cl) as the dopant viathermal evaporation. An indium tin oxide (ITO) transparent electrode was used to achieve ohmic contact to the ZnS:Cl NRs. The conductivity of the Cl-doped ZnS NRs was significantly improved as compared with the undoped ones and could be tuned to a wide range of 3–4 orders of magnitude by adjusting the Cl doping level. High-performance nano-photodetectors were constructed based on the ZnS:Cl NRs, which show high sensitivity to the UV light while are nearly blind to the visible light. Notably, the ZnS:Cl NR photodetectors have a photoconductive gain as high as ∼107, which is amongst the highest values obtained for UV nano-photodetectors so far. Our results demonstrate that the n-type ZnS NRs with tunable optoelectronic properties are promising building blocks for nano-optoelectronic devices.

A low-cost, green, and reproducibly non-injection one-pot synthesis of high-quality CdS quantum dots (QDs) is reported. The synthesis was performed in the open air by mixing precursors cadmium stearate and S powder into a new solvent N-oleoylmorpholine. An overlapped nucleation-growth stage followed by a dominated growth stage was observed. The resulting QDs exhibited well-resolved absorption fine substructure and a dominant band-edge emission with a narrow size distribution (the full width at half maximum (fwhm) was only 22–24 nm). The maximum photoluminescence (PL) quantum yield (QY) was as high as 46.5%. Highly monodispersed CdS QDs with tunable sizes and similar PL fwhm and QYs could also be obtained from the CdS QDs in a large-scale synthesis. The high-resolution transmission electron microscopy (HRTEM) images and powder X-ray diffraction (XRD) pattern suggested that the as-prepared QDs with high crystallinity had a cubic structure. A significant PL improvement and a continuous QY increase for the CdS QDs were observed during a long storage time in air and in a glovebox under room temperature. A slow surface reconstruction was proposed to be the cause for the PL enhancement of CdS QDs.Graphical abstractWith no aid of any nucleation initiators, a low-cost, green, and reproducibly one-pot approach was reported for the highly monodispersed CdS QDs with a narrow size distribution and excellent optical properties.Research highlights► A one-pot approach was developed for the synthesis of high-quality CdS QDs at the absence of any nucleation initiators. ► A new, air-stable, and low-cost benign solvent of N-oleoylmorpholine was used. ► An overlapped nucleation-growth mechanism was proposed. ► The long-term continuous PL enhancement and QY increase were observed.

Hierarchical nanostructures are of particular interest to researchers for their promising applications in functional materials. This work focused on the large-scale construction of 2-fold-symmetrical hierarchical ZnO nanostructure through wet-chemical route on preformed caky Zn substrate via the electroplating method. The result suggested that the preferential layer-by-layer dissolution of Zn plating, the in situ growth of ZnO nanowire arrays, and the gradual dissolution of the Zn substrate with the ongoing synthetic reaction jointly led to the growth of the hierarchical ZnO nanostructure. Meanwhile, the formation of the caky Zn substrate can be attributed to the spiral dislocation growth behavior of Zn plating and the existence of the precipitated H2 bubbles serving as the template. Multiple morphologies of such hierarchical ZnO nanostructure could be readily obtained not only by changing the synthetic conditions, but also by well-designing the structural parameters of the caky Zn substrate through controlling the electroplating conditions, including the employed cathode potential and the composition of the electrolyte.

The high temperature oxide thermoelectric materials of p-type Ca3Co4−xAgxO9 (denoted as p-Co349/Agx) and n-type Ca1−ySmyMnO3 (denoted as n-Mn113/Smy) were prepared by the self-ignition method combined with a sintering technique. The influence of doping Ag and Sm on the thermoelectric properties of the corresponding materials was evaluated. The figures of merit, ZT, for the p-Co349/Ag0.2 and n-Mn113/Sm0.02 materials reached maxima of 0.20 and 0.15 at 973 K, respectively. The performances of thermoelectric devices constructed with the p- and n-type pairs were evaluated in terms of the maximum output power (Pmax) and manufacturing factor. The Pmax and volume power density for the four-leg devices reached 36.8 mW and 81.9 mW cm−3 at ΔT of 523 K, respectively.Highlights► Doping of Ag and Sm on the thermoelectric properties of high temperature oxide thermoelectric materials of Ca3Co4O9 and CaMnO3 was evaluated. ► The figures of merit ZT for p-Ca3Co3.8Ag0.2O9 and n-Ca0.98Sm0.02MnO3 materials were up to 0.20 and 0.15 at 973 K, respectively. ► The devices constructed with the p- and n-type pairs could generate up to 36.8 mW, which corresponds to volume power density of 81.9 mW cm−3 at ΔT of 523 K.

Ternarysemiconductor Zn0.3Cd0.7Te nanoribbons are, firstly, synthesized via a two-step process, and the structure characterizations reveal that the as-synthesized nanoribbons are single-crystalline with a zinc blende structure and a crystal growth direction of [1–10]. Nano-field-effect transistors are fabricated based on single nanoribbon, and the electron transport characteristics demonstrate that the Zn0.3Cd0.7Te ribbons have p-type conductivity with a mobility (μh) of 5.7 cm2V−1S−1 and carrier concentration (nh) about 1.1 × 1017 cm−3. The prepared nanoribbons with significant p-type conductivity will be a very attractive candidate for nanoelectronic devices.

Ordered CdSe nanowire branched arrays were designed and synthesized while merging two particular structural features within a single nanomaterial. This novel CdSe nanostructure combines a branched structure and ordered single-crystalline character. The stems and branches consist of wurtzite CdSe single crystals. When measuring field-emission properties, the CdSe novel nanostructure demonstrated a low turn-on field at 4.3 ± 0.2 V μm–1 for the current densities of 10 μA cm–2, high field-enhancement factor (1160 ± 50), and long emission stability. It indicates that the CdSe novel nanostructure could potentially be used as field emitters. The excellent field-emission performance is due to the unique morphology of CdSe, e.g., high structural order, branched structure, perfect single-crystallinity, and tapered nanotips. In addition, red lasing, in a range 700–720 nm, of the ordered CdSe nanowire branched arrays were demonstrated. The nature of the observed lasing emission accords with coherent random lasing behavior. A lower lasing threshold was achieved due to the homoepitaxial growth of CdSe nanowire branches on the CdSe microrods stems as well.

Single-crystalline intrinsic and N-doped p-type ZnTe nanoribbons (NRs) were synthesized via the thermal evaporation method in argon-mixed hydrogen and nitrogen-mixed ammonia, respectively. Both intrinsic and doped ZnTe nanoribbons had zinc blende structure and uniform geometry. X-ray diffraction peaks of N-doped ZnTe nanoribbons had an obvious shift toward higher angle direction as compared with intrinsic ZnTe. X-ray photoelectron spectroscopy detection confirmed that the dopant content of nitrogen in ZnTe nanoribbons was close to 1%. Field-effect transistors based on both intrinsic and N-doped ZnTe nanoribbons were constructed. Electrical measurements demonstrated that N-doping led to a substantial enhancement in p-type conductivity of ZnTe nanoribbons with a high hole mobility of 1.2 cm−2 V−1 S−1 and a low resistivity of 0.14 Ω cm in contrast to the 6.2 × 10−3 cm−2 V−1 S−1 and 45.1 Ω cm for intrinsic nanoribbons. Moreover, the defect reaction mechanism was proposed to explain the p-type behaviors of both the intrinsic and the N-doped ZnTe nanoribbons.The ZnTe nanoribbons with enhanced p-type conductivity may have important potential applications in nanoelectronic and optoelectronic devices.

Ag-doped Na1.7Co2O4 thermoelectric oxides have been synthesized via a simple self-ignition route, which have different nominal compositions in the formula of Na1.7AgyCo2−yO4 (y = 0, 0.1, 0.2, 0.3, 0.4, 0.5). The ceramic samples showed the property of high-crystallographic orientation. The electrical resistivity and Seebeck coefficient were measured using four silver probes method. Analysis showed that phase composition, thermoelectric performance and density of the Ag-doped Na1.7Co2O4 ceramics were influenced by Ag dopant. In the whole measurement temperature, Na1.7Ag0.2Co1.8O4 performed the best thermoelectric properties. The power factor of the doped oxide reached 687.431 μW m−1 K−1 at 873 K.

High-quality CdSe quantum dots with less common zinc blende structure were prepared in non-coordinating solvent 1-octadecene, with environment-friendly N,N-dimethyl-oleoyl amide as an alternative chemical to replace trioctylphoshine for Se powder, oleic acid as primary capping ligands, and benzophenone as secondary ligands. The temporal evolution of the optical properties of the nanocrystals with different growth temperature was monitored. Significant redshifts occurred with the increase of the growth temperature. The sharpness of the first absorption peaks and the narrow emission band with full width at the half-maximum of about 30 nm indicates that the size distribution of the resulting quantum dots is narrow.

Ternary CdSXSe1−X single-crystal nanoribbons (NRs) with uniform and controllable compositions (0 < X < 1) were synthesized for the first time via sulfurizing the CdSe nanoribbons. The product was characterized by means of X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Analysis results revealed that the CdSXSe1−X nanoribbons had a wurtzite structure and grew along the [0001] direction. Photoluminescence measurements showed the CdSXSe1−X NRs had tunable and sharp near-band gap emissions and lasing action from 542 to 668 nm. Metal oxide semiconductor field-effect transistor devices based on single CdS0.25Se0.75 nanoribbons showed a pronounced gating effect, a threshold voltage of 4.9 V, a transconductance of 95 nS, and an on−off ratio of 105. Electron mobility and carrier concentration of the CdS0.25Se0.75 NR were estimated to be 14.8 cm2/(V s) and 3.9 × 1016 cm−3, respectively.

•Synthesizing PbS QDs by exploiting a cation exchange reaction.•A multi-junction heterojunction was constructed using the cation exchanged QDs.•An efficiency of 7.89% been reported.•An excellent air-storage stability was achieved.PbS colloidal quantum dots (QDs) have emerged as one of the most promising photovoltaic solar cells material. The synthesis of PbS QDs generally uses TMS2S as sulfur source. However, the volatile and environmentally unfriendly properties of TMS2S will limit its industrial applications. This paper presents a new method of synthesizing PbS QDs employing a CdS QDs/ODE solution as the sulfur precursor by exploiting a cation exchange reaction. The resulting QDs show a performance comparable with previous work for solar cells. Through optimizing the architecture of the photoactive layer, excellent stability in air is achieved. An efficiency of 7.89% is retained in air after 110 days.Download high-res image (270KB)Download full-size image

The stearate-capped CdTe quantum dots (QDs) have been first prepared via direct reaction of cadmium stearate with Te powder in N-oleoylmorpholine solvent, which was a kind of clean, air-stable and conveniently synthesized acylamide, and can readily dissolve precursors cadmium stearate and Te powder at a relative low temperature. The as-prepared CdTe QDs exhibited size-dependent optical properties, steep absorbance edge and narrow photoluminescence full width at half maximum. The high-resolution transmission electron microscopy images and X-ray diffraction revealed that the highly monodisperse CdTe QDs were of regular spherical morphology with zinc blende crystal structure displaying mean sizes of about 4 nm. The energy dispersed spectrometry measurement indicated the presence of Cd and Te, with the Cd:Te ratio being close to 1:1. Fourier transform infrared transmission spectra confirmed the existence of stearate on the CdTe QDs surfaces. The experimental results also demonstrated that the stearate-capped CdTe QDs had an unexpected good stability.

Vertically aligned nanowire arrays (NWAs) of semiconductor materials, combined with the merits of the large surface-to-volume ratio and low reflectance induced by light scattering and trapping, have attracted growing interests in the fabrication of high-performance optoelectronic nano-devices due to their exceptional geometrical structure and device architecture. However, an inexpensive synthesis of II–VI group semiconductor NWAs, e.g. CdS, CdSe NWAs, especially their heterostructures, is still a great challenge, and the devices (photodetector, field emitter, etc.) based on these NWA heterostructures have therefore been rarely studied. Here, we report a new method of synthesizing high-quality vertical CdS NWAs which heteroepitaxially grow on CdSe single-crystalline sheets (SCSs). The CdS NWA/CdSe SCS heterostructures as a whole are designed and fabricated into novel photodetectors via E-beam lithography. The obtained photodetectors exhibit excellent performance with high photosensitivity, responsivity, and external quantum efficiency, alongside fast response speed, and wide range response spectrum. Additionally, field-emission data of these vertically tapered CdS NWAs on CdSe SCS show enhanced properties with low turn-on field, high enhancement factor, and good stability. The results indicate that the synthesized CdS NWA/CdSe SCS heterostructure is a good candidate for broadband (ultraviolet-visible) photodetectors and field-emitters.

Sb-doped ZnTe nanoribbons (NRs) with enhanced p-type conductivity were successfully synthesized by a simple thermal co-evaporation method. Nanodevices, including nano-field-effect transistors (FETs) and nano-photodetectors (nanoPDs), were constructed based on the ZnTe:Sb NRs and their structure dependent device performances were systemically investigated. It is found that the transport properties of the ZnTe nanostructures as well as the device structures play a critical role in determining the device performances. In contrast to the nano-metal-oxide-semiconductor FETs (nanoMOSFETs) with back-gate structure, the top-gate nano-metal-insulator-semiconductor FETs (nanoMISFETs) show much enhanced performances in all aspects. On the other hand, owing to the appropriate p-type doping, nano-photodetectors (nanoPDs) based on the ZnTe:Sb NRs exhibit excellent device performances, such as high responsivity and photoconductive gain, fast response speed, large detectivity and so on. Moreover, the response time could be effectively shortened by using nano-heterojunction photodetectors (nanoHPDs). It is expected that knowledge gained from this work could be readily extended to nanodevices based on other nanostructures.

Tetragonal CsPb2Br5 nanosheets were obtained by an oriented attachment of orthorhombic CsPbBr3 nanocubes, involving a lateral shape evolution from octagonal to square. Meanwhile, the experimental results, together with DFT simulation results, indicated that the tetragonal CsPb2Br5 is an indirect bandgap semiconductor that is PL-inactive with a bandgap of 2.979 eV.

A new structure nonvolatile memory, with large conductance switching (on/off ratio > 106), has been constructed from a p-ZnS nanoribbon (NR)/n-Si heterojunction. The p-type ZnS NRs were obtained using cuprous sulfide (Cu2S) as the Cu dopant. Excellent Ohmic contact to p-type ZnS NRs was achieved by using a Cu/Au bilayer electrode, which contributed to the formation of the thin Cu2S interfacial layer between the electrode and the NR, as confirmed from the combined X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analysis. These devices exhibit a stable and reproducible hysteresis and excellent memory characteristics with a long retention time of 1 × 105 s and good endurance >6 months at room temperature. The electrical switching behavior could be attributed to the charge trapping and detrapping in interface states at the junction. The approach could potentially provide a viable way to create new advanced nonvolatile memory devices with simple structure and to fabricate large conductance switching and large-capacity data storage.

Self-powered photodetectors based on CdS:Ga nanoribbons (NR)/Au Schottky barrier diodes (SBDs) were fabricated. The as-fabricated SBDs exhibit an excellent rectification characteristic with a rectification ratio up to 106 within ±1 V in the dark and a distinctive photovoltaic (PV) behavior under light illumination. Photoconductive analysis reveals that the SBDs were highly sensitive to light illumination with very good stability, reproducibility and fast response speeds at zero bias voltage. The corresponding rise/fall times of 95/290 μs represent the best values obtained for CdS based nano-photodetectors. It is expected that such self-powered high performance SBD photodetectors will have great potential applications in optoelectronic devices in the future.

The incorporation of colloidal CdTe quantum dots into an inorganic matrix, BaSO4, through a handy and rapid co-precipitation method is demonstrated for the first time. Owing to the protection of the BaSO4 matrix, the resulting composites show stronger luminescence, longer fluorescent lifetime, and higher photo- and thermal stability as well as being more anti-acid compared to the parental CdTe QDs. Moreover, the composites hold several advantages for industrial applications. White light-emitting diodes (WLEDs) utilizing the composites as a red color conversion layer are fabricated, and produce bright white light with high color-rendering properties including a CIE coordinate of (0.34, 0.33), an Ra of 88, and a Tc of 5112 K at 20 mA, suggesting their great potential application in a solid-state lighting system with high color-rendering properties.

Sb-doped p-type ZnTe nanoribbons (NRs) and Ga-doped n-type CdSe NRs were synthesized via a co-thermal evaporation method in a horizontal tube furnace, respectively. Crossbar heterojunction diode (HD) devices were constructed from p-ZnTe:Sb NRs and n-CdSe NRs by a convenient route. The p-ZnTe/n-CdSe NR HD device exhibits a significant rectification characteristic with a rectification ratio up to 103 within ±5 V and a low turn-on voltage of 2.6 V. Photoresponse analysis reveals that such HD devices were highly sensitive to light illumination with excellent stability, reproducibility and fast response speeds of 37/118 μs at reverse bias voltage. It is expected that such HD devices will have great potential applications in electronic and optoelectronic devices in the future.

A low-intensity ultraviolet photodetector (PD), with a gain as high as ∼2.4 × 106, has been successfully constructed based on gallium (Ga) doped zinc sulfide (ZnS) nanoribbons (NRs). The device exhibits excellent photoconductive properties upon a bias voltage as low as ∼0.01 V in terms of high sensitivity to UV light with an intensity of 1 μW cm−2 (corresponding to an incident power of 10−14 W), relatively fast response times of ∼3.2 ms, and an extremely high detectivity of ∼1.3 × 1019 cm Hz1/2 W−1. The high gain and fast response time are attributed to the excellent ohmic contact obtained by using a high quality ITO electrode and having a carrier mobility as high as 130 cm2 V−1 s−1, which was confirmed from the back-gate field effect transistors. These results show that the single-crystalline n-type ZnS:Ga NRs will have potential applications in future high-performance low-intensity ultraviolet photodetectors.

Efficient n-type doping of ZnS nanoribbons (NRs) were accomplished by using chlorine (Cl) as the dopant viathermal evaporation. An indium tin oxide (ITO) transparent electrode was used to achieve ohmic contact to the ZnS:Cl NRs. The conductivity of the Cl-doped ZnS NRs was significantly improved as compared with the undoped ones and could be tuned to a wide range of 3–4 orders of magnitude by adjusting the Cl doping level. High-performance nano-photodetectors were constructed based on the ZnS:Cl NRs, which show high sensitivity to the UV light while are nearly blind to the visible light. Notably, the ZnS:Cl NR photodetectors have a photoconductive gain as high as ∼107, which is amongst the highest values obtained for UV nano-photodetectors so far. Our results demonstrate that the n-type ZnS NRs with tunable optoelectronic properties are promising building blocks for nano-optoelectronic devices.

Designing Prussian blue with optimally exposed crystal planes and confining it in a conductive matrix are critical issues for improving its sodium storage performance, and will result in much improved sodium ion adsorption and diffusion, together with improved electron mobility. Here, we firstly illustrate through DFT simulations that the {100} lattice planes and [100] direction of the KxFeFe(CN)6 crystal are the preferred occupation sites and diffusion route for sodium ions. In addition, through coupling with RGO, KxFeFe(CN)6 electrodes exhibit better electronic conductivity. Accordingly, {100} plane-capped cubic K0.33FeFe(CN)6 wrapped in RGO was fabricated using a facile CTAB-assisted method. Due to the highly robust framework, higher specific surface area, greatly reduced number of lattice water defects and conductive RGO coating, K0.33FeFe(CN)6/RGO exhibits superior electrochemical performance in sodium-ion batteries. As a cathode, the RGO-coated K0.33FeFe(CN)6 yields an initial discharge–charge capacity of 160 mA h g−1 at a rate of 0.5C, and an excellent capacity retention of 92.2% at 0.5C and 90.1% at 10C after 1000 and 500 cycles. Furthermore, XRD, DFT simulation, XANES and EXAFS verified that the structural changes during the Na-ion insertion–extraction processes are highly reversible. All these results suggest that {100} plane-capped K0.33FeFe(CN)6/RGO has excellent potential as a cathode for sodium-ion batteries.

MoS2, the classical representative of layered structure transition metal dichalcogenides (TMDCs), has been widely used as an ideal n-type semiconductor, offering an interesting opportunity to construct heterostructures with other 2D layered or 3D bulk materials for ultrafast optoelectronic applications. In this work, we report the synthesis of ultrathin MoS2 nanopetals via a solution-processable route, and the solution assembly of a 2D MoS2 nanopetal/GaAs n–n homotype heterojunction using graphene as the carrier collector. The fabricated devices have excellent photoresponse characteristics including a good detectivity of ∼2.28 × 1011 Jones, a noise current approaching 0.015 pA Hz−1/2 at zero bias and notably a very fast response speed, up to ∼1.87/3.53 μs with a broad photoresponse range. More interestingly, the device could respond to fast pulsed illumination up to 1 MHz, far exceeding the performance of many current congeneric 2D nanostructured and solution-processable photodetectors reported. These results suggest that our devices, together with the solution assembly methodology of the device described herein, can be utilized to give large-scale integration of low-cost, high-performance photodetectors, thus opening up new possibilities for 2D layered material-based photovoltaic and optoelectronic applications in the future.