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Infrared photodetectors (IRPDs) are of importance devices with wide applications from face identification to space communication. With the investigation of thermoelectric materials, perovskite and three-dimensional (3D) graphene have been demonstrated and fabricated to thermoelectric PDs with response to terahertz bands separately. Herein, we develop thermoelectric PD based on 3D graphene and perovskite hybrid material with good IR performance. The responsivity at 1 V bias reaches to 0.1 A/W, under the illumination of 1064 nm laser with the power density of 3.1 mW, corresponding noise equivalent power (NEP) 1 nW∙Hz-1/2 , the rise time 10.8 ms and fall time 12.8 ms, respectively. These results demonstrate these hybrid IRPDs show good IR performance, and can provide a reference for other spectral range such as terahertz bands.
Graphene is a new type of two-dimensional (2D) nanomaterial composed of single-layer carbon atoms. It has high carrier mobility, good optical performance, good mechanical performance and thermal conductivity. Three-dimensional (3D) reduce graphene oxide (rGO) foam integrates the structure of 2D graphene with three-dimensional network connected structure of carbon nanomaterials, which is in a seamless connection possessing better optical and electrical properties. 3D GF has achieved some results in solar cells and supercapacitors, however, field effect transistors are rarely studied. In this paper, a kind of field effect transistor (FET) based on 3D rGO foam has been fabricated and its photoelectric response characteristics have been studied. The results show that an obvious photocurrent could be measured when the laser irradiate on the 3D rGO foams channel. The magnitude of the photocurrent can be effectively modulated by the back-gate voltage. The device exhibits a “V” shape transfer curves and stabile and reproducible photocurrent cycles. Particularly, a high photoresponsivity of 7.8 mA W-1 is achieved, which reveals 3D rGO foams a good candidate for photodetectors.
All-inorganic perovskite quantum dots (QDs) have widely used in a lot of micro-nano photoelectric devices. However, resistive random access memory (RRAM) devices based on All-inorganic perovskite QDs are relatively scarce. In this work, a RRAM, which exhibits the write-once-read-many-times (WORM) memory effect, based on CsPbBr3 QDs was successfully fabricated by solution processed method at room temperature. The CsPbBr3 QDs based memory shows great reproducibility, good data retention ability, irreversible electrical transition from the high resistance state (HRS) or OFF state to the low resistance state (LRS) or ON state and the resistance ratio (ON/OFF) can reach almost 107. To study the CsPbBr3 QDs based WORM memory provides an opportunity to develop the next generation high-performance and stable WORM devices.
All-inorganic cesium lead halide perovskite quantum dots (PQDs) have been applied in optoelectronic fields owing to their unique properties including high carrier mobility, air stabilities and highly efficient photoluminescence. To overcome existing limitations in photodetection for light with particular wavelength and cost of state-of-the-art systems, new-style device structures and composite material systems are needed with low-cost fabrication and high performances. Here we synthesized the CsPbX3 (X = Cl, Br, and I) PQDs by changing the composition at room temperature and fabricated vertical field effect phototransistors (VFEpTs) with Au/Ag nanowires as the transparent source electrode and composition-dependent CsPbX3 (X = Cl, Br, and I) PQDs as active materials. It dominates to obtain photoresponse for specific wavelength in the visible spectrum and high performances. Particularly, VFEpTs based on CsPbCl1.5Br1.5 CsPbBr3, and CsPbBr1.5I1.5 PQDs are sensitive for blue, green, and red lights, respectively. It is worth mentioning that the device exhibits quantitative characterization for the contents of white light. Furthermore, CsPbX3 VFEpTs exhibit high performances including a short photoresponse time (less than 6 ms) and a high photoresponsivity (<9 × 104 AW−1). Allinorganic PQDs open up opportunities to integrate inorganic semiconductors, into high performances and flexible devices by using low cost, room temperature, large area, and solution based methods.
To overcome existing limitations in sensitivity and cost of state-of-the-art systems, new-style device structures and composite material systems are needed with low-cost fabrication and high performance. Vertical field effect photodetectors are fabricated with Au/Ag nanowires as the transparent source electrode and with vertically stacked layers of CsPbBr3 and lead sulfide quantum dots, which formed heterojunctions. The built-in electric field in the layered heterojunction aids the separation of photoinduced excitons, while the short channel enables efficient carrier transport across the active region. Both of these benefits enable a high photo performance and fast photoresponse. This vertical phototransistors exhibit a wide response spectrum from 400 to 2100 nm, a high photoresponsivity of more than 9 × 108 AW−1, and a high detectivity of up to 2 × 1017 Jones (cm Hz1/2 W−1) under infrared illumination. Additionally, this vertical phototransistor had a response time of 3 μs. The solution –based fabrication process and excellent device performances strongly underscore vertical architecture combined with the layered heterojunction as a promising approach for future photodetection field.
Organic-inorganic hybrid perovskites with good intrinsic physical properties have received substantial interest for solar cell and optoelectronic applications. However, perovskite film always suffers from a low carrier mobility due to its structural imperfection including sharp grain boundaries and pinholes, restricting their device performance and application potential. Here we demonstrate a straightforward strategy based on multi-step annealing process to improve the performance of perovskite photodetector. Annealing temperature and duration greatly affects the surface morphology and optoelectrical properties of perovskites which determines the device property of phototransistor. The perovskite films treated with multi-step annealing method tend to form highly uniform, well-crystallized and high surface coverage perovskite film, which exhibit stronger ultraviolet-visible absorption and photoluminescence spectrum compare to the perovskites prepared by conventional one-step annealing process. The field-effect mobilities of perovskite photodetector treated by one-step direct annealing method shows mobility as 0.121 (0.062) cm2V-1s-1 for holes (electrons), which increases to 1.01 (0.54) cm2V-1s-1 for that treated with muti-step slow annealing method. Moreover, the perovskite phototransistors exhibit a fast photoresponse speed of 78 μs. In general, this work focuses on the influence of annealing methods on perovskite phototransistor, instead of obtains best parameters of it. These findings prove that Multi-step annealing methods is feasible to prepared high performance based photodetector.
Ultrasensitive near-infrared phototransistors based on Lead sulfide (PbS) quantum dots (QDs)-graphene hybrid channel are fabricated by facile solution processing. The device combines the advantages of the large light absorbance of QDs high mobility of graphene. Under light illumination, the photogenerated carriers will transfer from QDs to graphene. As result, the phototransistor exhibits fast response speed with rise time of 1.4 ms and fall time of 1.3 ms at 36 mW/cm2 illumination of 808 nm wavelength, meaning the device can follow a fast switched optical signal. The responsivity (R), effective quantum efficiency (EQE) of the device are 6 A/W and 961% under 166mW/cm2 illumination, respectively. It expected that the PbS QDs–graphene hybrid devices are promising for fast response, low-cost and easy fabrication photoelectronics
The optical responsivity of bulk-heterojunction field effect phototransistors (BH-FEpTs) based on poly [2-methoxy-5-(2´- ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) and PbS quantum dot hybrids is very low. A main reason for the low responsivity is the low carrier mobility of the blends. To overcome the shortcoming, graphene with high carrier mobility (~200,000 cm2V-1s-1) can be used for improving the responsivity of BH-FEpTs. However, the influence of monolayer graphene on the photo response of BH-FEpTs still has been not studied. In this papers, BH-FEpTs and GBH-FEpTs (single layer graphene beneath the BH layer in BH-FEpTs) were fabricated. Experimentally, the GBH-FEpTs showed ultrahigh mobility for both holes and electrons (μH and μE) of 183 and 169 cm2V−1s−1, while 11.3 and 6.2 cm2V−1s−1 in BH-FEpT. Due to the greatly promoted carrier mobility and highly ordered channels for GBH-FEpTs, higher α, μ and β are obtained for GBH-FEpTs. The responsivity of GBH-FEpTs is improved to 101 A/W, which is two orders magnitude larger than BH-FEpTs (10-1 A/W).
We fabricate and investigate the photoelectrical characterization of PbSe QDs FEpTs Field Effect photo Transistors in lateral (LQFEpT) and vertical architectures (VQFEpT) respectively. Both LQFEpT and VQFEpT apply PbSe quantum dots as active layer, with different channel length of 0.1mm and 678nm respectively. The VQFEpT apply Au/Ag nanowires (NWs) as source transparent electrode connecting with Au source electrode. The ambipolar operation of both FEpTs show low power consumption, delivering high drain current at VSD = VG = ± 4 V. The VQFEpT exhibit higher photocurrent up to 4mA, three orders magnitude higher than that in LQFEpTs (16μA), owing to the superior carrier transportion in the shorter channel. As a result, higher photo responsivity (8×104A/W), specific detectivity (2×1012Jones) and gain (1.3× 105) are achieved in VQFEpT. The all-solution processing vertical architecture provide a convenient way for IR photo detectors with high performances.
Stable and homogeneous dye-doped cholesteric liquid crystals (DDCLCs) were prepared. The lasers generated from DDCLCs can be tuned by temperature, and the working temperature range of DDCLCs was from 20 °C to 60 °C. After adding bi-functional monomer RM257 and photoinitiator Irgacure 2959, the working temperature range of lasers from DDCLCs was enhanced from 20-60 °C to 20-70 °C.
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