Lead sulfide quantum dot and organic semiconductor compounded flexible near-infrared photoelectric detector

Abstract

The invention provides a near-infrared photoelectric transistor based on lead sulfide quantum dots. The near-infrared photoelectric transistor structurally comprises a high dielectric material P (VDF-TrFE-CFE) serving as a dielectric layer, a DPP-DTT organic film serving as a conducting channel material, and PbS quantum dots covering the surface of a DPP-DTT electrode layer and serving as a light absorption layer. The lead sulfide quantum dot with oleic acid as a ligand is combined with DPP-DTT, the near-infrared photoelectric transistor with high response rate is prepared by using the excellent switch ratio and high mobility of DPP-DTT and the near-infrared light sensitive response characteristic of the lead sulfide quantum dot, and the near-infrared photoelectric transistor can be widely applied to the medical health fields of photoelectric detection, electronic skin and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic devices, and particularly to a flexible near-infrared phototransistor based on lead sulfide quantum dots and a preparation method thereof. Background Art

[0002] High-sensitivity near-infrared (NIR) photodetectors are crucial for sensing and imaging applications, such as health monitoring, thermal imaging, and night vision, where the detected optical signals are relatively weak. Among various photodetector structures, phototransistors provide high sensitivity and tunable gain by controlling unbalanced charge transport through a light-controlled gate terminal. Conventional phototransistors are made of inorganic materials such as silicon and III-V semiconductors. Colloidal quantum dots (CQDs) offer an attractive low-cost alternative to traditional bulk, epitaxially grown materials. Lead sulfide quantum dots have excellent light absorption properties in the near-infrared region, with a Bohr radius of approximately 18 nm, a small bandgap that can be continuously adjusted from 0.4 to 2.0 V, and can be synthesized and processed in large quantities through solution processing techniques with controllable size distribution, which has attracted extensive research interest in the field of near-infrared detection. This enables these photodetectors to be easily integrated with complementary metal-oxide semiconductor platforms and flexible substrates. In addition, the detectivity of solution-processed PbS CQD photoconductive photodetectors at room temperature reaches 1.8*10 13 Jons, exceeding that of externally grown InGaAs photodetectors.

[0003] For the light-absorbing and hole-transporting materials, we selected a recently developed narrow-bandgap polymer, poly(n-alkyl diketopyrrolodithiophene[3,2-b]thiophene) (DPP-DTT). It exhibits high field-effect hole mobility and a high on / off ratio (10 6 ) in a field-effect transistor (FET), and has high near-infrared absorption ability.

[0004] By combining lead sulfide quantum dots and DPP-DTT, the excellent light absorption properties of lead sulfide quantum dots and the high carrier mobility of DPP-DTT are combined to improve the device performance, and the gate effect is induced by applying a gate voltage to enhance and modulate the performance of the phototransistor. Summary of the Invention

[0005] The purpose of the present invention is to provide a near-infrared phototransistor based on lead sulfide quantum dots and a preparation method thereof, and the phototransistor has excellent response and detection in the near-infrared band.

[0006] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a flexible near-infrared phototransistor based on quantum dots. Its structure includes a PET substrate, an aluminum electrode evaporated on the surface of the PET substrate, a high dielectric material P(VDF-TrFE-CFE) spin-coated by solution method on the aluminum electrode as the dielectric layer, a DPP-DTT layer spin-coated by solution method on the dielectric layer as the channel material, an Au electrode layer evaporated on the surface of the DPP-DTT layer, and a lead sulfide quantum dot layer covering the surface of the Au electrode layer. The electrode pair is a parallel electrode pair.

[0008] Preferably, the DPP-DTT layer is formed by spin-coating a dichlorobenzene solution of DPP-DTT on a device treated with OTS.

[0009] Preferably, the distance between the electrode pairs is 0.08 - 2.5 mm.

[0010] Preferably, the thickness of the lead sulfide quantum dot layer is 20 - 70 nm; the lead sulfide quantum dot layer is formed by spin-coating lead sulfide quantum dots; the ligand of the lead sulfide quantum dots is oleic acid, and more preferably TBAI is used as the ligand of the lead sulfide quantum dots; the particle size of the lead sulfide quantum dots is 5 - 20 nm.

[0011] The present invention provides a preparation method of the near-infrared phototransistor described in the above technical solution, including the following steps:

[0012] Dissolve DPP-DTT in dichlorobenzene to prepare a DPP-DTT-dichlorobenzene solution, coat the DPP-DTT-dichlorobenzene solution on the upper surface of PVDF, and form a DPP-DTT layer after annealing treatment.

[0013] Evaporate electrode materials at both ends of the upper surface of the DPP-DTT layer to form a DPP-DTT-electrode layer.

[0014] Spin-coat a lead sulfide quantum dot solution on the upper surface of the DPP-DTT-electrode layer, and form a lead sulfide quantum dot layer after annealing; obtain the phototransistor.

[0015] Preferably, the concentration of DPP-DTT-dichlorobenzene is 3 - 5 mg / mL, the annealing temperature is 100 - 120 °C, and the annealing time is 30 - 50 min.

[0016] Preferably, the annealing temperature of the lead sulfide quantum dots is 70 - 120 °C, and the annealing time is 20 - 40 min.

[0017] Preferably, the evaporation is vacuum evaporation; the electrode materials are metal aluminum and gold.

[0018] The present invention provides a near-infrared phototransistor based on lead sulfide quantum dots, whose structure includes a DPP-DTT organic thin film as a conductive channel material and PbS quantum dots covering the surface of the DPP-DTT electrode layer as a light-absorbing layer.

[0019] The present invention combines lead sulfide quantum dots with oleic acid as a ligand and DPP-DTT, and utilizes the excellent on-off ratio and high mobility of DPP-DTT and the near-infrared light-sensitive response characteristics of lead sulfide quantum dots to prepare a near-infrared phototransistor with a high response rate, which can be widely applied to medical and health fields such as photoelectric detection and electronic skin. Brief Description of the Drawings

[0021] Figure 1 It is the device structure diagram of the near-infrared flexible phototransistor prepared in Example 1 of the present invention; Figure 2 The absorption spectrum diagram of the lead sulfide quantum dots and DPP-DTT prepared in Example 1 of the present invention; Figure 3 The transfer curve of the near-infrared flexible phototransistor prepared in Example 1 of the present invention under a 1550 nm light source; Figure 4 The time-current curve of the near-infrared flexible phototransistor prepared in Example 1 of the present invention under a 1550 nm light source. Embodiment

[0022] A near-infrared flexible phototransistor based on quantum dots, whose structure includes a DPP-DTT organic thin film as a conductive channel material and PbS quantum dots covering the surface of the DPP-DTT electrode layer as a light-absorbing layer.

[0023] In the present invention, the DPP-DTT layer is obtained by the solution spin-coating method. Prepare a DPP-DTT-dichlorobenzene solution with a concentration of 3-5 mg / mL, spin-coat it on the upper surface of the PET substrate, and then perform annealing to form the DPP-DTT layer; the annealing temperature is 100-120 °C, and the annealing time is 20-40 min.

[0024] In the present invention, the electrode pair is arranged in parallel at both ends of the DPP-DTT layer surface to form a DPP-DTT electrode layer; the parallel spacing of the parallel electrode pair is preferably 0.08-2.5 mm. In a specific embodiment of the present invention, the material of the electrode pair is preferably metal Au.

[0025] In the present invention, the thickness of the lead sulfide quantum dot layer is 20 - 70 nm; the lead sulfide quantum dot layer is formed by lead sulfide quantum dots; the ligand of the lead sulfide quantum dots is oleic acid, and more preferably ammonium iodide or TBAI is used as the ligand of the lead sulfide quantum dots; the particle size of the lead sulfide quantum dots is 5 - 20 nm.

[0026] The present invention provides a method for preparing the near-infrared phototransistor according to the above technical solution, comprising the following steps:

[0027] Dissolve DPP-DTT in dichlorobenzene to prepare a DPP-DTT-dichlorobenzene solution, spin-coat the DPP-DTT-dichlorobenzene solution on the upper surface of the PET substrate, and form a DPP-DTT layer after annealing.

[0028] Evaporate electrode materials at both ends of the upper surface of the DPP-DTT layer to form a DPP-DTT-electrode layer.

[0029] Spin-coat a lead sulfide quantum dot solution on the upper surface of the DPP-DTT-electrode layer, and anneal at 100 °C for 30 min to form a lead sulfide quantum dot layer; thus obtaining a phototransistor.

[0030] In the present invention, the DPP-DTT layer is obtained by spin-coating. Prepare a DPP-DTT-dichlorobenzene solution with a concentration of 3 - 5 mg / mL, spin-coat it on the upper surface of the PET substrate, and then perform annealing to form a DPP-DTT layer; the annealing temperature is 100 - 120 °C, and the annealing time is 30 - 50 min. The DPP-DTT organic semiconductor material used in the present invention is a commercially available DPP-DTT organic semiconductor material.

[0031] The present invention preferably washes the PET substrate before evaporating the aluminum electrode. In the embodiments of the present invention, the washing liquid used for the washing is preferably acetone, isopropanol, and deionized water. The present invention preferably washes with acetone and isopropanol once to three times each, and then washes with deionized water once to three times.

[0032] The present invention preferably performs OTS treatment on the PVDF dielectric layer before spin-coating the DPP-DTT layer.

[0033] The present invention preferably performs OTS treatment on the PVDF dielectric layer before spin-coating the DPP-DTT layer.

[0034] In the present invention, electrode materials are evaporated at both ends of the upper surface of the DPP-DTT layer to form a pair of parallel electrodes arranged oppositely. In the present invention, the evaporation is preferably vacuum evaporation.

[0035] After forming the DPP-DTT electrode layer, a lead sulfide quantum dot solution is spin-coated on the upper surface of the DPP-DTT electrode layer and annealed at 100 °C for 30 min to form a lead sulfide quantum dot layer. In the present invention, the solvent in the lead sulfide quantum dot solution is preferably toluene, octane or tetrachloroethylene. In the present invention, the ligand of the lead sulfide quantum dots is oleic acid, and more preferably TBAI is used as the ligand of the lead sulfide quantum dots. In the present invention, the spin coating is preferably carried out under a fume hood.

[0036] The present invention has no special limitation on the source of the lead sulfide quantum dots in the lead sulfide quantum dot solution, and commercially available lead sulfide quantum dots well-known to those skilled in the art or prepared according to the preparation methods of lead sulfide quantum dots well-known to those skilled in the art can be used. The present invention has no special limitation on the purification and cleaning processes, and technical solutions well-known to those skilled in the art can be used.

[0037] The near-infrared phototransistors provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0038] Example 1 The present invention uses a Schlenk system to synthesize lead sulfide quantum dots by a thermal injection method.

[0039] Synthesis of quantum dots: 0.231 g of lead oxide (PbO), 1.5 mL of oleic acid (OA) and 18 mL of octadecene (OD) are added to a 50 mL three-necked flask with magnetic stirring. Nitrogen is introduced into the flask to remove the air in the flask. Connect a vacuum pump and evacuate for 3 minutes, then fill with nitrogen for 3 minutes, and repeat 3 times. Under the evacuation state, the solution is heated to 100 °C and kept warm for 1 hour, and then under the nitrogen filling state, the solution is heated to 120 °C and kept warm for 30 minutes. 30 μL of hexamethyldisilathiane ((TMS)2S) is dissolved in 1.5 mL of toluene, ultrasonically treated for 30 min, and then quickly injected into the three-necked flask with a syringe, and the reaction is carried out for 3 - 20 min. Quantum dots of different sizes will be obtained at different growth times. Finally, the three-necked flask is immersed in an ice-water bath to completely quench the growth, and the quantum dot solution in the three-necked flask is collected.

[0040] Purification of quantum dots: After adding an equal volume of n-hexane to the obtained quantum dot solution, centrifuge at 8000 revolutions per minute for 5 minutes. After removing the supernatant, repeat the centrifugation operation. Disperse the quantum dots adhering to the centrifuge tube wall after the previous centrifugation with 3 mL of toluene. A lead sulfide quantum dot solution is obtained, and the ligand of the lead sulfide quantum is oleic acid.

[0041] Dissolve the DPP-DTT powder in dichlorobenzene to prepare a DPP-DTT-dichlorobenzene solution with a concentration of 3 mg / mL. Spin-coat the DPP-DTT-dichlorobenzene solution on the upper surface after OTS treatment, and anneal it at 120 °C for 30 min in a glove box to form a DPP-DTT layer;

[0042] Paste the upper surface of the DPP-DTT layer onto a mask, and perform vacuum evaporation of the Au electrode to form a DPP-DTT-Au layer;

[0043] Spin-coat the lead sulfide quantum dot solution on the DPP-DTT-electrode layer; anneal it at 100 °C for 30 min to obtain a near-infrared photodetector.

[0044] The device structure diagram of the near-infrared phototransistor prepared in this embodiment is as Figure 1 shown. Its structure includes a PET substrate, a DPP-DTT layer on the surface of the PET substrate, a DPP-DTT-electrode layer formed by electrode pairs on the surface of the DPP-DTT layer, a lead sulfide quantum dot layer covering the surface of the DPP-DTT-electrode layer. The electrode pairs are parallel electrode pairs, and the electrode pairs are arranged at both ends of the surface of the DPP-DTT layer.

[0045] The absorption spectrum diagram of the lead sulfide quantum dots prepared in this embodiment is as Figure 4 shown.

[0046] The transfer curve of the visible-near-infrared photodetector prepared in this embodiment under a 1550 nm light source when the channel voltage is 20 V is as Figure 5 shown.

[0047] The time-current curve of the visible-near-infrared photodetector prepared in this embodiment under a 1550 nm light source is as Figure 6 shown.

[0048] As can be seen from the above embodiments, the present invention provides a near-infrared phototransistor based on quantum dots, which combines lead sulfide quantum dots with oleic acid as a ligand and DPP-DTT. Utilizing the excellent on-off ratio and high mobility of DPP-DTT, and the near-infrared light-sensitive response characteristics of lead sulfide quantum dots, a near-infrared phototransistor with a high response rate is prepared, which can be widely applied in the field of photoelectric detection.

[0049] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. The present invention provides a flexible near-infrared phototransistor based on quantum dots, and its structure includes a PET substrate, an aluminum electrode evaporated on the surface of the PET substrate, a high-dielectric material P(VDF-TrFE-CFE) spin-coated by solution method on the aluminum electrode as a dielectric layer, a DPP-DTT layer spin-coated by solution method on the dielectric layer as a channel material, an Au electrode layer evaporated on the surface of the DPP-DTT layer, and a lead sulfide quantum dot layer covering the surface of the Au electrode layer. The electrode pair is an electrode pair arranged in parallel. The DPP-DTT layer is formed by spin-coating a dichlorobenzene solution of DPP-DTT on the OTS-treated device. The thickness of the lead sulfide quantum dot layer is 20-70 nm; the lead sulfide quantum dot layer is formed by spin-coating lead sulfide quantum dots; the ligand of the lead sulfide quantum dots is oleic acid, and more preferably TBAI is used as the ligand of the lead sulfide quantum dots; the particle size of the lead sulfide quantum dots is 5-20 nm.

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