Wide-spectrum response multiplication type near-infrared photoelectric detector based on ternary system

Abstract

The invention provides a wide-spectrum response multiplication type near-infrared photoelectric detector based on a ternary system, which adopts a ternary system laminated structure design and comprises a conductive anode layer, a hole transport layer, an active layer and a conductive cathode layer. The active layer is composed of a P3HT donor material with matched energy levels, a fullerene receptor PC71BM and a non-fullerene receptor COTIC-4F mixed film according to the ratio of 100: 1: 1, and the thickness of the active layer is 230-450 nanometers. According to the design, a unique structure that a large number of donor materials wrap a small number of acceptors is achieved, and the multiplication effect is achieved under illumination and external bias voltage through an electron trap and an energy band bending mechanism. The detector shows wide spectrum response of 350-1000 nanometers, the visible light external quantum efficiency reaches up to 4630%, and the external quantum efficiency at 850 nanometers is 486%. The method is simple in manufacturing process, low in cost and suitable for manufacturing large-area wearable equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor photoelectric devices, and in particular relates to an amplified near-infrared organic photodetector. Background Art

[0002] As a key device for converting optical signals into electrical signals, photodetectors are widely used in environmental monitoring, industrial automation, missile guidance, infrared imaging and other fields. With the rise of organic semiconductor materials, they are gradually becoming a new choice for photodetectors due to their adjustable spectral absorption range, flexible application potential brought by low hardness, and reduced production costs through solution-based processes.

[0003] Organic photodetectors show many advantages, but they still face challenges in multiplication devices. Multiplication-type organic photodetectors can achieve an external quantum efficiency of more than 100% by adjusting the device structure and the ratio of the active layer, but the response time is long. At present, the multiplication effect is mainly achieved by adjusting the ratio of the donor and the acceptor in the active layer. However, this method is limited in applications in the infrared band. Since a small energy difference is required to detect infrared light, exciton recombination is easy, which reduces the carrier generation efficiency and external quantum efficiency, making it difficult for the detector to achieve a multiplication effect in the near-infrared band. Therefore, designing an multiplication-type organic photodetector that can detect infrared light and has a high multiplication gain has become a problem that needs to be solved urgently. Summary of the invention

[0004] In view of the above problems, the present invention aims to provide a wide-spectrum response multiplied near-infrared organic photodetector based on a ternary system dual receptor with a response band covering 350-1000nm. The organic photodetector has low cost, simple manufacturing process, excellent performance, and can be used for large-area preparation, flexible wearable device preparation, etc.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] In the first aspect, the present invention provides an amplified near-infrared organic photodetector, comprising a conductive anode layer, a hole transport layer, an active layer and a conductive cathode layer arranged in a stacked structure, wherein the active layer is a mixed film, which is composed of an electron donor material and an electron acceptor material with an energy level matching mass ratio of 100:2, wherein the electron donor material is P3HT, and the electron acceptor material is a mixture of a fullerene derivative PC71BM and a non-fullerene acceptor COTIC-4F with a mass ratio of 1:1. This unique energy level combination not only optimizes the electron transmission efficiency, but also significantly improves the overall performance of the detector.

[0007] Furthermore, the electron donor material is P3HT, whose HOMO energy level is -5.1ev and LUMO energy level is -2.9ev.

[0008] Furthermore, the HOMO energy level of the fullerene derivative PC71BM is -6.0 eV, and the LUMO energy level is -4.0 eV; the HOMO energy level of the non-fullerene acceptor COTIC-4F is -5.2 eV, and the LUMO energy level is -4.1 eV.

[0009] Furthermore, the thickness of the active layer is 230-450 nm.

[0010] Furthermore, the conductive anode layer is made of ITO (indium tin oxide).

[0011] Furthermore, the hole transport layer is made of PEDOT:PSS and has a thickness of 35-40 nm.

[0012] Furthermore, the conductive cathode layer is made of a low work function metal material (such as aluminum) and has a thickness of 60-100 nm.

[0013] Furthermore, the multiplication-type near-infrared organic photodetector has a response band covering 350-1000nm, and a maximum EQE value of 4630% in the visible light band and a maximum EQE value of 486% in the near-infrared band, showing a good multiplication effect.

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0015] 1. In order to realize the multiplication type organic photodetector in the near-infrared spectral range, the present invention incorporates the energy-level-matched third component non-fullerene acceptor COTIC-4F into the traditional multiplication system P3HT:PC71BM as the active layer. Due to the small energy level difference between P3HT and COTIC-4F, the detection in the near-infrared spectral range is realized, and the multiplication effect is retained.

[0016] 2. The conductive anode layer in the structure of the present invention can be replaced with a flexible material and applied to wearable devices, which has certain commercial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural design diagram of the multiplication type near-infrared organic photodetector of the present invention;

[0018] Figure 2 is an energy level structure diagram of the multiplication type near-infrared organic photodetector of the present invention;

[0019] Figure 3 It is a preparation flow chart of the multiplication type near-infrared organic photodetector of the present invention;

[0020] Figure 4It is a curve diagram of the variation of the EQE of the device with the wavelength of the incident light under different bias voltages of the multiplication type near-infrared organic photodetector of the present invention;

[0021] Figure 5 The graph is a graph showing the change of EQE of the device with the wavelength of incident light under -18V bias for photodetectors with active layer ratios of 100:1:0, 100:1:1, and 100:1:2;

[0022] Figure 6 The comparison chart of the EQE values ​​of the devices in the range of 700 to 1000 nm for the photodetectors with active layer ratios of 100:1:0 and 100:1:1 under a bias voltage of -18 V;

[0023] Figure 7 It is a light / dark current comparison diagram of the device of the multiplication type near-infrared organic photodetector of the present invention under 850nm near-infrared light irradiation and dark state conditions.

[0024] Among them, 1-glass substrate, 2-conductive anode layer (ITO), 3-hole transport layer, 4-active layer, 5-conductive cathode layer. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0027] Existing photodetectors based on inorganic materials are basically photovoltaic type, with EQE less than 100%. When applied, an amplifier circuit is usually designed in the circuit, which is relatively complicated to use. The avalanche photodiode with multiplication effect has a complex manufacturing process, high bias voltage when working, and needs to work in a low temperature environment, and has high working conditions.

[0028] Most of the multiplication-type photodetectors based on organic materials have response bands in the visible light band, and few have response bands reaching the infrared light range.

[0029] The following are the full names and chemical molecular structures of the materials used in this example:

[0030] 1.PEDOT:PSS: Chinese full name poly (3,4-ethylenedioxythiophene) - poly (styrene sulfonic acid)

[0031]

[0032] 2. P3HT: Chinese full name 3-hexyl substituted polythiophene

[0033]

[0034] 3. PC71BM: Chinese full name [6,6]-phenyl C71 butyric acid methyl ester

[0035]

[0036] 4.COTIC-4F: Full English name 2,2'-((2Z,2'Z)-(((4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl)bis(4-(2-ethylhexy) loxy)thiophene-5,2-diyl))bis(methanylylidene))bis(5,6-dichloro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile

[0037]

[0038] Combination Figure 1 In an embodiment of the present invention, the multiplied near-infrared organic photodetector comprises: a conductive anode layer 1, on which a hole transport layer 2, an active layer 3 and a conductive cathode layer 4 are sequentially stacked, and the active layer 3 is a mixed film composed of an electron donor material and an electron acceptor material; the mass ratio of the electron donor material to the electron acceptor material is 100:2.

[0039] In the embodiment of the present invention, we use a non-fullerene acceptor COTIC-4F and a fullerene derivative PC71BM with a mass ratio of 1:1 as acceptors and P3HT as donors to produce a multiplied near-infrared organic photodetector with photoelectric response capability in the near-infrared band (700-1000nm). The energy level diagram of each component of the detector is shown in FIG. Figure 2As shown. The LUMO energy level difference between the large-proportion donor P3HT and the small-proportion acceptors PC71BM and COTIC-4F reaches 1.1ev and 1.2ev respectively, which can form deep electron traps. When exposed to light, the electron traps capture a large number of electrons and accumulate to bend the interface layer, weaken the Schottky barrier, induce hole multiplication injection, and achieve a multiplication effect. The smaller bandgap between P3HT and COTIC-4F allows it to absorb near-infrared light.

[0040] Combination Figure 3 In an embodiment of the present invention, a specific preparation method of a multiplication type near-infrared organic photodetector is as follows:

[0041] (1) The previously etched ITO-covered glass substrate was ultrasonically cleaned in deionized water, acetone, and isopropanol for 10 minutes to remove impurities attached to the surface, and then placed in a 50°C drying oven to remove residual liquid on the substrate surface. After drying, it was cleaned in an ultraviolet ozone cleaner for 3 minutes to remove organic impurities on the ITO surface and increase the viscosity of the ITO surface, which facilitates the spin coating of the hole transport layer in the next step.

[0042] (2) Spin coating PEDOT:PSS on the ITO treated in (1) for 40 seconds at a speed of 2500 rpm. After spin coating, place on a heated magnetic stirrer and anneal at 100°C for 10 minutes to form a hole transport layer of 35 to 40 nm. After annealing, wipe off the excess PEDOT:PSS solution with ethanol. After wiping off the excess solution, transfer to a glove box filled with nitrogen atmosphere.

[0043] (3) In a glove box filled with nitrogen atmosphere, P3HT, PC71BM, and COTIC-4F were dissolved in o-dichlorobenzene solvent in a mass ratio of 100:1:1 to form a mixed solution. The total concentration of the mixed solution was 40 mg / mL. The mixed solution was placed on a heated magnetic stirrer at 100°C and 100 rpm for 6 hours to allow the solute to fully dissolve. Then, in the glove box, 60 μL of the above solution was spin-coated on the hole transport layer treated by (2) at a spin-coating speed of 600 rpm for 60 seconds. After spin coating, anneal at 100°C for 10 minutes on a heated magnetic stirrer to form an active layer of 230 to 450 nm. After annealing, wipe off the excess solution with acetone. After wiping off the excess solution, place the complete substrate on a mask plate and then transfer it to a vacuum evaporation chamber.

[0044] (4) Vacuum evaporation is used to deposit the conductive cathode layer. When the pressure in the vacuum evaporation chamber is lower than 9.9×10 -4 Pa, the evaporation speed is controlled to be greater than 1 angstrom / s, and the aluminum metal is rotary evaporated to the upper surface of the active layer to form a conductive cathode layer with a thickness of 60 to 100 nm.

[0045] (5) The substrate obtained after the evaporation in step (4) is taken out from the vacuum evaporation chamber and placed in a glove box filled with nitrogen atmosphere. An appropriate amount of UV glue is applied on the grooved glass prepared in advance, and the glass substrate is packaged in the glove box. After packaging, the glass substrate is taken out from the glove box and irradiated under a UV lamp for 5 minutes to cure the UV glue, thereby obtaining an amplified near-infrared organic photodetector, and the next step of performance characterization test is carried out.

[0046] Performance characterization test:

[0047] Figure 4 The graph is a graph showing the variation of EQE of the multiplication type near-infrared organic photodetector prepared in this embodiment with the wavelength of incident light. It can be seen from the graph that the EQE of the organic photodetector prepared in this embodiment in the near-infrared light band exceeds 100% under -15V and -18V bias voltages, and has a multiplication effect.

[0048] Figure 5-6 The images of two groups of detectors are compared with the multiplication type near-infrared organic photodetector prepared in this embodiment. Three different ratios of active layers were prepared according to the mass ratio of P3HT:PC71BM:COTIC-4F of 100:1:0, 100:1:1 and 100:1:2, among which: Figure 4 The graphs show the EQE of the detectors with three different active layer ratios under -18V bias voltage as the wavelength of the incident light changes. It can be seen from the figure that when the ratio of P3HT:PC71BM:COTIC-4F is 100:1:0, the EQE value of the device in the near-infrared region is 0, and it does not have the ability to detect near-infrared light; when the ratio of P3HT:PC71BM:COTIC-4F is 100:1:2, the EQE value of the device is significantly lower than the EQE value of the device prepared in this embodiment, because too much COTIC-4F causes too many defects on the surface of the active layer, resulting in a weakened light response, thereby reducing the EQE of the device. Figure 5 The graph is a graph showing the EQE of the photodetector with active layer ratios of 100:1:1 and 100:1:0 in the near-infrared band at a bias voltage of -18V as a function of the wavelength of the incident light. It can be seen from the graph that the device prepared in this embodiment has good detection capability in the near-infrared region, and the highest EQE value can reach 486%.

[0049] Figure 7 The current-voltage curves of the amplified near-infrared organic photodetector prepared in this embodiment in the dark state and under illumination are shown under the conditions of 850nm and 1.5μW near-infrared light irradiation. It can be seen from the figure that the amplified near-infrared organic photodetector prepared in this embodiment has a lower dark current and a higher photocurrent.

[0050] In the embodiment of the present invention, the prepared organic photodetector adopts organic materials and can be prepared on different substrates. When the substrate has flexible characteristics, it can be used to make wearable devices to monitor the wearer's heart rate, blood oxygen and other vital signs. In addition, because the detector has a multiplication effect and can amplify the optical signal, it can simplify the circuit in practical applications, which has important practical significance.

[0051] The above describes the basic principle, manufacturing process and advantages of the present invention. However, the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modification, equivalent substitution and improvement made by any person skilled in the art within the spirit and principle of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A near-infrared photodetector with a wide spectrum response and multiplication, characterized in that: The invention comprises a conductive anode layer, a hole transport layer, an active layer and a conductive cathode layer arranged in a stacked structure. The active layer is a mixed film, which is composed of an electron donor material and an electron acceptor material with an energy level matching mass ratio of 100:2, wherein the electron donor material is P3HT, and the electron acceptor material is a mixture of a fullerene derivative PC71BM and a non-fullerene acceptor COTIC-4F with a mass ratio of 1:

1.

2. The wide spectrum response multiplication type near-infrared photodetector according to claim 1, characterized in that: The electron donor material is P3HT, whose HOMO energy level is -5.1ev and LUMO energy level is -2.9ev.

3. The wide spectrum response multiplication type near-infrared photodetector according to claim 1, characterized in that: The HOMO energy level of the fullerene derivative PC71BM is -6.0 eV, and the LUMO energy level is -4.0 eV; the HOMO energy level of the non-fullerene acceptor COTIC-4F is -5.2 eV, and the LUMO energy level is -4.1 eV.

4. The wide spectrum response multiplication type near-infrared photodetector according to claim 1, characterized in that: The thickness of the active layer is 230-450 nm.

5. The wide spectrum response multiplication type near-infrared photodetector according to claim 1, characterized in that: The conductive anode layer is made of ITO.

6. The wide spectrum response multiplication type near-infrared photodetector according to claim 1, characterized in that: The hole transport layer is made of PEDOT:PSS and has a thickness of 35-40 nm.

7. The wide spectrum response multiplication type near-infrared photodetector according to claim 1, characterized in that: The conductive cathode layer is made of a low work function metal material and has a thickness of 60-100 nm.

8. The wide spectrum response multiplication type near-infrared photodetector according to claim 1, characterized in that: The response band of this multiplied near-infrared organic photodetector can cover 350-1000nm, and the maximum EQE value in the visible light band is 4630%, and the maximum EQE value in the near-infrared band is 486%, which has a good multiplication effect.

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