Quick response organic photoelectric detector with planar heterojunction structure

Abstract

The invention discloses a quick-response organic photoelectric detector with a planar heterojunction structure. The quick-response organic photoelectric detector sequentially comprises a transparent substrate, an anode, a hole transport layer, an electron transport layer, a hole barrier layer and a metal cathode, the material of the hole transport layer is MCBP or TCTA; the thickness of the hole transport layer is 75-85 nm; the anode is made of indium tin oxide, a conductive polymer or metal Au; the hole blocking layer is made of BCP; the thickness of the hole blocking layer is 8-12nm; a potential barrier formed by the hole transport layer and the anode reduces injection of an external circuit under high bias voltage; and meanwhile, the hole barrier layer reduces injection at one side of the cathode. The MCBP or TCTA is used as a hole transport layer material, and the BCP is used as a hole barrier layer material, so that the dark current of the device is inhibited, the electric field intensity in the device and the drift speed of carriers are improved, the detector can stably work under high bias voltage, and the response speed of the device can be improved.

Description

Technical Field

[0001] The present invention relates to the field of organic optoelectronic detectors, and particularly to a fast-response organic optoelectronic detector with a planar heterojunction structure. Background Art

[0002] Compared with traditional inorganic optoelectronic detectors, organic optoelectronic detectors exhibit a series of remarkable and unique advantages. Due to the high extinction coefficient of organic semiconductor bulk materials, organic optoelectronic detectors can achieve extremely high light absorption efficiency even at sub-micron film thicknesses, thus ensuring excellent optoelectronic conversion performance. Notably, the overall thickness of organic optoelectronic detectors is much lower than that of their inorganic counterparts, which provides the possibility for high-density integration of optoelectronic devices and indicates great potential in improving system integration. In terms of fabrication processes, organic optoelectronic detectors greatly simplify the fabrication process, eliminating the need for processes such as epitaxial growth, photolithography, etching, and doping required for inorganic optoelectronic detectors. Instead, organic optoelectronic detectors can be fabricated using simpler thermal evaporation or solution processing techniques, which significantly reduces production costs and improves production efficiency. In addition, organic optoelectronic detectors have the characteristic of adjustable bandgap, which endows them with the ability to detect optical signals of specific wavelengths without relying on optical filters, which is difficult to achieve in inorganic optoelectronic detectors. This unique advantage not only broadens the application scope of organic optoelectronic detectors but also provides new possibilities for the flexibility and diversity of optical signal processing.

[0003] In recent years, the field of organic optoelectronic detectors has witnessed rapid development. With its unique advantages, it is expected to be applied in multiple cutting-edge fields. For example, ultra-high-gain multiplication-type organic optoelectronic detectors exhibit excellent performance in detecting weak optical signals; flexible organic optoelectronic detectors have been innovatively applied to detect human pulse oximetry signals; in addition, organic optoelectronic detector pixel matrices have successfully achieved imaging functions. These application examples fully demonstrate the wide range of uses of organic optoelectronic detectors. However, in high-frequency application fields such as the field of autonomous driving and the field of optical communication, extremely stringent requirements are imposed on the response speed of the detector, which needs to be able to accurately receive optical signals emitted by lasers on the nanosecond scale or even the picosecond time scale. However, due to the relatively low mobility of organic semiconductor materials, the response speed of organic optoelectronic detectors has been difficult to effectively improve, which makes inorganic optoelectronic detectors still dominant in these high-frequency application scenarios. Therefore, it is necessary to improve the response speed of organic optoelectronic detectors so that they can be more applied in the communication field. Summary of the Invention

[0004] To overcome the above-mentioned drawbacks and deficiencies of the prior art, the purpose of the present invention is to provide a fast-response organic optoelectronic detector with a planar heterojunction structure, which uses MCBP or TCTA as the material of the hole transport layer, uses BCP as the material of the hole blocking layer, and controls the thickness of the hole transport layer and the hole blocking layer at the same time, suppressing the dark current of the device, increasing the electric field strength in the device and the drift velocity of carriers, enabling the detector to operate stably under high bias voltage, and helping to improve the response speed of the device.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A fast-response organic optoelectronic detector with a planar heterojunction structure, which sequentially includes a transparent substrate, an anode, a hole transport layer, an electron transport layer, a hole blocking layer, and a metal cathode;

[0007] The material of the hole transport layer is MCBP or TCTA; the thickness of the hole transport layer is 75 - 85 nm;

[0008] The anode is indium tin oxide, a conductive polymer, or metal Au;

[0009] The material of the hole blocking layer is BCP; the thickness of the hole blocking layer is 8 - 12 nm;

[0010] The potential barrier formed by the hole transport layer and the anode reduces the injection of the external circuit under high bias voltage; at the same time, the hole blocking layer reduces the injection on the cathode side.

[0011] Preferably, the response time of the fast-response organic optoelectronic detector under a -9V bias voltage is 5.2 - 6.8 ns.

[0012] Preferably, the dark current density of the fast-response organic optoelectronic detector under a -9V bias voltage is 2×10 -6 A / cm.

[0013] Preferably, the external quantum efficiency of the fast-response organic optoelectronic detector under a -9V bias voltage is 35% - 50%.

[0014] Preferably, the material of the electron transport layer is C 60 or C 70 ; the thickness of the electron transport layer is 60 - 80 nm.

[0015] Preferably, the material of the metal cathode is Al, Ag, or Au; the thickness of the metal cathode is 100 - 200 nm.

[0016] Preferably, the material of the transparent substrate is glass, quartz, polyethylene terephthalate, polyimide, or polydimethylsiloxane.

[0017] Preferably, the specific structure of the fast-response organic optoelectronic detector with a planar heterojunction structure is: Glass / ITO / TCTA (80 nm) / C 70 (60 nm) / BCP (10 nm) / Al (200 nm).

[0018] Preferably, the specific structure of the fast-response organic optoelectronic detector with a planar heterojunction structure is: Glass / ITO / MCBP (80 nm) / C 70 (60 nm) / BCP (10 nm) / Al (200 nm).

[0019] Preferably, the hole transport layer, electron transport layer, hole blocking layer and metal cathode are prepared by vacuum evaporation.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) For the fast-response organic optoelectronic detector with a planar heterojunction structure of the present invention, MCBP or TCTA is used as the material of the hole transport layer. The lowest unoccupied molecular orbital (LUMO) of the above material has a high energy difference with the anode, forming a high potential barrier, reducing the injection of the external circuit under high bias voltage. This design strategy significantly suppresses the dark current of the device. At the same time, BCP is used as the material of the hole blocking layer, and the thicknesses of the hole transport layer and the hole blocking layer are controlled. Meanwhile, the introduction of the BCP material as the hole blocking layer reduces the injection on the cathode side (at a high bias voltage of -9V, the dark current density is as low as 2×10 -6 A / cm 2 ), which enables the detector to operate stably under high bias voltage and helps to improve the response speed of the device. In addition, by selecting appropriate thicknesses of the hole transport layer and the electron transport layer, the electric field strength and the drift velocity of carriers in the device are increased, realizing an organic optoelectronic detector with a nanosecond-level response time.

[0022] (2) The fast-response organic optoelectronic detector with a planar heterojunction structure of the present invention has low cost and fast response speed, and has great application potential in signal transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the fast-response organic optoelectronic detector prepared in the embodiment of the present invention. In the figure, 1 is a transparent substrate, 2 is an anode, 3 is a hole transport layer, 4 is an electron transport layer, 5 is a hole blocking layer, and 6 is a metal cathode.

[0024] Figure 2 It is a dark current curve diagram of the fast-response organic optoelectronic detector based on the planar heterojunction structure in Embodiment 1 of the present invention.

[0025] Figure 3 This is the external quantum efficiency curve graph of the fast-response organic optoelectronic detector based on the planar heterojunction structure in Example 1 of the present invention.

[0026] Figure 4 This is the transient photocurrent response curve graph of the fast-response organic optoelectronic detector based on the planar heterojunction structure in Example 1 of the present invention under a 660 nm laser.

[0027] Figure 5 This is the dark current curve graph of the fast-response organic optoelectronic detector based on the planar heterojunction structure in Example 2 of the present invention.

[0028] Figure 6 This is the external quantum efficiency curve graph of the fast-response organic optoelectronic detector based on the planar heterojunction structure in Example 2 of the present invention.

[0029] Figure 7 This is the transient photocurrent response curve graph of the fast-response organic optoelectronic detector based on the planar heterojunction structure in Example 2 of the present invention under a 660 nm laser. Detailed implementation manners

[0030] The following combines examples to further elaborate on the present invention in detail, but the implementation manners of the present invention are not limited thereto.

[0031] The following are the full names and molecular structural formulas of some materials used in the present invention:

[0032] 1. TCTA: The full Chinese name is 4,4',4”-tris(carbazol-9-yl)triphenylamine, and the structure is as follows:

[0033]

[0034] 2. MCBP: The full Chinese name is 3,3′-bis(9H-carbazol-9-yl)-1,1′-biphenyl, and the structure is as follows:

[0035]

[0036] 3. C 70 : The full Chinese name is fullerene C 70 , and the structure is as follows:

[0037]

[0038] 4. BCP: The full Chinese name is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine), and the structure is as follows:

[0039]

[0040] ITO full Chinese name: Indium tin oxide.

[0041] Example 1

[0042] As Figure 1 shown, the fast - response organic optoelectronic detector based on the planar heterojunction structure of the present invention sequentially includes a transparent substrate 1, an anode 2, a hole - transport layer 3, an electron - transport layer 4, a hole - blocking layer 5, and a metal cathode 6.

[0043] In this embodiment, the transparent substrate is glass; the anode is indium tin oxide (ITO); the hole - transport layer is TCTA with a thickness of 80 nm; the electron - transport material is C 70 , with a thickness of 60 nm; the hole - blocking layer is BCP with a thickness of 10 nm; the cathode is metal aluminum with a thickness of 200 nm.

[0044] The specific preparation method of the fast - response organic optoelectronic detector based on the planar heterojunction structure in this embodiment is as follows:

[0045] Place the glass substrate with attached ITO in a cleaning solution and ultrasonically clean it for 90 minutes, scrub it, and blow away the water droplets on the surface with nitrogen. Then place it in a vacuum oven at 120 °C and bake for 30 minutes to remove the residual moisture on the ITO glass; place the dried ITO glass substrate in an oxygen atmosphere with a pressure of 15 Pa, set the ionization voltage to 300 V, and perform oxygen plasma treatment for 4 minutes to further remove the residual impurities on the surface of the ITO glass. Subsequently, transfer it into the vacuum evaporation chamber. When the vacuum degree in the vacuum evaporation chamber reaches 10 -5 Pa, sequentially deposit the hole - transport layer 3, the electron - transport layer 4, the hole - blocking layer 5, and the metal cathode 6 on the ITO electrode. Among them, the overlapping part of the two electrodes forms the effective light - detection area of the device, and its effective area is 1 mm 2 . Finally, a fast - response organic optoelectronic detector with a planar heterojunction structure of Glass / ITO / TCTA(80 nm) / C 70 (60 nm) / BCP(10 nm) / Al(200 nm) is fabricated.

[0046] Figure 2 Fig. is the dark - current curve of the planar heterojunction - type fast - response organic optoelectronic detector involved in Example 1 at different bias voltages. It can be clearly observed from the figure that the dark current of the device remains at an extremely low level. Specifically, at a bias voltage of - 9 V, the dark - current density is on the order of 10 -6 A / cm -2 , indicating that the device can still work at a bias voltage of - 9 V. This data strongly proves that the device can still work stably at a bias voltage of - 9 V. In addition, further increasing the bias voltage is expected to increase the drift velocity and collection efficiency of the carriers in the device, thereby enhancing the response speed and external quantum efficiency of the device.

[0047] Figure 3 It is the external quantum efficiency curve of the fast-response organic optoelectronic detector with a planar heterojunction structure involved in Example 1 under different bias voltages. It can be seen from the figure that as the reverse bias voltage increases, the external quantum efficiency of the device gradually increases. At a bias voltage of -9V, the external quantum efficiency of the device reaches a maximum of 50%.

[0048] Figure 4 It is the transient photocurrent response curve of the fast-response organic optoelectronic detector with a planar heterojunction structure in Example 1 under different bias voltages. It can be seen from the figure that at a bias voltage of -9V, the response time of the device can be as low as 5.2ns.

[0049] Example 2

[0050] The fast-response organic optoelectronic detector based on the planar heterojunction structure of the present invention sequentially includes a transparent substrate, an anode, a hole transport layer, an electron transport layer, a hole blocking layer, and a metal cathode.

[0051] In this embodiment, the transparent substrate is glass; the anode is indium tin oxide (ITO); the hole transport layer is MCBP with a thickness of 80nm; the electron transport material is C 70 , with a thickness of 60nm; the hole blocking layer is BCP with a thickness of 10nm; the cathode is metal aluminum with a thickness of 200nm.

[0052] The specific preparation method of the fast-response organic optoelectronic detector based on the planar heterojunction structure in this embodiment is as follows:

[0053] Place the glass substrate with ITO attached in the cleaning solution and ultrasonically clean it for 90 minutes. Rub it and blow off the water droplets on the surface with nitrogen. Then place it in a vacuum oven at 120°C and bake it for 30 minutes to remove the residual moisture on the ITO glass; place the dried ITO glass substrate in an oxygen atmosphere with a pressure of 15Pa, set the ionization voltage to 300V, and perform oxygen plasma treatment for 4 minutes to further remove the residual impurities on the surface of the ITO glass. Subsequently, transfer it into the vacuum evaporation chamber. When the vacuum degree in the vacuum evaporation chamber reaches 10 -5 Pa, sequentially deposit the hole transport layer, electron transport layer, hole blocking layer, and metal cathode on the ITO electrode. Among them, the overlapping part of the two electrodes forms the effective light detection area of the device, and its effective area is 1mm 2 . Finally, a fast-response organic optoelectronic detector with a planar heterojunction structure of Glass / ITO / MCBP(80nm) / C 70 (60nm) / BCP(10nm) / Al(200nm) is fabricated.

[0054] Figure 5 Dark current curves of the planar heterojunction type fast-response organic optoelectronic detector involved in Example 2 under different bias voltages. It can be clearly observed from the figure that the dark current of this device is maintained at an extremely low level. Specifically, at a bias voltage of -9V, the dark current density is 10 -6 Acm -2 orders of magnitude, indicating that the device can still work at a bias voltage of -9V. This data strongly proves that the device can still work stably at a bias voltage of -9V. In addition, further increasing the bias voltage is expected to increase the drift velocity and collection efficiency of the carriers in the device, thereby enhancing the response speed and external quantum efficiency of the device.

[0055] Figure 6 External quantum efficiency curve graphs of the fast-response organic optoelectronic detector with a planar heterojunction structure involved in Example 2 under different bias voltages. It can be seen from the figure that as the reverse bias voltage increases, the external quantum efficiency of the device gradually increases. At a bias voltage of -9V, the external quantum efficiency of the device reaches a maximum of 35%.

[0056] Figure 7 Transient photocurrent response curves of the fast-response organic optoelectronic detector with a planar heterojunction structure in Example 2 under different bias voltages. It can be seen from the figure that at a bias voltage of -9V, the response time of the device can be as low as 6.8 ns.

[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the described embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A fast-response organic optoelectronic detector with a planar heterojunction structure, characterized in that, The method comprises, in sequence, a transparent substrate, an anode, a hole transport layer, an electron transport layer, a hole blocking layer and a metal cathode; The material of the hole transport layer is MCBP or TCTA; the thickness of the hole transport layer is 75-85 nm; The anode is made of indium tin oxide, conductive polymer or metal Au; The material of the hole blocking layer is BCP; the thickness of the hole blocking layer is 8 to 12 nm; The potential barrier formed by the hole transport layer and the anode reduces the injection of the external circuit under high bias; at the same time, the hole blocking layer reduces the injection on the cathode side.

2. The fast-response organic optoelectronic detector with a planar heterojunction structure according to claim 1, characterized in that, The fast-response organic photodetector has a response time of 5.2 to 6.8 ns under a bias voltage of -9 V.

3. The fast-response organic optoelectronic detector with a planar heterojunction structure according to claim 1, characterized in that, The dark current density of the rapid response organic optoelectronic detector under a bias voltage of -9V is 2×10 -6 A / cm.

4. The fast-response organic optoelectronic detector with a planar heterojunction structure according to claim 1, wherein The external quantum efficiency of the fast-response organic photodetector under a bias voltage of -9V is 35% to 50%.

5. The fast-response organic optoelectronic detector with a planar heterojunction structure according to claim 1, characterized in that, The material of the electron transport layer is C 60 or C 70 ; the thickness of the electron transport layer is 60 - 80 nm.

6. The fast-response organic optoelectronic detector with a planar heterojunction structure according to claim 1, characterized in that, The material of the metal cathode is Al, Ag or Au; the thickness of the metal cathode is 100-200nm.

7. The fast-response organic optoelectronic detector with a planar heterojunction structure according to claim 1, wherein The transparent substrate is made of glass, quartz, polyethylene terephthalate, polyimide or polydimethylsiloxane.

8. The fast-response organic optoelectronic detector with a planar heterojunction structure according to claim 1, characterized in that, Its specific structure is: Glass / ITO / TCTA(80nm) / C 70 (60nm) / BCP(10nm) / Al(200nm).

9. The fast-response organic optoelectronic detector with a planar heterojunction structure according to claim 1, characterized in that, Its specific structure is: Glass / ITO / MCBP (80nm) / C 70 (60nm) / BCP (10nm) / Al (200nm).

10. The fast-response organic optoelectronic detector with a planar heterojunction structure according to claim 1, characterized in that, The hole transport layer, electron transport layer, hole blocking layer and metal cathode are prepared by vacuum evaporation method.

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