An ultrafast response organic photodetector based on light field control

Abstract

The application discloses an ultrafast response organic photoelectric detector based on light field control, which has a bulk heterojunction structure and sequentially comprises a transparent substrate, an anode, a hole transport layer, a photosensitive layer, an electron transport layer, a hole blocking layer and a cathode. 70 The photosensitive layer is a blending layer of an electron donor material and an electron acceptor material. 60 The electron transport layer material is C 60 The material of the hole transport layer is Rubrene or TAPC. The application adopts the light field control mode, suppresses the diffusion process of excitons, realizes the ultrafast response speed, reaches the sub-nanosecond response in the red light band, and the highest bandwidth is up to 970MHz.

Description

Technical Field

[0001] This invention relates to the field of organic optoelectronic devices, and in particular to an ultrafast response organic photodetector based on light field control. Background Technology

[0002] With the development of digital lifestyles, flexible electronic devices have attracted much attention due to their enormous application potential in emerging fields such as implantability, stretchability, and wearability. In recent years, flexible electronic devices have achieved significant technological advancements in many application areas, including electronic skin, optical communication, batteries, and stretchable circuits. Data communication has always been an indispensable part of the numerous applications of flexible wearable electronic devices. Photodetectors convert incident light signals into electrical signals and are an important component of communication systems. Currently, photodetectors based on inorganic semiconductor materials (such as Si, III-V compounds) are quite mature, but they still have some significant drawbacks, such as difficulty in fabricating flexible devices, high energy consumption during fabrication, and high manufacturing costs. To overcome the shortcomings of inorganic photodetectors, photodetectors based on organic semiconductor materials have become a research hotspot in recent years. Compared with traditional inorganic semiconductor materials, organic semiconductor materials have many unique advantages, such as light weight, low processing cost, good compatibility with flexible substrates, and the ability to be fabricated over large areas. Furthermore, theoretically, people can synthesize organic semiconductor materials with different properties through molecular structure design, thereby adapting to various application requirements. Based on these advantages, organic photodetectors have developed rapidly in the past decade or so, and in many aspects they have matched or even surpassed traditional silicon-based photodetectors.

[0003] However, the response speed of organic photodetectors is still much slower than that of traditional inorganic photodetectors. To date, the fastest organic photodetector is the one reported by Peumans et al. in 2000, based on a multilayer planar composite structure and possessing an ultra-high bandwidth of 430 MHz. However, its device structure is complex, its fabrication conditions are demanding, requiring ultra-high vacuum fabrication, and its reproducibility is poor. Currently, the electron transport layer or hole transport layer also absorbs light in the detection band. After the absorbed light forms excitons, it requires a long diffusion process to form a photocurrent. This results in a slow response speed for organic photodetectors, hindering their application. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the present invention aims to provide an ultrafast response organic photodetector based on optical field control. By selecting electron transport layer and hole transport layer that absorb very little in the target wavelength band, the main absorption position of light is confined to the photosensitive layer, and the long-distance diffusion process of photogenerated excitons is actively suppressed. Thus, an ultrafast response speed is achieved by optical field control, reaching a sub-nanosecond response in the red light band, with a maximum bandwidth of up to 970MHz.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] An ultrafast response organic photodetector based on light field control has a bulk heterojunction structure, which sequentially includes a transparent substrate, an anode, a hole transport layer, a photosensitive layer, an electron transport layer, a hole blocking layer, and a cathode.

[0007] The photosensitive layer is a blend of an electron donor material and an electron acceptor material; the electron donor material is Rubrene or TAPC; the electron acceptor material is C. 70 ;

[0008] The electron transport layer material is C. 60 ;

[0009] The hole transport layer is made of Rubrene or TAPC.

[0010] Preferably, the ultrafast response organic photodetector based on light field control operates in the infrared band, where light absorption is suppressed at the photosensitive layer; more preferably, the operating band is 660 nm.

[0011] Preferably, the hole-blocking layer is made of BCP or C. 60 .

[0012] Preferably, the thickness of the hole transport layer is 5~60 nm.

[0013] Preferably, the thickness of the photosensitive layer is 40~100 nm.

[0014] Preferably, the thickness of the electron transport layer is 5~100 nm.

[0015] Preferably, the transparent substrate is glass, quartz, polyethylene terephthalate, polyimide, or polydimethylsiloxane.

[0016] Preferably, the anode is ITO, a conductive polymer, or Cu.

[0017] Preferably, the cathode is made of Al, Ag, or Au.

[0018] Preferably, the doping concentration of the electron donor material is 5 wt% to 80 wt%.

[0019] More preferably, the response time of the ultrafast response organic photodetector based on light field control is 0.8~0.9ns.

[0020] More preferably, the thickness of the cathode is 50~500 nm.

[0021] More preferably, the doping concentration of the electron donor material is 10 wt% to 50 wt%.

[0022] The fabrication method of the ultrafast response organic photodetector based on light field control is as follows:

[0023] A transparent substrate with an anode material is cleaned, and then a hole transport layer, a photosensitive layer, an electron transport layer, a hole blocking layer, and a metal cathode are sequentially deposited to obtain an ultrafast response organic photodetector based on light field control.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] (1) The ultrafast response organic photodetector based on light field control of the present invention selects electron transport layer and hole transport layer that absorb very little in the target wavelength band, thereby restricting the main absorption position of light to the photosensitive layer and actively suppressing the long-distance diffusion process of photogenerated excitons. Thus, ultrafast response speed is achieved by using light field control, achieving sub-nanosecond response in the red light band, with a maximum bandwidth of up to 970 MHz.

[0026] (2) The ultrafast response organic photodetector based on light field control of the present invention uses organic materials with high mobility (Rubrene, TAPC, C). 70 C 60 (BCP), which effectively reduces the carrier transport time inside the device.

[0027] (3) The ultrafast response organic photodetector based on light field control of the present invention can use flexible materials as substrates, and its response speed can also reach sub-nanosecond, with a maximum bandwidth of 900 MHz, which can be applied to wearable devices. Attached Figure Description

[0028] Figure 1 The Rubrene-based, C-based material prepared in Example 1 of this invention 70 and C 60 A schematic diagram of the ultrafast response organic photodetector with a bulk heterojunction structure. In the figure, 11 is the transparent substrate, 12 is the anode, 13 is the hole transport layer, 14 is the photosensitive layer, 15 is the electron transport layer, 16 is the hole blocking layer, and 17 is the metal cathode.

[0029] Figure 2 The materials Rubrene and C involved in Example 1 of this invention 70 and C 60 Normalized absorption spectrum of the thin film.

[0030] Figure 3 The diagram shows the response waveforms of the ultrafast organic photodetector involved in Embodiment 1 of the present invention at different frequencies.

[0031] Figure 4 This is a numerical statistical distribution diagram of the response speeds of the 25 ultrafast organic photodetectors involved in Example 1.

[0032] Figure 5 The image shows the pulse response waveform of the ultrafast organic photodetector involved in Example 1.

[0033] Figure 6 The above is the frequency response characteristic curve of the ultrafast organic photodetector involved in Example 1.

[0034] Figure 7 This is a pulse response waveform diagram of the flexible ultrafast organic photodetector involved in Example 1.

[0035] Figure 8 The frequency response characteristic curve of the flexible ultrafast organic photodetector involved in Example 1 is shown.

[0036] Figure 9 The Rubrene and C-based material prepared for Comparative Example 1 in this invention 70 A schematic diagram of the structure of the organic photodetector system. In the figure, 21 is the transparent substrate, 22 is the anode, 23 is the hole transport layer, 24 is the photosensitive layer, 25 is the electron transport layer, 26 is the hole blocking layer, and 27 is the metal cathode.

[0037] Figure 10 This is a comparison of the response waveforms of the two organic photodetectors involved in Example 1 and Comparative Example 1 of this invention.

[0038] Figure 11 This is a schematic diagram illustrating the mechanism by which the response speeds of the two organic photodetectors involved in Example 1 and Comparative Example 1 of this invention differ significantly.

[0039] Figure 12 The TAPC-based, C-based material prepared in Example 2 of this invention 70 and C 60 A schematic diagram of the structure of the ultrafast organic photodetector with a bulk heterojunction structure. In the figure, 31 is the transparent substrate, 32 is the anode, 33 is the hole transport layer, 34 is the photosensitive layer, 35 is the electron transport layer, 36 is the hole blocking layer, and 37 is the metal cathode.

[0040] Figure 13 In Example 2 of the present invention, the materials TAPC and C involved 70 and C 60 Normalized absorption spectrum curve of the film

[0041] Figure 14 Response waveform diagrams of the ultrafast organic optoelectronic detector involved in Example 2 of the present invention at different frequencies

[0042] Figure 15 Pulse response waveform diagram of the ultrafast organic optoelectronic detector involved in Example 2

[0043] Figure 16 Frequency response characteristic curve of the ultrafast organic optoelectronic detector involved in Example 2

[0044] Figure 17 Pulse response waveform diagram of the flexible ultrafast organic optoelectronic detector involved in Example 2

[0045] Figure 18 Frequency response characteristic curve of the flexible ultrafast organic optoelectronic detector involved in Example 2

[0046] Figure 19 In the present invention, the organic optoelectronic detector prepared in Comparative Example 2 based on TAPC and C 70 Schematic structural diagram of the organic optoelectronic detector of the system. In the figure, 41 is a transparent substrate, 42 is an anode, 43 is a hole transport layer, 44 is a photosensitive layer, 45 is an electron transport layer, 46 is a hole blocking layer, and 47 is a metal cathode

[0047] Figure 20 Response waveform comparison diagram of the two organic optoelectronic detectors involved in Example 2 and Comparative Example 2 of the present invention Specific embodiments

[0048] The present invention will be further described in detail below in conjunction with the embodiments, but the embodiments of the present invention are not limited thereto

[0049] The terms used in the present invention generally have the meanings commonly understood by those of ordinary skill in the art, unless otherwise specified. The following are the full names and molecular structural formulas of some of the materials used in the present invention

[0050] 1. Rubrene: The full Chinese name is rubrene, and the structure is as follows

[0051]

[0052] 2. TAPC: The full Chinese name is 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline], and the structure is as follows

[0053]

[0054] 3. C 70 Full name in Chinese: Fullerene C 70 The structure is as follows:

[0055]

[0056] 4. C 60 Full name in Chinese: Fullerene C 60 The structure is as follows:

[0057]

[0058] 5. BCP: Full Chinese name is 2,9-dimethyl-4,7-diphenyl-1,10-o-diazaphenanthroline (bath copper spirit), the structure is as follows:

[0059]

[0060] 6. ITO stands for Indium Tin Oxide.

[0061] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0062] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following embodiments are commercially available.

[0063] Example 1

[0064] Based on Rubrene, C 70 and C 60 Organic photodetectors with bulk heterojunction structures (structures such as...) Figure 1 As shown, it includes a transparent substrate 11, an anode 12, a hole transport layer 13, a photosensitive layer 14, an electron transport layer 15, a hole blocking layer 16, and a metal cathode 17 arranged sequentially.

[0065] In this embodiment 1, based on Rubrene and C... 70 and C 60 The system comprises an organic photodetector, wherein the transparent substrate is glass or flexible PET; the anode is indium tin oxide (ITO); the hole transport layer is Rubrene with a thickness of 30 nm; and the photosensitive layer is a blended film of electron donor and electron acceptor materials with a thickness of 50 nm. Specifically, the electron donor material is Rubrene, and the electron acceptor material is C. 70The electron donor material in the photosensitive layer has a mass concentration of 30 wt%; the electron transport material is C. 60 The thickness of the cathode is 60 nm; the hole blocking layer is BCP with a thickness of 10 nm; the cathode is aluminum with a thickness of 400 nm.

[0066] This embodiment 1 is based on Rubrene and C. 70 and C 60 The specific fabrication method of the ultrafast organic photodetector with a bulk heterojunction structure is as follows:

[0067] The ITO-coated glass substrate was ultrasonically cleaned in a cleaning solution for 90 minutes, then rubbed with deionized water and the surface water droplets were blown away with nitrogen. It was then baked in a vacuum oven at 120°C for 60 minutes to remove any residual moisture from the ITO glass. The dried ITO glass substrate was then placed in an oxygen atmosphere at 15 Pa pressure, with an ionization voltage of 300 V, for 4 minutes of oxygen plasma treatment to further remove residual impurities on the ITO glass surface and improve the ITO work function. It was then placed in the chamber of a vacuum evaporation equipment. The vacuum level in the vacuum evaporation chamber was evaporated to ~10 using a mechanical pump and a molecular pump. -5 Pa, followed by the sequential deposition of organic material layers and a metal cathode onto the ITO electrode. The overlapping portion of the two electrodes forms the effective photodetector region of the device. The final fabricated structure is Glass or PET / ITO / Rubrene (30 nm) / Rubrene:C 70 (3:7,50 nm) / C 60 Organic photodetector of (60 nm) / BCP (10 nm) / Al (400 nm).

[0068] Figure 2 The figure shows the normalized absorption spectrum of the main material of the ultrafast organic photodetector involved in Example 1. As can be seen from the figure, the light absorption region of Rubrene is mainly in the ultraviolet region, with very weak absorption in the red light region after 600 nm. 70 and C 60 It exhibits good absorption in the visible light range, with an absorption intensity much greater than that of Rubrene in the visible light region. 60 and C 70 The absorption spectrum ranges from 300 to 800 nm. However, in the red light band (e.g., 660 nm), C 60 The absorption strength is much smaller than that of C. 70 It can be ignored.

[0069] Figure 3The images show the response waveforms of the ultrafast organic photodetector described in Example 1 at different frequencies. In this test, the device was excited by a 660 nm laser and operated at a reverse bias of -8 V. The device area was 0.016 mm². 2 (The corresponding device capacitance is 6 pF). The response time of the device at different frequencies (the slower of the rise and fall times) was calculated using an oscilloscope, and the results were: 0.86 ns (50 MHz), 0.87 ns (25 MHz), 0.87 ns (10 MHz), and 0.90 ns (5 MHz). This result demonstrates that the device exhibits an ultrafast sub-nanosecond response speed while maintaining consistency from low to high frequencies.

[0070] Figure 4 This figure shows the numerical statistical distribution of the response speeds of the 25 ultrafast organic photodetectors involved in Example 1. Based on the Gaussian function fitting results (black curve in the figure), the average response time of the ultrafast organic photodetectors is approximately 800 ps, ​​with the fastest being approximately 700 ps and the slowest approximately 950 ps. All devices achieved sub-nanosecond response times, and approximately 70% of the devices had response speeds close to the average. This statistical result demonstrates the good repeatability of the ultrafast organic photodetectors with sub-nanosecond response times involved in the examples.

[0071] Figure 5 The pulse response waveform of the ultrafast organic photodetector involved in Example 1 under a reverse bias of 15 V is shown in the figure. As can be seen from the figure, the full width at half maximum (FWHM) of the device's pulse response waveform is only 400 ps, ​​and the fall time (t...) is... fall 280 ps.

[0072] Figure 6 This is the frequency response characteristic curve of the ultrafast organic photodetector involved in Example 1. This curve was obtained by Fourier transforming the impulse response waveform. As can be seen from the figure, the device's bandwidth (-3dB bandwidth) is 970MHz.

[0073] Figure 7 The figure shows the pulse response waveform of the ultrafast fully flexible organic photodetector involved in Example 1 under a reverse bias of 15 V. As can be seen from the figure, the full width at half maximum (FWHM) of the device's pulse response waveform is 510 ps, ​​and the fall time is 320 ps.

[0074] Figure 8This is the frequency response characteristic curve of the ultrafast fully flexible organic photodetector involved in Example 1. The curve was obtained by Fourier transforming the impulse response waveform. As can be seen from the figure, the device's bandwidth (-3dB bandwidth) is 900 MHz.

[0075] Comparative Example 1

[0076] Based on Rubrene and C 70 High-speed organic photodetectors of the system (structure as follows) Figure 9 As shown, this device does not employ optical field control and includes a transparent substrate 21, an anode 22, a hole transport layer 23, a photosensitive layer 24, an electron transport layer 25, a hole blocking layer 26, and a metal cathode 27 arranged sequentially.

[0077] In the high-speed organic photodetector with a bulk heterojunction structure in Comparative Example 1, the transparent substrate is glass; the anode is indium tin oxide (ITO); the hole transport layer is Rubrene with a thickness of 30 nm; and the photosensitive layer is a blended film of electron donor and electron acceptor materials with a thickness of 50 nm. Specifically, the electron donor material is Rubrene, and the electron acceptor material is C. 70 The electron donor material in the photosensitive layer has a mass concentration of 30 wt%; the electron transport material is C. 70 The thickness of the cathode is 60 nm; the hole blocking layer is BCP with a thickness of 10 nm; the cathode is aluminum with a thickness of 400 nm.

[0078] Comparative Example 1 is based on Rubrene and C. 70 The specific fabrication method of the high-speed organic photodetector system is as follows: The ITO-coated glass substrate is ultrasonically cleaned in a cleaning solution for 90 minutes, then rubbed with deionized water and the surface water droplets are blown away with nitrogen. It is then baked in a vacuum oven at 120℃ for 60 minutes to remove residual moisture from the ITO glass. The dried ITO glass substrate is then placed in an oxygen atmosphere at 15 Pa pressure, with an ionization voltage of 300 V, and subjected to oxygen plasma treatment for 4 minutes to further remove residual impurities on the ITO glass surface and improve the ITO work function. It is then placed in the cavity of a vacuum evaporation equipment. The vacuum degree in the vacuum evaporation cavity is evaporated to ~10 using a mechanical pump and a molecular pump. -5 Pa, followed by the sequential deposition of organic material layers and a metal cathode onto the ITO electrode. The overlapping portion of the two electrodes forms the effective photodetector region of the device. The final fabricated structure is Glass / ITO / Rubrene (30 nm) / Rubrene:C 70 (3:7, 50 nm) / C 70Organic photodetector (60 nm) / BCP (10 nm) / Al (400 nm).

[0079] Figure 10 The diagram shows a comparison of the response waveforms of the two organic photodetectors involved in Example 1 and Comparative Example 1. Both devices have the same RC time constant and an applied bias voltage of −8 V. The only difference is that the device involved in Example 1 uses a RC time constant of −8 V. 60 As an electron transport layer, the devices involved in Comparative Example 1 use C 70 This is the electron transport layer. As can be seen from the figure, the response waveform of the device involved in Example 1 is closer to a square wave, indicating that the device responds faster to changes in external optical signals. The response times of the two types of devices were calculated using an oscilloscope, and the specific results are as follows: At a frequency of 50 MHz, the response times of both organic photodetectors involved in Example 1 and Comparative Example 1 reached the sub-nanosecond level, at 0.86 ns and 0.97 ns respectively. However, in reality, the waveform of the device involved in Comparative Example 1 did not reach its highest steady state. When the frequencies were 25 MHz, 10 MHz, and 5 MHz, the response time of the device involved in Comparative Example 1 became 4.3 ns, while the response time of the device involved in Example 1 remained at the sub-nanosecond level. This comparison demonstrates the superior performance of the device involved in Example 1.

[0080] Figure 11 This section analyzes the mechanism underlying the significant difference in response speed between the two organic photodetectors involved in Example 1 and Comparative Example 1. Figure (Ⅰ), (Ⅱ), and (Ⅲ) represent three processes occurring within the device: (Ⅰ) generation of photoexcitons; (Ⅱ) diffusion of photoexcitons; and (Ⅲ) dissociation of photoexcitons. When a beam of 660 nm red light is irradiated onto the device involved in Comparative Example 1, combined with… Figure 2 The absorption spectra of the materials used in Example 1 and Comparative Example 1 reveal the distribution of the main exciton generation regions in both examples. The distributions of the main exciton generation regions in Example 1 and Comparative Example 1 are shown below. Figure 11 (a) and Figure 11 As shown in (b). In Example 1 and Comparative Example 1, after irradiation at 660 nm, both Rubrene and C... 70 The photosensitive layer is more widely distributed. The difference is that in Comparative Example 1, the electron transport layer C... 70 Light absorption can also produce significant absorption, as seen in Example 1, where C... 60 Absorption at 660 nm is very low, resulting in minimal exciton formation. Comparative Example 1 shows the electron transport layer C... 70The excitons generated by light absorption require a relatively long diffusion process to effectively dissociate in the photosensitive layer, resulting in a slow response speed. However, in Example 1, the excitons formed in the electron transport layer and hole transport layer are negligible, eliminating diffusion limitations. Therefore, the response speed of the device in Example 1 is significantly improved compared to Comparative Example 1. In Example 1, the method of actively suppressing exciton diffusion by controlling the generation region of photogenerated excitons by utilizing the difference in absorption spectra of the two materials is called optical field control. The ultrafast response speed of the organic photodetector involved in Example 1 is obtained through optical field control.

[0081] Example 2

[0082] Based on TAPC, C 70 and C 60 Organic photodetectors with bulk heterojunction structures (structures such as...) Figure 12 As shown, it includes a transparent substrate 31, an anode 32, a hole transport layer 33, a photosensitive layer 34, an electron transport layer 35, a hole blocking layer 36, and a metal cathode 37 arranged sequentially.

[0083] In this embodiment 2, based on TAPC and C 70 and C 60 The system comprises an organic photodetector, wherein the transparent substrate is glass or flexible PET; the anode is indium tin oxide (ITO); the hole transport layer is TAPC with a thickness of 20 nm; and the photosensitive layer is a blended film of electron donor and electron acceptor materials with a thickness of 75 nm. Specifically, the electron donor material is TAPC, and the electron acceptor material is C... 70 The electron donor material in the photosensitive layer has a mass concentration of 30 wt%; the electron transport material is C. 60 The thickness of the cathode is 60 nm; the hole blocking layer is BCP with a thickness of 10 nm; the cathode is aluminum with a thickness of 400 nm.

[0084] This embodiment 2 is based on TAPC, C 70 and C 60 The specific fabrication method of the ultrafast organic photodetector with a bulk heterojunction structure is as follows:

[0085] The ITO-coated glass substrate was ultrasonically cleaned in a cleaning solution for 90 minutes, then rubbed with deionized water and the surface water droplets were blown away with nitrogen. It was then baked in a vacuum oven at 120°C for 60 minutes to remove any residual moisture from the ITO glass. The dried ITO glass substrate was then placed in an oxygen atmosphere at 15 Pa pressure, with an ionization voltage of 300 V, for 4 minutes of oxygen plasma treatment to further remove residual impurities on the ITO glass surface and improve the ITO work function. It was then placed in the chamber of a vacuum evaporation equipment. The vacuum level in the vacuum evaporation chamber was evaporated to ~10 using a mechanical pump and a molecular pump. -5 Pa, followed by the sequential deposition of organic material layers and a metal cathode onto the ITO electrode. The overlapping portion of the two electrodes forms the effective photodetector region of the device. The final fabricated structure is Glass or PET / ITO / TAPC (20 nm) / TAPC:C 70 (3:7, 75nm) / C 60 Organic photodetector of (60 nm) / BCP (10 nm) / Al (400 nm).

[0086] Figure 13 The figure shows the normalized absorption spectrum of the main material of the ultrafast organic photodetector involved in Example 2. As can be seen from the figure, the light absorption region of TAPC is mainly in the ultraviolet region, with only very weak absorption in the visible light region. 70 and C 60 It exhibits good absorption in the visible light range, with an absorption intensity much greater than that of TAPC in the visible light region. 60 and C 70 The absorption spectrum ranges from 300 to 800 nm. However, in the red light band (e.g., 660 nm), C 60 The absorption strength is much smaller than that of C. 70 It can be ignored.

[0087] Figure 14 The images show the response waveforms of the ultrafast organic photodetector described in Example 2 at different frequencies. In this test, the device was excited by a 660 nm laser and operated at a reverse bias of -8 V. The device area was 0.012 mm². 2 (The corresponding device capacitance is 5 pF). The response time of the device at different frequencies (the slower of the rise and fall times) was calculated using an oscilloscope, and the results were: 0.82 ns (50 MHz), 0.82 ns (25 MHz), 0.88 ns (10 MHz), and 0.90 ns (5 MHz). This result demonstrates that the device exhibits an ultrafast sub-nanosecond response speed while maintaining consistency from low to high frequencies.

[0088] Figure 15 The image shows the pulse response waveform of the ultrafast organic photodetector described in Example 2 under a 15 V reverse bias. As can be seen from the figure, the full width at half maximum (FWHM) of the device's pulse response waveform is only 500 ps, ​​and the fall time (t...) is... fall 410 ps.

[0089] Figure 16 This is the frequency response characteristic curve of the ultrafast organic photodetector involved in Example 2. The curve was obtained by Fourier transforming the impulse response waveform. As can be seen from the figure, the device's bandwidth (-3dB bandwidth) is 730 MHz.

[0090] Figure 17 The figure shows the pulse response waveform of the ultrafast fully flexible organic photodetector involved in Example 2 under a reverse bias of 15 V. As can be seen from the figure, the full width at half maximum (FWHM) of the device's pulse response waveform is 640 ps, ​​and the fall time is 480 ps.

[0091] Figure 18 This is the frequency response characteristic curve of the ultrafast fully flexible organic photodetector involved in Example 2. The curve was obtained by Fourier transforming the impulse response waveform. As can be seen from the figure, the device's bandwidth (-3dB bandwidth) is 700 MHz.

[0092] Comparative Example 2

[0093] Based on TAPC and C 70 High-speed organic photodetectors of the system (structure as follows) Figure 19 As shown, this device does not employ optical field control and includes a transparent substrate 41, an anode 42, a hole transport layer 43, a photosensitive layer 44, an electron transport layer 45, a hole blocking layer 46, and a metal cathode 47 arranged sequentially.

[0094] In Comparative Example 2, the high-speed organic photodetector with a bulk heterojunction structure has a transparent substrate of glass; an anode of indium tin oxide (ITO); a hole transport layer of TAPC with a thickness of 20 nm; and a photosensitive layer of a blended film of electron donor and electron acceptor materials with a thickness of 75 nm. Specifically, the electron donor material is TAPC, and the electron acceptor material is C... 70 The electron donor material in the photosensitive layer has a mass concentration of 30 wt%; the electron transport material is C. 70 The thickness of the cathode is 60 nm; the hole blocking layer is BCP with a thickness of 10 nm; the cathode is aluminum with a thickness of 400 nm.

[0095] Comparative Example 2 is based on TAPC and C. 70 The specific fabrication method of the high-speed organic photodetector system is as follows: The ITO-coated glass substrate is ultrasonically cleaned in a cleaning solution for 90 minutes, then rubbed with deionized water and the surface water droplets are blown away with nitrogen. It is then baked in a vacuum oven at 120℃ for 60 minutes to remove residual moisture from the ITO glass. The dried ITO glass substrate is then placed in an oxygen atmosphere at 15 Pa pressure, with an ionization voltage of 300 V, and subjected to oxygen plasma treatment for 4 minutes to further remove residual impurities on the ITO glass surface and improve the ITO work function. It is then placed in the cavity of a vacuum evaporation equipment. The vacuum degree in the vacuum evaporation cavity is evaporated to ~10 using a mechanical pump and a molecular pump. -5 Pa, followed by the sequential deposition of organic material layers and a metal cathode onto the ITO electrode. The overlapping portion of the two electrodes forms the effective photodetector region of the device. The final fabricated structure is Glass / ITO / TAPC (20 nm) / TAPC:C 70 (3:7, 75 nm) / C 70 Organic photodetector (60 nm) / BCP (10 nm) / Al (400 nm).

[0096] Figure 20 The diagram shows a comparison of the response waveforms of the two organic photodetectors involved in Example 2 and Comparative Example 2. The RC time constants of the two devices are equal, and the applied bias voltage is −8 V for both. The only difference is that the device involved in Example 2 uses a RC time constant of −8 V. 60 As an electron transport layer, the devices involved in Comparative Example 2 are based on C 70 This is the electron transport layer. As can be seen from the figure, the response waveform of the device involved in Example 2 is closer to a square wave, indicating that the device responds faster to changes in external optical signals. The response times of the two types of devices were calculated using an oscilloscope, and the specific results are as follows: at frequencies of 50 MHz, 25 MHz, 10 MHz, and 5 MHz, the response times of the two organic photodetectors involved in Example 2 and Comparative Example 2 are 0.82 ns and 2.2 ns, 0.82 ns and 3.0 ns, 0.88 ns and 4.0 ns, and 0.90 ns and 4.0 ns, respectively. This comparison demonstrates the superior response speed performance of the device involved in Example 2 and further proves that sub-nanosecond OPDs can be fabricated through optical field control.

[0097] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An ultrafast response organic photodetector based on light field control, characterized in that, It has a bulk heterojunction structure, which includes, in sequence, a transparent substrate, an anode, a hole transport layer, a photosensitive layer, an electron transport layer, a hole blocking layer, and a cathode; The photosensitive layer is a blend of an electron donor material and an electron acceptor material; the electron donor material is Rubrene or TAPC; the electron acceptor material is C. 70 ; The electron transport layer material is C. 60 ; The hole transport layer is made of Rubrene or TAPC.

2. The ultrafast response organic photodetector based on light field control according to claim 1, characterized in that, Its operating band is the infrared band, under which light absorption is suppressed at the photosensitive layer.

3. The ultrafast response organic photodetector based on light field control according to claim 1, characterized in that, The hole-blocking layer is made of BCP or C. 60 .

4. The ultrafast response organic photodetector based on light field control according to claim 1, characterized in that, The thickness of the hole transport layer is 5~60 nm.

5. The ultrafast response organic photodetector based on light field control according to claim 1, characterized in that, The thickness of the photosensitive layer is 40~100 nm.

6. The ultrafast response organic photodetector based on light field control according to claim 1, characterized in that, The thickness of the electron transport layer is 5~100 nm.

7. The ultrafast response organic photodetector based on light field control according to claim 1, characterized in that, The transparent substrate is glass, quartz, polyethylene terephthalate, polyimide, or polydimethylsiloxane.

8. The ultrafast response organic photodetector based on light field control according to claim 1, characterized in that, The anode is ITO, a conductive polymer, or Cu.

9. The ultrafast response organic photodetector based on light field control according to claim 1, characterized in that, The cathode is made of Al, Ag, or Au.

10. The ultrafast response organic photodetector based on light field control according to claim 1, characterized in that, The doping concentration of the electron donor material is 5 wt% to 80 wt%.

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