A self-powered ultraviolet photodetector based on PEDOT:PSS / SiC organic-inorganic heterojunction

Abstract

The present invention discloses a self-powered ultraviolet photodetector based on a PEDOT:PSS / SiC organic-inorganic heterojunction and a preparation method thereof, including a substrate; a PEDOT:PSS organic layer, the PEDOT:PSS organic layer is p-type conductive, and the PEDOT:PSS organic layer is attached to the surface of the substrate; a first electrode, forming an ohmic contact with the substrate; and a second electrode, forming an ohmic contact with the PEDOT:PSS organic layer. The present invention can achieve a self-powered photodetection mode, that is, the conversion from optical signal to electrical signal can be completed even under zero bias voltage, with a large responsivity and a high external quantum efficiency. The preparation method is simple and the use cost is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of wide bandgap semiconductor optoelectronic devices, and particularly relates to a self-powered ultraviolet photodetector based on a PEDOT:PSS / SiC organic-inorganic heterojunction. Background Art

[0002] Ultraviolet photodetectors can identify optical signals in the 10 - 400 nm band and have important applications in fields such as space exploration, national defense early warning, fire alarms, environmental monitoring, and biochemical analysis. Especially with the rapid development of Internet of Things technology, highly integrated information sensors have put forward urgent requirements for device performance such as low energy consumption, long battery life, light weight, and small volume, which has made self-powered ultraviolet photodetectors a hot topic in the field of optoelectronic devices. Self-powered photodetectors mainly rely on the built-in electric field generated inside the material to drive the separation of electron-hole pairs, and have the advantage of zero power consumption; and no additional drive circuit is required during the integrated design process, greatly reducing the device preparation cost and physical volume.

[0003] In order to convert ultraviolet photons into detectable electrical signals, the active layer of a photodetector needs to use a semiconductor material with a bandgap width greater than 3.1 eV (corresponding to an absorption cut-off wavelength of 400 nm). So far, a large number of wide bandgap semiconductor materials such as aluminum nitride (6.2 eV), diamond (5.5 eV), gallium oxide (4.9 eV), zinc sulfide (3.6 eV), gallium nitride (3.39 eV), zinc oxide (3.35 eV), and silicon carbide (3.2 eV) have been developed and studied for the preparation of ultraviolet photodetectors. Among them, SiC has become a remarkable ultraviolet light sensing material due to its suitable response band (<390 nm), high breakdown field strength (2.5 MV / cm), large electron mobility (1000 cm 2 / V·s), and strong radiation resistance (the displacement energy of Si atoms is 35 eV, and the displacement energy of C atoms is 21 eV). Currently, Schottky junction or heterojunction devices based on SiC can already achieve basic self-powered light detection functions, and the responsivity has reached 0.17 A / W. However, compared with other developed wide bandgap materials such as gallium oxide and gallium nitride, SiC-based self-powered optoelectronic devices still have great room for performance improvement. The self-powered responsivities of gallium oxide and gallium nitride have respectively achieved 2.82 A / W and 9.78 A / W, while the self-powered performance of SiC-based photodetectors has not exceeded the level of A / W.

[0004] Therefore, developing high-performance self-powered ultraviolet photodetectors based on SiC is an important link in realizing its practical application process. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this section, the abstract, and the title, but such simplifications or omissions shall not be used to limit the scope of the present invention.

[0006] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0007] One object of the present invention is to provide a self-powered ultraviolet photodetector based on a PEDOT:PSS / SiC organic-inorganic heterojunction, which can achieve a self-powered photodetection mode, that is, the conversion of optical signals to electrical signals can be completed even under zero bias voltage.

[0008] To solve the above technical problems, the present invention provides the following technical solution: A self-powered ultraviolet photodetector based on a PEDOT:PSS / SiC organic-inorganic heterojunction, comprising,

[0009] A substrate;

[0010] A PEDOT:PSS organic layer, the PEDOT:PSS organic layer being p-type conductive, and the PEDOT:PSS organic layer being attached to the surface of the substrate;

[0011] A first electrode, forming an ohmic contact with the substrate; and,

[0012] A second electrode, forming an ohmic contact with the PEDOT:PSS organic layer.

[0013] As a preferred embodiment of the self-powered ultraviolet photodetector based on a PEDOT:PSS / SiC organic-inorganic heterojunction of the present invention, wherein: the substrate is n-type conductive, and the resistivity of the substrate is 0.001 to 0.1 Ω·cm.

[0014] As a preferred embodiment of the self-powered ultraviolet photodetector based on a PEDOT:PSS / SiC organic-inorganic heterojunction of the present invention, wherein: the substrate is a SiC single crystal substrate.

[0015] As a preferred embodiment of the self-powered ultraviolet photodetector based on a PEDOT:PSS / SiC organic-inorganic heterojunction of the present invention, wherein: the thickness of the PEDOT:PSS organic layer is 10 to 500 nm, and the conductivity is 10 to 1000 S / cm.

[0016] As a preferred embodiment of the self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction of the present invention, wherein: the first electrode comprises a single layer formed of one of nickel, aluminum, copper, silver, gold, platinum, titanium, gallium, indium, and scandium, or a stack formed of a plurality of them.

[0017] As a preferred embodiment of the self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction of the present invention, wherein: the second electrode comprises a single layer formed of one of nickel, aluminum, copper, silver, gold, platinum, titanium, gallium, indium, and scandium, or a stack formed of a plurality of them.

[0018] Another object of the present invention is to provide a method for preparing the self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction as described in any one of the above, including,

[0019] Providing a substrate;

[0020] Using a spin coating method to spin coat a precursor solution of the PEDOT:PSS organic layer on the surface of the substrate, and evaporating the solvent to form the PEDOT:PSS organic layer;

[0021] Using a magnetron sputtering technique or a melting method to form a first electrode with ohmic contact on the substrate and a second electrode with ohmic contact on the PEDOT:PSS organic layer.

[0022] As a preferred embodiment of the method for preparing the self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction of the present invention, wherein: the substrate is provided by one of the techniques of physical vapor transport method, top-seeded solution growth method, or high-temperature chemical vapor deposition method, and N element doping is carried out during the preparation process, and the doping concentration is 10 17 ~10 20 cm -3 .

[0023] As a preferred embodiment of the method for preparing the self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction of the present invention, wherein: the precursor solution is a mixture of an aqueous solution of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate with a volume ratio of 5:1 to 50:1 and isopropanol.

[0024] As a preferred embodiment of the method for preparing the self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction of the present invention, wherein: for evaporating the solvent, the evaporation temperature is 70 to 150 °C, and the evaporation time is 5 to 20 min.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The self-powered ultraviolet photodetector based on PEDOT:PSS / SiC organic-inorganic heterojunction provided by the present invention can achieve a self-powered photodetection mode, that is, the conversion from optical signal to electrical signal can be completed even under zero bias voltage, with large responsivity, high external quantum efficiency, simple preparation method and low use cost, and is suitable for commercial applications and scientific research. Brief Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts. Among them:

[0028] Figure 1 FIG. is a schematic structural diagram of a self-powered ultraviolet photodetector based on PEDOT:PSS / SiC organic-inorganic heterojunction provided in Embodiment 1 of the present invention;

[0029] Figure 2 FIG. is the XRD pattern of the SiC single crystal substrate and the PEDOT:PSS / SiC heterojunction.

[0030] Figure 3 FIG. is the dark current and photocurrent current-voltage curves of the PEDOT:PSS / SiC heterojunction photodetector under dark room conditions and 254 nm light illumination.

[0031] Figure 4 FIG. is the photocurrent response of the PEDOT:PSS / SiC heterojunction photodetector with the optical cycle switch under zero bias and 254 nm ultraviolet light irradiation of 500 μW / cm 2 2.

[0032] Figure 5 FIG. is the photocurrent response curve of the PEDOT:PSS / SiC heterojunction photodetector with the change of 254 nm light intensity under zero bias.

[0033] Figure 6 FIG. is the spectral response curve measured for the PEDOT:PSS / SiC heterojunction photodetector in the wavelength range of 200-700 nm under zero bias.

[0034] Figure 7 FIG. is the built-in voltage of the PEDOT:PSS / SiC heterojunction measured by the capacitance-voltage method. Detailed Embodiments

[0035] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given in conjunction with the embodiments of the specification.

[0036] In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways than those specifically described herein. Those skilled in the art can make similar generalizations without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0037] Secondly, as used herein, "one embodiment" or "an embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or alternative embodiments that exclude each other.

[0038] Unless otherwise specified, the raw materials used in the examples are commercially purchased. Unless otherwise specified, the means involved in the examples are conventional technical means in the art.

[0039] Example 1

[0040] As Figure 1 shown, a self-powered ultraviolet photodetector based on a PEDOT:PSS / SiC organic-inorganic heterojunction provided in this Example 1 includes a 4H-SiC single crystal substrate 100 that conducts n-type, a p-type conductive PEDOT:PSS organic layer 200 deposited on the surface of the 4H-SiC single crystal substrate 100, a first electrode 300 that forms an ohmic contact with the SiC, a second electrode 400 that forms an ohmic contact with the PEDOT:PSS, and a space charge layer formed at the PEDOT:PSS / SiC heterojunction interface.

[0041] The specific preparation method of the above self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction is as follows:

[0042] (1) By physical vapor transport method, a 4H-SiC single crystal with an N element doping concentration of about 5×10 19 cm -3 was prepared, and its resistivity was about 0.005 Ω·cm; the SiC single crystal was processed into a square substrate of 10*10 mm 2 and washed for later use.

[0043] (2) Filter the poly(3,4-ethylenedioxythiophene) / polystyrenesulfonate aqueous solution with a 0.24 μm water-based filter, and configure a PEDOT:PSS organic material precursor solution with isopropanol at a volume ratio of 10:1.

[0044] (3) Based on the spin coating method, spin coat a layer of precursor liquid on the SiC substrate, and heat it on a heating stage at 110 °C for 12 min to obtain a PEDOT:PSS / SiC organic-inorganic heterojunction.

[0045] (4) Using magnetron sputtering and a mask plate, a 1*1 mm square array of titanium-gold electrodes was prepared on the PEDOT:PSS surface of the heterojunction; using the melting method, a circular indium electrode with a diameter of 1 mm was prepared on the SiC surface to obtain a self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction. 2 The XRD patterns of the SiC single-crystal substrate and the PEDOT:PSS / SiC heterojunction are as

[0046] shown. 4H-SiC exhibits a (0001) orientation. After covering the PEDOT:PSS organic film layer, due to absorption and scattering effects, the intensity of the (0004) peak of SiC slightly decreases. The SiC single crystal has a smooth surface, and the surface roughness measured by atomic force microscopy is only 0.145 nm, and the surface roughness after covering the PEDOT:PSS organic layer is also only 1.35 nm. The atomic-level surface roughness indicates that the prepared PEDOT:PSS / SiC heterojunction interface is flat and has good contact. Figure 2 The XRD patterns of the SiC single-crystal substrate and the PEDOT:PSS / SiC heterojunction are as shown. 4H-SiC exhibits a (0001) orientation. After covering the PEDOT:PSS organic film layer, due to absorption and scattering effects, the intensity of the (0004) peak of SiC slightly decreases. The SiC single crystal has a smooth surface, and the surface roughness measured by atomic force microscopy is only 0.145 nm, and the surface roughness after covering the PEDOT:PSS organic layer is also only 1.35 nm. The atomic-level surface roughness indicates that the prepared PEDOT:PSS / SiC heterojunction interface is flat and has good contact.

[0047] Example 2

[0048] Select a pair of upper and lower electrodes and test them under dark and light conditions. The obtained current-voltage curves are as Figure 3 shown. The dark current exhibits a typical rectifying effect, indicating the formation of a PN junction at the heterojunction interface. The photocurrent has an obvious photovoltaic effect. The short-circuit current under 254 nm illumination is 8.4 μA, and the open-circuit voltage is 1.1 V, indicating that the prepared PEDOT:PSS / SiC heterojunction photodetector can operate in a self-powered mode.

[0049] To verify the working effect of the self-powered mode, the device was placed under zero bias, and only irradiated with 254 nm light with a light power density of 500 μW / cm 2 . The measured response current change curve is as Figure 4 shown. The prepared PEDOT:PSS / SiC heterojunction photodetector has high sensitivity. Its photocurrent instantaneously saturates with the appearance of light and instantaneously decreases with the disappearance of light. By changing the light power density (5 - 600 μW / cm 2 ), the obtained self-powered responsivity and external quantum efficiency are as Figure 5 shown. Under zero bias and 254 nm illumination with a light power density of 5 μW / cm 2 , the self-powered responsivity and external quantum efficiency of the heterojunction photodetector are 2.15 A / W and 1053% respectively, and the self-powered performance is superior to currently known SiC-based photodetectors.

[0050] To verify that the PEDOT:PSS / SiC heterojunction device provided by the present invention belongs to an ultraviolet photodetector, spectral tests were conducted on it in the wavelength range of 200 - 700 nm, and the obtained spectral response curve is as shown in Figure 6 . The response interval of the constructed SiC-based heterojunction is in the wavelength range of 200 - 390 nm, and the position of the response cut-off curve is approximately 370 nm, indicating that the PEDOT:PSS / SiC heterojunction device provided by the present invention belongs to an ultraviolet photodetector.

[0051] Furthermore, in order to trace the physical origin of the ultra-high self-powered optical responsivity of the PEDOT:PSS / SiC heterojunction photodetector, the present invention provides the capacitance-voltage curve of the PEDOT:PSS / SiC vertical heterojunction, and through conversion and deduction, the built-in voltage (V bi ) formed at the heterojunction interface is obtained as 0.5 V, as shown in Figure 7 . The built-in voltage at the heterojunction interface originates from the formation of the space charge region of the material contact. The built-in electric field generated by the built-in voltage can drive the photo-excited electron-hole pairs to perform self-separation, realizing the conversion from optical signal to electrical signal under zero bias.

[0052] According to the test results of the examples, it shows that the PEDOT:PSS / SiC organic-inorganic heterojunction photodetector prepared according to the present invention is a self-powered ultraviolet photodetector with excellent performance.

[0053] Comparative Example 1

[0054] This Comparative Example 1 provides a CuI / SiC heterojunction photodetector. The device preparation method and steps are the same as those in Example 1, only replacing the PEDOT:PSS organic material precursor solution with the precursor solution of CuI.

[0055] A pair of upper and lower electrodes were selected, and the optoelectronic properties of the CuI / SiC heterojunction photodetector were tested under darkroom and light illumination conditions. Under the irradiation of 254 nm light with an intensity of 500 μW / cm 2 , the short-circuit current of the CuI / SiC heterojunction photodetector is 46 nA, and the open-circuit voltage is 0.2 V. The device can achieve a basic self-powered detection function, but its response performance is far inferior to that of the PEDOT:PSS / SiC heterojunction photodetector. Under zero bias and 254 nm light illumination with an intensity of 5 μW / cm 2 , the self-powered responsivity and external quantum efficiency of the CuI / SiC heterojunction photodetector are 12 mA / W and 6% respectively, and the self-powered performance does not reach the A / W level.

[0056] Description of a comparative example of a CuI / SiC heterojunction photodetector. The PEDOT:PSS / SiC heterojunction photodetector benefits from the excellent carrier transport characteristics of PEDOT:PSS and a suitable heterojunction energy band structure, and can generate a larger self-powered photocurrent.

[0057] In the present invention, by using a highly doped n-type SiC single crystal and an improved PEDOT:PSS organic material, a PEDOT:PSS / SiC organic-inorganic heterojunction is constructed, providing a high-performance PEDOT:PSS / SiC heterojunction self-powered ultraviolet photodetector. The constructed PEDOT:PSS / SiC organic-inorganic heterojunction forms a space charge layer at the heterojunction interface and generates a built-in voltage, driving the self-separation of photon-excited electron-hole pairs, realizing photoelectric conversion without external energy supply, and enabling the prepared PEDOT:PSS / SiC heterojunction photodetector to obtain a self-powered working mode. The high electron concentration of the highly doped SiC photosensitive layer increases the probability of photon excitation to form electron-hole pairs. The improved PEDOT:PSS organic material and precisely controlled spin coating process improve the quality of the heterojunction interface, enabling the PEDOT:PSS / SiC heterojunction to generate a large built-in voltage and enhancing the electron-hole pair separation ability of the device. Based on the above advantages, the violet photodetector prepared based on the PEDOT:PSS / SiC heterojunction in the present invention achieves a self-powered responsivity exceeding A / W. The PEDOT:PSS / SiC organic-inorganic heterojunction self-powered ultraviolet photodetector provided by the present invention has a large responsivity, a high external quantum efficiency, a simple preparation method, and a low use cost, and is suitable for practical applications and scientific research.

[0058] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A self-powered ultraviolet photodetector based on a PEDOT:PSS / SiC organic-inorganic heterojunction, characterized in that: Comprising, a substrate; a PEDOT:PSS organic layer, the PEDOT:PSS organic layer being p-type conductive, the PEDOT:PSS organic layer being attached to the surface of the substrate; a first electrode, forming an ohmic contact with the substrate; and, a second electrode, forming an ohmic contact with the PEDOT:PSS organic layer; Among them, the substrate is n-type conductive, and its doping concentration is 10 17 ~10 20 cm -3 , the resistivity of the substrate is 0.001~0.1 Ω·cm; the substrate is a single crystal SiC substrate, the thickness of the PEDOT:PSS organic layer is 10~500 nm, and the conductivity is 10~1000 S / cm.

2. The self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction according to claim 1, wherein: the first electrode comprises a single layer formed of one of nickel, aluminum, copper, silver, gold, platinum, titanium, gallium, indium, and scandium or a laminate composed of a plurality of them.

3. The self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction according to claim 1, characterized in that: the second electrode comprises a single layer formed of one of nickel, aluminum, copper, silver, gold, platinum, titanium, gallium, indium, and scandium or a laminate composed of a plurality of them.

4. The preparation method of the self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction according to any one of claims 1 to 3, characterized in that: Comprising, providing a substrate; spin-coating a precursor solution of the PEDOT:PSS organic layer on the surface of the substrate by spin coating, and evaporating the solvent to form the PEDOT:PSS organic layer; using magnetron sputtering technology or melting method to form a first electrode with an ohmic contact on the substrate and a second electrode with an ohmic contact on the PEDOT:PSS organic layer.

5. The preparation method of the self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction according to claim 4, characterized in that: The providing of the substrate is prepared by one of physical vapor transport method, top-seeded solution growth method, or high-temperature chemical vapor deposition method, and N element doping is carried out during the preparation process.

6. The preparation method of the self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction according to claim 4 or 5, characterized in that: The precursor solution is a mixture of an aqueous solution of poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate and isopropanol with a volume ratio of 5:1 to 50:

1.

7. The preparation method of the self-powered ultraviolet photodetector based on the PEDOT:PSS / SiC organic-inorganic heterojunction according to claim 6, characterized in that: The evaporation of the solvent is carried out at an evaporation temperature of 70 to 150 °C and an evaporation time of 5 to 20 min.

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