CN114613911A - Heterojunction structure and photoelectric detector based on tungsten diselenide and IEICO-4F and preparation thereof - Google Patents

Abstract

The invention discloses a heterojunction structure and a photoelectric detector based on tungsten diselenide and IEICO-4F and preparation thereof, wherein a single-layer tungsten diselenide film is synthesized on a silicon substrate by a chemical vapor deposition method, and then an IEICO-4F layer is prepared on the tungsten diselenide film by a spin coating process. The heterojunction energy bands are arranged in a II type (staggered) manner, so that the photoelectric current formed by photo-generated carriers generated by incident light can be rapidly separated, and the photoluminescence peak of the tungsten diselenide is remarkably quenched along with the increase of the thickness of the organic semiconductor layer, so that the device has more excellent photoresponse characteristics. The heterojunction and the photoelectric detector thereof have the advantages of simple preparation method, low cost and compatibility with silicon process. The photoelectric detector composed of the heterojunction structure has the excellent characteristics of high response rate, high detection rate, high stability, wide spectral response and the like, and provides new guiding significance for a new generation of photoelectric detectors based on tungsten diselenide.

Description

Heterojunction structure and photoelectric detector based on tungsten diselenide and IEICO-4F and preparation thereof

Technical Field

The invention relates to a heterojunction, the technical field of a photoelectric detector based on the heterojunction, in particular to a heterojunction based on tungsten diselenide and IEICO-4F (2,2 ' - ((2Z,2 ' Z) - ((4,4,9,9-tetrakis (4-hexylphenyl) -4, 9-dihydris-indaceno [1,2-b:5,6-b ' ] dithiophene-2,7-diyl) bis (4- ((2-ethylhexyl) oxy) thiophene-5, 2-di)) bis (5,6-difluoro-3-oxo-2, 3-dihydrido-1H-indene-2, 1-diyl)) dihydrino), a photoelectric detector and a preparation method thereof.

Background

Photoelectric Detectors (PDs) have become key components in the modern miniaturized electronic industry as an important information sensing device, and have wide application prospects in the fields of scientific research, national defense, civil use and the like. The research and application of the photoelectric detector greatly promote the progress and development of society. Photodetectors based on conventional semiconductor materials such As Si, Ge, In Ga As, In Sb, Hg Cd Te, and type II superlattices have been widely used In the spectral ranges of ultraviolet, visible, near-infrared to far-infrared. In recent years, the rise of the fields of artificial intelligence, the internet of things and the like puts higher demands on the functions of the photoelectric information sensing device. However, due to the band gap limitation, material rigidity and lattice mismatch of the conventional semiconductor material, the requirements of the next generation of intelligent sensing device with high sensitivity, adjustable multiband, silicon-based integration, light weight and low cost are difficult to meet. The two-dimensional material has the following characteristics at the same time: (1) the atomic-level thickness, the carrier concentration, the conductivity type and other characteristics of the atomic-level thickness are easy to regulate and control; (2) strong light-substance interaction properties; (3) the flexibility is flexible; (4) the surface has no dangling bond, and various functional heterostructures are easy to construct by a manual stacking method, so that the material becomes one of candidate materials of next-generation electronic and optoelectronic devices.

The transition metal chalcogenide (TMDCs) is a material with wide application prospect, has larger specific surface area, excellent electrochemical performance and good flexibility, and ensures the multifunctionality. The material properties differ according to the size and charge difference of the two elements, transition metal and chalcogen. Compared with other two-dimensional transition metal chalcogenide compounds, the selenium-based material has higher conductivity so that ions can be rapidly transmitted between the electrodes.

Tungsten diselenide (WSe), an emerging two-dimensional material of the group 10 transition metal chalcogenides₂) The material has adjustable band gap and high carrierMobility and other excellent properties and other common characteristics of two-dimensional materials; at the same time, WSe₂Also has own unique and excellent characteristics, WSe₂The material has a two-dimensional layered structure, which has the advantages of high specific capacity, stable structure, easy integration and the like, and is compatible with the WS in a common stable phase₂In contrast, WSe of stationary phase₂Has higher charge transfer rate, and becomes a new material applied to the photoelectric detector. In addition, the thin film synthesis process is well developed, and includes a mechanical lift-off method, a Chemical Vapor Deposition (CVD) method, a Thermal Assisted Conversion (TAC) method, a Molecular Beam Epitaxy (MBE) method, a Chemical Vapor Transport (CVT) method, and the like.

Due to WSe₂Has excellent photoelectric characteristics and simple preparation, and currently, many WSe-based photoelectric devices₂The constructed photodetector structure is reported (Tan H.L et al, ACS Nano, 11 2017, 12817-12823), but the photodetector structure has the problems of low response rate, small detectable wavelength range and the like.

Disclosure of Invention

Aiming at the defects in the field, the invention provides an IEICO-4F/tungsten diselenide/silicon heterojunction structure and a photoelectric detector based on the heterojunction structure. The photoelectric detector composed of the structure has the excellent characteristics of high response rate, high detection rate, low dark current, high stability, wide spectral response and the like, and paves the way for the new generation of photoelectric detectors. The invention adopts the following technical scheme:

a heterojunction structure based on tungsten diselenide and IEICO-4F, said heterojunction structure being an IEICO-4F/tungsten diselenide/silicon heterojunction, comprising:

(1) a silicon layer;

(2) a tungsten diselenide layer on the silicon layer;

(3) an organic semiconductor IEICO-4F layer on the tungsten diselenide layer.

The tungsten diselenide is a two-dimensional semiconductor phase single-layer structure and is about 0.79nm thick.

Further, the thickness of the organic semiconductor IEICO-4F layer is about 2.0 to about 6.0 nm; preferably 4.0 to 6.0 nm.

The invention also provides a preparation method of the IEICO-4F/tungsten diselenide/silicon heterojunction structure, which comprises the following steps:

(1) manufacturing a tungsten diselenide thin film on the silicon layer to form tungsten diselenide/silicon;

(2) and preparing an IEICO-4F thin film on the tungsten diselenide layer to form an IEICO-4F/tungsten diselenide/silicon heterojunction structure.

Further, the preparation of the tungsten diselenide thin film is performed by methods conventional in the art, such as Chemical Vapor Deposition (CVD), Thermal Assisted Conversion (TAC), Molecular Beam Epitaxy (MBE), and Chemical Vapor Transport (CVT), and includes:

(1) 200mg of WO₃Placing the powder and 150mg Se powder between the first heating temperature zone and the second heating temperature zone of a tube furnace respectively, and mixing 10mm × 10mm SiO₂the/Si silicon wafer substrate is placed in WO₃5mm before the powder;

(2) vacuumizing the tube furnace for 10min, and introducing argon to restore the tube furnace to normal pressure;

(3) during the reaction, the flow of argon was maintained at 100 sccm; heating the first temperature zone to 900 ℃ at a heating rate of 45 ℃/min; when the first temperature zone reaches 450 ℃, heating the second temperature zone to 300 ℃ at the heating rate of 30 ℃/min, and starting the chemical vapor deposition reaction;

(4) since the reducibility of Se powder is weak, 10sccm of hydrogen gas is introduced as an auxiliary gas at the beginning of the chemical vapor deposition reaction.

(5) After 10min, the reaction was completed by stopping the introduction of hydrogen and shutting down the tube furnace.

Further, the preparation method of the IEICO-4F film comprises the following steps:

(1) dissolving a quantity of IEICO-4F powder in a quantity of chloroform solution to provide a solution having a solubility in the range of 0.5g/L to 1.5 g/L;

(2) the solution was used to prepare an IEICO-4F layer on a tungsten diselenide layer.

The present invention uses spin coating to prepare the IEICO-4 layer, but other methods such as printing, etc. can also be used. The invention realizes effective regulation and control of the thickness of the IEICO-4F film in the heterostructure by controlling the rotating speed of the spin-coating chloroform solution containing the IEICO-4F. With the increase of the thickness of the IEICO-4F organic material, a photoluminescence peak of the IEICO-4F/tungsten diselenide heterojunction is subjected to blue shift, the photoluminescence peak of the tungsten diselenide is gradually inhibited and even quenched, and the obvious quenching behavior shows that stronger charge transfer is generated at the interface of the second heterojunction, so that the effective separation and collection of photogenerated electron-hole pairs are facilitated. Therefore, controlling the thickness of the IEICO-4F thin film can adjust the optical absorption and the photoelectric response of the heterojunction, thereby influencing the characteristics of the IEICO-4F/tungsten diselenide/silicon heterojunction photodetector.

The invention also provides a photoelectric detector based on the IEICO-4F/tungsten diselenide/silicon heterojunction structure, and the photoelectric detector further comprises: an electrode in electrical contact with said IEICO-4F layer, said electrode selected from a metallic material or a non-metallic conductive material; preferably, the non-metallic conductor material is selected from graphene or PEDOT: PSS. The PEDOT and PSS refer to a high-molecular polymer aqueous solution with high conductivity, and aqueous solutions with different conductivities can be obtained according to different formulas. The product is composed of PEDOT and PSS. PEDOT is a polymer of EDOT (3, 4-ethylenedioxythiophene monomer), PSS is polystyrene sulfonate; preferably, the metal conductor material is selected from Au, Ag, Al, etc.;

further, the process for manufacturing a photodetector includes:

(1) manufacturing a tungsten diselenide thin film on the silicon layer to form tungsten diselenide/silicon;

(2) preparing an IEICO-4F thin film on the tungsten diselenide layer to form an IEICO-4F/tungsten diselenide/silicon heterojunction structure;

(3) preparing an electrode on the IEICO-4F layer to form an electrode/IEICO-4F/tungsten diselenide/silicon photoelectric detector structure;

furthermore, the invention adopts a method of transferring Au electrode to prepare the electrode of the photoelectric detector. The preparation method of the Au electrode is characterized by comprising the following steps:

(1) by magnetron sputtering on SiO₂Preparation of Au electrode on/Si substrateA pole;

(2) transferring the Au electrode to an IEICO-4F/tungsten diselenide heterojunction;

the electrode can be prepared by a suitable preparation method, such as thermal evaporation, electron beam deposition, sputtering, solution method, etc., depending on the characteristics of the electrode material.

The invention also provides application of the heterojunction based on the tungsten diselenide thin film and the IEICO-4F as a photoelectric detector. Analysis of the energy band structure of the IEICO-4F/tungsten diselenide heterojunction revealed that the conduction band bottom of a single layer of tungsten diselenide is lower than the LUMO level of IEICO-4F, while the valence band top is lower than the HOMO level of IEICO-4F, and thus the IEICO-4F/tungsten diselenide heterojunction is a type II (staggered) energy band arrangement structure. Generally, after the IEICO-4F and the tungsten diselenide form a heterojunction, electrons in the IEICO-4F layer are transferred towards the tungsten diselenide layer, and holes in the tungsten diselenide layer are transferred towards the IEICO-4F layer. Therefore, the photo-generated carriers generated by the photodetector under the irradiation of the incident light can be rapidly separated to form a large photocurrent.

The IEICO-4F layer in the IEICO-4F/tungsten diselenide/silicon heterojunction can also influence the photoluminescence characteristic of the heterojunction, and as the thickness of the organic material IEICO-4F layer is increased, the photoluminescence peak of the IEICO-4F/tungsten diselenide heterojunction appears blue shift, and WSe₂The photoluminescence peak of the photo-luminescent material is gradually inhibited, and the obvious quenching behavior shows that a stronger charge transfer phenomenon occurs at the heterojunction interface, so that the response characteristic of the photo-detector can be effectively improved. Experiments prove that the heterojunction optical detector composed of IEICO-4F and tungsten diselenide has good optical response in the range from visible light to infrared. For example, under the irradiation of a laser source with 808nm, the maximum response rate and the specific detectivity of the photoelectric detector can reach 8.32A/W and 4.65 multiplied by 10¹¹Jones, in general. Through the calculation of density functional theory, the method is combined with single WSe₂Compared with a photoelectric detector made of IEICO-4F material, the device has smaller forbidden band width, which shows that the effective photoelectric detection range of the device can be expanded to 1550nm, and the excellent photoelectric detector with high stability, wide spectral response, high response rate and high detection rate is more likely to be realized.

Compared with the prior art, the invention has the main advantages that:

(1) the IEICO-4F/tungsten diselenide heterojunction is in a type II (staggered) energy band arrangement structure. The obvious quenching behavior shows that stronger charge transfer occurs at the heterojunction interface, and the response characteristic of the photoelectric detector can be effectively improved. Experiments prove that the heterojunction optical detector consisting of IEICO-4F and tungsten diselenide has good optical response in the range from visible light to infrared.

(2) The preparation method of the IEICO-4F/tungsten diselenide/silicon heterojunction structure is simple, the high-quality IEICO-4F/tungsten diselenide/silicon heterojunction heterostructure can be obtained in a short time by using simple equipment, the preparation process of the IEICO-4F/tungsten diselenide/silicon heterojunction heterostructure is compatible with a silicon-based CMOS process, the preparation efficiency and yield are improved, and the preparation cost is low.

(3) The IEICO-4F/tungsten diselenide/silicon heterojunction structure has excellent stability.

(4) The photoelectric detector prepared by the IEICO-4F/tungsten diselenide/silicon heterojunction has the excellent characteristics of high response rate, high specific detection rate, high stability, wide spectral response and the like. And has excellent optical response from visible light to infrared region, such as response rate and specific detectivity of 8.32A/W and 4.65 × 10 under 808nm light source¹¹Jones。

The invention focuses only on two-dimensional WSe₂Heterojunction with IEICO-4F is illustrated, but in two-dimensional material systems there are other narrow bandgap two-dimensional semiconductor materials, such as PtSe₂、MoS₂、WS₂Etc.; and in organic semiconductor material systems, there are also organic semiconductors that can form heterojunctions with two-dimensional materials, such as TiOPc, PTCDA, etc.; the idea or structure of the invention is equally applicable to heterojunctions formed by these two-dimensional materials with organic semiconductors and their application as photodetectors.

Drawings

Fig. 1 (a) shows a process for preparing an electrode/IEICO-4F/tungsten diselenide/silicon heterojunction photodetector according to the present invention; fig. 1 (b) is a schematic structural diagram of the photodetector;

fig. 2 (a) is an optical microscope image of a single layer of tungsten diselenide prepared according to the present invention; fig. 2 (b) is a scanning electron microscope image of a single layer of tungsten diselenide;

fig. 3 (a) is a raman characterization spectrum of single-layer tungsten diselenide prepared according to the present invention; FIG. 3 (b) is a Raman characterization spectrum of the organic semiconductor IEICO-4F;

FIG. 4 is a graph of characterization of IEICO-4F (-6.0 nm)/tungsten diselenide/silicon heterostructure photodetectors prepared in example 1 under 532nm light source illumination; FIG. 4 (a) is an I-V curve of a device under different intensity light sources; FIG. 4 (b) is an I-T curve of the device under different intensity light sources; FIG. 4 (c) is the response time of the device; FIG. 4 (d) shows the responsivity and specific detectivity of the device at different light source intensities;

FIG. 5 is a graph of characterization of the IEICO-4F (-6.0 nm)/tungsten diselenide/silicon heterostructure photodetector prepared in example 1 under illumination of a 808nm light source; FIG. 5 (a) is an I-V curve of a device under different intensity light sources; FIG. 5 (b) is an I-T curve of the device under different intensity light sources; FIG. 5 (c) is the response time of the device; FIG. 5 (d) shows the responsivity and specific detectivity of the device at different light source intensities;

FIG. 6 is a graph of characterization of the IEICO-4F (-4.1 nm)/tungsten diselenide/silicon heterostructure photodetector prepared in example 1 under the illumination of a 808nm light source; FIG. 6 (a) is an I-T curve of the device under different intensity light sources; FIG. 6 (b) shows the responsivity and specific detectivity of the device at different light source intensities;

FIG. 7 (a) is a single layer WSe₂And SiO₂Photoluminescence characteristics of the Si substrate; FIG. 7 (b) shows photoluminescence characteristics of different thicknesses of the organic semiconductor IEICO-4F; FIG. 7 (c) is a WSe of IEICO-4F films of varying thickness₂The photoluminescence characteristics of the IEICO-4F heterojunction;

in FIG. 8 (a) is WSe prepared in comparative example 2₂Preparing a photoelectric detector; in FIG. 8, (b) is WSe₂The structure of the photoelectric detector is schematic; FIG. 8 (c) shows a flow of preparing an IEICO-4F photodetector prepared in comparative example 2; in FIG. 8 (d) is the junction of the IEICO-4F photodetectorA schematic diagram;

fig. 9(a) is a graph comparing the light absorption of the photodetectors prepared in example 1 and comparative example 2; FIG. 9(b) is the I-T curves of the photodetectors prepared in example 1 and comparative example 2 under the irradiation of 1550nm light source;

table 1 summarizes the performance of the devices of example 1 and comparative example 1 and other reported photodetector performance parameters for similar device structures.

Detailed Description

The invention is further described with reference to the following drawings and specific examples. It should be understood that the description is intended for purposes of illustration only and is not intended to limit the scope of the present disclosure. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers.

A schematic flow chart of the preparation of the IEICO-4F/tungsten diselenide/silicon heterojunction of example 1 and the photodetector based on the heterojunction is shown in FIG. 1, and the WSe of comparative example 2₂A schematic flow chart of the preparation of the photodetector and the IEICO-4F photodetector is shown in FIG. 8.

Example 1

The basic structure and the preparation steps of the photodetector described in this example 1 are described below with reference to fig. 1:

1. clean Si substrate (i.e. SiO) with 285nm oxide layer₂/Si). Cutting SiO with silicon wafer cutting pen₂Cutting the/Si sheet into square substrates of 10mm multiplied by 10mm, sequentially putting the square substrates into acetone, absolute ethyl alcohol and deionized water for ultrasonic cleaning, and finally taking out the square substrates and drying the square substrates by using nitrogen;

2. 200mg of WO₃Placing the powder and 150mg Se powder between the first heating temperature zone and the second heating temperature zone of a tube furnace respectively, and mixing 10mm × 10mm SiO₂the/Si silicon wafer substrate is placed in WO₃5mm before the powder;

3. vacuumizing the tube furnace for 10min, and introducing argon to restore the tube furnace to normal pressure;

4. during the reaction, the flow of argon was maintained at 100 sccm; heating the first temperature zone to 900 ℃ at a heating rate of 45 ℃/min; when the first temperature zone reaches 450 ℃, heating the second temperature zone to 300 ℃ at the heating rate of 30 ℃/min, and starting the chemical vapor deposition reaction;

5. because the reducibility of the Se powder is weaker, 10sccm of hydrogen is required to be introduced as auxiliary gas when the chemical vapor deposition reaction starts;

6. after 10min, stopping introducing hydrogen and closing the tube furnace to complete the reaction;

7. dissolving 10mg of IEICO-4F powder in 10ml of chloroform solution;

8. dropping the solution on the tungsten diselenide layer by using a liquid-transferring gun, and spin-coating at the speed of 4500 rmp/min for 30 seconds to form a 6.0nm IEICO-4F layer; spin-coating at 6000 rmp/min for 30 seconds to form-4.1 nm IEICO-4F layer;

9. by magnetron sputtering on SiO₂Preparing an Au electrode on a Si substrate;

10. the Au electrode was transferred to an IEICO-4F/tungsten diselenide heterojunction.

The invention can change the spin coating speed and the solubility of the solution to obtain IEICO-4F layers with different thicknesses.

In this embodiment, conventional techniques such as Chemical Vapor Deposition (CVD), Thermal Assisted Conversion (TAC), Molecular Beam Epitaxy (MBE), and Chemical Vapor Transport (CVT) may be used to deposit the tungsten diselenide thin film.

In this embodiment, the IEICO-4F film can be prepared using conventional techniques such as spin coating, printing, and the like.

In this embodiment, the electrode material may be one of conductive materials such as Au, Al, Ag, graphene, PEDOT: PSS, etc. In this example, Au was used as the electrode material.

In this embodiment, the fabrication of the photodetector may be accomplished by fabricating the electrodes using conventional techniques such as thermal evaporation, sputtering, e-beam deposition, transfer, and the like.

In the above preparation steps, the order of the preparation steps can be properly adjusted according to actual conditions.

For example 1, the present invention characterizes the performance of the prepared IEICO-4F/tungsten diselenide/silicon heterogeneous photodetector, and the characterization results are shown in fig. 4 to 7.

FIG. 4 is a graph of characterization of IEICO-4F (-6.0 nm)/tungsten diselenide/silicon heterostructure photodetectors prepared in example 1 under 532nm light source illumination; FIG. 4 (a) is an I-V curve of a device under different intensity light sources; FIG. 4 (b) is an I-T curve of the device under different intensity light sources; FIG. 4 (c) is the response time of the device; FIG. 4 (d) shows the responsivity and specific detectivity of the device at different light source intensities;

wherein, the responsivity is a physical quantity describing the photoelectric conversion capability of the device, and the responsivity is related to the material and the wavelength of light of the device. Specific detectivity is a parameter that characterizes the ability of the detector to detect low light signals. The calculation formula is as follows:

in the formula:

r-responsivity (A/W);

I_p-a photocurrent (A);

I_d-dark current (a);

p-illumination intensity (W);

d x-specific detectivity (Jones);

e-element charge (1.602X 10)^-19C)。

FIG. 5 is a graph of characterization of the IEICO-4F (-6.0 nm)/tungsten diselenide/silicon heterostructure photodetector prepared in example 1 under illumination of a 808nm light source; FIG. 5 (a) is an I-V curve of a device under different intensity light sources; FIG. 5 (b) is an I-T curve of the device under different intensity light sources; FIG. 5 (c) is the response time of the device; FIG. 5 (d) shows the responsivity and specific detectivity of the device at different light source intensities;

FIG. 6 is a graph of characterization of the IEICO-4F (-4.1 nm)/tungsten diselenide/silicon heterostructure photodetector prepared in example 1 under the illumination of a 808nm light source; FIG. 6 (a) is an I-T curve of the device under different intensity light sources; FIG. 6 (b) shows the responsivity and specific detectivity of the device at different light source intensities;

FIG. 7 (a) is a single layer WSe₂And SiO₂Photoluminescence characteristics of the Si substrate; FIG. 7 (b) shows the photoluminescence characteristics of the IEICO-4F with different thicknesses; FIG. 7 (c) is a WSe of IEICO-4F films of varying thickness₂The photoluminescence characteristics of the IEICO-4F heterojunction; as can be seen from the analysis of FIG. 7 of example 1, increasing the thickness of the organic semiconductor IEICO-4F layer suppresses WSe₂The larger the thickness is, the more remarkable the charge transfer effect is, so that the responsivity and the specific detectivity are greatly improved.

Comparative example 1

Comparative example 1 reference is made to the prior art n-WSe₂Photodetector, p-WSe₂Photodetector and pn-WSe₂A photodetector [ Mitta, S.B.; ali, f.; yang, z.; moon, i.; yoo, W.J. Gate-Modulated ultrasonic Visible and Near-extracted photon emission of Oxygen-Plasma Treated WSe₂ Lateral pn–Homojunctions.ACS Appl.Mater. Interfaces 2020,12,23261–23271.】。

Comparing the results of example 1 and comparative example 1, it can be seen that the IEICO-4F/tungsten diselenide/silicon heterostructure photodetector prepared by the present invention has a type II (staggered) energy band arrangement structure, and can affect the photoluminescence characteristics of the heterojunction, and the significant quenching behavior indicates that a strong charge transfer phenomenon occurs at the heterojunction interface, and the response characteristics of the photodetector can be effectively improved. Compared with n-WSe₂Photodetector, p-WSe₂Photodetector and pn-WSe₂The homojunction photodetector has higher responsivity and specific detectivity in the visible and near infrared spectral ranges (see table 1 for details).

Comparative example 2

The basic structure and the preparation steps of the photodetector described in this comparative example 2 are described below with reference to fig. 8:

1. clean Si substrate (i.e. SiO) with 285nm oxide layer₂/Si). Cutting SiO with silicon wafer cutting pen₂Si wafer cuttingCutting into square substrates of 10mm × 10mm, sequentially placing the substrates into acetone, absolute ethyl alcohol and deionized water for ultrasonic cleaning, and finally taking out the substrates and drying the substrates by using nitrogen;

2. preparation of WSe₂/Si photoelectric detector

(1) 200mg of WO₃Placing the powder and 150mg Se powder between the first heating temperature zone and the second heating temperature zone of a tube furnace respectively, and mixing 10mm × 10mm SiO₂the/Si silicon wafer substrate is placed in WO₃5mm before the powder;

(2) vacuumizing the tube furnace for 10min, and introducing argon to restore the tube furnace to normal pressure;

(3) during the reaction, the flow of argon was maintained at 100 sccm; heating the first temperature zone to 900 ℃ at a heating rate of 45 ℃/min; when the first temperature zone reaches 450 ℃, heating the second temperature zone to 300 ℃ at the heating rate of 30 ℃/min, and starting the chemical vapor deposition reaction;

(4) because the reducibility of the Se powder is weaker, 10sccm of hydrogen is required to be introduced as auxiliary gas when the chemical vapor deposition reaction starts;

(5) after 10min, stopping introducing hydrogen and closing the tube furnace to complete the reaction;

(6) by magnetron sputtering on SiO₂Preparing an Au electrode on a Si substrate;

(7) the Au electrode was transferred to the tungsten diselenide layer.

In this comparative example, a conventional technique such as Chemical Vapor Deposition (CVD) was used, but a tungsten diselenide thin film may be deposited using a Thermal Assisted Conversion (TAC) method, Molecular Beam Epitaxy (MBE) method, Chemical Vapor Transport (CVT) method, and the like.

3. Preparation of IEICO-4F/Si photoelectric detector

(1) Dissolving 10mg of IEICO-4F powder in 10ml of chloroform solution;

(2) dropping the solution on a Si substrate by using a liquid-transfering gun, and spin-coating at the speed of 4500 rmp/min for 30 seconds to form a 6.0nm IEICO-4F layer;

(3) by magnetron sputtering on SiO₂Preparing an Au electrode on a Si substrate;

(4) the Au electrode was transferred to the IEICO-4F layer.

To characterize the difference between the photoelectric performance of an IEICO-4F/tungsten diselenide/silicon heterostructure photodetector compared to a single layer tungsten diselenide photodetector or an IEICO-4F photodetector. In this comparative example, a photodetector (WSe) comprising only a single layer of tungsten diselenide was prepared by performing only step 1 and step 2₂Si); by performing only step 1 and step 3, a photodetector containing only IEICO-4F (IEICO-4F/Si) can be prepared.

In this comparative example, the IEICO-4F film can be prepared using conventional techniques such as spin coating, printing, and the like.

In the present comparative example, the electrode material may be one of conductive materials such as Au, Al, Ag, graphene, PEDOT: PSS, etc. In this example, Au was used as the electrode material.

In this comparative example, fabrication of the photodetector may be accomplished by fabricating the electrode using conventional techniques such as thermal evaporation, sputtering, electron beam deposition, transfer, and the like.

For comparative example 2, the invention characterizes the WSe prepared₂The performance and characterization results of the photodetector and the IEICO-4F photodetector are shown in FIG. 9.

Fig. 9(a) is a graph comparing the light absorption of the photodetectors prepared in example 1 and comparative example 2;

FIG. 9(b) is an I-T curve of the photodetectors prepared in example 1 and comparative example 2 under the irradiation of a 1550nm light source;

as can be seen from fig. 9(a), the heterojunction structure photodetector described in example 1 is compared with WSe₂The photoelectric detector or IEICO-4F photoelectric detector has stronger light absorption capacity; as can be seen from FIG. 9(b), WSe in comparative example 2₂The photoelectric detector or the IEICO-4F photoelectric detector has almost no optical response current under the irradiation of a light source with the wavelength of 1550nm, but the photoelectric detector with the heterojunction structure in the embodiment 1 can expand the measurement wavelength range of the photoelectric detector, so that the device has optical response under the irradiation of infrared light with the wavelength of 1550 nm. In addition, the photodetector described in embodiment 1 is compared with WSe₂The photoelectric detector or IEICO-4F photoelectric detector is in II-type (staggered) energy band arrangement structure, can influence the photoluminescence characteristic of the heterojunction, and is remarkableThe quenching behavior shows that stronger charge transfer occurs at the heterojunction interface, and the response characteristic of the photoelectric detector can be effectively improved.

The present invention compares the performance of the associated photodetectors as summarized in Table 1. Table 1 shows a summary of device performance of example 1 and comparative example 1 and other reported photodetector performance parameters for similar device structures.

TABLE 1

Note: the literature in table 1 is as follows:

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as can be seen from the example 1 of FIG. 4, under the irradiation of the laser source with the wavelength of 532nm, the responsivity of the IEICO-4F (6.0 nm)/tungsten diselenide/silicon heterostructure photoelectric detector is 6.8A/W, and the specific detectivity is 1.25 multiplied by 10¹¹Jones, rise and fall times of 2.81ms and 2.94ms, respectively;

as can be seen from the embodiment 1 of FIG. 5 and FIG. 6, under the irradiation of the laser source with 808nm, as the thickness of the organic semiconductor material IEICO-4F is increased from 4.1nm to 6.0nm, the responsivity of the device is improved from 4A/W to 8.32A/W, and the specific detectivity of the device is increased from 1.5 × 10¹¹Jones boost to 4.65X 10¹¹Jones；

As can be seen from the comparison between the example 1 in FIG. 5 and the comparative example 1 in Table 1, under the irradiation of the near-infrared light source, the responsivity of the IEICO-4F (-6.0 nm)/tungsten diselenide heterojunction photodetector is 8.32A/W, and the specific detectivity is 4.65 multiplied by 10¹¹Jones；n-WSe₂The responsivity of the photoelectric detector is 0.023A/W, and the specific detectivity is 2.3 multiplied by 10¹⁰ Jones；p-WSe₂The responsivity of the photoelectric detector is 0.037A/W, and the specific detectivity is 1 x 10¹⁰Jones； pn-WSe₂The responsivity of the photoelectric detector is 2A/W, and the specific detectivity is 7.2 multiplied by 10¹⁰Jones; shows that the IEICO-4F/tungsten diselenide heterojunction photoelectric detector is compared with a single WSe₂Photodetectors or WSe₂The homojunction photoelectric detector has higher responsivity and specific detectivity under the irradiation of a near infrared light source;

as can be seen from example 1 of fig. 7, asThe increase of the thickness of the organic semiconductor can make the photoluminescence phenomenon of the IEICO-4F layer more remarkable, and the WSe₂Gradually suppressed;

as can be seen by comparing example 1 with comparative example 2 in FIG. 9, the IEICO-4F/tungsten diselenide heterojunction photodetector has stronger light absorption capability and has light response under the irradiation of a 1550nm laser source.

As can be seen from Table 1 comparing with the prior art, the invention based on IEICO-4F/tungsten diselenide/silicon heterojunction photoelectric detector has comprehensive performance (responsivity, specific detectivity and the like) compared with that based on MoS₂/n-Si、 MoS₂/Graphene、WSe₂/ReSe₂、PbI₂/CH₃NH₃PbI₃、PtSe₂/SiNWA and WS₂The performance of photoelectric detectors such as p-Si is good.

Due to the limitation of test conditions, the invention only adopts lasers of 532nm, 808nm and 1550nm to test the photoelectric response of the photoelectric detector based on IEICO-4F/tungsten diselenide/silicon heterojunction, but does not exclude the response of the photoelectric detector in other spectral ranges.

The excellent parameters obtained from the above characterization indicate that: the IEICO-4F/tungsten diselenide/silicon heterogeneous photoelectric detector has high responsivity, specific detectivity, high response speed and wide response range, and can meet the requirements of practical application.

The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by those skilled in the art that the scope of the invention herein disclosed is not limited to the particular combination of features described above, but also encompasses other embodiments in which any combination of the features described above or equivalent features thereof can be combined without departing from the novel concept of the present invention.

Claims (7)

1. A heterojunction structure based on tungsten diselenide and an organic semiconductor IEICO-4F, characterized in that the heterojunction structure is an IEICO-4F/tungsten diselenide/silicon heterojunction structure, and comprises:

(1) a silicon layer;

(2) a tungsten diselenide layer on the silicon layer;

(3) an organic semiconductor IEICO-4F layer on the tungsten diselenide layer.

2. The heterojunction structure of claim 1 wherein said tungsten diselenide layer is a single layer structure of two-dimensional semiconductor phase and has a thickness of about 0.79 nm.

3. The heterojunction structure of claim 1 wherein said IEICO-4F layer is about 2.0 to 6.0nm thick; preferably 4.0 to 6.0 nm.

4. The method of fabricating a heterojunction structure according to claim 1, wherein the fabrication process comprises:

(1) manufacturing a tungsten diselenide thin film on the silicon layer to form tungsten diselenide/silicon;

(2) and preparing an IEICO-4F thin film on the tungsten diselenide layer to form an IEICO-4F/tungsten diselenide/silicon heterojunction structure.

5. The method of making the IEICO-4F film of claim 4, comprising:

(1) dissolving a quantity of IEICO-4F powder in a quantity of chloroform liquid to form a solution having a solubility of 0.5g/L to 1.5 g/L;

(2) the solution was used to prepare an IEICO-4F layer on a tungsten diselenide layer.

6. A heterojunction structure according to claim 1 as a photodetector; preferably, the photodetector further includes: an electrode in electrical contact with said IEICO-4F layer; preferably, the electrode is selected from a metal material or a non-metal conductor material; preferably, the metal conductor material is selected from Au, Ag, Al, etc.; preferably, the non-metallic conductor material is selected from graphene, PEDOT: PSS; preferably, the photodetector has a response in the visible to infrared spectral range and an optical response in the near infrared (808nm) spectrumDegree of 8.32A/W and specific detectivity of 4.65X 10¹¹Jones。

7. The method of claim 6, wherein the preparing process comprises:

(1) manufacturing a tungsten diselenide thin film on the silicon layer to form tungsten diselenide/silicon;

(2) preparing an IEICO-4F thin film on the tungsten diselenide layer to form an IEICO-4F/tungsten diselenide/silicon heterojunction structure;

(3) and preparing an electrode on the IEICO-4F layer to form an electrode/IEICO-4F/tungsten diselenide/silicon photoelectric detector structure.

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