Novel monolithic integrated lead sulfide detector and preparation method thereof

Abstract

The invention discloses a novel monolithic integrated lead sulfide detector and a preparation method thereof. The novel monolithic integrated lead sulfide detector sequentially comprises a bottom electrode layer, a hole transport layer, a P-type layer, an N-type layer, an electron transport layer and a top electrode layer, the P-type layer is used for absorbing photons, so that electrons in the P-type layer are transited to a conduction band, and holes are reserved in a valence band; the N-type layer is used for transmitting electrons, transmitting the electrons generated by the P-type layer to a conduction band of the N-type layer and enabling holes to stay in the P-type layer, and the electrons and the holes are separated in space; wherein the P-type layer comprises PbS (lead sulfide); and the N type layer comprises CdSe. According to the embodiment of the invention, the N-type layer of cadmium selenide and the P-type layer of PbS are utilized to construct a heterogeneous p-n junction, so that the monolithic integrated lead sulfide detector has a time constant of less than 1 microsecond, high-frame-rate work can be allowed, and rapid change of an object can be tracked.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor optoelectronic devices, and particularly relates to a novel monolithic integrated lead sulfide detector and a preparation method thereof. Background Art

[0002] In nature and during human activities, low-energy infrared radiation is usually generated, and this energy is generally invisible to the human eye. By using an infrared radiation detector, humans can perceive invisible objects, greatly broadening the human vision.

[0003] Currently, there are several high-performance hybrid architecture infrared detectors, covering the wavelength bands from short-wave infrared to long-wave infrared. The focal plane arrays of these detectors include indium gallium arsenide, indium antimonide, indium arsenide, and mercury cadmium telluride, etc., which are prepared by methods such as metal-organic chemical vapor deposition or molecular beam epitaxial deposition. The processes are complex and expensive. In addition, in order to work properly, detectors such as indium antimonide, indium arsenide, and mercury cadmium telluride need liquid nitrogen cooling. Therefore, these detectors cannot be widely applied on a large scale.

[0004] The intrinsic absorption cut-off wavelength of lead sulfide material can reach 3 microns at room temperature, and the Auger recombination coefficient is low, having advantages in terms of cost and performance. Currently, lead sulfide photoconductive detectors have excellent photoconductive properties, but it is difficult to fabricate monolithic integrated detectors. Because lead sulfide photoconductive detectors usually require a high-temperature halogen or oxygen sensitization process, which has a destructive effect on the readout circuit. In addition, the time constant of existing lead sulfide photoconductive detectors is several hundred microseconds, and p-n junction type detectors have a large dark current and a low signal-to-noise ratio, resulting in limited application scenarios for the detectors. For example, the monitoring of weak light environments and fast-moving objects. In view of this, the present invention provides a novel monolithic integrated lead sulfide detector and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that in order to solve various deficiencies existing in the existing lead sulfide photoconductive detectors, the present invention provides a novel monolithic integrated lead sulfide detector and a preparation method thereof.

[0006] To solve the above technical problem, an embodiment of the present invention provides a novel monolithic integrated lead sulfide detector, which successively includes: a bottom electrode layer, a hole transport layer, a P-type layer, an N-type layer, an electron transport layer, and a top electrode layer;

[0007] The P-type layer is used to absorb photons, causing electrons inside the P-type layer to transition to the conduction band and holes to remain in the valence band;

[0008] The N-type layer is used to transport electrons, transport the electrons generated by the P-type layer to the conduction band of the N-type layer, and keep holes in the P-type layer, so as to spatially separate electrons and holes;

[0009] The electron transport layer is used to transport electrons, so that the electrons in the N-type layer are transported into the electron transport layer;

[0010] The hole transport layer is used to transport holes, so that the holes in the P-type layer are transported into the hole transport layer;

[0011] Among them, the P-type layer includes PbS; the N-type layer includes CdSe.

[0012] Preferably, the electron transport layer includes one or more combinations of SnO2, TiO2, ZnO, and PC 61 BM; the hole transport layer includes MoO3.

[0013] Preferably, the photons are photons emitted by light waves in a wavelength band less than or equal to 3 microns.

[0014] Preferably, the bottom electrode layer includes one or more combinations of Au, ITO, and FTO; the top electrode layer includes one or more combinations of Al, Ag, ITO, and FTO.

[0015] Preferably, the novel monolithic integrated lead sulfide detector further includes a substrate; the substrate is located behind the bottom electrode layer; the substrate includes one or more of silicon, quartz, glass, sapphire, calcium fluoride, PEI, PEN, PI, and PC.

[0016] The embodiment of the present invention also provides a method for manufacturing a novel monolithic integrated lead sulfide detector. The method for manufacturing the novel monolithic integrated lead sulfide detector is used to manufacture the above-mentioned novel monolithic integrated lead sulfide detector, and includes the following steps:

[0017] S1, Preparation of the bottom electrode: Evaporate the bottom electrode on the substrate by electron beam thermal evaporation method or directly use the circuit bottom electrode;

[0018] S2, Preparation of the hole transport layer: Deposit the hole transport layer on the bottom electrode by magnetron sputtering or solution spin coating method;

[0019] S3, Preparation of the P-type layer: Mix the sodium hydroxide solution and the lead nitrate solution in equal proportions to obtain a precursor solution, and then mix it with the thiourea solution to form a mixed solution; Place the hole transport layer in step S2 in the mixed solution, and keep it in a constant temperature oven at 20°C to 30°C for 2h to 4h to obtain the P-type layer;

[0020] S4, N-type layer: After mixing cadmium chloride solution and selenourea solution in equal proportions, a second mixed solution is formed; an acid-base regulator is added to the second mixed solution to make the pH value of the second mixed solution 7.8; the P-type layer in step S3 is placed in the second mixed solution and kept warm in an incubator at 20°C to 30°C for 0.5 h to 2 h to obtain the N-type layer.

[0021] S5, Preparation of the electron transport layer: The electron transport layer is deposited on the N-type layer in S4 by magnetron sputtering or solution spin coating.

[0022] S6, Preparation of the top electrode layer: The top electrode layer is deposited on the electron transport layer in S5 by magnetron sputtering or thermal evaporation.

[0023] Preferably, in S3, the concentration of the sodium hydroxide solution is 0.01 g / mL to 0.02 g / mL; the concentration of the lead nitrate solution is 0.02 g / mL to 0.03 g / mL; the concentration of the thiourea solution is 0.01 g / mL to 0.02 g / mL; the content ratio of the precursor solution to the thiourea solution is 150:1 to 300:1.

[0024] Preferably, in S4, the concentration of the cadmium chloride solution is 1 mg / mL to 3 mg / mL; the concentration of the selenourea solution is 0.5 mg / mL to 2 mg / mL; the acid-base regulator includes one or more combinations of dilute nitric acid and ammonia water.

[0025] Preferably, the electron transport layer includes one or more combinations of SnO2, TiO2, ZnO, and PC 61 BM; the hole transport layer includes MoO3.

[0026] Preferably, the bottom electrode layer includes one or more combinations of Au, ITO, and FTO; the top electrode layer includes one or more combinations of Al, Ag, ITO, and FTO.

[0027] Implementing the embodiments of the present invention has the following beneficial effects:

[0028] (1) The embodiments of the present invention use the N-type layer of cadmium selenide and the P-type layer of PbS to construct a heterojunction p-n junction, enabling the monolithic integrated lead sulfide detector to significantly reduce the dark current of the device body, improve the signal-to-noise ratio, and have a time constant of less than 1 microsecond, allowing high-frame-rate operation and realizing the tracking of rapid changes of objects.

[0029] (2) In the embodiments of the present invention, the P-type layer and the N-type layer are formed by the chemical bath method, and a monolithic integrated lead sulfide detector is prepared without low-temperature refrigeration. This not only realizes the greening of the solvent, reduces energy consumption, reduces the carbon footprint of the entire production process, minimizes the impact on the environment, but also saves costs and maximizes benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 Schematic structural diagram of a novel monolithic integrated lead sulfide detector provided for the embodiments of the present invention;

[0032] Figure 2 Flowchart of a preparation method of a novel monolithic integrated lead sulfide detector provided for the embodiments of the present invention;

[0033] Figure 3 Current-voltage characteristic curve of a novel monolithic integrated lead sulfide detector tested at different temperatures provided for the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0035] See Figure 1 , the embodiments of the present invention also provide a novel monolithic integrated lead sulfide detector. The novel monolithic integrated lead sulfide detector sequentially includes: a bottom electrode layer 60, a hole transport layer 50, a P-type layer 40, an N-type layer 30, an electron transport layer 20, and a top electrode layer 10.

[0036] The P-type layer 40 is used to absorb photons, causing electrons inside the P-type layer 40 to transition to the conduction band, and holes to remain in the valence band. The N-type layer 30 is used to transport electrons, transporting the electrons generated by the P-type layer 40 to the conduction band of the N-type layer 30. And the holes are made to stay in the P-type layer 40, achieving the spatial separation of the electrons and holes. The electron transport layer 20 is used to transport electrons, enabling the electrons of the N-type layer 30 to be transported into the electron transport layer 20 and blocking the transport of the holes into the electron transport layer 20. The hole transport layer 50 is used to transport holes, enabling the holes of the P-type layer 40 to be transported into the hole transport layer 50. The bottom electrode layer 60 and the top electrode layer 10 are respectively used to collect the electrons and holes. Among them, the bottom electrode layer 60 is used to collect the holes. The top electrode layer 10 is used to collect the electrons.

[0037] The P-type layer 40 includes PbS and is a PbS thin film. The N-type layer 30 includes CdSe and is a CdSe thin film. The electron transport layer 20 includes one or more combinations of: SnO2, TiO2, ZnO, and PC 61 BM to form a SnO2, TiO2, ZnO, or PC 61 BM thin film. The hole transport layer 50 includes: MoO3 and is a MoO3 thin film. The bottom electrode layer 60 includes one or more combinations of: Au, ITO, FTO to form an Au, ITO, or FTO bottom electrode layer 60. The top electrode layer 10 includes one or more combinations of: Al, Ag, ITO, FTO to form an Al, Ag, ITO, or FTO top electrode layer 10.

[0038] The photons are photons emitted by light waves in the wavelength band less than or equal to 3 microns., thereby providing a new path for the research and development of the monolithic integrated lead sulfide detector for high-performance photodetectors and image sensors at room temperature in the wavelength band less than or equal to 3 microns.

[0039] The P-type layer 40 can be prepared by methods such as liquid-phase chemical deposition (water or organic solvents), thermal evaporation, molecular beam epitaxy, magnetron sputtering, atomic layer deposition, chemical vapor deposition, etc. The thickness of the P-type layer 40 is arbitrary. The N-type layer 30 can be prepared by methods such as liquid-phase chemical deposition (water or organic solvents), electrochemistry, thermal evaporation, molecular beam epitaxy, chemical vapor deposition, etc. The thickness of the N-type layer 30 is arbitrary. The bottom electrode layer 60, the hole transport layer 50, the electron transport layer 20, and the top electrode layer 10 are all prepared by conventional methods or purchased through commercial channels.

[0040] The present invention constructs a heterojunction p-n junction by using CdSe as the N-type layer 30 and PbS of the P-type layer 40, and uses SnO2, TiO2, ZnO, or PC 61BM uses various materials as the electron transport layer 20, and uses metal elements such as aluminum (Al), silver (Ag), gold (Au) or indium tin oxide (ITO), a transparent conductive oxide, as the top and bottom electrodes to construct a photodetector device. The core of this device lies in the heterojunction p-n junction formed by CdSe and PbS. Under the irradiation of infrared light with a wavelength less than 3 microns, PbS absorbs light to generate photo-generated carriers. Since CdSe and PbS can form a type-II energy band alignment, the photo-generated electrons can be effectively separated by the built-in electric field and transported to the CdSe layer; at the same time, the valence band of CdSe is deeper, which can reduce the probability of holes in the PbS layer being transported to the CdSe layer, reduce the dark current density of the device, and also reduce the recombination loss of photo-generated carriers. On the other hand, the lattice mismatch between cubic CdSe and cubic PbS is only 1.9%, and the interface state density between the two is on the order of 10 13 cm -3 magnitude, and it will not cause a large amount of recombination of carriers here. Therefore, the photocurrent of the device will not be greatly affected. Therefore, the monolithic integrated lead sulfide detector can greatly reduce the dark current of the device body and improve the signal-to-noise ratio. In addition, the detector has a time constant of less than 1 microsecond, which can allow high frame rate operation and realize the tracking of rapid changes of objects.

[0041] The novel monolithic integrated lead sulfide detector further includes: a substrate (not shown); the substrate is located behind the bottom electrode layer; the substrate materials include but are not limited to rigid and flexible substrates such as silicon / quartz / glass / sapphire / calcium fluoride / PEI / PEN / PI / PC and readout circuits. When the readout circuit is used as the substrate, the finally obtained is the monolithic integrated lead sulfide detector focal plane array. When other materials are used as the substrate, the obtained is a unit device.

[0042] As Figure 2 shown, the present embodiment also discloses a preparation method of a novel monolithic integrated lead sulfide detector. The preparation method of the novel monolithic integrated lead sulfide detector includes the following steps:

[0043] S1, preparation of the bottom electrode: evaporate the bottom electrode on the substrate by electron beam thermal evaporation method or directly use the circuit bottom electrode;

[0044] S2, preparation of the hole transport layer: deposit the hole transport layer on the bottom electrode by magnetron sputtering or solution spin coating method;

[0045] S3, preparation of the P-type layer: mix sodium hydroxide solution and lead nitrate solution in equal proportions to obtain a precursor solution, and then mix it with thiourea solution to form a mixed solution; place the hole transport layer in step S2 in the mixed solution and keep it in an incubator at 20 °C to 30 °C for 2 h to 4 h to obtain the P-type layer;

[0046] S4, N-type layer: Mix cadmium chloride solution and selenium urea solution in equal proportions to form a second mixed solution; add an acid-base regulator to the second mixed solution to make the pH value of the second mixed solution 7.8; place the P-type layer in step S3 in the second mixed solution and keep it warm in an incubator at 20°C - 30°C for 0.5h - 2h to obtain the N-type layer;

[0047] S5, Preparation of the electron transport layer: Deposit the electron transport layer on the N-type layer in S4 by magnetron sputtering or solution spin coating;

[0048] S6, Preparation of the top electrode layer: Deposit the top electrode layer on the electron transport layer in S5 by magnetron sputtering or thermal evaporation.

[0049] In step S1, before evaporating the bottom electrode on the substrate, the substrate needs to be cleaned. The specific method is: clean the substrate with deionized water, ethanol, and isopropanol solvents in sequence. The substrate material includes, but is not limited to, rigid and flexible substrates such as silicon / quartz / glass / sapphire / calcium fluoride / PEI / PEN / PI / PC, etc. The bottom electrode includes one or more combinations of Au, ITO, and FTO. When the readout circuit is the substrate, the bottom electrode is the circuit bottom electrode.

[0050] In step S2, the hole transport layer includes MoO3; step S2 is specifically: deposit a MoO3 thin film on the bottom electrode by magnetron sputtering or solution spin coating.

[0051] In step S3, the concentration of the sodium hydroxide solution is 0.01g / mL - 0.02g / mL, preferably 0.012g / mL. The concentration of the lead nitrate solution is 0.02g / mL - 0.03g / mL, preferably 0.025g / mL. The concentration of the thiourea solution is 0.01g / mL - 0.02g / mL, preferably 0.114g / mL. The content ratio of the precursor solution to the thiourea solution is 150:1 - 300:1, preferably 200:1. Among them, the precursor solution is 20mL and the thiourea solution is 0.1mL. The temperature of the incubator is preferably 25°C and the time is 3h. The P-type layer is a lead sulfide thin film.

[0052] In step 4, the concentration of the cadmium chloride solution is 1 mg / mL to 3 mg / mL, preferably 2 mg / mL. The concentration of the selenourea solution is 0.5 mg / mL to 2 mg / mL, preferably 1 mg / mL. The acid-base regulator includes one or more combinations of dilute nitric acid and ammonia water. After measuring the specific pH value of the second mixed solution, dilute nitric acid or ammonia water is selected to decrease or increase the pH value of the second mixed solution so that the final pH value of the second mixed solution is 7.8. The temperature of the constant temperature box is preferably 25 °C and the time is 1 h. The N-type layer is a cadmium selenide thin film.

[0053] In step 5, the electron transport layer includes one or more combinations of SnO2, TiO2, ZnO, and PC 61 BM. Step S5 is specifically: depositing a layer of SnO2, TiO2, ZnO, or PC 61 BM electron transport layer material on the cadmium selenide thin film in S4 by magnetron sputtering or solution spin coating to obtain an electron transport layer.

[0054] In step 6, the top electrode layer is one or more combinations of Al, Ag, ITO, and FTO. Among them, when ITO is selected as the top electrode layer material, the ITO top electrode layer is prepared on the electron transport layer by magnetron sputtering. When Al or Ag is used as the top electrode layer material, the Al or Ag top electrode layer is prepared on the electron transport layer by thermal evaporation.

[0055] Through the above steps, different devices can be obtained according to different substrates. Using the readout circuit as the substrate, the finally obtained is a monolithic integrated lead sulfide detector focal plane array. Using other materials as the substrate, the obtained are unit devices.

[0056] See Figure 3 , Figure 3 For the current-voltage characteristic curves of the above-mentioned novel monolithic integrated lead sulfide detector tested at different temperatures, which show the dark current and open-circuit current performance of the device at different temperatures. Among them, the six curves from light green to dark blue represent the dark-state current-voltage characteristic curves of the device. In the direction indicated by the arrow, the temperatures are 300 K, 280 K, 240 K, 200 K, 120 K, and 80 K in sequence; the six curves from light pink to dark red represent the current-voltage characteristic curves of the device under illumination, and the temperatures are 300 K, 280 K, 240 K, 200 K, 120 K, and 80 K in sequence. The dark current density value of the device at a specific bias voltage and temperature can be read out from it, and the open-circuit voltage value can also be obtained.

[0057] The above-disclosed is only a preferred embodiment of the present invention. Of course, it cannot be used to limit the scope of the rights of the present invention. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A novel monolithic integrated lead sulfide detector, characterized in that: Including in order: bottom electrode layer, hole transport layer, P-type layer, N-type layer, electron transport layer and top electrode layer; The P-type layer is used to absorb photons, so that electrons inside the P-type layer transition to the conduction band, and holes remain in the valence band; The N-type layer is used to transmit electrons, transmit electrons generated by the P-type layer to the conduction band of the N-type layer, and keep holes in the P-type layer, so that electrons and holes are separated in space; The electron transport layer is used to transport electrons, so that the electrons in the N-type layer are transported to the electron transport layer; The hole transport layer is used to transport holes, so that the holes in the P-type layer are transported to the hole transport layer; Wherein, the P-type layer includes PbS; and the N-type layer includes CdSe.

2. The novel monolithic integrated lead sulfide detector according to claim 1, characterized in that: The electron transport layer includes: SnO2, TiO2, ZnO and PC 61 One or more combinations of BM; the hole transport layer includes: MoO3.

3. The novel monolithic integrated lead sulfide detector according to claim 1, characterized in that: The photons are photons emitted by light waves in a wavelength band less than or equal to 3 micrometers.

4. The novel monolithic integrated lead sulfide detector according to claim 1, characterized in that: The bottom electrode layer includes: one or more combinations of Au, ITO, and FTO; the top electrode layer includes: one or more combinations of Al, Ag, ITO, and FTO.

5. The novel monolithic integrated lead sulfide detector according to claim 1, characterized in that: The novel monolithic integrated lead sulfide detector further comprises: a substrate; the substrate is located behind the bottom electrode layer; the substrate comprises: one or more of silicon, quartz, glass, sapphire, calcium fluoride, PEI, PEN, PI, and PC.

6. A method for preparing any one of the novel monolithic integrated lead sulfide detectors according to claims 1-5, characterized in that: The following steps are involved: S1, preparation of bottom electrode: depositing the bottom electrode on the substrate by electron beam thermal evaporation method or directly using the circuit bottom electrode; S2, preparation of a hole transport layer: depositing a hole transport layer on the bottom electrode by magnetron sputtering or solution spin coating; S3, preparation of the P-type layer: mixing a sodium hydroxide solution and a lead nitrate solution in equal proportions to obtain a precursor solution, and then mixing the precursor solution with a thiourea solution to form a mixed solution; Placing the hole transport layer in step S2 in the mixed solution, and keeping it in a constant temperature box at 20° C. to 30° C. for 2 h to 4 h to obtain a P-type layer; S4, N-type layer: mixing the cadmium chloride solution and the selenourea solution in equal proportions to form a second mixed solution; Adding an acid-base regulator to the second mixed solution to make the pH value of the second mixed solution 7.8; placing the P-type layer in the step S3 in the second mixed solution, and keeping it in a constant temperature box at 20° C. to 30° C. for 0.5 h to 2 h to obtain an N-type layer; S5, preparation of an electron transport layer: depositing an electron transport layer on the N-type layer in S4 by magnetron sputtering or solution spin coating; S6, preparation of a top electrode layer: depositing a top electrode layer on the electron transport layer in S5 by magnetron sputtering or thermal evaporation.

7. The method for preparing a novel monolithic integrated lead sulfide detector according to claim 6, characterized in that: In S3, the concentration of the sodium hydroxide solution is 0.01 g / mL to 0.02 g / mL; the concentration of the lead nitrate solution is 0.02 g / mL to 0.03 g / mL; the concentration of the thiourea solution is 0.01 g / mL to 0.02 g / mL; and the content ratio of the precursor solution to the thiourea solution is 150:1 to 300:

1.

8. The method for preparing the novel monolithic integrated lead sulfide detector according to claim 6, characterized in that: In S4, the concentration of the cadmium chloride solution is 1 mg / mL to 3 mg / mL; the concentration of the selenourea solution is 0.5 mg / mL to 2 mg / mL; and the acid-base regulator includes: one or more combinations of dilute nitric acid and ammonia water.

9. The method for preparing a novel monolithic integrated lead sulfide detector according to claim 6, characterized in that: The electron transport layer includes: SnO2, TiO2, ZnO and PC 61 One or more combinations of BM; the hole transport layer includes: MoO3.

10. The novel monolithic integrated lead sulfide detector preparation method according to claim 6, characterized in that: The bottom electrode layer includes: one or more combinations of Au, ITO, and FTO; the top electrode layer includes: one or more combinations of Al, Ag, ITO, and FTO.

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