Wavelength tunable photomultiplication detector based on optical microcavity

Abstract

The invention discloses a wavelength-tunable photomultiplier detector based on an optical microcavity, which is used for solving the problems of complex structure, low light utilization efficiency and the like of the traditional silicon-based RGB three-color detector. The wavelength tunable photomultiplier detector based on the optical microcavity comprises a transparent electrode ITO, a hole transport layer PEDOT: PSS, an organic active layer P3HT: PC71BM (100: 1, w / w), a metal electrode Al and the optical microcavity which are sequentially arranged from bottom to top, and the structure of the optical resonance microcavity is Ag / LiF / Ag. According to the device, a trap auxiliary multiplication mechanism in a photomultiplication detector and a spectrum narrowing regulation and control function of an optical microcavity are integrated, so that the detection wavelength can be tuned, and a response spectrum can be limited to three characteristic narrow bands, namely, RGB (Red, Green, Blue). By means of the obvious photomultiplication effect in the RGB wave band, the responsivity and the quantum efficiency are improved by more than two orders of magnitude compared with those of a traditional RGB detector without a multiplication mechanism, and an effective solution is provided for weak light detection.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectric detection, and particularly relates to a wavelength tunable photomultiplier detector based on an optical microcavity. BACKGROUND

[0002] The color perception of the human eye depends on the spectral response characteristics of red (Red, ~620 nm), green (Green, ~560 nm), and blue (Blue, ~450 nm) cone cells, and this physiological mechanism inspires modern imaging systems to achieve color reconstruction by independently detecting RGB three primary colors. A typical visible light imaging system is composed of a filter, an optical lens, a photodetector, and a signal processing circuit, wherein the photodetector as a core component undertakes the conversion function of optical signal to electrical signal. The mainstream technology currently adopts a silicon-based photodiode combined with a filter to achieve RGB detection, but the silicon material itself lacks wavelength selectivity and needs to rely on an external filter to separate the spectral band. Since the spectral width of the RGB channel is up to ~100 nm, it is necessary to integrate a wideband filter into the system, which not only increases the complexity of the module, but also limits the imaging accuracy due to spectral crosstalk.

[0003] Organic semiconductor materials provide a new technical path for RGB detectors due to the advantages of energy level designability, solution processability, and low cost. Studies have shown that they can achieve filter-free narrowband detection through strategies such as narrowband absorption materials, internal charge transfer (ICT), charge collection narrowing (CCN), and charge injection narrowing (CIN). However, existing schemes have significant limitations: on the one hand, most technologies can only achieve narrowband response at a single fixed wavelength, making it difficult to dynamically cover the RGB three bands; on the other hand, organic photodiodes (OPD) are limited by carrier collection efficiency, and the external quantum efficiency (EQE) is generally lower than 100%, making it difficult to guarantee signal detection accuracy in a weak light environment. The dual defects of insufficient wavelength selection flexibility and low quantum efficiency seriously restrict the application value of organic RGB detectors in practical scenarios.

[0004] Therefore, there is an urgent need to develop a new organic photoelectric detection mechanism that combines dynamic tunable RGB three bands, narrowband spectral response, and ultra-high quantum efficiency. SUMMARY

[0005] In view of the difficulties of existing research, the application proposes to couple a Fabry-Perot optical resonance microcavity (F-P cavity) with a photomultiplier detector (OPMD), and utilize the flexible tuning effect of the F-P cavity and the high responsivity and high EQE of the OPMD to achieve a wavelength tunable photomultiplier detector based on an optical microcavity.

[0006] In order to achieve the above object, the present application adopts the following technical scheme to achieve the above object: A wavelength tunable photomultiplier detector based on an optical microcavity includes three RGB narrowband detectors, each of which includes a transparent substrate, an anode layer, a hole transport layer, a photoactive layer, a cathode layer and an optical microcavity structure arranged in the order from bottom to top.

[0007] Specifically, the transparent substrate is quartz glass with a size of 20mm*20mm; the material of the anode layer is indium tin oxide (ITO) with a thickness of 180nm; the material of the hole transport layer is poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) with a thickness of 40nm; and the material of the cathode layer is Al with a thickness of 15nm.

[0008] As a preferred mode, the photoactive layer is prepared from a mixed solution of an electron donor material and an acceptor material, and has a thickness of 450nm; wherein the donor material is poly 3-hexylthiophene (P3HT), and the acceptor material is [6,6]-phenyl-C71-butyric acid methyl ester (PC 71 BM) mixed and dissolved in o-dichlorobenzene (1,2-dichlorobenzene (o-DCB)) at a mass ratio of 100:1.

[0009] As a preferred mode, the optical microcavity structure includes silver layers (Ag), lithium fluoride layers (LiF) and silver layers (Ag) stacked in the order from bottom to top; wherein the thicknesses of the optical microcavities of each narrowband detector are different, and are as follows:

[0010] The configuration corresponding to blue light B is: the thickness of the Ag layer is 25nm, the thickness of the LiF layer is 105nm, and the thickness of the Ag layer is 25nm.

[0011] The configuration corresponding to green light G is: the thickness of the Ag layer is 25nm, the thickness of the LiF layer is 145nm, and the thickness of the Ag layer is 25nm.

[0012] The configuration corresponding to red light R is: the thickness of the Ag layer is 30nm, the thickness of the LiF layer is 170nm, and the thickness of the Ag layer is 30nm.

[0013] The present application also provides a preparation method of the above-mentioned RGB tunable photomultiplier detector, including the following steps:

[0014] S1: etching ITO on the upper surface of the transparent substrate, sequentially performing ultrasonic cleaning on the transparent substrate with ITO in a detergent, ionized water, acetone and isopropyl alcohol, drying in a 45℃ oven, and irradiating with a UV-LED light source for 3 minutes to obtain an anode layer with surface impurities removed.

[0015] S2: spin-coat the poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid aqueous solution on the anode layer at a rotation speed of 2500 rpm for 40 seconds, and then anneal at 100 DEG C for 10 minutes in an air environment at normal pressure to obtain a hole transport layer.

[0016] S3: dissolve P3HT and PC 71 Dope BM in o-dichlorobenzene solvent at a mass ratio of 100:1 to prepare a blended solution with a concentration of 40 mg / mL, and stir at 100 DEG C for 12 hours; transfer the substrate with the hole transport layer prepared in S2 into an inert gas glove box, spin-coat the blended solution at a rotation speed of 600 rpm for 60 seconds, and then anneal at 100 DEG C for 10 minutes in an inert gas environment to form a photoactive layer.

[0017] S4: place the substrate with the photoactive layer formed in S3 into a vacuum evaporation device, and evaporate Al on the photoactive layer at a deposition rate of 0.1 A / s to a thickness of 15 nm to obtain a cathode layer. - 4 Evaporate Al on the photoactive layer at a deposition rate of 0.1 A / s to a thickness of 15 nm to obtain a cathode layer under the condition of a vacuum degree ≤1*10

[0018] S5: deposit Ag layer, LiF layer and Ag layer in sequence on the cathode layer to form an optical microcavity; wherein the deposition rate of the Ag layer is 0.1 A / s, the deposition rate of the LiF layer is 0.1 A / s, and the deposition rate of the Ag layer is 0.1 A / s.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] Compared with the traditional silicon-based RGB detector, the present application has the following beneficial effects:

[0021] (1) The resonant wavelength tuning characteristics of the optical microcavity are used to regulate the wide spectral response to three narrow-band characteristic wavebands (red light 620 nm, green light 560 nm, and blue light 450 nm), and the full width at half maximum (FWHM) is ≤85 nm, which significantly reduces the channel crosstalk.

[0022] (2) Based on the hole injection type multiplication mechanism, the external quantum efficiency (EQE) >30000% and the specific detectivity (D*) ≥1.5*10 11 Jones, the external quantum efficiency EQE and the responsivity index are more than two orders of magnitude higher than those of the traditional RGB detector without multiplication mechanism, and it is one of the best performances among the RGB three-color organic detectors reported at present. ​​

[0023] (3) The microcavity replaces the filter group to eliminate the light splitting optical element, thereby effectively reducing the thickness of the detector module and greatly improving the integration level.

[0024] The above-mentioned characteristics jointly constitute the basis of a new generation of photoelectric detection technology with narrow-band spectral selectivity, ultra-high quantum efficiency and compact structure. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Figure 1 is a structural schematic diagram of a photoelectric detector of the present application.

[0026] Figure 2 Figure 4 is an external quantum efficiency curve of a blue light selective photomultiplier detector.

[0027] Figure 3 Figure 6 is a specific detectivity curve of the blue light selective photomultiplier detector under -5V.

[0028] Figure 4 Figure 9 is an external quantum efficiency curve of a green light selective photomultiplier detector.

[0029] Figure 5 Figure 11 is a specific detectivity curve of the green light selective photomultiplier detector under -5V.

[0030] Figure 6 Figure 14 is an external quantum efficiency curve of a red light selective photomultiplier detector.

[0031] Figure 7 Figure 16 is a specific detectivity curve of the red light selective photomultiplier detector under -5V. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0033] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, but cannot be understood as limiting the present application. On the contrary, the embodiments of the present application include all changes, modifications and equivalents falling within the spirit and scope of the appended claims.

[0034] The technical solutions of the various embodiments of the present invention can be combined with each other, but only if they can be implemented by those skilled in the art. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0035] The following section will further introduce the specific implementation method, as well as the technical difficulties and inventive points of this invention, using this design example as an example:

[0036] like Figure 1 As shown, a flexible photodetector based on organic semiconductors comprises, from bottom to top, a transparent substrate, an anode layer, a hole transport layer, an active layer, a cathode layer, and an optical microcavity structure stacked sequentially. The transparent substrate is quartz glass with dimensions of 20 mm × 20 mm. The anode layer is made of indium tin oxide (ITO) with a thickness of 180 nm; the hole transport layer is made of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) with a thickness of 40 nm; and the cathode layer is made of Al with a thickness of 15 nm.

[0037] The photoactive layer of this invention is prepared from a mixed solution of an electron donor material and an acceptor material, with a thickness of 450 nm; wherein the donor material is poly(3-hexylthiophene) (P3HT) and the acceptor material is methyl [6,6]-phenyl-C71-butyrate (PC). 71 BM) was dissolved in o-dichlorobenzene (o-DCB) at a mass ratio of 100:1.

[0038] Under the condition of a donor-acceptor material mass ratio of 100:1, the concentration of P3HT was significantly higher than that of PC. 71 BM, PC 71 The photomask (BM) is dispersed within the bulk heterojunction, forming localized electron-trapping states capable of capturing photogenerated electrons. Under illumination, the electrons trapped in these states induce holes at the donor-acceptor interface, which are then injected into the external circuit via tunneling, resulting in a significantly enhanced photocurrent. Furthermore, photogenerated electrons near the cathode induce holes to tunnel into the active layer, where they combine with holes to form excitons. These excitons diffuse to the donor-acceptor interface and separate into free carriers: holes are transported to the anode by the donor material P3HT, while electrons are transported to the acceptor material PC. 71 The charge is transported to the cathode, and due to the potential difference, a built-in electric field is formed inside the active layer, which further promotes charge separation and transport.

[0039] The present application adopts an optical resonance microcavity structure of Ag / LiF / Ag. The Fabry-Perot cavity is composed of two parallel mirrors, and light is reflected back and forth between the two mirrors to form resonance. When white light is incident on a specific resonant microcavity, part of the light will transmit through the microcavity, part of the light will be reflected due to the multiple reflection and interference effect in the resonant cavity, and another part of the light will be absorbed due to the resonant loss. For a resonant microcavity that transmits blue light, due to the wavelength selectivity of the resonant cavity, only a specific wavelength (such as blue light) is allowed to transmit.

[0040] The resonant wavelength of the optical microcavity structure is determined by the multiple interference in the resonant cavity and follows the following interference formula:

[0041]

[0042] Where d and n respectively represent the thickness and the refractive index of the spacer layer, and Φ represents the total phase change caused by multiple reflections at the mirror / spacer layer interface. When the light satisfies equation (1), the light waves can constructively interfere after multiple reflections, i.e. form a standing wave. By precisely designing the thickness of each layer of the resonant cavity, selective enhancement and suppression of specific wavelength light waves can be achieved, thereby optimizing the optical performance of the device.

[0043] The present application uses FDTD Solutions software to simulate and obtain the optimal conditions of RGB selective optical microcavity: for blue light (B), the configuration is: Ag layer thickness 25 nm, LiF layer thickness 105 nm, Ag layer thickness 25 nm; for green light (G), the configuration is: Ag layer thickness 25 nm, LiF layer thickness 145 nm, Ag layer thickness 25 nm; for red light (R), the configuration is: Ag layer thickness 30 nm, LiF layer thickness 170 nm, Ag layer thickness 30 nm.

[0044] Example 1

[0045] The present embodiment provides a preparation method of a blue light (B) narrow-band photomultiplier detector based on an optical microcavity, comprising the following steps:

[0046] S1: etching ITO on the upper surface of a transparent substrate, sequentially performing ultrasonic cleaning on the transparent substrate with ITO in a detergent, ionized water, acetone and isopropyl alcohol, drying in a 45℃ oven, and irradiating with a UV-LED light source for 3 minutes to obtain an anode layer with surface impurities removed;

[0047] S2: spin-coating a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid aqueous solution on the anode layer at a speed of 2500 rpm for 40 seconds, and then annealing at 100℃ for 10 minutes in an atmospheric air environment to obtain a hole transport layer;

[0048] S3: mixing P3HT and PC 71The BM was dissolved in o-dichlorobenzene solvent at a mass ratio of 100:1 to prepare a blending solution with a concentration of 40 mg / mL, and stirred at 100°C for 12 hours; the substrate with the hole transport layer prepared in S2 was transferred into an inert gas glove box, and the blending solution was spin-coated at a rotation speed of 600 rpm for 60 seconds, and then annealed at 100°C for 10 minutes in an inert gas environment to form the photoactive layer;

[0049] S4: The substrate with the photoactive layer prepared in S3 was placed in a vacuum evaporation device, and Al with a thickness of 15 nm was deposited on the photoactive layer at a deposition rate of 0.1 A / s under the condition of a vacuum degree ≤1×10 - 4 Pa, and a cathode layer was obtained by using a thermal evaporation method, first depositing Al with a thickness of 15 nm on the photoactive layer at a deposition rate of 0.1 A / s, and then depositing Ag with a thickness of 25 nm on the Al layer at a deposition rate of 0.1 A / s.

[0050] S5: On the cathode layer, an Ag layer, a LiF layer and an Ag layer were sequentially deposited to form an optical microcavity; wherein the deposition rate of the Ag layer was 0.1 A / s, the deposition rate of the LiF layer was 0.1 A / s, and the deposition rate of the Ag layer was 0.1 A / s. Under the condition of a vacuum degree ≤1×10 -4 Pa, Ag was evaporated to a thickness of 25 nm, LiF was evaporated to a thickness of 105 nm, and Ag was evaporated to a thickness of 25 nm.

[0051] The performance of the photodetector prepared in this embodiment was detected, analyzed and characterized, J-V characteristics were tested using a tungsten lamp light source and a Keithley 2450 SourceMeter, incident light power was calibrated using a Thorlabs DET36A2, and responsivity and EQE were calculated. The calculation formula of the EQE and the responsivity R of the photomultiplier detector is as follows:

[0052]

[0053] R' = (I J -I D ) / P (3)

[0054] Where h is Planck's constant, c is the speed of light, λ is the wavelength of incident light, I J is the light current, I D is the dark current, P is the incident light power, and R' is the responsivity. The calculated blue light external quantum efficiency spectrum is shown in Figure 2 The peak value of the EQE of the blue light selective photomultiplier detector under a bias voltage of -5V reached 1280%, and the EQE spectrum showed a clear narrow peak. In order to study the effect of bias voltage on the performance of the detector, the EQE value was recorded every -5V from -5V to -20V. The EQE of the blue light selective multiplier detector under a bias voltage of -20V was more than 32000%.

[0055] ​​A square wave was generated by RIGOLD G1062 signal generator with a 3 W power LED, and the transient response and response bandwidth were recorded by Tektronix MSO4054 oscilloscope. The measurement of noise signal was carried out by Tektronix RSA5106A spectrum analyzer in a dark environment, and an external bias voltage of -5 V was applied by Stanford Research Systems Model SR570 and the noise signal was amplified. The specific detectivity D of the photomultiplier detector * The calculation formula of D is

[0056]

[0057] wherein A is the photosensitive area of the detector (unit: cm 2 ), and B' is the bandwidth.

[0058] The specific detectivity of the blue light detector calculated by formula (4) is shown in Figure 3 The responsivity of the multiplication detector under a bias voltage of -5 V can reach 4.7 A / W, and the specific detectivity of the blue light selective multiplication detector can reach 1.5 x 10 11 Jones.

[0059] The preparation method of the green light (G) narrow-band type photomultiplier detector is the same as that of the blue light detector, and the thickness of the evaporated LiF is changed to 145 nm. The calculated external quantum efficiency spectrum of the green light is shown in Figure 4 The EQE of the green light selective multiplication detector under a bias voltage of -20 V can reach 30500%, which is lower than that of the blue light and red light detectors, but still shows a high photoelectric conversion efficiency. The calculated specific detectivity of the green light detector is shown in Figure 5 The specific detectivity of the green light selective organic multiplication detector under a bias voltage of -5 V can reach 1.5 x 10 11 Jones, and conforms to the transmission law of the optical resonant cavity.

[0060] The preparation method of the red light (R) narrow-band type photomultiplier detector is the same as that of the blue light detector, and the thickness of the evaporated Ag is changed to 30 nm and the thickness of the evaporated LiF is changed to 170 nm. The calculated external quantum efficiency spectrum of the red light detector is shown in Figure 6 The EQE of the red light selective multiplication detector under a bias voltage of -20 V can reach 33000%, and the EQE spectrum shows a clear narrow peak. The calculated specific detectivity of the red light detector is shown in Figure 7 The specific detectivity of the red light selective organic multiplication detector under a bias voltage of -5 V can exceed 1.5 x 10 11 Jones, and conforms to the transmission law of the optical resonant cavity.

[0061] In summary, the application adopts Ag / LiF / Ag optical resonant cavity with RGB spectrum selectivity and P3HT:PC 71 The full-color response PM-OPD coupling of BM (100:1, w / w) can obtain the RGB visible light narrow-band response spectrum. By adjusting the thickness of the optical spacer layer, the transmission spectrum of the optical resonant cavity can be controlled, thereby further adjusting the photo-generated electron distribution near the Al electrode, and optimizing the spectral response range of the PM-OPD coupled with the optical resonant cavity. The selective photomultiplier detector made by using the strategy exhibits high external quantum efficiency (EQE>33000%) and narrow spectrum detection potential (FWHM<100nm). In the future, color resolution detection technology will be more and more widely used, and the method provided by the application discards the combination of traditional detectors and optical filters, so that the detector develops in the direction of miniaturization and lightening, and has potential application value.

Claims

1. An optical microcavity-based wavelength-tunable photomultiplier detector, characterized by: The three RGB narrow-band detectors each comprise, from bottom to top, a transparent substrate, an anode layer, a hole transport layer, a photoactive layer, a cathode layer and an optical microcavity structure.

2. The wavelength-tunable optomechanically enhanced photomultiplier detector based on optical microcavities according to claim 1, wherein: The transparent substrate is quartz glass with a size of 20mm x 20mm.

3. The wavelength-tunable optomechanically enhanced photomultiplier detector based on optical microcavities of claim 1, wherein: The anode layer is made of ITO with a thickness of 180nm; the hole transport layer is made of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid with a thickness of 40nm; and the cathode layer is made of Al with a thickness of 15nm. 4.The wavelength-tunable optically microcavity-based photomultiplier detector according to claim 1, wherein: The photoactive layer is prepared from a mixed solution of an electron donor material and an acceptor material, and has a thickness of 450nm; wherein the donor material is poly 3-hexylthiophene, and the acceptor material is [6,6]-phenyl-C71-butyric acid methyl ester, which are dissolved in o-dichlorobenzene at a mass ratio of 100:

1.

5. The wavelength-tunable optomechanically enhanced photomultiplier detector based on optical microcavities of claim 1, wherein: The optical microcavity structure comprises, from bottom to top, a silver layer, a lithium fluoride layer and a silver layer.

6. The wavelength-tunable optically microcavity-based photomultiplier detector according to claim 5, wherein, The thicknesses of the optical microcavities of each narrow-band detector are different, and are as follows: The configuration corresponding to blue light B is: an Ag layer with a thickness of 25nm, a LiF layer with a thickness of 105nm, and an Ag layer with a thickness of 25nm; The configuration corresponding to green light G is: an Ag layer with a thickness of 25nm, a LiF layer with a thickness of 145nm, and an Ag layer with a thickness of 25nm; The configuration corresponding to red light R is: an Ag layer with a thickness of 30nm, a LiF layer with a thickness of 170nm, and an Ag layer with a thickness of 30nm.

7. The wavelength-tunable photomultiplier detector based on optical microcavities according to any one of claims 1-6, characterized in that: the optical resonance effect regulates the response spectrum of the organic photomultiplier detector to three narrow-band characteristic wavelength bands, with central wavelengths of 450nm for blue light, 560nm for green light and 620nm for red light; the full-widths at half maximum of the narrow-band characteristic wavelength bands satisfy: ≤85nm for the blue light band, ≤75nm for the green light band, and ≤70nm for the red light band; The organic multiplication detector realizes photoelectric multiplication effect in the above narrow-band characteristic waveband, and the specific detectivity at the center wavelengths of the three narrow-band characteristic wavebands is all ≥1.5×10 11 Jones.

8. A method of fabricating an optical microcavity-based wavelength-tunable photomultiplier detector according to any one of claims 1 to 7, characterized in that, comprising the following steps: S1: etching ITO on the upper surface of the transparent substrate, ultrasonic cleaning the transparent substrate with ITO through detergents, ionized water, acetone and isopropyl alcohol in sequence, drying in a 45℃ oven, and irradiating with a UV-LED light source for 3 minutes to obtain an anode layer with surface impurities removed; S2: spin-coating poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid aqueous solution on the anode layer at a speed of 2500rpm for 40 seconds, and then annealing at 100℃ for 10 minutes in an air environment at normal pressure to obtain a hole transport layer; S3: P3HT and PC 71 BM was dissolved in o-dichlorobenzene solvent at a mass ratio of 100:1 to prepare a blended solution with a concentration of 40 mg / mL, and stirred at 100°C for 12 hours; the substrate with the hole transport layer prepared in S2 was transferred into an inert gas glove box, and the blended solution was spin-coated at a speed of 600 rpm for 60 seconds, and then annealed at 100°C for 10 minutes in an inert gas environment to form a photoactive layer; S4: The substrate with the photoactive layer prepared in S3 is placed in a vacuum evaporation device, and Al is evaporated on the photoactive layer at a vacuum degree of ≤ 1 x 10 -4 Pa, and a deposition rate of 0.5 nm / s, to form a cathode layer with a thickness of 15 nm. Pa, and a deposition rate of 0.5 nm / s, to form a cathode layer with a thickness of 15 nm. S5: depositing an Ag layer, a LiF layer and an Ag layer in sequence on the cathode layer to form an optical microcavity; wherein the deposition rate of the Ag layer is 0.1-0.3 nm / s, the deposition rate of the LiF layer is 0.1-0.3 nm / s, and the deposition rate of the Ag layer is 0.1-0.3 nm / s. The deposition rate of the LiF layer is 0.1-0.3 nm / s.

9. A test method for characterizing performance parameters of a photodetector, characterized in that, comprising the following steps: Step 1, measuring the current density-voltage characteristics, responsivity and external quantum efficiency EQE of the photomultiplier detector: using a spectrally adjustable light source to irradiate the photomultiplier detector to be measured, using a semiconductor characteristic analyzer to measure the electrical output, and using a calibrated optical power meter to calibrate the incident light power and calculate the responsivity and external quantum efficiency EQE; Step 2, measuring the noise power spectral density of the photomultiplier detector: placing the photomultiplier detector to be measured in a dark environment, applying an external bias voltage of -5V to it through a low-noise current preamplifier and amplifying the output noise signal, and using a radio frequency spectrum analyzer to measure the power spectral density of the amplified noise signal.

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