Electron barrier layer and optical adjustment layer for realizing visible light blind type near-infrared perovskite photoelectric detector

Abstract

The invention relates to a visible light blind type near-infrared perovskite photoelectric detector, and belongs to the technical field of photoelectric materials and devices. Aiming at the problems of visible light interference and insufficient near-infrared detection efficiency of an existing detector, a collaborative optimization scheme adopting a polymer-based composite electron barrier layer and an optical adjustment layer is provided. The composite electron blocking layer realizes photo-induced electron blocking and efficient hole migration through LUMO / HOMO energy level matching of a high hole mobility polymer and a cross-linkable small molecule material; the optical adjusting layer selectively absorbs visible light of 600-780 nm, and the near-infrared selectivity is enhanced. The device adopts an integrated structure of a transparent electrode, a hole transport layer, a perovskite layer, a passivation layer, an electron blocking layer, an organic active layer, a cathode layer and a metal electrode, and the responsivity of 0.49 A / W, the external quantum efficiency of 72.41% and the specific detection rate of 6.74 * 10 < 12 > Jones are achieved at the wavelength of 840 nm. The device is suitable for infrared imaging, optical communication and biomedical sensing, and the problem of precise near-infrared detection under ambient light interference is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of near-infrared narrow-band photodetectors, and relates to a novel electron blocking layer composite material and an optical adjustment layer for a visible-blind near-infrared perovskite photodetector. The invention uses a composite film composed of a polymer with a high hole mobility and a crosslinkable small molecule hole transport material as the electron blocking layer (EBL), and at the same time combines an external optical adjustment layer (OAL), and realizes the effective blocking of photo-generated electrons in the perovskite layer and the selective detection of near-infrared light through the synergistic effect. Tests show that the device has an excellent responsivity of 0.49 A / W at a wavelength of 840 nm, which is the highest performance level of the current visible-blind near-infrared perovskite photodetectors of the same kind. The innovation lies in the dual design of the internal electron blocking layer and the external optical adjustment layer of the device, which effectively suppresses the collection of electrons induced by visible light and minimizes the loss of carriers induced by near-infrared light, thereby realizing the highly selective near-infrared detection function. Background Art

[0002] A photodetector (PD) converts the captured optical signal into an identifiable electrical signal. According to the different optical response ranges, photodetectors can be divided into broadband photodetectors and narrow-band photodetectors. Broadband photodetectors currently dominate the mainstream photodetectors, but with the rise of emerging applications, the demand for photodetectors capable of detecting narrow spectral ranges is increasing.

[0003] Traditional narrow-band photodetectors are mainly realized based on broadband absorption semiconductor material systems, and typical representatives include amorphous silicon (a-Si:H), crystalline silicon (c-Si), gallium phosphide (GaP), gallium arsenide phosphide (GaAsP), and indium gallium arsenide (InGaAs), etc. Since these broadband absorption semiconductors cannot directly identify light of specific wavelengths within the target spectral range, spectral processing is required, and optical elements are used to decompose light into different spectral components to achieve narrow-band or monochromatic detection. Although these broadband absorption semiconductors can be integrated with filters / filter arrays to achieve narrow-band (monochromatic) detection, they are still limited by the absorption layer material and the filter, and this limitation is particularly prominent in narrow-band detection in the near-infrared band.

[0004] Using metal halide perovskite (PVSK) as the absorption layer of a narrow-band photodetector stems from the excellent optoelectronic properties of perovskite and the simple and friendly preparation method. Metal halide perovskites are a class of semiconductor materials with the general formula AMX3, where A is a monovalent organic or inorganic cation (such as CH3NH3 + , CH(NH2)2 + (abbreviated as MA + , FA + ), Cs + , Rb +), M is a divalent metal cation (such as Pb 2+ , Sn 2+ , Cu 2+ , or Mn 2+ ), X is a halogen anion (such as Cl - , Br - , or I - ). Such an ionic structure endows perovskite with advantages such as long carrier diffusion length, high mobility, large optical absorption coefficient, and low exciton binding energy, showing broad application prospects in the preparation of high-performance optoelectronic devices.

[0005] In addition, for narrow-band photodetectors, researchers have also developed some new methods to achieve spectral selective detection, such as (1) using charge transfer (CT) absorption between donors and acceptors to achieve near-infrared response; (2) manipulating the internal quantum efficiency through charge collection narrowing (CCN); (3) manipulating the dissociation of Frenkel excitons through exciton dissociation narrowing (EDN). However, there are still some deficiencies in the above-mentioned schemes: for example, the CT absorption is much weaker than the intrinsic absorption of organic semiconductors, resulting in an external quantum efficiency (EQE) less than 10% [Adv.Mater.2021,33(26),2100582] , and even with the help of an accurately resonant optical cavity, it is still very difficult for the EQE level in the near-infrared region to exceed 50% [Nat.Commun.2017,8(1),15421] ; the CCN technology uses the absorption difference of light with different wavelengths by the thickness of the active layer to achieve narrow-band response. However, due to serious charge recombination in organic bulk heterojunction (OBHJ) thick-film devices, the near-infrared narrow-band photodetectors (NIR NPDs) based on the CCN principle also exhibit relatively low EQE values; the EDN strategy constructs a cascade energy level structure (such as broadband-gap donor / narrow-band-gap acceptor stratification) to prevent charge recombination, so it can maintain a relatively high EQE value of the device and achieve high responsiveness. However, similar to CCN devices, a relatively thick active layer is still used in EDN PDs [Adv.Mater.2016,28(37),8144] , and due to the relatively low carrier mobility of organic semiconductors, the increase in film thickness will prolong the time of charge transport and collection, inevitably having a negative impact on the response speed of the device. To achieve narrow-band infrared detection and reduce the extraction of ultraviolet-visible light-induced carriers, Chen et al. [ACS Appl.Mater.Interfaces ,2023 , 15(43),50312]A visible-blind NIR NPD (ITO / PEDOT:PSS / PVSK / CuSCN / OBHJ / BCP / Ag) was constructed by integrating perovskite, CuSCN, and organic semiconductor thin films. The lowest unoccupied molecular orbital (LUMO) energy level of the CuSCN layer is -1.8 eV, which can effectively block the visible light-induced electrons from the perovskite layer, thus achieving near-infrared selective detection. This strategy has been widely verified in many studies. However, aiming at the incomplete absorption problem of the 600 - 800 nm thick perovskite thin film in the 600 - 780 nm band, the present invention further introduces an optical absorption layer (OAL), and realizes the selectivity of near-infrared narrow-band detection by selectively absorbing specific visible light wavelengths.

[0006] Since the visible light response of the integrated photodetector (IPD) is mainly controlled by the perovskite layer, selective near-infrared narrow-band detection can be achieved by developing a new type of electron blocking layer material to effectively suppress the visible light-induced charges generated by the perovskite layer. Currently, CuSCN and poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) are mainly used as electron blocking layer materials for narrow-band near-infrared photodetectors (NPDs), and these schemes have been widely verified in many studies. However, CuSCN and PFN are sensitive to moisture and oxygen, which limits their device applications. Although CuSCN exhibits excellent performance advantages, it is easy to penetrate into the underlying perovskite layer Nano Energy 2017 ,32,2211 , and it is necessary to use irritating and expensive diisopropyl sulfide as a solvent, which increases the problems of safety and manufacturing. For PFN, its electron transport performance Nat.Photon.2012,6(9),1749 fundamentally limits the hole extraction efficiency, especially significantly in thick active layer structures. These defects highlight the urgent need to develop new EBL materials. TFB is widely used as a hole transport layer (HTL) material for cadmium-based quantum dot light-emitting diodes (QLEDs) due to its high hole mobility, and the cross-linked small molecule CBP-V is expected to improve the solvent resistance of TFB. Such an electron blocking layer with an appropriate thickness can block the electrons generated by the perovskite layer absorbing short-wavelength light, and this type of material has moisture / oxygen stability, can avoid the problem of solvent compatibility, and at the same time maintain the optimal charge management performance. We use this hybrid interface material as the electron blocking layer between the perovskite and OBHJ layers, and at the same time use an optical adjustment layer material outside the device, and successfully achieve a high-performance visible-blind near-infrared hybrid NPD. The prepared NPD has an EQE as high as 72.41% in the near-infrared region, and the specific detectivity is 6.74×10 12Jones has a near-infrared responsivity of 0.49 A / W, which is one of the highest values among current visible-blind near-infrared perovskite photodetectors. Summary of the Invention

[0007] The object of the present invention is to provide an electron blocking layer material and an optical adjustment layer suitable for visible-blind near-infrared perovskite photodetectors. The electron blocking layer material is composed of a polymer with a high hole mobility and a crosslinkable small molecule hole transport material. Its high LUMO energy level can effectively prevent the transmission of electrons generated by visible light from the perovskite layer to the OBHJ layer; the optical adjustment layer is composed of polymer PM6 and small molecule PTIC, and by selectively absorbing specific visible light wavelengths, the selectivity of near-infrared narrowband detection is significantly improved.

[0008] The polymer-based composite electron blocking layer material is composed of a polymer and a small molecule, and is prepared by spin coating, where the mass ratio of the polymer to the small molecule is 2:1.

[0009] The optical adjustment layer material is composed of polymer PM6 and small molecule PTIC, and is prepared by spin coating, where the mass ratio of PM6 to PTIC is 1:1 to 1:5.

[0010] The present invention also provides a visible-blind near-infrared perovskite photodetector device, which is characterized in that: through the synergistic effect of the polymer-based composite electron blocking layer material and the optical adjustment layer, visible light interference is suppressed and the selective detection of near-infrared light is enhanced.

[0011] The technical solution of the present invention: The polymer and small molecule hybrid material system involved in the present invention is used to prepare an electron blocking layer (EBL) and an optical adjustment layer (OAL) by spin coating. Among them, the EBL layer is in direct contact with the perovskite active layer (or its passivation layer), and it has a high LUMO energy level of -2.88 eV, which can effectively block the collection of visible light-induced electrons in the perovskite layer; at the same time, its HOMO energy level of -5.50 eV is well matched with the -5.55 eV HOMO energy level of the perovskite, which is beneficial to the efficient transmission of near-infrared photo-generated holes from the OBHJ layer to the PVSK layer. The OAL layer is arranged on the outside of the device (in contact with the glass substrate), and specifically absorbs visible light in the 600-780 nm band, effectively making up for the absorption deficiency problem of the 600-800 nm thick perovskite thin film in this wavelength range. Through the synergistic effect of EBL and OAL, the present invention successfully realizes a high-performance visible-blind near-infrared narrowband photodetector based on a thin perovskite (600-800 nm).

[0012] The present invention has the following characteristics and advantages:

[0013] 1. The innovative electron blocking layer material has excellent solubility and film-forming uniformity, and its high LUMO energy level can effectively block the collection of visible light-induced electrons in the perovskite layer.

[0014] 2. The uniquely designed optical adjustment layer (OAL) is in direct contact with the glass substrate, selectively absorbing only visible light in a specific wavelength range (600 - 780 nm) without affecting the detection performance in the near-infrared region.

[0015] 3. The optimized annealing process parameters (temperature and time) of the EBL layer are precisely regulated and will not cause thermal damage to the perovskite active layer.

[0016] 4. The visible-blind near-infrared narrow-band photodetector prepared based on this scheme exhibits excellent comprehensive performance, including key indicators such as high external quantum efficiency (EQE), excellent responsivity, and outstanding specific detectivity. Description of the Drawings

[0017] Figure 1 Schematic diagram of the molecular structures of the electron blocking layer (TFB:CBP-V), optical adjustment layer (PM6:PTIC), and organic active layer materials (wide-bandgap conjugated polymer donor material D18, non-fullerene fused-ring small molecule electron acceptor material BTP-eC9-4F) selected in Example 1.

[0018] Figure 2 Schematic diagram of the device structure of the photodetector prepared in Example 1.

[0019] Figure 3 Schematic diagram of the device structure of the photodetector prepared in Comparative Example 1.

[0020] Figure 4 Normalized ultraviolet thin film absorption diagram of the optical adjustment layer (PM6:PTIC) and organic active layer (D18:BTP-eC9-4F) of the near-infrared perovskite photodetector prepared in Example 1.

[0021] Figure 5 External quantum efficiency (EQE) diagram of the near-infrared perovskite photodetector prepared in Example 1.

[0022] Figure 6 Responsivity (R) diagram of the near-infrared perovskite photodetector prepared in Example 1.

[0023] Figure 7 Specific detectivity (D*) diagram of the near-infrared perovskite photodetector prepared in Example 1.

[0024] Figure 8 External quantum efficiency (EQE) diagram of the photodetector prepared in Comparative Example 1. Detailed implementation mode

[0025] In one embodiment of the present invention, the electron blocking layer is composed of a mixed film of polymer TFB and small molecule CBP-V.

[0026] In one embodiment of the present invention, the optically active layer is composed of a mixed film of polymer PM6 and small molecule PTIC.

[0027] In one embodiment of the present invention, the organic active layer (OBHJ) is composed of a mixed film of polymer D18 and small molecule BTP-eC9-4F.

[0028] In one embodiment of the present invention, the thickness of the electron blocking layer is 12 - 15 nm.

[0029] In one embodiment of the present invention, the material constituting the transparent electrode is a conductive material that is transparent or semi-transparent in the visible light region, and its light transmittance is greater than 50%.

[0030] In one embodiment of the present invention, the material of the transparent electrode (anode) of the inverted perovskite solar cell is indium tin oxide (ITO).

[0031] In one embodiment of the present invention, the thickness of the perovskite active layer is 600 - 800 nm.

[0032] In one embodiment of the present invention, the material of the hole transport layer (or hole injection layer) of the infrared perovskite photodetector is an organic compound or metal oxide material with hole transport ability, such as nickel oxide nanoparticles (NiO x ) or [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) or [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz), and the thickness of the hole transport layer is 1 - 100 nm.

[0033] In one embodiment of the present invention, the material of the metal electrode (cathode) of the inverted perovskite solar cell is selected from silver.

[0034] Example 1:

[0035] Prepare a perovskite precursor solution with a chemical formula of (FA 0.98 MA 0.02 ) 0.95 Cs 0.05 Pb(I 0.98 Br 0.02) 3 was dissolved in 1 ml of a mixed solvent of DMF:DMSO (volume ratio 4:1) in proportion to prepare a 1.7 M perovskite precursor solution. Then, a film was formed by spin coating as the active layer material of the inverted perovskite solar cell device.

[0036] The device structure adopted is: Optical Active Layer (OAL) / Glass / ITO / NiO x (Hole Transport Layer) / 2PACz (Self-Assembled Layer) / PVSK Active Layer / Passivation Layer (p-F-PEAI) / Electron Blocking Layer / Organic Active Layer / BCP (Electron Transport Layer) / Ag (100 nm), as Figure 2 shown. The preparation process of the device is as follows:

[0037] 1) The pre-cleaned ITO (transparent electrode) glass substrate was treated with an ultraviolet ozone cleaner (UVO) for 25 min.

[0038] 2) NiO x nanoparticles were dispersed in deionized water with a concentration of 15 mg / mL to form a NiO x nanoparticle solution.

[0039] It was spin-coated on the ITO substrate at a speed of 4000 rpm and then annealed at 150 °C in ambient air for 10 min.

[0040] 3) 2PACz (Self-Assembled Layer) was spin-coated on the NiO x layer at a speed of 4000 rpm, and then annealed at 70 °C in air for 2 min to self-assemble on the upper layer of the hole transport layer.

[0041] 4) The prepared perovskite precursor was spin-coated at speeds of 1000 rpm and 4000 rpm, and chlorobenzene was used as an anti-solvent to wash away the excess precursor solution. Then it was annealed on a hot plate at 100 °C for 15 min, and the thickness of the active layer was 600 - 800 nm.

[0042] 5) p-F-PEAI was used as the passivation layer and deposited on the perovskite active layer by solution spin coating.

[0043] 6) After the electron blocking layer material (TFB:CBP-V) was spin-coated on the perovskite film, it was annealed in two steps at 130 °C and 170 °C for crosslinking.

[0044] 7) The organic layer active layer material (D18:BTP-eC9-4F) was dissolved in chloroform, spin-coated on the single electron blocking layer, and then annealed for 10 min. The thickness of the active layer was about 100 nm.

[0045] 8) The optical adjustment layer material (PM6:PTIC) is dissolved in chloroform and spin-coated on the back of the glass substrate.

[0046] 9) Under the condition of a vacuum degree of 3×10 -7 Torr, Ag (100 nm) is deposited on the electron transport layer

[0047] / cathode interface layer by thermal evaporation as the metal electrode.

[0048] Testing of device performance: EQE data is obtained using a solar cell spectral response measurement system (QER3011, Enli Technology Co., Ltd), and the intensity is calibrated with a standard single-crystalline silicon photovoltaic cell. The responsivity and specific detectivity are calculated using the following formulas:

[0049]

[0050]

[0051] where h is Planck's constant, c is the speed of light, q is the charge, λ is the wavelength of the incident light; A is the area of the active layer, B is the bandwidth frequency, and NEP is the noise equivalent power.

[0052] The optimal performance of the visible-blind near-infrared perovskite photodetector prepared by using EBL and OAL is as follows: the full width at half maximum in the near-infrared absorption region is 81.25 nm, and the EQE is as high as 72.41% ( Figure 5 ), the near-infrared responsivity is 0.49 A / W ( Figure 6 ), and the specific detectivity is 6.74×10 12 Jones ( Figure 7 ).

[0053] Comparative Example 1 (control group): A reference device is prepared according to the method of Example 1, except that there is no electron blocking layer and optical adjustment layer in the device. The prepared device has a broadband response of 300 - 1000 nm ( Figure 8 ).

[0054] The experimental results of Example 1 and Comparative Example 1 show that the device structure using PM6:PTIC as the optical adjustment layer and introducing the TFB:CBP-V hybrid electron blocking layer can effectively suppress the carrier response in the visible light region and successfully achieve the function of visible-blind near-infrared detection. Among them, the near-infrared response characteristics are mainly provided by the OBHJ thin film composed of narrow-bandgap acceptors. The perovskite layer with a thickness of 600 - 800 nm has a dual function: on the one hand, it can fully absorb the short-wavelength light in the signal spectrum, and on the other hand, it acts as a high-performance hole transport layer. It is particularly worth noting that the composite thin film composed of the high-hole mobility polymer TFB and the crosslinkable small molecule can effectively block the transmission of visible light-induced electrons from the perovskite layer to the OBHJ layer due to its high LUMO energy level characteristics. The test data shows that the device achieves a maximum external quantum efficiency (EQE) of 72.41%, the specific detectivity reaches 6.42×10 12 Jones, and the near-infrared responsivity is as high as 0.49 A / W, demonstrating excellent comprehensive performance.

[0055] The above has made a detailed introduction to the materials of the electron blocking layer and the optical adjustment layer and the preparation method of the visible-blind near-infrared perovskite photodetector device provided by the present invention. The experimental data confirm that adopting this solution can effectively suppress the response of the device in the visible light band, thereby significantly improving its detection performance in the infrared light region.

[0056] Specific examples are cited in this article to illustrate the principles and implementation methods of the present invention, but these examples are not used to limit the present invention. Any simple modification of the present invention without departing from the principles of the present invention also falls within the scope of the claims of the present invention.

Claims

1. A polymer-based composite electron blocking layer material and optical adjustment layer for a visible-blind near-infrared perovskite photodetector, characterized in that: Through the synergistic effect of the polymer-based composite electron blocking layer material and the optical adjustment layer, visible light interference is suppressed and the selective detection of near-infrared light is enhanced.

2. The polymer-based composite electron blocking layer material according to claim 1, wherein: Composed of a high hole mobility polymer (hole mobility greater than 1×10 -3 cm 2 V -1 s -1 ) and a crosslinkable small molecule hole transport material. The crosslinkable small molecule hole transport material contains a carbazole or arylamine group and can undergo a crosslinking reaction under heating (greater than 50 degrees Celsius) or light conditions.

3. The optical adjustment layer according to claim 1, wherein: It is composed of polymer PM6 and small molecule PTIC, where the mass ratio of PM6 to PTIC ranges from 1:1 to 1:

5. It can partially absorb visible light in the 600-780 nm band and has no absorption in the near-infrared band.

4. A visible-blind type near-infrared perovskite photodetector, characterized in that: The device structure of the visible-light-blind near-infrared perovskite photodetector sequentially includes: an optical adjustment layer, glass, a transparent electrode (anode), a hole transport layer, a perovskite active layer, a passivation layer, an electron blocking layer, an organic active layer, a cathode interface layer, and a metal electrode (cathode).

5. The visible-blind near-infrared perovskite photodetector according to claim 4, wherein: The material of the hole transport (or hole injection) layer is an organic compound or a metal oxide material with hole transport ability, such as nickel oxide nanoparticles (NiO x ), [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) or [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz), etc., and the hole transport layer has a thickness of less than 100 nm.

6. The visible-blind near-infrared perovskite photodetector according to claim 4, characterized in that: The light absorption band of the perovskite active layer is mainly 300-750 nm, and the thickness is 500-900 nm.

7. The visible-blind near-infrared perovskite photodetector according to claim 4, wherein: The electron blocking layer can be prepared by solution processing and then cross-linked by a thermal annealing process. Preferably, it includes a two-step annealing process: annealing at 130 °C first and then at 170 °C.

8. The visible-blind near-infrared perovskite photodetector according to claim 4, wherein: The thickness of the organic active layer is 50-300 nm and is composed of a polymer electron donor and a small molecule electron acceptor. Preferably, the organic active layer is composed of polymer D18 and small molecule BTP-eC9-4F.

9. The visible-blind type near-infrared perovskite photodetector according to claim 4, wherein: The transparent electrode is indium tin oxide (ITO), with a light transmittance greater than 50% in the visible light region and a thickness of 100-200 nm.

10. The visible-blind near-infrared perovskite photodetector according to claim 4, characterized in that: The metal electrode is a silver (Ag) or aluminum (Al) electrode, with a thickness of 50-200 nm, prepared by vacuum evaporation.

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