A Bi₂O₂Se / PbS quantum dot heterojunction short-wave infrared photodetector for broadband imaging and its fabrication method.
By designing a Bi2O2Se/PbS quantum dot heterojunction structure and a SnO2 nanocrystal buffer passivation layer, the problems of low photogenerated carrier separation efficiency and high dark current in traditional PbS quantum dot photodetectors are solved, achieving high responsivity, wide spectral response and fast imaging effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- KUNMING INST OF PHYSICS
- Filing Date
- 2026-04-28
- Publication Date
- 2026-07-10
AI Technical Summary
Traditional PbS quantum dot photodetectors suffer from problems such as low photogenerated carrier separation efficiency, high dark current, low photocurrent to dark current ratio, dense surface defect states, and severe carrier recombination loss, which limit their application in high-performance photodetectors.
Bi2O2Se nanofilms were used to replace PbS-EDT as the hole transport layer to form a Bi2O2Se/PbS quantum dot heterojunction structure. The surface defect states were reduced by SnO2 nanocrystal buffer passivation layer. By combining the bandgap tuning of PbS quantum dots and the high mobility of Bi2O2Se, the band structure was optimized to achieve efficient electron blocking and carrier transport.
It significantly reduces dark current, improves responsivity and detectivity, broadens the spectral response range, increases response speed, and maintains excellent air stability to meet broadband imaging requirements.
Smart Images
Figure CN122373487A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photoelectric detection and imaging technology, specifically to a Bi2O2Se / PbS quantum dot heterojunction short-wave infrared photodetector for broadband imaging and its fabrication method. Background Technology
[0002] PbS colloidal quantum dots (CQDs) have become a core candidate material for next-generation short-wave infrared (SWIR) photodetectors due to their solution processability, size-tunable bandgap, high absorption coefficient, and multiexciton generation capability. Their monolithic integration with silicon readout integrated circuits (ROICs) provides a feasible approach for fabricating high-sensitivity, low-cost SWIR detectors.
[0003] Traditional PbS quantum dot photodetectors typically use PbS-EDT (ethylene dithiol) as the hole transport layer. This structure has the following technical drawbacks: poor band matching between PbS-EDT and the light absorption layer limits the separation efficiency of photogenerated carriers, resulting in high dark current and low photocurrent-to-dark current ratio; dense defect states on the surface of the PbS quantum dot film lead to severe carrier recombination loss, which restricts the improvement of responsivity and detectivity.
[0004] In recent years, the two-dimensional layered material Bi₂O₂Se has attracted widespread attention in the fields of electronics and optoelectronics due to its high carrier mobility and good air stability. However, as an indirect bandgap semiconductor, Bi₂O₂Se has limited intrinsic light absorption in the short-wave infrared band, resulting in insufficient quantum efficiency when used alone as a photosensitive layer. Furthermore, without a reasonable heterojunction bandgap structure design, its high mobility characteristics cannot effectively suppress dark current, limiting its application in high-performance photodetectors. Summary of the Invention
[0005] The purpose of this invention is to prepare a Bi2O2Se / PbS quantum dot heterojunction short-wave infrared photodetector for broadband imaging, thereby expanding the application fields of important optoelectronic detection devices.
[0006] A Bi₂O₂Se / PbS quantum dot heterojunction short-wave infrared photodetector for broadband imaging, wherein the detector is a vertically stacked heterojunction diode structure, and its structure from top to bottom consists of: an ITO top electrode layer, an electron transport layer, a quantum dot light absorption layer, a hole transport layer, an electrode layer, and a substrate, wherein:
[0007] The electron transport layer includes a SnO2 nanocrystal buffer passivation layer and a SnO2 thin film layer;
[0008] The quantum dot light absorption layer is a PbS quantum dot film treated with short-chain amine ligand exchange.
[0009] The hole transport layer is a Bi2O2Se nanofilm formed by high-temperature rapid annealing and oxidation of Bi2Se3 thin film in air.
[0010] Furthermore, the thickness of the electrode layer is 80-100 nm; the thickness of the hole transport layer is 10-30 nm; the thickness of the quantum dot light absorption layer is 200-400 nm; the thickness of the SnO2 nanocrystal buffer passivation layer is 30-100 nm; the thickness of the SnO2 thin film layer is 100-200 nm; and the thickness of the ITO top electrode layer is 100-200 nm.
[0011] A method for fabricating a Bi₂O₂Se / PbS quantum dot heterojunction short-wave infrared photodetector for broadband imaging, comprising the following steps:
[0012] S1, SiO2 / Si substrates are pre-cleaned in an ultrasonic bath of ethanol, acetone and deionized water for 10-25 min;
[0013] S2, an Au electrode layer is deposited on the substrate using a vacuum physical deposition method;
[0014] S3, Bi2Se3 target material is sputtered and deposited on the Au electrode by magnetron sputtering, and then rapidly annealed in air atmosphere for 5~30 min to form Bi2O2Se nanofilm;
[0015] S4, PbS quantum dot powder is dissolved in an organic solvent to obtain PbS quantum dot ink, and then the PbS quantum dot ink is spin-coated onto the surface of the Bi2O2Se nanofilm at a speed of 2000~4000 rpm for 20~40 s. Subsequently, it is annealed at 80~120 ℃ for 10~30 min to obtain the PbS quantum dot light absorption layer.
[0016] S5, the SnO2 nanocrystal dispersion is spin-coated onto the surface of the PbS quantum dot light absorption layer at a rotation speed of 2500~5500 rpm for 5~30 s to obtain the SnO2 nanocrystal buffer passivation layer.
[0017] S6, a SnO2 thin film layer is deposited on the surface of the SnO2 nanocrystalline buffer passivation layer by magnetron sputtering, with a sputtering power of 100~200 W, a deposition pressure of 1.5~2.7 Pa, and an oxygen-argon flow ratio controlled at 1:66.
[0018] S7, an ITO film is deposited on the surface of the SnO2 film as the top electrode using magnetron sputtering.
[0019] The beneficial effects of this invention are as follows:
[0020] 1) Significantly reduced dark current: This invention uses a Bi2O2Se nanofilm to replace the traditional PbS-EDT as the hole transport layer. Through the heterojunction band structure design between Bi2O2Se and PbS quantum dots, efficient electron blocking is achieved, effectively suppressing carrier reverse injection. The photocurrent to dark current ratio is as high as approximately 10 at a bias voltage of -1 V. 4（ (λ=1550 nm, light intensity 1.2 mW / cm²), which solves the problem of high dark current caused by poor band matching in traditional PbS-EDT structures;
[0021] 2) Significantly improved responsivity and detectivity: The high carrier mobility of Bi2O2Se accelerates hole transport and reduces interfacial recombination losses. Meanwhile, the SnO2 nanocrystalline buffer passivation layer effectively reduces the surface defect state density of PbS quantum dots. The device achieves a responsivity R of up to 0.879 A / W and a detectivity D* of 4.27 × 10¹² cm·Hz¹ / ²·W. – ¹, overcoming the shortcomings of traditional PbS quantum dot thin films, such as severe carrier recombination loss and limited responsivity and detectivity caused by dense surface defect states;
[0022] 3) Significantly broadened spectral response range: The band gap of PbS quantum dots can be tuned after short-chain amine ligand exchange treatment. Combined with the wide spectral transmission characteristics of Bi2O2Se, the device can achieve a wide spectral response of 550~2000 nm under zero bias voltage, covering the visible light to short-wave infrared band, which meets the requirements of wide spectrum imaging.
[0023] 4) Significantly improved response speed: Due to the high mobility of Bi2O2Se and the optimized interface states, the carrier transport time is greatly shortened, with device rise / fall times of 1.58 μs and 1.65 μs, respectively;
[0024] 5) Excellent air stability: Bi2O2Se itself has good air stability, and the SnO2 nanocrystal buffer layer effectively passivates the surface defects of PbS quantum dots. The photoelectric performance of the device remains stable after 80 days of air exposure, solving the problem of insufficient long-term stability of traditional structures in air environment. Attached Figure Description
[0025] Figure 1 A flowchart illustrating the preparation of a Bi2O2Se / PbS quantum dot heterojunction short-wave infrared photodetector using this method.
[0026] Figure 2 This is a schematic diagram and SEM cross-sectional view of a Bi2O2Se / PbS quantum dot heterojunction short-wave infrared photodetector.
[0027] Figure 3 A schematic diagram of the band arrangement of the detector prepared by this method.
[0028] Figure 4 The figure shows the logarithmic JV curves of the device at a wavelength of 1550 nm and an illumination intensity of 1.2 mW / cm² under different HTLs (Bi2O2Se and PbS-EDT), where the vertical axis represents the current density and the horizontal axis represents the voltage.
[0029] Figure 5 The graph shows the responsivity of a Bi2O2Se / PbS quantum dot device as a function of light intensity, where the vertical axis represents responsivity and the horizontal axis represents light intensity.
[0030] Figure 6 The graph shows the detectivity of a Bi2O2Se / PbS quantum dot device as a function of light intensity, where the vertical axis represents the detectivity and the horizontal axis represents the light intensity.
[0031] Figure 7 The visible light to short-wave infrared single-pixel imaging effect of the Bi2O2Se / PbS quantum dot detector on the metal mask "N". Detailed Implementation
[0032] Example 1: A method for fabricating a Bi2O2Se / PbS quantum dot heterojunction short-wave infrared photodetector, achieved through the following steps:
[0033] S1. Place the SiO2 / Si substrate in ethanol, acetone and deionized water and ultrasonically clean it for 10-25 min in sequence to remove surface organic contaminants and particulate impurities.
[0034] S2, an Au film is deposited on the SiO2 / Si substrate as a bottom electrode using a vacuum physical deposition method, with a thickness of 80~100 nm.
[0035] S3, Bi2Se3 target material is sputtered and deposited on the surface of the Au film by magnetron sputtering for 3~15s and the deposition thickness is 10~30 nm. Then, it is rapidly annealed in air at 350~550 ℃ for 5~30 min to oxidize Bi2Se3 into Bi2O2Se nanofilm.
[0036] S4, PbS quantum dot powder is dissolved in an organic mixture to prepare PbS quantum dot ink, and then the PbS quantum dot ink is spin-coated onto the surface of the Bi2O2Se nanofilm at a speed of 2000~4000 rpm for 20~40 s. Subsequently, it is annealed at 80~120 ℃ for 10~30 min to obtain a PbS quantum dot light absorption layer with a thickness of 200~400 nm.
[0037] S5, the SnO2 nanocrystal dispersion is spin-coated onto the surface of the PbS quantum dot light absorption layer at a rotation speed of 2500~5500 rpm for 5~30 s to form a SnO2 nanocrystal buffer passivation layer with a thickness of 30~100 nm.
[0038] S6. A SnO2 thin film was deposited on the surface of the SnO2 nanocrystalline buffer passivation layer by magnetron sputtering. The sputtering power was 100~200 W, the deposition pressure was 1.5~2.7 Pa, the oxygen-argon flow ratio was controlled at 1:66, and the film thickness was 100~200 nm.
[0039] S7, an ITO film is deposited on the surface of the SnO2 film as the top electrode using magnetron sputtering, with a thickness of 100~200 nm.
[0040] Comparative Example: The fabrication method of a traditional PbS-EDT quantum dot photodetector is achieved through the following steps:
[0041] S1~S2, same as the embodiment;
[0042] S3, PbS quantum dot powder is dissolved in an organic solvent to prepare PbS quantum dot ink, and then the PbS quantum dot ink is spin-coated onto the surface of the Au film at a speed of 2500 rpm for 10-40 s. Subsequently, it is treated with EDT (ethylene dithiol) ligand solution for 10-50 s. The above steps are repeated for 10-20 layers to obtain a PbS-EDT hole transport layer.
[0043] S4~S6 are the same as S5~S7 in the embodiment.
[0044] Compared to the conventional PbS quantum dot detector structure in the comparative example, the Bi2O2Se / PbS quantum dot heterojunction detector in this embodiment can efficiently separate photogenerated carriers. The high mobility and better electrical properties of the Bi2O2Se thin film improve hole transport performance, and the good interface states can effectively reduce recombination loss and improve photon absorption and utilization efficiency.
[0045] like Figure 4 As shown in the comparison of logarithmic JV curves of devices fabricated with different HTLs (Bi2O2Se and PbS-EDT), it can be seen that the Bi2O2Se / PbS quantum dot heterojunction device of the embodiment has lower dark current and higher photocurrent, and the overall performance is significantly improved compared with the comparative example.
[0046] like Figure 5As shown in the curve, the responsivity of the Bi2O2Se / PbS quantum dot heterojunction device varies with the light intensity. It can be seen that as the light intensity increases, the device responsivity gradually decreases due to the saturated trap state photocarrier filling effect. When the light intensity is 0.012 mW / cm², the responsivity at a bias voltage of -0.5 V reaches a maximum of 0.879 A / W.
[0047] like Figure 6 As shown, the detectivity of the Bi₂O₂Se / PbS quantum dot heterojunction device varies with light intensity, and its trend is consistent with the responsivity. When the light intensity is 0.012 mW / cm², the detectivity reaches a maximum of 4.27 × 10¹² cm·Hz¹ / ²·W under a bias voltage of -0.5 V. – ¹.
[0048] like Figure 7 As shown, the visible light to short-wave infrared single-pixel imaging effect of the Bi2O2Se / PbS quantum dot detector on the metal mask "N" shows that the device has excellent imaging performance in the 1550 nm short-wave infrared spectral range.
Claims
1. A Bi₂O₂Se / PbS quantum dot heterojunction short-wave infrared photodetector for broadband imaging, characterized in that, The detector is a vertically stacked heterojunction diode structure, which, from top to bottom, consists of: an ITO top electrode layer, an electron transport layer, a quantum dot light absorption layer, a hole transport layer, an electrode layer, and a substrate, wherein: The electron transport layer includes a SnO2 nanocrystal buffer passivation layer and a SnO2 thin film layer; The quantum dot light absorption layer is a PbS quantum dot film treated with short-chain amine ligand exchange. The hole transport layer is a Bi2O2Se nanofilm formed by high-temperature rapid annealing and oxidation of Bi2Se3 thin film in air.
2. The Bi₂O₂Se / PbS quantum dot heterojunction short-wave infrared photodetector for broadband imaging as described in claim 1, characterized in that... The electrode layer has a thickness of 80-100 nm; the hole transport layer has a thickness of 10-30 nm; the quantum dot light absorption layer has a thickness of 200-400 nm; the SnO2 nanocrystal buffer passivation layer has a thickness of 30-100 nm; the SnO2 thin film layer has a thickness of 100-200 nm; and the ITO top electrode layer has a thickness of 100-200 nm.
3. A method for fabricating a Bi₂O₂Se / PbS quantum dot heterojunction short-wave infrared photodetector for broadband imaging, as described in claim 1, characterized in that... The preparation steps are as follows: S1, SiO2 / Si substrates are pre-cleaned in an ultrasonic bath of ethanol, acetone and deionized water for 10-25 min; S2, an Au electrode layer is deposited on the substrate using a vacuum physical deposition method; S3, Bi2Se3 target material is sputtered and deposited on the Au electrode by magnetron sputtering, and then rapidly annealed in air atmosphere for 5~30 min to form Bi2O2Se nanofilm; S4, PbS quantum dot powder is dissolved in an organic solvent to obtain PbS quantum dot ink, and then the PbS quantum dot ink is spin-coated onto the surface of the Bi2O2Se nanofilm at a speed of 2000~4000 rpm for 20~40 s. Subsequently, it is annealed at 80~120 ℃ for 10~30 min to obtain the PbS quantum dot light absorption layer. S5, the SnO2 nanocrystal dispersion is spin-coated onto the surface of the PbS quantum dot light absorption layer at a rotation speed of 2500~5500 rpm for 5~30 s to obtain the SnO2 nanocrystal buffer passivation layer. S6, a SnO2 thin film layer is deposited on the surface of the SnO2 nanocrystalline buffer passivation layer by magnetron sputtering, with a sputtering power of 100~200 W, a deposition pressure of 1.5~2.7 Pa, and an oxygen-argon flow ratio controlled at 1:
66. S7, an ITO film is deposited on the surface of the SnO2 film as the top electrode using magnetron sputtering.