Chiral perovskite semiconductor circularly polarized light emission enhancement structure and preparation method and application thereof

Abstract

The present application relates to a kind of chiral perovskite semiconductor circular polarization light emitting enhancement structure and its preparation method and application, belong to chiral photoelectric semiconductor material and micro-nano device technical field.The structure is formed by two layers of chiral perovskite semiconductor nanosheet through controllable twist angle stacking homojunction, and twist angle range is 0 ° to 90 °.By adjusting interlayer twist angle, the polarization of circular polarization light emitting is continuously regulated and significantly enhanced, especially in parallel stacking (0 ° twist angle), the polarization of circular polarization light emitting is compared with single nanosheet and vertical stacking (90 ° twist angle), and it is 3 times to improve.The enhancement effect is derived from twist angle-dependent interlayer coupling, promotes spin-selective charge transfer, enhances exciton binding energy and inhibits electron-phonon scattering.The present application provides an effective way to regulate polarization by twist angle, and is suitable for circular polarization light emitting device, spin optoelectronic device and quantum information processing and other fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chiral optoelectronic semiconductor materials, nanophotonics and spintronic semiconductor devices, and particularly relates to a method for significantly enhancing the circularly polarized luminescence performance of chiral semiconductor materials and devices by precisely controlling the interlayer twist angle. BACKGROUND

[0002] As a new type of semiconductor material, chiral perovskites can interact specifically with the angular momentum (spin) of photons due to the structural chirality introduced by organic components, thereby producing unique "chiral-spin-optical" coupling effects such as circularly polarized luminescence, which has broad application prospects in the fields of 3D display, circularly polarized photodetection, quantum information, spin light-emitting diodes and biological chirality sensing.

[0003] However, the key challenge currently faced by the field is that the circularly polarized luminescence polarization degree of most chiral perovskite materials is generally low, and there is a lack of effective and continuous control means.

[0004] Twistronics, as a new paradigm, provides a new degree of freedom for controlling the electronic band, exciton behavior and optical properties of materials by introducing controllable interlayer rotation in two-dimensional materials. However, this powerful technology is currently mainly applied to non-chiral inorganic material systems such as graphene and transition metal sulfides, and has not been systematically combined with chiral organic semiconductor materials, failing to actively manipulate the spin and polarized optical properties of materials using twist angles.

[0005] Therefore, it is an urgent problem in the field to develop a method that can efficiently and continuously control the chiral optical response (circularly polarized luminescence behavior) by simply adjusting a physical structure parameter such as the twist angle. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provide a chiral perovskite semiconductor circularly polarized luminescence enhancement structure with clear structure and excellent performance. This structure can achieve wide-range, continuous and significant enhancement of the circularly polarized luminescence polarization degree (DCP) by changing the interlayer twist angle, a single physical parameter.

[0007] Another object of the present application is to provide a preparation method for the above structure, which is controllable and has good repeatability, and can accurately construct any specific twist angle ranging from 0° to 90°.

[0008] Another object of the present application is to provide a circularly polarized luminescence device comprising the above structure, which exhibits excellent circularly polarized luminescence characteristics and demonstrates its application potential in the fields of high-performance chiral optoelectronics and spintronics such as circularly polarized photodetection, circularly polarized light display and circularly polarized laser.

[0009] To solve the above technical problems, the technical scheme of the present application is as follows: A circularly polarized luminescence enhancement structure of chiral perovskite semiconductor material: comprising two layers of chiral perovskite semiconductor nanosheets with the same chiral configuration, the nanosheets are stacked by in-plane rotation and with a controllable twist angle θ, wherein the twist angle θ is continuously adjustable in the range of 0° to 90°, and the continuous regulation of the structure's circularly polarized luminescence polarization degree can be realized by changing the twist angle θ, the chiral perovskite homojunction is two layers of R-type or two layers of S-type enantiomers, with a chemical formula of (R-MBA)2PbI4 or (S-MBA)2PbI4, where MBA is C6H5C2H4NH3 + .

[0010] Preferably, when the twist angle θ is 0° (i.e. parallel stacking structure), the circularly polarized luminescence polarization degree reaches a maximum value, which is at least 3 times higher than that of a single nanosheet and a homojunction with a vertical stacking structure.

[0011] Preferably, the parallel stacking structure has a type II band arrangement, with a conduction band or valence band energy level offset of 15-50 meV.

[0012] Preferably, the parallel stacking structure has an enhanced exciton binding energy, with an exciton binding energy that is 20-40 meV higher than that of a single nanosheet.

[0013] Preferably, the parallel stacking structure has an inhibited electron-phonon coupling strength, so that the value of its circularly polarized luminescence polarization degree can be maintained at 10% when the temperature is raised to room temperature. In contrast, the circularly polarized light polarization degree of a single chiral perovskite nanosheet and a homojunction with a vertical stacking structure can only be less than 1% when the temperature is raised to room temperature.

[0014] Preferably, the reduction of the twist angle θ leads to a reduction of the interlayer coupling distance between the upper and lower nanosheets, and the reduced interlayer distance significantly enhances the interface wave function overlap and electron coupling strength.

[0015] To solve the above technical problems, another technical scheme of the present application is as follows: A method for preparing any of the circularly polarized luminescence enhancement structures of chiral perovskite semiconductor, comprising the following steps:

[0016] (1) Synthesizing R-type or S-type chiral perovskite semiconductor nanosheets by a solution method;

[0017] (2) Stacking two layers of the nanosheets with a preset twist angle by a dry transfer method;

[0018] (3) Confirming the stacking angle and structure by optical or scanning probe microscopy.

[0019] To solve the above technical problems, another technical scheme of the present application is as follows: A circularly polarized light-emitting device, wherein the active light-emitting layer comprises the chiral perovskite circularly polarized light-emitting enhancement structure according to any one of the above. The device takes full advantage of the high polarization degree, continuous tunability and high stability of the structure, and is suitable for circularly polarized light-emitting diodes, spin-polarized lasers and chiral photodetectors and other applications.

[0020] Preferably, the polarization degree of the circularly polarized light-emitting device reaches a peak value when the twist angle θ is 0°.

[0021] Structure regulation based on twist angle and performance enhancement mechanism:

[0022] The present application discloses the quantitative structure-activity relationship between the twist angle θ and the circularly polarized light-emitting performance, and determines the key to achieving performance breakthrough.

[0023] Continuous regulation characteristics: the circularly polarized light-emitting polarization degree monotonically increases with the decrease of the twist angle θ, realizing continuous and seamless regulation from vertical stacking (90° twist angle) to parallel stacking (0° twist angle).

[0024] Optimal performance configuration: when the twist angle θ is 0°, i.e. forming a parallel stacking structure, the circularly polarized light-emitting polarization degree reaches a maximum value. Experiments have proved that the polarization degree of this configuration can be improved by up to 3 times compared with a single nanosheet and a 90° vertical stacking structure.

[0025] Band structure regulation: parallel stacking induces the formation of type II band arrangement, and the conduction band and valence band energy level offset is in the range of 15-50 meV, providing an effective driving force for spin-selective interlayer charge transfer.

[0026] Interface coupling and stability improvement: the interlayer coupling distance of the parallel stacking structure (0° twist angle) is about 8.5 Å, while the interlayer coupling distance of the vertical stacking structure (90° twist angle) is about 9.5 Å. As the angle decreases, the interlayer coupling distance decreases, enhancing the interface electron coupling. The parallel stacking structure has higher exciton binding energy (improved by 20-40 meV) and suppressed electron-phonon coupling strength, which together ensure that the polarization degree value of the circularly polarized light-emitting device of the parallel stacking structure can still reach 10% at room temperature, while the polarization degree value of the single nanosheet and the vertical structure homojunction is less than 1%.

[0027] Compared with the prior art, the present application has the following remarkable beneficial effects:

[0028] 1. Continuous, dynamic and reversible regulation of chiral optical properties is achieved.

[0029] The present application realizes, for the first time, the continuous and seamless regulation of the polarization degree of circularly polarized luminescence from a basic value to a peak value through simple physical angle rotation (0° to 90°). This breaks the limitation of traditional chiral devices that can only work in fixed and discrete polarization states, and provides a new technical path for developing dynamically tunable photonic devices (such as polarization encoders and intelligent display units). This "one-key" continuous regulation mechanism simplifies the system structure and reduces the control complexity.

[0030] 2. The parallel stacking configuration has a huge enhancement effect on circularly polarized luminescence, and the performance has been broken through:

[0031] The present application discloses and utilizes the new phenomenon that chiral perovskite nanosheets produce the strongest chiral optical response when stacked in parallel (0° twist angle). Experiments have proved that the polarization degree of circularly polarized luminescence in this configuration is significantly improved by up to 3 times compared with single nanosheets and the traditional vertical stacking (90° twist angle) configuration. This discovery breaks the traditional understanding that "vertical structure is beneficial to performance improvement", and pushes the chiral luminescence performance in this field to a new height.

[0032] 3. The clear guidance of "structure-performance" relationship is provided, and the mechanism is clear:

[0033] Through systematic angle-dependent research, the present application establishes the quantitative correspondence between the continuous structural change from "parallel (0° twist angle)" to "vertical (90° twist angle)" and the circularly polarized luminescence performance. This not only proves that the performance enhancement is due to the optimal electronic coupling and chiral transmission when stacked in parallel, but also provides a solid theoretical basis and practical blueprint for precisely designing the macroscopic optical performance through microstructure design in the future.

[0034] 4. It has excellent performance and good application prospect:

[0035] The present application integrates the breakthrough performance improvement (3 times enhancement) and the convenient continuous regulation ability. The physical rotation method adopted is highly compatible with existing micro-nano processing technology, and is easy to realize high-density integration and large-scale preparation of devices, which has great industrialization application potential in the fields of ultra-high-density optical storage, dynamic stereoscopic display, quantum information processing, etc. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Circularly polarized luminescence characteristics of chiral perovskite homojunctions of single nanosheets, vertical structures and parallel structures. Among them, Figure 1 Fig. (a) is a curve graph, Figure 1 Fig. (b) is a polarization degree (DCP) statistics.

[0037] Figure 2 Interface characteristics under different stacking configurations. Among them,Figure 2 Figure 9. AFM images and corresponding KPFM surface potential maps of individual nanosheets, vertical and parallel homojunctions. Figure 2 Figure 9. AFM images and corresponding KPFM surface potential maps of individual nanosheets, vertical and parallel homojunctions. Figure 2 Figure 9. AFM images and corresponding KPFM surface potential maps of individual nanosheets, vertical and parallel homojunctions. Figure 2 Figure 9. AFM images and corresponding KPFM surface potential maps of individual nanosheets, vertical and parallel homojunctions.

[0038] Figure 3 Figure 10. Optical dynamics of different stacking configurations. Wherein, Figure 3 Figure 10. Optical dynamics of different stacking configurations. Wherein, Figure 3 Figure 10. Optical dynamics of different stacking configurations. Wherein, Figure 3 Figure 10. Optical dynamics of different stacking configurations. Wherein, Figure 3 Figure 10. Optical dynamics of different stacking configurations. Wherein,

[0039] Figure 4 Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, Figure 4 Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, Figure 4 Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, Figure 4 Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, Figure 4 Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, Figure 4 Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, E b Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, E g Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, Figure 4 Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, E g Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, N f Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein, ν Figure 11. Exciton binding energy and electron-phonon coupling of different stacking configurations. Wherein,

[0040] Figure 5 Figure 12. Optical photos and degree of circular polarization (DCP) of R-type (top) and S-type (bottom) chiral perovskite semiconductor homojunctions with different twist angles.

[0041] Figure 6 Schematic diagram of a light emitting device measurement. DETAILED DESCRIPTION

[0042] To make the purpose, technical solutions and advantages of the present application more clear, the present application is described in detail below in combination with the drawings and specific examples. It should be noted that the degree of circular polarization (DCP) of the circularly polarized light of chiral materials is easily affected by factors such as the quality of material synthesis (different synthesis methods have different qualities), nanosheet thickness, and material type. Therefore, the DCP values of different chiral material nanosheets are not comparable. In the present application, the comparison of the degree of polarization is based on different regions of the same nanosheet. For example, a parallel stacked R-type homojunction layer region and a non-layer region (i.e., a single nanosheet) are compared.

[0043] Example 1: Preparation and performance of R-type homojunction with a 0° twist angle (parallel stacking)

[0044] 1. Preparation of chiral semiconductor single crystal bulk material:

[0045] The chiral perovskite semiconductor single crystal bulk material R-(C6H5C2H4NH3)2PbI4 (abbreviated as (R-MBA)2PbI4) used in this example was synthesized by solution crystallization method. The specific steps are as follows:

[0046] First, under the conditions of ice bath and strong magnetic stirring, (R)-(+)-α-methylbenzylamine (R-MBA) was neutralized with an excess of 57% hydroiodic acid (HI) aqueous solution, and the stirring was continued for 2 hours to prepare an R-MBAI precursor solution with a concentration of 2 mmol / mL. Subsequently, the precursor solution and lead oxide (PbO) powder were dissolved in a HI / H3PO2 (volume ratio 4:1) mixed aqueous solution system at a stoichiometric ratio of 2:1, and the solution was continuously stirred at 150°C until the reaction was complete. After stopping the stirring, the resulting yellow clear solution was naturally cooled to room temperature and left to stand overnight to allow the crystals to fully grow. Finally, the product was separated by suction filtration and completely dried in an oven to obtain the final product (R-MBA)2PbI4.

[0047] All the chemical raw materials used in this example were purchased from the National Pharmaceutical Chemical Reagent Group Co., Ltd. with a purity of 99.999%.

[0048] 2. Preparation of chiral semiconductor single crystal nanosheet:

[0049] The mechanical exfoliation method for preparing high-quality nanosheets from chiral perovskite single crystal bulk materials is as follows:

[0050] First, a clean dust-free paper or elastic polymer (such as polydimethylsiloxane, PDMS) substrate is used to make a controlled slight contact and rubbing with the surface of the (R-MBA)2PbI4 single crystal bulk. Through this process, a thin layer of atoms on the surface of the single crystal is mechanically peeled off from the bulk.

[0051] Subsequently, the substrate with the peeled material is gently pressed against the surface of the target substrate (a silicon wafer covered with 300 nm silicon oxide). By controlling the pressing force and time, the transfer of the peeled material to the target substrate can be achieved. The thickness of the peeled nanosheet selected in the present application is about 10 nm.

[0052] Finally, the transferred sample is annealed (for example, at a temperature of 80 °C for 10 minutes under inert gas protection) to remove the residual contaminants at the interface and enhance the adhesion between the nanosheet and the substrate, and finally obtain a (R-MBA)2PbI4 nanosheet with uniform thickness and clean surface.

[0053] 3. Stack preparation of R-type chiral perovskite homojunctions:

[0054] Two pieces of (R-MBA)2PbI4 nanosheets (10 nm thick) obtained by mechanical peeling are precisely stacked using a dry transfer technique to construct a homojunction structure. The specific steps are as follows:

[0055] (1) Preparation and positioning: First, two substrates with target (R-MBA)2PbI4 nanosheets (as transfer sheets) and a substrate to be stacked (as target sheets) are fixed in a dry transfer system equipped with a high-precision optical microscope and a micro manipulator. Through microscopic observation, the preselected nanosheet on the target sheet is precisely positioned at the center of the field of view.

[0056] (2) Polymer carrier pickup: A transfer stamp with a transparent elastomer (such as PDMS) is selected, and its three-dimensional movement is controlled by a micro manipulator. The stamp is slowly lowered until it makes reliable contact with the nanosheet as the "transfer sheet". Then, by controlling the vertical upward movement of the stamp, the nanosheet is peeled off from the original substrate by van der Waals force and firmly attached to the lower surface of the stamp.

[0057] (3) Precise alignment and stacking: Under real-time monitoring by the microscope, the micro manipulator is operated to precisely move and position the stamp with the "transfer sheet" above the "target sheet" above the target substrate. By fine adjustment of the lateral (X-Y) and vertical (Z) positions, the two nanosheets are ensured to reach the preset stacking angle (0° twist angle, i.e. parallel stacking, lattice parallel) and achieve edge or in-plane precise alignment.

[0058] (4) Slow contact and release: The stamp is controlled to descend vertically at a slow and controllable speed, so that the "transfer sheet" makes flat contact with the "target sheet" on the substrate. After applying slight and uniform pressure to ensure full adhesion, the elastomeric stamp is separated from the nanosheet by further reducing the stamp height or by using a "bouncing" release technique, thereby releasing the "transfer sheet" completely and stacking it on the "target sheet".

[0059] 4. Optical performance characterization:

[0060] The circularly polarized photoluminescence (CPPL) of this homojunction was measured at 80 K. Figure 1 As shown, its left-handedness (σ) - ) and right-handed (σ) + The difference in luminescence intensity is significant. Calculations show that the circularly polarized emission polarization degree of the homogeneous stacked region is 30%, while the polarization degree of the non-stacked region (individual nanosheets) is 10%. In other words, by stacking homogeneous structures with a 0° twist angle, DCP is improved by 3 times compared to individual nanosheets.

[0061] Example 2: Preparation and Properties of S-Type Homojunctions with 0° Twist Angle (Parallel Stacking)

[0062] The preparation of the S-type chiral semiconductor single crystal block material is the same as in Example 1, except that the chiral enantiomer is changed to S-type, as follows.

[0063] First, (S)-(+)-α-methylbenzylamine (S-MBA) was neutralized with an excess of 57% hydrogen iodide (HI) aqueous solution under ice bath and strong magnetic stirring conditions for 2 hours to obtain a 2 mmol / mL S-MBAI precursor solution. Subsequently, the precursor solution and lead oxide (PbO) powder were dissolved together in a 2:1 stoichiometric ratio in a mixed aqueous solution of HI / H3PO2 (volume ratio 4:1) and stirred continuously at a constant temperature of 150°C until the reaction was complete. After stirring was stopped, the resulting yellow clear solution was allowed to cool naturally to room temperature and stand overnight to allow the crystals to grow completely. Finally, the product was separated by vacuum filtration and thoroughly dried in an oven to obtain the final product (S-MBA)2PbI4.

[0064] The nanosheet preparation, heterojunction stacking, and optical performance characterization processes are the same as in Example 1.

[0065] The obtained performance was the same as in Example 1, namely, the polarization degree of circularly polarized emission was improved by 3 times compared to the single nanosheet. Figure 1 )

[0066] Example 3: Preparation and Properties of R-type Homojunctions with a 90° Twist Angle (Vertical Stacking)

[0067] The fabrication of the 90° twist angle (vertical stacking, lattice perpendicular) R-type homojunction is the same as in Example 1, except that the stacking angle is changed to 90° during the third step of homojunction stacking. The circularly polarized emission polarization degree of the stacked homojunction region is 10%, and the polarization degree of the non-stacked region (individual nanosheets) is also 10%. That is to say, through the stacking of homojunction structures with a 90° twist angle, the circularly polarized emission polarization degree is no different from that of individual nanosheets. Figure 1 ).

[0068] Example 4: Preparation and Properties of S-Type Homojunctions with a 90° Twist Angle (Vertical Stacking)

[0069] The fabrication of the 90° twist angle (vertical stacking) S-shaped homojunction was the same as in Example 1, except that the chiral enantiomer was changed to S-shape and the stacking angle was changed to 90° during the third step of homojunction stacking. The circularly polarized emission polarization degree of the homojunction stacked region was 10%, and the polarization degree of the non-stacked region (individual nanosheets) was also 10%. That is to say, through the stacking of homojunction structures with a 90° twist angle, the circularly polarized emission polarization degree did not change compared to individual nanosheets. Figure 1 ).

[0070] Example 5: Comparison of characterization and mechanism analysis of R-type homojunctions with 0° twist angle (vertical stacking) and 90° twist angle (vertical stacking)

[0071] The samples used for characterization and mechanism analysis in this embodiment are from Examples 1 and 3.

[0072] (1) Interface and dynamic analysis:

[0073] Charge transfer: KPFM measurements show ( Figure 2 (a) Figure 2 In (b), the surface potential of the parallel stacked regions is significantly lower than that of individual regions, revealing a strong interlayer charge transfer. First-principles calculations confirm that this structure is a II band arrangement (staggered type), meaning that the valence band top and conduction band bottom of the upper nanosheet are staggered with those of the lower nanosheet. Figure 2 In (c), the vertical contact exhibits nearly flat band alignment, while the parallel configuration shows a significant type II band shift. The conduction band to valence band shift in the parallel configuration is in the range of 15-50 meV, providing a driving force for charge transfer. The surface potential of the vertically stacked region is almost identical to that of the isolated region, indicating that interlayer charge transfer is negligible. Band calculations show that ( Figure 2 In the middle (c), the energy bands of this structure are almost flush, and there is no potential barrier to drive charge transfer.

[0074] Interlayer coupling: First-principles calculations show that the effective interlayer spacing of the vertically stacked structure is approximately 9.5 Å ( Figure 2Medium (d), larger than the 8.5 Å of the parallel stack, leading to weak interlayer coupling, which is consistent with the weak charge transfer and the enhanced polarization characteristics.

[0075] Carrier dynamics: Through the optical dynamics study of different structures, time-resolved PL (TRPL) tests show that the carrier lifetime of the parallel structure is significantly prolonged to ~ 1.06 ns, which is much longer than that of the isolated nanosheet (~ 0.72 ns) and the vertical structure (~ 0.70 ns), confirming the formation of a long-lifetime interlayer charge transfer state. Figure 3

[0076] Exciton behavior: Power-dependent PL measurements (PDP) show that the fitting index k of the parallel structure is ~ 0.78, which is higher than that of the isolated sheet (k ≈ 0.64-0.65), reflecting the enhancement of the exciton recombination channel. Figure 3

[0077] Exciton binding energy and electron-phonon coupling: Variable-temperature DCP fitting (PDP) confirms that the exciton binding energy of the parallel structure is significantly higher than that of the isolated and vertical structures (increased by 20-40 meV) (Medium (a)), photoluminescence (PL) integral intensity fitting (Medium (b)), and line width analysis (Medium (c)). Figure 4 Figure 4 Figure 4 E b Figure 4 E LO N f Figure 4 Figure 4

[0078] Example 6: R-type homojunctions with continuously variable twist angle

[0079] Stack preparation: We systematically prepared a series of R-type homojunctions with twist angles from 0° to 90° under the microscope of the dry transfer platform by precisely controlling the twist angle with a mechanical arm (optical photos are shown in FIG. 6a). Figure 5 The preparation method is the same as that in Example 1, except that the stack angle is continuously regulated.

[0080] Systematic verification: As shown in FIG. 6b, the polarization degree value monotonically increases as the twist angle decreases from 90° to 0° and reaches a peak at 0°. This fully proves that the twist angle is a continuous and effective control parameter for regulating chiral optical response, rather than a specific angle-specific phenomenon. Figure 5

[0081] ​​​​​​​​​​​​Example 7: S-type homojunction with continuously varied twist angle

[0082] Stack preparation: We systematically prepared a series of S homojunctions with twist angles from 0° to 90° under the microscope of the dry transfer platform by precisely controlling the twist angle with a mechanical arm (optical photos are shown in Figure 5 ). The preparation method is the same as Example 1, except that the stack angle is continuously regulated, and the chiral enantiomer is changed to S type.

[0083] Systematic verification: As shown in Figure 5 , the polarization degree value monotonically increases from 90° to 0° and reaches a peak at 0°. This fully proves that the twist angle is a continuous and effective control parameter for regulating chiral optical response, rather than a specific phenomenon at a specific angle. This method is not only effective for R type, but also effective for S type.

[0084] Example 8: Room temperature circularly polarized luminescence performance

[0085] Based on the 0° and 90° R-type homojunctions described in Example 1 and Example 3, as well as the individual nanosheets. The variable-temperature polarization degree value measurement (PL) Figure 4 indicates that due to the higher exciton binding energy and weaker electron-phonon coupling (PL Figure 4 , Figure 4 ), the polarization degree value of the parallel structure can remain similar to that of the individual or vertical structure at low temperature (80 K) when the temperature is raised to room temperature (300 K) (10%). The polarization degree values of the individual nanosheets and the vertical nanosheets are less than 1% at room temperature. This indicates that the parallel stack structure can better stabilize the spin polarization, allowing the device to maintain high performance over a wider temperature range and have practical application value.

[0086] This example directly utilizes the structures in Example 1 and Experimental Example 3, and utilizes the principle of photoluminescence to realize a demonstration of a circularly polarized luminescence device. The specific circularly polarized photoluminescence device is shown in the optical device measurement schematic diagram Figure 6 . Using the method of polarization detection, the homojunction is excited by linearly polarized light, and then a quarter-wave plate is rotated to measure the spectral lines of left-handed circularly polarized luminescence (σ - ) and right-handed circularly polarized luminescence (σ + ). The results are shown in Figure 1 .

[0087] Comparative example: individual chiral perovskite nanosheets

[0088] As a comparison, the polarization degree values of individual R-type or S-type nanosheets are low, only 10% at 80 K (PL Figure 4 , Figure 4Medium (a). Short carrier lifetime (~0.72 ns, Figure 3 Medium (c). Small exciton binding energy Figure 4 Medium (e). Strong electron-phonon coupling Figure 4 Medium (f). This contrasts the unique advantage and necessity of the present application in improving and tuning the circularly polarized emission performance by constructing small twist angles (especially 0° parallel stacking) homojunctions.

[0089] In summary, the present application has proven conclusively through a series of twist angle experiments that the circularly polarized emission performance of chiral perovskite homojunctions can be systematically and continuously enhanced by reducing the interlayer twist angle (especially achieving parallel stacking). The enhancement mechanism is due to stronger interlayer coupling induced by small twist angles, spin-selective charge transfer promoted by II band alignment, enhanced exciton binding energy, and suppressed electron-phonon scattering. The present application opens up new avenues for the development of high-performance, programmable chiral optoelectronic devices.

Claims

1. A chiral perovskite semiconductor circularly polarized light emission enhancement structure, characterized in that: The invention comprises two layers of chiral perovskite semiconductor nanosheets with the same chiral configuration. The nanosheets are stacked by in-plane rotation at a controllable twist angle θ to form a chiral perovskite homojunction. The twist angle θ is continuously adjustable in the range of 0°-90°. By changing the twist angle θ, the polarization degree of the circularly polarized emission of the structure can be continuously controlled. The chiral perovskite homojunction is a two-layer R-type or two-layer S-type enantiomer with the chemical formula (R-MBA)2PbI4 or (S-MBA)2PbI4, where MBA is C6H5C2H4NH3⁺. The chiral perovskite semiconductor nanosheets are prepared from a chiral perovskite single-crystal bulk material by mechanical exfoliation. The thickness of the exfoliated nanosheets is 10 nm.

2. The chiral perovskite semiconductor circularly polarized light emission enhancement structure according to claim 1, characterized in that: When the twist angle θ is 0°, i.e., in a parallel stacked structure, the polarization degree of circularly polarized emission reaches its maximum value. Compared with a single nanosheet and a homojunction with a vertically stacked structure, the polarization degree of circularly polarized emission is increased by 3 times.

3. The chiral perovskite semiconductor circularly polarized light emission enhancement structure according to claim 2, characterized in that: The parallel stacked structure has a type II band arrangement, and its conduction band or valence band level offset is 15-50 meV.

4. The chiral perovskite semiconductor circularly polarized light emission enhancement structure according to claim 2, characterized in that: The parallel stacked structure has enhanced exciton binding energy, which is 20-40 meV higher than that of a single nanosheet.

5. A circularly polarized light-emitting device, characterized in that: It includes the chiral perovskite semiconductor circularly polarized light emission enhancement structure as described in any one of claims 1-4.

6. The circularly polarized light-emitting device according to claim 5, characterized in that: The polarization degree of the circularly polarized emission of the device reaches its peak when the twist angle θ is 0°.

7. The application of the circularly polarized light-emitting device according to claim 5, characterized in that: The device is used in circularly polarized photodetectors, circularly polarized light displays, or circularly polarized lasers.

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