A wide-spectrum circularly polarized light detector

Abstract

The present invention discloses a wide-spectrum circularly polarized light detector, which prepares a photosensitive charge transport layer by physically blending a chiral molecule and a conjugated polymer, so that the obtained device has a wide-spectrum chiral optical response, thereby enabling the differential detection of left-handed and right-handed circularly polarized light at multiple wavelengths. The circularly polarized light detector of the present invention can encrypt information, and has good electrical properties and optical response, and the manufacturing method is simple and the cost is low, having good application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of photodetectors, and particularly relates to the preparation of a wide-spectrum circularly polarized light detector. Background Art

[0002] Circularly polarized light plays an important role in many photon technologies, including tomography based on circularly polarized ellipsometers, optical communication and spin information, and quantum-based optical computing and information processing. In order to fully utilize the function of circularly polarized light in these fields, an integrated optoelectronic sensor capable of detecting circularly polarized light is essential. Traditional circularly polarized light detectors require a linear polarizer and a quarter-wave plate in front of the detector, and the measurement of circularly polarized light is achieved by rotating the linear polarizer or the quarter-wave plate. The single measurement of this device can only obtain the information of a single polarization state, and it is large in size and not easy to integrate and miniaturize. The optoelectronic detector based on chiral materials can directly detect circularly polarized light due to its inherent optical activity, without being coupled with a polarizer and a quarter-wave plate like traditional optoelectronic detectors, which is beneficial to miniaturization and integration.

[0003] Due to the advantages of adjustable spectral bandgap, easy solution processing, and molecular designability of chiral organic semiconductors themselves, they have become promising building blocks in circularly polarized light detectors. The chiral optical response of organic semiconductors requires the molecules to have a strong helical twisted structure, and this asymmetry of molecular packing will greatly reduce the charge transport characteristics of the semiconductor, thus limiting the application. Summary of the Invention

[0004] Based on the deficiencies of the above-mentioned prior art, the present invention provides a wide-spectrum circularly polarized light detector. By simply blending chiral molecules with an organic semiconductor, the intermolecular force formed between the two causes chiral transfer, thereby broadening the spectrum. At the same time, combining the excellent charge transport characteristics of the organic semiconductor and the chiral optical response of the chiral molecules, it is expected to achieve the differential detection of left-handed circularly polarized light and right-handed circularly polarized light at multiple wavelengths.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A wide-spectrum circularly polarized light detector, characterized in that: the circularly polarized light detector includes a substrate as a gate electrode, and a gate insulating layer, a modification layer, and a photosensitive charge transport layer sequentially disposed on the substrate, and a source electrode and a drain electrode are disposed on the photosensitive charge transport layer; the photosensitive charge transport layer is a physical blend layer of chiral molecules and a donor-acceptor (D-A) conjugated polymer.

[0007] Further, the chiral molecule is one of polythiophene-b-polyisocyanide conjugate polymer (P3HT-PPI), chiral polyacetylene, and chiral limonene; the donor-acceptor type conjugate polymer is one of poly(3,4-ethylenedioxythiophene)-pyrrolopyrrole dione (DPP-TT), or a random copolymer (CP) of azaisoindigo and bis(2-oxodihydro-7-azaindole-3-ylidene)benzodifuranedione. In the photosensitive charge transport layer, due to intermolecular forces such as intermolecular stacking and hydrogen bonding, the chiral signal that originally only existed in the chiral molecule is transferred, thereby broadening the spectrum and enabling the photosensitive charge transport layer to have chiral activity in the wavelength range of 200-800 nm. When the device is irradiated with left-handed and right-handed circularly polarized light in this wavelength band, since the drain current I DS values generated by the detector for light with different circular polarizations and different wavelengths are different, the detection of circularly polarized light with a wide spectrum can be achieved.

[0008] Further: the gate electrode is silicon, and the gate insulating layer is one of SiO 2 layer, Al 2 O 3 layer or polymethyl methacrylate (PMMA) layer, and the modification layer is at least one of octadecyltrichlorosilane, dodecanethiol, 1-decanethiol, octadecyldihydroxyethylamine oxide, and perfluoro(1-butenyl vinyl ether) polymer (CYTOP).

[0009] Further, the source electrode and the drain electrode are selected as Au electrodes.

[0010] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0011] 1. For the first time, the present invention realizes the transfer of chiral signals from chiral molecules to organic conjugate polymers through simple physical blending, so that the photosensitive charge transport layer has chiral activity in a wide wavelength range of 200-800 nm, and the prepared organic field effect transistor device can achieve the detection of circularly polarized light with a wide spectrum.

[0012] 2. The circularly polarized light detector of the present invention can encrypt information and has excellent stability.

[0013] 3. The circularly polarized light detector of the present invention has excellent light response performance and electrical performance, and the manufacturing method is simple and the cost is low, having good application prospects.

[0014] 4. The device structure of the present invention provides an important device physics and technical basis for realizing miniaturization, integration, and high-performance circular polarization detection. Description of the Drawings

[0015] Figure 1Schematic structural diagram of the circularly polarized light detector of the present invention. In the figure, reference numeral 1 is a substrate; 2 is a gate insulating layer; 3 is a modification layer; 4 is a photosensitive charge transport unit; 5 is a source electrode; 6 is a drain electrode.

[0016] Figure 2 Chemical structural formulas of two enantiomers, chiral polythiophene-b-polyisocyanide conjugated polymers P3HT-PPI(D) and P3HT-PPI(L), in Example 1 of the present invention;

[0017] Figure 3 Is a random copolymer (CP) of azaisoindigo and bis(2-oxodihydro-7-azaindole-3-ylidene)benzodifurandione ( Figure 3 (a)) and chemical structural formulas of two donor-acceptor (D-A) conjugated polymers, poly(thieno[3,2-b]thiophene)-pyrrolopyrrolidione (DPP-TT) ( Figure 3 (b));

[0018] Figure 4 Circular dichroism absorption spectra of chiral polythiophene-b-polyisocyanide conjugated polymers P3HT-PPI(D) and P3HT-PPI(L) in Example 1 of the present invention ( Figure 4 (a)) and circular dichroism absorption spectra of a blend film prepared from a random copolymer (CP) of azaisoindigo and bis(2-oxodihydro-7-azaindole-3-ylidene)benzodifurandione and chiral polythiophene-b-polyisocyanide conjugated polymers P3HT-PPI(D) and P3HT-PPI(L) at a volume ratio of (1:1) ( Figure 4 (b));

[0019] Figure 5 Curves of the drain current (I Figure 5 ) varying with the gate voltage (V Figure 5 ) when the circularly polarized light detector of the present invention in Example 1 is irradiated with right-handed and left-handed circularly polarized lights at 405 nm ( Figure 5 (a)), 532 nm ( DS )(b), 750 nm ( G )(c). In the figure, Dark is the dark current, RCPL is the right-handed circularly polarized light, and LCPL is the left-handed circularly polarized light;

[0020] Figure 6 For the circularly polarized light detector in Example 1 of the present invention, the change in the drain current (I D ) under the irradiation of right-handed and left-handed circularly polarized lights can achieve information encryption of Morse code. Detailed implementation manners

[0021] The embodiments of the present invention will be described in detail below. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0022] Embodiment 1

[0023] As Figure 1 shown, this embodiment provides a wide-spectrum circularly polarized light detector. A gate insulating layer 2 is provided on a substrate 1 serving as a gate electrode. A modification layer 3 is provided on the gate insulating layer 2. A photosensitive charge transport layer 4 is provided on the modification layer 3. A source electrode 5 and a drain electrode 6 are provided on the photosensitive charge transport layer 4. Specifically, in this embodiment: the material used for the photosensitive charge transport layer is a blend layer of CP and chiral P3HT-PPI; the substrate is Si, which also serves as the gate electrode of the device; the gate insulating layer is a 300-nm-thick SiO 2 layer; the modification layer is a CYTOP layer; the source electrode and the drain electrode are selected as Au electrodes, and the distance between the two is 100 μm. The circularly polarized detector device of this embodiment is fabricated according to the following method:

[0024] Take a silicon wafer with an SiO 2 layer on its surface. First, wash it with a mixed solution of 98% concentrated sulfuric acid and 30% hydrogen peroxide with a volume ratio of (70:30), then wash it with deionized water, and then dry it with a nitrogen gas stream. Spin-coat CYTOP on the surface of the SiO 2 layer as the modification layer. Dissolve CP and chiral P3HT-PPI in chloroform respectively, and the concentration of both is 3 mg / mL, and finally obtain a mixed solution with a volume ratio of 1:1. In the glove box, spin-coat the mixed solution on the substrate, continue for 40 s at a rotation speed of 3000 rpm, and then dry it in a vacuum oven without heating to remove the solvent. Subsequently, first thermally evaporate Au onto the photosensitive charge transport layer through a mask plate to form source and drain electrodes with a thickness of about 40 nm, where the length and width of the channel are 100 μm and 1000 μm respectively.

[0025] The photosensitive charge transport layer of this embodiment blends a non-chiral conjugated polymer with a chiral molecule. Due to the intermolecular stacking effect and the intermolecular hydrogen bond effect, the chiral signal existing in the chiral molecule is transferred to the non-chiral semiconductor polymer. As Figure 4 shown, the circular dichroism spectrum shows that the blend film has a chiral optical response in a wide wavelength range of 200 - 800 nm.

[0026] In the case of no light illumination, for the circularly polarized light detector device of this embodiment, by applying a certain voltage to the gate electrode, a conductive path is formed in the channel between the source and drain electrodes, and then a certain voltage is applied to the drain electrode to make the charge move directionally to form a current. When circularly polarized light irradiates the conductive channel between the source and drain electrodes, excitons will be generated, and the excitons will separate to form photo-generated electrons and holes. Carriers such as electrons and holes move directionally under the action of the electric field between the source electrode and the drain electrode, generating a photocurrent. Since the absorption coefficients of the photosensitive charge layer for left-handed and right-handed circularly polarized light are different, the number of photo-generated carriers generated is different, and the photocurrent gain is different. According to the magnitude of the drain electrode current value (I DS ), the left-handed and right-handed circularly polarized light can be distinguished. In addition, since the chiral optical response of the photosensitive charge transport layer covers a wide spectral range of 200-800 nm, the left-handed and right-handed circularly polarized light of different wavelengths irradiated on the circularly polarized light detector can be distinguished by different drain electrode current values (I DS ). As shown in Figure 5 , when the left-handed and right-handed circularly polarized light of wavelengths 405 nm, 532 nm, and 750 nm are irradiated on the circularly polarized light detector, the drain electrode current values (I DS ) generated by the device have obvious differences, and the handedness of the circularly polarized light can be judged by this.

[0027] The circularly polarized light detector of this embodiment can be used for information encryption by the different drain electrode current values (I DS ) generated under the irradiation of circularly polarized light of different handedness. As shown in Figure 6 , by using the different handedness of circularly polarized light, different magnitudes of drain current values are assigned. The smaller current value generated under the irradiation of right-handed circularly polarized light is assigned as a short dot signal "."; the larger current value generated under the irradiation of left-handed circularly polarized light is assigned as a long signal "-" that maintains for a certain time. This working method can realize the encryption and processing of information by simply regulating the handedness of circularly polarized light.

[0028] In summary, the present invention prepares a wide-spectrum circularly polarized light detector that is easy to miniaturize and integrate. The photosensitive charge transport layer of the circularly polarized light detector can be obtained by simply physically blending and spin-coating a semiconductor polymer and a chiral molecule, which not only has good chiral optical activity but also excellent charge transport performance. And information can be encrypted based on circularly polarized light of different handedness and wavelengths.

[0029] The above are only exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A broadband circularly polarized light detector, characterized in that: the circularly polarized light detector includes a substrate as a gate electrode, and a gate insulating layer, a modification layer, and a photosensitive charge transport layer sequentially disposed on the substrate, and a source electrode and a drain electrode are disposed on the photosensitive charge transport layer; the photosensitive charge transport layer is a physical blend layer of a chiral molecule and a donor-acceptor type conjugated polymer; in the photosensitive charge transport layer, the chiral signal that only exists in the chiral molecule itself is transferred due to intermolecular forces, thereby broadening the spectrum, so that the photosensitive charge transport layer has chiral activity in the wavelength range of 200-800 nm.

2. The circularly polarized light detector according to claim 1, characterized in that: the drain current values generated by the detector for lights with different polarization directions and different wavelengths are different, so that the detection of broadband circularly polarized light can be realized.

3. The circularly polarized light detector according to claim 1, characterized in that: The gate electrode is silicon, and the gate insulating layer is one of SiO 2 layer, Al 2 O 3 layer or a polymethyl methacrylate layer, and the modification layer is at least one of octadecyltrichlorosilane, dodecanethiol, 1-decanethiol, octadecyl dihydroxyethylamine oxide, and perfluoro(1-butenyl vinyl ether) polymer.

4. The circularly polarized light detector according to claim 1, characterized in that: the chiral molecule is one of polythiophene-b-polyisocyanide conjugate polymer, chiral polyacetylene, and chiral limonene; the donor-acceptor type conjugated polymer is one of poly(3,4-ethylenedioxythiophene)-pyrrolopyrrole dione, or a random copolymer of azaisoindigo and bis(2-oxodihydro-7-azaindole-3-ylidene)benzodifuran dione.

5. The circularly polarized light detector according to claim 1, characterized in that: the source electrode and the drain electrode are made of Au electrodes.

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