CN108807683A - A kind of multiplication type organic photodetector of wide spectrum response - Google Patents

Abstract

The invention discloses a multiplication type organic photodetector with wide spectral response, which comprises a substrate, a transparent conductive layer, an anode modification layer, a photosensitive layer, a hole blocking layer and a cathode layer which are sequentially stacked, wherein the photosensitive layer is composed of Prepared from a mixture of organic small molecule donor material (BODIPY) and organic small molecule acceptor material (PC ₆₁ BM or PC ₇₁ BM); BODIPY is an organic fluorescent dye with a high molar absorptivity and a wide absorption range , has obvious photoelectric response in the near-infrared light band, and realizes the function of wide spectral response of the photodetector; it also significantly improves the responsivity or external quantum efficiency to the detection of optical signals, and the EQE under forward bias can exceed 100 %, the maximum EQE has reached more than 350%; the device has a simple structure and manufacturing process, low cost, can be used for large-area preparation, and has great advantages in the field of organic photodetectors.

Description

A Multiplied Organic Photodetector with Broad Spectral Response

technical field

The invention belongs to the technical field of photoelectric materials, and in particular relates to a multiplication type organic photodetector with wide spectral response.

Background technique

A photodetector is a device that converts an optical signal into an electrical signal (current or voltage). After processing by a subsequent circuit system, the system can respond to the optical signal, and can also restore the electrical signal to an optical signal. According to the different response wavelength ranges of photodetectors, they can be divided into wide spectral response photodetectors and narrow spectral response photodetectors. Among them, photodetectors with wide spectral response have important applications in many aspects such as image sensing, remote control, and day and night surveillance.

According to the different types of photodetectors, two-terminal photodetectors can be divided into photodiodes and avalanche photodiodes. They are all photovoltaic devices, in which photodiodes have no internal gain, and the upper limit of their external quantum efficiency (EQE) is 100%, that is, there is no multiplication effect on the incident light signal; the avalanche photodiode can have a multiplication effect on the photogenerated carriers, so its external quantum efficiency can exceed 100%, but the avalanche photodiode is generally made of inorganic semiconductor materials. The manufacturing process is complicated, the cost is high, and the external bias voltage (100-200V) is high during operation, the dark current is large, and it needs to work in a low temperature environment, and there are many restrictive conditions.

Compared with inorganic photodetectors, organic photodetectors have the advantages of good flexibility, low manufacturing cost, large-scale preparation and wide range of material selection, but the response range of organic photodetectors is usually limited to the near-ultraviolet to visible light band. , there are not many reports on organic photodetectors with high responsivity in the near-infrared light. There is a certain energy level difference between the donor-acceptor material, and the detection of near-infrared light requires a small energy gap, and the decrease of the energy gap makes it difficult to obtain a material with a high degree of energy level matching with the acceptor material; the energy gap The reduction facilitates exciton recombination thereby reducing the carrier generation efficiency. In addition, there are few reports on organic photodetectors that have a multiplier effect on near-infrared light, and almost all photodetectors work under reverse bias (the anode is connected to negative voltage) and can work under forward bias. Moreover, there are no relevant reports on photodetectors with a multiplication effect.

Therefore, designing and fabricating an organic photodetector that can work under forward bias while having broad spectral response and multiplication effect will be an important supplement to the type of photodetection devices.

Contents of the invention

In view of the above existing problems, the present invention aims to provide an organic photodetector with a response range covering the ultraviolet-near-infrared light region, a wide spectral response and a multiplication effect. The preparation cost of the organic photodetector is low, the preparation process is simple, and the performance is excellent, it can be used for large-area preparation, and has a wide range of applications.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows: a multiplication type organic photodetector with wide spectral response, including a substrate, a transparent conductive layer, an anode modification layer, a photosensitive layer, and a hole blocking layer that are sequentially stacked. and the cathode layer, wherein the photosensitive layer is prepared from a mixture comprising an organic small molecule donor material (BODIPY) and an organic small molecule acceptor material (PC ₆₁ BM or PC ₇₁ BM), wherein the PC ₆₁ BM is C ₆₀ Derivatives, the PC ₇₁ BM is a derivative of C ₇₀ .

Further, the BODIPY material is selected from any of the following structures:

Further, the structure of PC ₆₁ BM is:

Further, the structure of PC ₇₁ BM is:

Further, the preparation material of the transparent electrode layer includes various high work function metals, ITO and graphene.

Further, the preparation material of the anode modification layer includes poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS) and molybdenum oxide (MO _{O 3} ).

Further, the preparation material of the hole blocking layer includes C ₆₀ , C ₇₀ , 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), Ca and Mg .

Further, the preparation material of the cathode layer includes low work function metals Al and Ag.

Further, the thickness of the transparent conductive layer is 100-150nm; the thickness of the anode modification layer is 30-50nm; the thickness of the photosensitive layer is 100-250nm; the thickness of the hole blocking layer is 3-10nm ; The thickness of the cathode layer is 80-150nm.

The beneficial effects of the present invention are: the device structure and manufacturing process of a multiplied organic photodetector with wide spectral response disclosed by the present invention are simple; The BODIPY organic fluorescent dye makes the detector have a photoelectric response in the near-infrared light band, realizing the function of wide spectral response; the photodetector has a multiplication effect on the incident light signal, and can significantly improve the responsivity and detection rate of the detection light signal; Low cost, can be used for large-area preparation; can be used to prepare flexible photodetectors, and has a wide range of applications.

Description of drawings

Fig. 1 is a structural composition schematic diagram of a multiplication type organic photodetector with wide spectral response of the present invention;

Fig. 2 is the normalized absorption spectrum curve figure of BODIPY-1 thin film in the photosensitive layer of organic photodetector prepared by the present invention;

Fig. 3 is the current-voltage curve diagram of the organic photodetector prepared by the present invention under dark state and illumination;

Fig. 4 is the graph of the relationship between the external quantum efficiency of the organic photodetector prepared by the present invention and the change of the wavelength of the incident light under the bias voltage of -5V;

Fig. 5 is a graph showing the relationship between the external quantum efficiency of the organic photodetector prepared in the present invention and the change of the wavelength of the incident light under the bias voltage of +4.2V.

Among them, 1-substrate, 2-transparent conductive layer, 3-anode modification layer, 4-photosensitive layer, 5-hole blocking layer, 6-cathode layer.

Detailed ways

In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

It should be noted that the described embodiments are only some preferred embodiments of the present invention. The present invention can be implemented in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to enable those skilled in the art to understand the disclosure content of the present invention more thoroughly and comprehensively. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts should be regarded as simple modifications of the present invention, and all are within the protection scope of the present invention.

Because the existing photodetectors based on inorganic semiconductor materials are basically photovoltaic, and the external quantum efficiency (EQE) does not exceed 100%, it is usually necessary to set a complex signal amplification circuit in the circuit in practical applications. However, avalanche photodiodes with photomultiplier effects are generally made of inorganic semiconductors. The manufacturing process is complicated, the cost is high, and the applied bias voltage is high during operation, and the dark current is large, so it needs to work in a low temperature environment. Although the photomultiplier tube has strong photoelectric response ability and large current gain, it has a significant amplification effect on optical signals, but its structure is complex and bulky, and it usually works at a very high voltage (the power supply voltage is generally above 1000V), which is not conducive to safety. operate.

Most of the photodetectors based on organic materials do not have the photomultiplication effect. Even if some literatures report multiplication photodetectors, their response range is limited to the visible light region. There are reports.

In this example, we use a class of BODIPY-1 material with near-infrared absorption and PC ₆₁ BM, an electron transport material commonly used in organic photovoltaic devices, to produce a photoelectric response in the ultraviolet to near-infrared region (300-900nm). An organic photodetector with a wide spectral response of capability, the photodetector has a multiplication effect at the same time, that is, the external quantum efficiency exceeds 100%, and the photodetector can also work under a forward bias voltage.

The specific structure of BODIPY-1 is:

The specific structure of PC ₆₁ BM is:

The specific preparation method of a multiplied organic photodetector with wide spectral response provided in the embodiment of the present invention is as follows:

(1) Preparation of the transparent conductive layer: first clean the substrate and dry it, then deposit ITO on the substrate by magnetron sputtering to form a transparent conductive layer, wherein the deposition thickness of the transparent conductive layer is 120nm;

(2) Treatment of the transparent conductive layer: Put the substrate deposited with the ITO transparent conductive layer into acetone and ethanol detergents for ultrasonic cleaning for 15 minutes, then put them in an oven, and heat them to 80°C to remove the detergents and ensure dryness , and then use ultraviolet ozone plasma to treat the formed ITO transparent conductive layer to remove organic impurities on the ITO surface, increase the viscosity of the ITO surface, and facilitate the formation of the subsequent anode modification layer;

(3) Preparation of the anode modification layer: the anode modification layer is a PEDOT:PSS film, which is coated on the transparent conductive layer by spin coating. The spin coating time is 60s. During the spin coating process, the rotation speed is 3000rpm, and finally the thickness 30nm film layer;

(4) Treatment of the anode modification layer: After the anode modification layer is spin-coated, put it into an oven with a temperature of 80°C and bake for 30 minutes to remove the solvent water in PEDOT:PSS to facilitate the formation of the photosensitive layer, and then cool it;

(5) Preparation of the photosensitive layer: First, dissolve BODIPY-1 and PC ₆₁ BM in the solvent 1,2-dichlorobenzene at a ratio of 3:10 to form a mixed solution, and then mix the formed solution by spin coating The solution is coated on the anode modification layer to form a film layer with a thickness of 200nm;

(6) Treatment of the photosensitive layer: put the material of the spin-coated photosensitive layer on a heating platform with a temperature of 80° C. and bake for 30 minutes to remove the solvent. This process is carried out in a glove box filled with nitrogen atmosphere;

(7) Preparation of hole blocking layer: TPBi is plated on the upper surface of the photosensitive layer by vacuum evaporation, wherein the hole blocking layer formed by TPBi has a thickness of 3nm;

(8) Preparation of cathode layer: Al was evaporated onto the upper surface of the hole blocking layer by vacuum evaporation to form a cathode layer with a thickness of 100 nm.

Performance Characterization Tests:

Referring to Figures 2 to 5, where Figure 2 is the normalized absorption spectrum curve of the BODIPY-1 film in the photosensitive layer, it can be seen from the figure that the material absorbs light from 300-900nm in the film state, Has a wide absorption range.

Fig. 3 is the graph of current-voltage relationship of the organic photodetector prepared in the present embodiment under dark state and illumination condition, as can be seen from the figure, the device has a lower dark current density and a higher photocurrent density, in The dark current and photocurrent density at -5V are 3.02×10 ^-4 A/cm ² and 3.02×10 ^-1 A/cm ² respectively; the dark current and photocurrent density at +5V are 1.40×10 ^-2 A/cm 2 ² and 1.40×10 ¹ A/cm ² . It shows that the dark current noise of the device is small and the photoresponse ability is strong.

Fig. 4 is the graph of the relationship between the external quantum efficiency of the organic photodetector prepared in this embodiment and the wavelength of the incident light. From the figure, it can be seen that the external quantum efficiency of the device does not exceed 100% under the reverse bias voltage, the highest It is also less than 50%, indicating that there is no doubling phenomenon. The curve of EQE as a function of wavelength has the same trend as the absorption spectrum of BODIPY-1.

Fig. 5 is a curve diagram of the relationship between the external quantum efficiency of the organic photodetector prepared in this embodiment and the change of the incident light wavelength under the bias voltage of +4.2V. It can be seen from the figure that under the bias voltage of +4.2V The detector prepared in this embodiment has an external quantum efficiency of more than 100% for near-infrared light, and a maximum external quantum efficiency of more than 350%, realizing the wide-spectrum response capability of the detector and having a photoelectric multiplication effect.

In the embodiment of the present invention, the organic photodetector is made of organic semiconductor material, and a large-area and low-cost organic detector can be prepared on a substrate of a variety of different materials. At the same time, when the substrate has a good When the function is flexible, it can be used to prepare flexible photodetectors, so that the application scenarios of the detector can be increased; at the same time, because the organic photodetector has a multiplication effect on the incident light signal, the device itself can amplify the light signal, so In practical application, it can simplify the circuit structure and reduce the complexity of the circuit system, which has great practical significance.

The basic principles, main features and advantages of the present invention have been shown and described above. However, the above descriptions are only specific examples of the present invention, and the technical features of the present invention are not limited thereto. Any other implementations that are obtained by those skilled in the art without departing from the technical solutions of the present invention should be included in this document. within the scope of the invention patent.

Claims (8)

1. A multiplying type organic photodetector of wide spectral response, it is characterized in that, comprises the substrate that stacks up successively, transparent conductive layer, anode modification layer, photosensitive layer, hole blocking layer and cathode layer, wherein, photosensitive layer is prepared _{from a mixture comprising BODIPY material and PC 61 BM, which is a derivative of C 60 , and} which is a derivative of C ₇₀ , or a mixture comprising _BODIPY material and PC ₇₁ BM. 2. the multiplying type organic photodetector of a kind of wide spectral response as claimed in claim 1, is characterized in that, described BODIPY material is selected from any one in following structure: 3. the multiplying type organic photodetector of a kind of wide spectral response as claimed in claim 2, is characterized in that, the structure of described PC ₆₁ BM is: The structure of the PC ₇₁ BM is: 4. The multiplying organic photodetector of a kind of broad spectral response as claimed in claim 3, is characterized in that, the preparation material of described transparent electrode layer comprises high work function metal, ITO and graphene. 5 . The multiplication type organic photodetector with wide spectral response according to claim 4 , wherein the preparation material of the anode modification layer comprises PEDOT:PSS and M _O O ₃ . 6 . The multiplication type organic photodetector with wide spectral response according to claim 5 , wherein the preparation material of the hole blocking layer comprises C ₆₀ , C ₇₀ , TPBi, Ca and Mg. 7. A multiplied organic photodetector with wide spectral response as claimed in claim 6, wherein the preparation material of the cathode layer comprises low work function metals Al and Ag. 8. The multiplying organic photodetector of a kind of wide spectral response as claimed in claim 7, it is characterized in that, the thickness of described transparent conductive layer is 100～150nm; The thickness of described anode modification layer is 30～50nm; The thickness of the photosensitive layer is 100-250nm; the thickness of the hole blocking layer is 3-10nm; the thickness of the cathode layer is 80-150nm.