All-polymer organic photovoltaic devices based on a three-element assisted fractional solution deposition and a preparation method thereof

Abstract

The present application relates to a kind of ternary auxiliary-based step-by-step solution deposition all-polymer organic photovoltaic device and its preparation method, belong to organic photovoltaic device preparation technical field, the present application selects the all-polymer system of current photoelectric conversion efficiency higher as intrinsic system, wherein polymer donor material is PBDB-T-2F, polymer acceptor material is PY-IT.In addition, polymer acceptor PDI-2T is selected as the third component, to modify the exciton diffusion behavior in intrinsic acceptor material PY-IT.Ternary (1+2) auxiliary step-by-step solution deposition strategy uses the preparation method of the order of first depositing 1 donor (PBDB-T-2F) and then depositing 2 blend acceptor (PY-IT:PDI-2T) to sequentially film forming.The method not only realizes the adjustment effect of sequential deposition strategy in ideal vertical phase distribution form, but also successfully retains the regulation effect of ternary strategy on exciton diffusion behavior.

Description

TECHNICAL FIELD

[0001] The present application relates to the preparation and application of high-efficiency all-polymer system solar cell devices, in particular to an all-polymer organic photovoltaic device based on ternary auxiliary step-by-step solution deposition and a preparation method thereof, and belongs to the technical field of organic photovoltaic device preparation. BACKGROUND

[0002] Under the background of global energy structure transformation and low-carbon development consensus, organic solar cells have gradually become an important branch direction to promote clean and renewable energy and green environmental protection industry. Organic solar cells prepared based on solution processing method have many advantages such as lightness, flexibility, semi-transparency, wearability and roll-to-roll printing, which cannot be achieved by inorganic semiconductor photovoltaic cells. In recent years, the power conversion efficiency of organic photovoltaic devices based on small molecule acceptors has soared to more than 19%, but compared with the efficiency of about 26% of traditional silicon-based solar cells, there is still a certain gap. In addition, in terms of long-term running stability of devices, large-area device preparation for commercialization and cost control, organic photovoltaic cells still have much room for improvement compared with traditional crystalline silicon photovoltaic industry. Focusing on the unique properties of organic photovoltaic, taking organic semiconductor technology as its own advantage to promote the industrialization of organic photovoltaic, it has become a hot field to develop high-efficiency and stable all-polymer organic photovoltaic system in recent years. All-polymer solar cells are mainly composed of polymer donor and polymer acceptor materials, which have irreplaceable advantages in device thermal stability, bending stability, donor-acceptor ratio tolerance and device running life compared with small molecule-based organic photovoltaic cells, which benefits from the excellent mechanical flexibility and intrachain carrier transport properties of polymer materials. In the past three years, with the exploration and development of high-molecularization technology of small molecule acceptors, the efficiency of all-polymer solar cells has exceeded 15%. From the global research results published, the power conversion efficiency of all-polymer solar cells has certain room for improvement compared with small molecule-based organic solar cells, which comes from the non-ideal vertical composition distribution caused by the blending behavior of polymer donor and polymer acceptor in the active layer.

[0003] The vertical distribution of donor and acceptor components in the active layer can adjust the diffusion and dissociation of excitons, and the transport and extraction of carriers, which will further affect the comprehensive performance of the photovoltaic device. The ideal vertical distribution is that the donor material is more distributed in the anode region, and the acceptor material is more distributed in the cathode region, thereby forming a gradient of the ratio of donor to acceptor along the depth direction of the film. Binary solution step deposition refers to a preparation technique in which a pure donor or acceptor film is first deposited on a substrate during the preparation of the active layer, and then a pure acceptor or donor film is deposited. The advantage is that a good gradient of the ratio of donor to acceptor can be formed, but this will to some extent make the crystalline size of the donor and acceptor too large and too far apart, which is not conducive to the process of exciton dissociation and charge transfer. The ternary strategy refers to adding a third component which can be an acceptor or a donor to the binary donor-acceptor blended solution to optimize the diffusion of excitons and the kinetics of carriers, but it is difficult to achieve the ideal optimization effect on the vertical phase distribution of the main donor-acceptor components. The two optimization methods are currently commonly used technical means for optimizing high-efficiency organic solar cells, and the details of the regulation and physical mechanisms have been widely and deeply studied, but few people combine the two technical means to take the advantages of each other. SUMMARY

[0004] In view of the non-ideal vertical phase distribution in the current all-polymer solar cell, the application provides an all-polymer organic photovoltaic device based on ternary auxiliary step solution deposition and a preparation method thereof to solve the problem, and the method has simple operation process and certain universality.

[0005] The present application selects a full polymer system with higher photoelectric conversion efficiency as the intrinsic system, wherein the polymer donor material is PBDB-T-2F, and the polymer acceptor material is PY-IT. In addition, the polymer acceptor PDI-2T is selected as the third component to modify the exciton diffusion behavior in the intrinsic acceptor material PY-IT. The three-component (1+2) auxiliary step-by-step solution deposition strategy adopts the sequential deposition method of depositing 1 donor (PBDB-T-2F) first and then depositing 2 blended acceptors (PY-IT:PDI-2T) to form films in sequence. This method not only realizes the adjustment of the sequential deposition strategy in the ideal vertical phase distribution form, but also successfully retains the regulation of the exciton diffusion behavior of the three-component strategy. In order to illustrate the adjustment of the vertical phase distribution form by the strategy, the present application uses in-situ low-pressure oxygen plasma thin film etching technology to analyze and explain in detail. In addition, the study on the transient optical response of the device shows that the introduction of the third component improves the exciton diffusion length, ensures that more excitons diffuse to the donor-acceptor interface under ideal phase separation, and promotes the generation of more carriers. The organic photovoltaic device prepared by adopting the three-component auxiliary step-by-step solution deposition strategy balances the vertical charge transport performance and three-dimensional exciton diffusion behavior, not only solves the problem of non-ideal vertical phase distribution form caused by the thermodynamic behavior of solution film formation in the preparation process of the full polymer photovoltaic device, but also successfully overcomes the problem of insufficient exciton diffusion distance under ideal distribution form. On this basis, the three-component auxiliary step-by-step solution deposition method effectively realizes the effective improvement of the short-circuit current density J SC and power conversion efficiency PCE of the organic solar cell, the simple operation process is suitable for the commercial production of organic photovoltaic devices, and has good application prospect.

[0006] Term explanation:

[0007] 1, PBDB-T-2F is a polymer material, the molecular formula is poly[(2,6-(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene))-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylh-exyl)-benzo[1,2-c:4,5-c']dithiophene-4,8-dione, mainly as a donor material for organic solar cells.

[0008] 2、PY-IT, is a kind of polymer photovoltaic material, molecular formula is Poly[(2,2'-((2Z,2'Z)-((12,13-bis(2-octyldodecyl)-3,9-diundecyl-12,13-dihydro[1,2,5]thiadiazolo[3,4e]thieno[2″,3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]-indole-2,10-diyl)bis(methanylylidene))bis(5-methyl-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile-co-2,5-thiophene, mainly as acceptor material of organic solar cell.

[0009] 3、PDI-2T, is a kind of polymer photovoltaic material, molecular formula is Poly[[1,2,3,8,9,10-hexahydro-2,9-bis(1-nonyldecyl)-1,3,8,10-tetraoxoanthra[2,1,9-def:6,5,10-d′e′f′]diisoquinoline-5,12-diyl][2,2′-bithiophe-ne]-5,5′-diyl], mainly as acceptor material of organic solar cell.

[0010] 4、PDINN, is a kind of polymer photovoltaic material, Aliphatic amine-functionalized Perylene-diimide, mainly as electron transport layer material of organic solar cell.

[0011] 5、PEDOT:PSS, is a kind of polymer photovoltaic material, molecular formula is Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate), mainly as hole transport layer material of organic solar cell.

[0012] The technical scheme of the present application is as follows:

[0013] A kind of ternary auxiliary based on step-by-step solution deposition all-polymer organic photovoltaic device, including glass substrate, transparent conductive film (anode) from bottom to top, hole transport layer, organic active layer, electron transport layer, top electrode (cathode), the active layer includes one polymer donor material and two polymer acceptor materials.Ternary auxiliary sequential solution deposition method is the preparation process of active layer in the device structure.Anode and cathode are two metal electrodes of battery structure, also known as positive and negative electrode.Except active layer, other layers are consistent with the preparation process in current conventional machine solar cell.

[0014] According to the application, preferably, the polymer donor material is PBDB-T-2F, the polymer acceptor material is PY-IT, and another polymer acceptor material is PDI-2T as the third component.

[0015] Based on the ternary auxiliary step-by-step solution deposition active layer preparation technology, the organic photovoltaic device is prepared using the polymer material: using step-by-step solution deposition method, PBDB-T-2F solution is first spin-coated and deposited into a film, then PY-IT and PDI-2T blended solution is spin-coated and deposited into a film on the PBDB-T-2F film, to obtain the organic photovoltaic device.

[0016] In the traditional binary all-polymer system (PBDB-T-2F:PY-IT) with non-ideal molecular configuration, the donor and acceptor components are relatively uniformly distributed inside the active layer, without obvious donor-rich and acceptor-rich regions. The device prepared by the ternary-assisted step-by-step solution deposition method has an ideal vertical component distribution pattern, i.e., the acceptor material is more distributed near the cathode to form an acceptor-rich region near the cathode, and the donor material is more distributed near the anode to form a donor-rich region near the anode. The ideal vertical phase distribution pattern forms an ideal charge transport channel, realizing more ideal carrier transport behavior in the active layer. According to the present application, the device prepared by the ternary-assisted step-by-step solution deposition method not only has an ideal vertical component distribution pattern, but also in the PY-IT:PDI-2T mixed acceptor phase, the exciton diffusion length (16 nm) is extended by 3-4 nm compared with the PY-IT pure phase, which fully ensures that more photo-generated excitons can diffuse to the dissociation interface under this vertical component distribution pattern, effectively improving the number density of photo-generated carriers in the active layer. This preparation process not only increases the yield of photo-generated carriers, but also suppresses the distribution of defect states in the active layer, weakening the current loss caused by trap-assisted recombination. In addition, the donor-rich region near the anode forms a good hole transport channel, and the acceptor-rich region near the cathode forms a good electron transport channel, which is beneficial to the extraction of photo-generated carriers by the electrode, thereby improving the photo-generated current of the all-polymer system. The device test results show that the ternary-assisted step-by-step solution deposition method improves the short-circuit current density of the all-polymer solar cell to 23.97 mA cm -2 , and improves the open-circuit voltage to 0.949 V, and the photoelectric conversion efficiency is also effectively broken through, which is improved to 16.03%.

[0017] According to the present application, the thickness of the organic active layer is 100 nm. Under standard sunlight illumination environment, the thickness of 100 nm of the organic active layer is an ideal value, which neither too thin to fully absorb photons, nor too thick to cause device performance decline due to limited point and transport ability. The mass ratio of PBDB-T-2F:PY-IT:PDI-2T in the ternary solution step-by-step spin-coated all-polymer device is 1.00:1.00:0.03, and the device parameters are not ideal under other ratios. Under the most preferred active layer thickness and component ratio, the photoelectric conversion efficiency of the organic solar cell device reaches the best.

[0018] According to the application, preferably, the glass substrate with ITO transparent conductive film is a transparent conductive substrate, the thickness of the ITO transparent conductive film is 130 nm, the hole transport layer material is PEDOT:PSS, the thickness is 30 nm, the electron transport layer material is PDINN, the thickness is 5 nm, and the top electrode material is aluminum (Al), the thickness is 100 nm.

[0019] The preparation method of the above-mentioned organic solar cell structure comprises the following steps:

[0020] (1) cleaning the transparent conductive substrate, wherein the transparent conductive substrate is a glass substrate with ITO transparent conductive film;

[0021] (2) preparing a hole transport layer PEDOT:PSS thin film on the transparent conductive substrate obtained in step (1) by using a conventional preparation method;

[0022] (3) preparing an organic active layer thin film, comprising:

[0023] a. respectively weighing 10 mg of PBDB-T-2F, 15 mg of PY-IT and 0.15-75 mg of PDI-2T by using a high-precision electronic analytical balance, then adding 0.5-2 mL of high-purity chloroform solvent (AR>99%) to the weighed PBDB-T-2F, and adding 0.5-3 mL of high-purity chloroform solvent (AR>99%) to the blended PY-IT and PDI-2T, and placing them on a magnetic stirrer that can be heated, and stirring at 30-50°C for 2-5 h to obtain a pure PBDB-T-2F solution with a concentration of 5-20 mg / mL, and a PDI-2T:PY-IT blended solution;

[0024] b. adding 1%vol of chloronaphthalene additive to the above-mentioned PDI-2T:PY-IT blended solution by using a high-precision pipette, and continuing to stir for 30 min to obtain a mixed acceptor solution with a PDI-2T:PY-IT mass ratio of 1:0.01 to 1:0.05;

[0025] c. spin-coating the PBDB-T-2F solution prepared in step a on the substrate with hole transport layer obtained in step (2) in an inert gas (N2) glove box, waiting for 30 s, then spin-coating the PDI-2T:PY-IT blended solution prepared in step b on the PBDB-T-2F thin film, and annealing the obtained active layer material-coated thin film in inert gas for 5-10 min;

[0026] (4) depositing an electron transport layer PDINN thin film on the organic active layer;

[0027] (5) evaporating the metal electrode material on the electron transport layer.

[0028] Most preferably, in the step (3)a, 1 mL of high-purity chloroform solvent (AR > 99%) is added to the weighed PBDB-T-2F, which is placed on a magnetic stirrer that can be heated, and stirred at 40°C for 2.5 h to obtain a pure PBDB-T-2F solution with a concentration of 10 mg / mL; 0.45 mg of PDI-2T and 1.5 mL of high-purity chloroform solvent (AR > 99%) are added to the weighed PY-IT, which is placed on a magnetic stirrer that can be heated, and stirred at 40°C for 2.5 h to obtain a donor solution with a concentration of 10.3 mg / mL, and the mass ratio of PY-IT:PDI-2T in the obtained blended solution is 1:0.03. Under the solution concentration and the corresponding stirring temperature, each component can be fully dissolved in the chloroform solvent.

[0029] According to the present application, preferably, in the step (3)c, the spin-coating speed of the active layer solution is: the spin-coating speed of PBDB-T-2F is 2500-3500 rpm, and the spin-coating speed of the PY-IT:PDI-2T blended solution is 2500-3500 rpm. The thickness of the obtained PBDB-T-2F layer is 40-60 nm, and the thickness of the obtained PY-IT:PDI-2T layer is 40-60 nm.

[0030] Further preferably, in the step (3)c, the spin-coating speed of PBDB-T-2F is 3000 rpm, and the spin-coating speed of the PY-IT:PDI-2T blended solution is 3000 rpm. The thickness of the obtained PBDB-T-2F layer is 45 nm, and the thickness of the obtained PY-IT:PDI-2T layer is 55 nm. In the device with the above-mentioned size of the donor layer, not only can the ideal vertical phase distribution of the donor and acceptor components be achieved, but also the active layer can fully absorb sunlight, while avoiding the loss of recombination current and voltage caused by excessive thickness. The annealing temperature of the active layer is 100°C, and the annealing time is 10 min. The annealing temperature can volatilize the residual solvent in the active layer film and improve the crystallinity of each phase of the donor and acceptor, thereby improving the transport capacity of the carriers. At the same time, the annealing process can also form good mutual penetration between the donor film and the acceptor film in the step (3)c, which is conducive to the formation of good vertical phase distribution and carrier transport channels.

[0031] The ternary auxiliary step-by-step solution deposition active layer preparation technology has the advantages that it breaks through the problem in the traditional binary solution step-by-step deposition technology that part of the photo-generated excitons cannot reach the donor-acceptor interface for separation when the donor and acceptor phases are excessively separated. In addition, the introduction of a small amount of the third component extends the diffusion distance of the photo-generated excitons, effectively ensures the photo-generated charge density, and does not have a negative impact on the vertical component distribution form of the donor and acceptor in the step-by-step deposition.

[0032] Most of the existing ternary component solutions are to blend three materials into a 1 donor + 2 acceptor or 2 donor + 1 acceptor blended solution to prepare a body heterojunction active layer structure by one-step spin coating. This preparation method is not conducive to forming an ideal vertical component distribution structure in a full polymer system. The ternary auxiliary step-by-step spin coating scheme described in the present application is different from the above scheme in that the donor solution and the acceptor solution are spin-coated layer by layer to form a film. The advantage of this scheme is that an ideal donor-acceptor vertical component distribution can be formed inside the active layer thin film, that is, a good donor-rich region and an acceptor-rich region are formed.

[0033] In addition, small molecules or fullerene materials are small in size, and their vertical distribution mode is easy to regulate when blended with polymers. Compared with the system composed of polymer donors and small molecule or fullerene acceptors, the present scheme is directed to a full polymer system which is more difficult to regulate, that is, all the donor and acceptor materials in the active layer are high molecular polymers. High molecular polymers have long chain structures and non-planar molecular shapes, which make the blending behavior of polymer donors and polymer acceptors more complex when blended, and the vertical component distribution is solidified during the solvent evaporation and annealing process. These factors make it difficult to regulate the vertical phase distribution in the thin film prepared by one-step spin coating.

[0034] The present application has the following advantages:

[0035] Compared with the current traditional pure donor and acceptor solution step-by-step deposition strategy, the present application introduces a third component into the acceptor component, realizing a ternary auxiliary distribution deposition technology. This technology has the following advantages: (1) it retains the relatively ideal vertical phase distribution form in the traditional binary solution step-by-step deposition technology, which includes a donor-rich region near the anode and an acceptor-rich region near the cathode, forming corresponding hole and electron transport channels, and realizing efficient transport and collection of photo-generated carriers in the active layer; (2) compared with the traditional binary solution step-by-step deposition strategy, the introduction of the third component effectively improves the diffusion behavior of photo-generated excitons, which ensures that more photo-generated excitons in the active layer diffuse to the donor-acceptor interface for dissociation under the ideal component distribution form, breaking the limitation of the balance relationship between exciton diffusion length and phase separation scale in the traditional binary solution step-by-step deposition strategy; (3) the device prepared by the ternary auxiliary solution step-by-step deposition method has a more efficient photoelectric conversion efficiency, and the photoelectric conversion efficiency can be broken through to more than 16% using the present application. This technology is based on the solution step-by-step deposition strategy and the ternary strategy, and has strong universality, opening up a new way for the future industrialization process of organic photovoltaics. (4) The preparation process proposed in the present scheme is simpler, greatly reducing the time and resource consumption of the preparation process. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1Schematic diagram of ternary auxiliary step-by-step solution deposition method for preparing active layer of organic solar cell in the present application;

[0037] Figure 2a In-situ tomographic absorption spectrum of active layer of organic solar cell prepared by ternary auxiliary step-by-step solution deposition method of Comparative Example 1;

[0038] Figure 2b Distribution of donor and acceptor components along the vertical direction of the film calculated according to the in-situ tomographic absorption spectrum of Example 2;

[0039] Figure 2c In-situ tomographic absorption spectrum of active layer of organic solar cell prepared by ternary blend solution one-step solution deposition method of Comparative Example 1;

[0040] Figure 2d Distribution of donor and acceptor components along the vertical direction of the film calculated according to the in-situ tomographic absorption spectrum of Example 2;

[0041] Figure 3a Schematic diagram of vertical component distribution of active layer of organic photovoltaic device prepared by traditional one-step solution deposition method;

[0042] Figure 3b Schematic diagram of vertical component distribution of active layer of organic photovoltaic device prepared by ternary auxiliary step-by-step solution deposition method of the present application;

[0043] Figure 4 Atomic force microscope height picture of surface of organic photosensitive active layer prepared by ternary auxiliary sequential solution deposition method in the present application;

[0044] Figure 5a Transient absorption response curve of pure acceptor phase (PY-IT) under high and low excitation light power density;

[0045] Figure 5b Transient absorption response curve of mixed acceptor phase (PY-IT:PDI-2T) under high and low excitation light power density. DETAILED DESCRIPTION

[0046] The present application is further described below by way of examples and with reference to the accompanying drawings, but is not limited thereto.

[0047] Example 1:

[0048] A full-polymer organic photovoltaic device based on ternary auxiliary step-by-step solution deposition, from bottom to top, is glass substrate, transparent conductive film (anode), hole transport layer, organic photosensitive active layer, electron transport layer, top metal electrode (cathode), as shown in Figure 1As shown, the preparation method of the organic photoactive layer is a ternary auxiliary step-by-step solution deposition method. The organic photoactive layer comprises a high molecular polymer donor and a high molecular polymer acceptor.

[0049] The transparent conductive substrate is a glass substrate with an ITO transparent conductive film, wherein the thickness of the ITO is 130 nm, and the square resistance is less than 15 Ωcm. -2 The hole transport layer is a high molecular polymer PEDOT:PSS, the thickness is 30 nm, the electron transport layer is PDINN, the thickness is 5 nm, and the top metal electrode is aluminum (Al), the thickness is 100 nm.

[0050] The high molecular polymer donor is PBDB-T-2F, and the high molecular polymer acceptor is PY-IT and PDI-2T. The ternary auxiliary distributed solution deposition strategy is a preparation strategy of the organic photoactive layer, and the preparation process comprises the following steps: a, forming a donor material film on the hole transport layer by spin coating a PBDB-T-2F solution, the thickness is 45 nm; b, forming an acceptor material film on the donor film by spin coating a PY-IT:PDI-2T mixed solution, the thickness is 55 nm. The total thickness of the organic photoactive layer is 100 nm.

[0051] The mass ratio of the two polymer materials in the PY-IT:PDI-2T mixed solution is 1:0.03, and the mass ratio of PBDB-T-2F:PY-IT:PDI-2T in the ternary solution step-by-step spin coating prepared all-polymer device is 1:1:0.03.

[0052] The ternary auxiliary step-by-step solution deposition strategy is used in the preparation of the organic photoactive layer, which forms a relatively ideal vertical component distribution of the donor and the acceptor, solves the problem that the device photoelectric conversion efficiency is limited due to the insufficient exciton diffusion length when the phase separation scale is too large, and provides a new idea for the industrialization process of the future organic photovoltaic field.

[0053] Example 2

[0054] A method for preparing the all-polymer organic photovoltaic device based on the ternary auxiliary step-by-step solution deposition described in Example 1, comprising the following steps:

[0055] (1) Cleaning the transparent conductive substrate: the transparent conductive substrate (i.e. the glass substrate with an ITO transparent conductive film) is sequentially cleaned with a detergent, deionized water, acetone, anhydrous ethanol and isopropanol in an ultrasonic machine for 20 min, and then dried with high-purity nitrogen gas (> 99%); the dried transparent conductive substrate is placed in an ultraviolet irradiation machine and irradiated with ultraviolet light for 15 min.

[0056] (2) Preparation of hole transport layer: in the air, using a spin coater, spin-coat a layer of hole transport layer material PEDOT:PSS with a thickness of 30 nm on a transparent conductive substrate treated with ultraviolet light, and then place the substrate with the spin-coated hole transport layer material on an annealing table at 150°C for 15 min; wherein the PEDOT:PSS is purchased from Xi'an Baolai Technology Co., Ltd., and before use, dilute the PEDOT:PSS with ultrapure water at a ratio of 1:1 and place it on a magnetic stirrer at 30°C for stirring for 30 min;

[0057] (3) Preparation of organic photoactive layer: dissolve pure PBDB-T-2F and the blend of PY-IT:PDI-2T in high-purity chloroform solvent (AR > 99%, concentration 5-10 mg mL -1 ) and dissolve the blend of PY-IT:PDI-2T in high-purity chloroform solvent (AR > 99%, wherein the concentration of PY-IT is 5-10 mg mL -1 , and the mass ratio of PDI-2T to PY-IT is 3% wt), and place the preliminarily prepared solution on a magnetic stirring heating table, stir at 40°C for 2.5 h to obtain a fully dissolved solution; spin-coat the PBDB-T-2F solution on the substrate annealed in step (2) in an inert gas nitrogen glove box, and after a solvent evaporation process of 30 s, an unstable crystalline PBDB-T-2F film is formed on the substrate, and then spin-coat the blend solution of PY-IT:PDI-2T on the PBDB-T-2F film, and place the substrate with the spin-coated active layer on an annealing table at 100°C for 10 min and then remove it;

[0058] (4) Preparation of electron transport layer: dissolve PDINN in high-purity methanol solvent (AR > 99%, concentration 1.5 mg mL -1 ), and place the preliminarily prepared PDINN solution on a magnetic stirring table, stir at room temperature for 5 h to obtain a fully dissolved PDINN solution; use a spin coater to spin-coat the fully dissolved PDINN solution on the organic photoactive layer annealed in step (3);

[0059] (5) Preparation of metal electrode: move the substrate with the hole transport layer / organic photoactive layer / electron transport layer obtained in step (4) into a physical vapor deposition chamber, start the vacuum system, and when the pressure in the chamber drops to 2.5 x 10 -4 Pa, heat the aluminum target to prepare an Al electrode on the substrate with a thickness of 100 nm.

[0060] The detailed steps for preparing the organic photoactive layer in step (3) above are as follows:

[0061] A. High-precision electronic balance (weighing range 0.02-30mg) was used to weigh the high molecular polymer, wherein 10.0mg of the high molecular polymer donor (Solarmer, >99%) PBDB-T-2F was weighed into a No. 1 glass sample bottle, and the high molecular polymer acceptor (Solarmer, >99%) was weighed according to the proportion of PY-IT 15mg, PDI-2T 0.45mg, and placed into a No. 2 glass sample bottle, obtaining a mass ratio of PY-IT:PDI-2T in the No. 2 sample bottle of 1:0.03;

[0062] B. The glass sample bottle in step A was placed in a nitrogen-protected glove box, 1mL of high-purity chloroform solvent (Sigma Aldrich, AR>99%) was added to the No. 1 sample bottle under a nitrogen atmosphere, and placed on a magnetic heating stirrer to heat and stir at a temperature of 40℃ for 2.5h, obtaining a fully dissolved high molecular donor solution with a concentration of 10mg mL -1 ;

[0063] C. Under a nitrogen atmosphere, 1.5mL of high-purity chloroform solvent (Sigma Aldrich, AR>99%) was added to the No. 2 sample bottle, and placed on a magnetic heating stirrer to heat and stir at a temperature of 40℃ for 2.5h, obtaining a fully dissolved high molecular acceptor solution with a total concentration of 10.3mg mL -1 , wherein the concentration of PY-IT is 10mg mL -1 , and the concentration of PDI-2T is 0.3mg mL -1 ;

[0064] D. Under a nitrogen atmosphere, 1%vol of chloronaphthalene additive (Sigma Aldrich, >99%) was added to the No. 2 acceptor solution sample bottle obtained in step C, and continued to stir for 30min before being used for spin coating to prepare the active layer;

[0065] E. Under a nitrogen atmosphere, the donor solution prepared in step B in the No. 1 sample bottle was spin coated on the PEDOT:PSS hole transport layer using a spin coater, as shown in Figure 1 , the speed was 3000rpm, and an organic donor layer with a thickness of 45nm was obtained;

[0066] F. Under a nitrogen atmosphere, the acceptor solution prepared in step D in the No. 2 sample bottle was spin coated on the organic donor layer prepared in step E using a spin coater, as shown in Figure 1 , the speed was 3000rpm, and a PY-IT:PDI-2T organic acceptor layer was obtained on the organic donor layer, and the total thickness of the organic photosensitive active layer was 100nm;

[0067] G. The substrate with the organic photoactive layer attached obtained in step F was placed on an electrically heated annealing table under a nitrogen atmosphere and annealed at 100°C for 10 minutes;

[0068] In the conventional step-by-step solution deposition strategy for preparing the organic photoactive layer, orthogonal solvents are generally used, i.e. the solvent used for the second layer solution has no or only poor solubility for the first layer organic thin film. In the ternary-assisted step-by-step solution deposition method described in the present application, the same solvent is selected, and this strategy combined with the thermal annealing process can realize the formation of a bicontinuous interpenetrating network between the donor and acceptor in the organic photoactive layer, which is conducive to the formation of suitable donor-rich and acceptor-rich regions.

[0069] Example 3

[0070] A method for preparing the all-polymer organic photovoltaic device based on ternary-assisted step-by-step solution deposition described in Example 1, the steps are as described in Example 2, except that in steps (3) B, C, stirring is performed on a heatable magnetic stirrer at 30°C for 5h.

[0071] Example 4

[0072] A method for preparing the all-polymer organic photovoltaic device based on ternary-assisted step-by-step solution deposition described in Example 1, the steps are as described in Example 2, except that in steps (3) B, C, stirring is performed on a heatable magnetic stirrer at 50°C for 2h.

[0073] Example 5

[0074] A method for preparing the all-polymer organic photovoltaic device based on ternary-assisted step-by-step solution deposition described in Example 1, the steps are as described in Example 2, except that in steps (3) E, F, the spin coating speed of PBDB-T-2F is 2500 rpm, and the spin coating speed of the PY-IT:PDI-2T blended solution is 2500 rpm. The thickness of the obtained PBDB-T-2F layer is 40 nm, and the thickness of the obtained PY-IT:PDI-2T layer is 60 nm.

[0075] Example 6

[0076] A method for preparing the all-polymer organic photovoltaic device based on ternary-assisted step-by-step solution deposition described in Example 1, the steps are as described in Example 2, except that in steps (3) E, F, the spin coating speed of PBDB-T-2F is 3500 rpm, and the spin coating speed of the PY-IT:PDI-2T blended solution is 3500 rpm. The thickness of the obtained PBDB-T-2F layer is 60 nm, and the thickness of the obtained PY-IT:PDI-2T layer is 40 nm.

[0077] Experimental Example

[0078] An organic photovoltaic device was prepared according to the device structure described in Example 1 and the operating steps of the ternary assisted step-by-step solution deposition strategy described in Example 2. The prepared organic photovoltaic device was tested under the illumination of AAA solar simulator. The spectral distribution of the solar simulator is AM1.5G, and the illumination intensity is calibrated to 100 mW cm -2 .

[0079] Comparative Example 1

[0080] An organic solar cell was prepared according to the ternary assisted step-by-step solution deposition strategy described in Example 2, with the difference that:

[0081] Step (5) was not performed. The device structure obtained from top to bottom is: electron transport layer (PDINN, 5 nm), all-polymer photosensitive active layer (100 nm), hole transport layer (PEDOT:PSS, 30 nm), ITO (130 nm), glass substrate.

[0082] An organic solar cell was prepared according to the ternary assisted step-by-step solution deposition strategy described in Example 2, with the difference that:

[0083] In step (3), a ternary active layer was prepared by one-step solution spin coating: high-precision electronic balance was used to weigh the polymers, and PBDB-T-2F 14 mg, PY-IT 14 mg, and PDI-2T 0.42 mg (Solarmer, >99%) were weighed according to the proportion; the weighed polymers constitute a ternary system of PBDB-T-2F:PY-IT:PDI-2T; the weighed polymers were poured into a sample bottle, and 2 mL of high-purity chloroform solvent was added to the sample bottle under the atmosphere of a nitrogen glove box. The sample bottle was placed on a magnetic heating stirrer and heated and stirred at a temperature of 40°C for 2.5 h to obtain a fully dissolved solution. Under a nitrogen atmosphere, 1% vol of chloronaphthalene additive was added to the active layer solution, and the solution was continuously stirred for 30 minutes before being used for spin coating to prepare the active layer. Under a nitrogen atmosphere, the prepared active layer solution was spin coated on the hole transport layer using a spin coater at a speed of 3000 rpm to obtain a bulk heterojunction organic active layer with a thickness of 100 nm. Step (5) was not performed. The device structure obtained from top to bottom is: electron transport layer (PDINN, 5 nm), all-polymer photosensitive active layer (prepared by one-step solution deposition, 100 nm), hole transport layer (PEDOT:PSS, 30 nm), ITO (130 nm), glass substrate.

[0084] Under the action of low-pressure oxygen plasma etching, the organic materials of the above device were etched layer by layer, thereby obtaining the absorption spectrum of each layer of material, such as Figure 2a andFigure 2c As shown in Figure 2a and Figure 2c , the etching direction is from top to bottom, and the absorption peak of the electron transport layer PDINN is observed in the uppermost layer. Then the film absorption curve corresponding to the depth position in the active layer is obtained according to the etching time, and the relative content distribution of the donor and acceptor at the position is obtained according to the relative intensity of the absorption peaks of the donor and acceptor materials in the absorption spectrum. As shown in Figure 2b , Figure 2d , the ternary auxiliary step-by-step solution deposition strategy prepared organic solar cell has a 50 nm thick acceptor material enrichment zone at a position of 0 nm (cathode) and a 50 nm thick donor material enrichment zone near 100 nm (anode), and the donor and acceptor enrichment zones are more enriched than the corresponding regions in the ternary active layer prepared by one-step solution spin coating. As shown in Figure 3a Figure 3b , the comparison schematic diagram Figure 3a , Figure 3b , it can be seen that the vertical phase distribution of the donor and acceptor materials in the organic photoactive layer obtained by the step-by-step solution deposition method is more ideal. The acceptor material is more distributed near the cathode to form a good energy band structure and an electron transport region, which is conducive to the movement of photo-generated electrons to the cathode under the action of an electric field and the timely extraction by the cathode. Similarly, the donor material is more distributed near the anode to form a good energy band structure and a hole transport region, which is conducive to the movement of photo-generated holes to the metal anode under the action of an electric field and the timely extraction. In addition, as shown in Figure 4 , the surface roughness of the organic photoactive layer is also controlled within an ideal level.

[0085] Comparative Example 2

[0086] The organic solar cell prepared according to the ternary auxiliary step-by-step solution deposition strategy described in Example 2 is different in that:

[0087] In step (3), a binary active layer is prepared by a binary one-step solution spin coating method: a high-precision electronic balance is used to weigh the polymer, and PBDB-T-2F 14 mg and PY-IT 14 mg (Solarmer, > 99%) are weighed according to the proportion respectively; the weighed polymer constitutes a PBDB-T-2F: PY-IT binary system; the weighed polymer is poured into a sample bottle, and 2 mL of high-purity chloroform solvent is added to the sample bottle under the atmosphere of a nitrogen-protected glove box, and placed on a magnetic heating stirrer to heat and stir at a temperature of 40°C for 2.5 h to obtain a fully dissolved solution, and the concentrations of PBDB-T-2F and PY-IT are 7 mg / mL -1 and 7 mg / mL -1; under the nitrogen atmosphere, the chloronaphthalene additive was added into the active layer solution at the proportion of 1%vol, and the solution was used to prepare the active layer after stirring for 30 minutes; under the nitrogen atmosphere, the prepared active layer solution was spin-coated on the hole transport layer using the spin coater at the speed of 3000 rpm to obtain the bulk heterojunction organic active layer with the thickness of 100 nm.

[0088] Comparative Example 3

[0089] The organic solar cell prepared according to the ternary auxiliary step-by-step solution deposition strategy of Example 2 is different in that:

[0090] In step (3), the binary active layer was prepared by using the binary step-by-step solution spin coating method: the high-precision electronic balance was used to weigh the polymer, and PBDB-T-2F 20 mg and PY-IT 20 mg were weighed into No. 1 and No. 2 sample bottles respectively (Solarmer, >99%); the weighed polymer was placed in the No. 1 and No. 2 sample bottles under the nitrogen protection glove box atmosphere, 2 mL of high-purity chloroform solvent was added, and the sample bottles were placed on the magnetic heating stirrer for heating and stirring at 40°C for 2.5 h to obtain a fully dissolved solution, and the concentrations of PBDB-T-2F and PY-IT were 10 mg / mL -1 , 10 mg / mL -1 ; under the nitrogen atmosphere, the chloronaphthalene additive was added into the No. 2 sample bottle at the proportion of 1%vol, and the solution was used to prepare the active layer after stirring for 30 minutes; under the nitrogen atmosphere, the prepared No. 1 solution was spin-coated on the hole transport layer using the spin coater at the speed of 3000 rpm to obtain the donor active layer with the thickness of 45 nm; the prepared No. 2 solution was spin-coated on the donor active layer using the spin coater at the speed of 3000 rpm to obtain the organic photosensitive active layer with the total thickness of 100 nm.

[0091] The device efficiency of the device prepared in the present comparative example was tested under the AAA solar simulator, and the test results are shown in Table 1:

[0092] Table 1

[0093]

[0094] As can be seen from the data in Table 1, among the organic photovoltaic devices prepared based on different preparation methods, the fill factor and photoelectric conversion efficiency of the device prepared by the ternary auxiliary step-by-step solution spin coating method are significantly improved compared with the other three methods, and the high-efficiency organic solar cell prepared by the ternary auxiliary step-by-step deposition is realized.

[0095] Comparative Example 4

[0096] The film structure of this comparative example is from bottom to top glass, organic active layer. The corresponding exciton dynamics processes extracted from the transient absorption spectrum are shown in Figure 5a , Figure 5b The results of the transient absorption dynamics processes extracted from the transient absorption spectrum of the pure PY-IT layer and the PY-IT:PDI-2T blend are shown in Table 2:

[0097] Table 2

[0098]

[0099] It is found that there is a longer exciton diffusion length in the PY-IT:PDI-2T blend system, and the exciton diffusion coefficient of pure PY-IT is smaller, which shows that PDI-2T as the second material provides an effective gain effect for the exciton diffusion in PY-IT, which helps to improve the J SC . In Figure 5, the abscissa represents time, the ordinate represents the normalized light absorption intensity, and the whole represents the change of the light absorption intensity of the sample with time.

Claims

1. A fully polymeric organic photovoltaic device based on ternary-assisted stepwise solution deposition, characterized in that, From bottom to top, the structure comprises a glass substrate, a transparent conductive film, a hole transport layer, an organic active layer, an electron transport layer, and a top electrode. The organic active layer includes a polymer donor material and two polymer acceptor materials. The polymer donor material is PBDB-T-2F, the polymer acceptor material is PY-IT, and the other polymer acceptor material is PDI-2T as a tertiary component. The mass ratio of PBDB-T-2F:PY-IT:PDI-2T is 1.00:1.00:0.

03. This all-polymer organic photovoltaic device is fabricated by distributed solution deposition, and the fabrication process includes the following: (1) Clean the transparent conductive substrate, wherein the transparent conductive substrate is a glass substrate with an ITO transparent conductive film attached; (2) A hole transport layer PEDOT:PSS thin film is prepared on the transparent conductive substrate obtained in step (1); (3) Preparation of organic active layer thin films, including: a. Weigh 10 mg PBDB-T-2F, 15 mg PY-IT, and 0.15-75 mg PDI-2T separately using a high-precision electronic analytical balance. Then, add 0.5-2 mL of high-purity chloroform solvent to the weighed PBDB-T-2F. After mixing PY-IT and PDI-2T, add 0.5-3 mL of high-purity chloroform solvent. Place the mixture on a heatable magnetic stirrer and stir for 2-5 hours at 30-50°C to obtain a pure PBDB-T-2F solution with a concentration of 5-20 mg / mL. PDI-2T: PY-IT blend solution; b. Using a high-precision pipette, add 1% vol of chloronaphthalene additive to the PY-IT:PDI-2T blend solution obtained above, and continue stirring for 30 min to obtain a mixed acceptor solution with a PY-IT:PDI-2T mass ratio of 1:0.01 to 1:0.

05. c. In an inert gas glove box, spin-coat the PBDB-T-2F solution prepared in step a onto the substrate with hole transport layer obtained in step (2). After waiting for 30 seconds, spin-coat the PY-IT:PDI-2T blend solution prepared in step b onto the PBDB-T-2F film. Then, anneal the resulting film with the active layer material in an inert gas for 5-10 minutes. (4) Deposit an electron transport layer PDINN thin film on the organic active layer; (5) The top electrode material is deposited on the electron transport layer.

2. The all-polymer organic photovoltaic device based on ternary assisted stepwise solution deposition according to claim 1, characterized in that, The thickness of the organic active layer is 100 nm.

3. The all-polymer organic photovoltaic device based on ternary assisted stepwise solution deposition according to claim 1, characterized in that, The glass substrate with an ITO transparent conductive film is a transparent conductive substrate with an ITO transparent conductive film thickness of 130 nm. The hole transport layer material is PEDOT:PSS with a thickness of 30 nm. The electron transport layer material is PDINN with a thickness of 5 nm. The top electrode material is aluminum (Al) with a thickness of 100 nm.

4. The all-polymer organic photovoltaic device based on ternary assisted stepwise solution deposition according to claim 1, characterized in that, In step (3)a, 1 mL of high-purity chloroform solvent was added to the weighed PBDB-T-2F, and the mixture was placed on a heatable magnetic stirrer and stirred at 40°C for 2.5 h to obtain a pure PBDB-T-2F solution with a concentration of 10 mg / mL. 0.45 mg of PDI-2T and 1.5 mL of high-purity chloroform solvent were added to the weighed PY-IT, and the mixture was placed on a heatable magnetic stirrer and stirred at 40°C for 2.5 h to obtain a receptor solution with a concentration of 10.3 mg / mL. The mass ratio of PY-IT to PDI-2T in the resulting blended solution was 1:0.

03.

5. The all-polymer organic photovoltaic device based on ternary assisted stepwise solution deposition according to claim 1, characterized in that, In step (3)c, the spin coating speed of the active layer solution is: 2500-3500 rpm for PBDB-T-2F and 2500-3500 rpm for PY-IT:PDI-2T blend solution. The resulting PBDB-T-2F layer thickness is 40-60 nm and the resulting PY-IT:PDI-2T layer thickness is 40-60 nm.

6. The all-polymer organic photovoltaic device based on ternary assisted stepwise solution deposition according to claim 5, characterized in that, In step (3)c, the spin coating speed of PBDB-T-2F is 3000 rpm, the spin coating speed of PY-IT:PDI-2T blend solution is 3000 rpm, the thickness of the obtained PBDB-T-2F layer is 45 nm, and the thickness of the obtained PY-IT:PDI-2T layer is 55 nm.

7. The all-polymer organic photovoltaic device based on ternary assisted stepwise solution deposition according to claim 1, characterized in that, In step (3)c, the annealing temperature of the organic active layer is 100°C and the annealing time is 10 min.

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