Method for predicting performance of organic photovoltaic system

Abstract

The invention discloses a method for predicting the performance of an organic photovoltaic system, and the method comprises the steps: testing the film forming process of an active layer of an organic solar cell through an in-situ absorption method, and calculating the aggregation degree of a material through the change of the absorption peak position and the absorption peak intensity of a donor material and an acceptor material in the active layer. And predicting the performance of the organic solar cell through the aggregation degree. The application range is a wide-band-gap BDT type polymer donor and a narrow-band-gap A-D-A type non-fullerene small molecule acceptor material system. According to the method, the in-situ characterization means is used for analyzing the film-forming dynamic process, and the evolution of the aggregation degree of donor and acceptor materials along with time is quantitatively characterized. The performance of the device is estimated through the evolution of the aggregation degree, and the purpose of screening the high-performance active layer material combination is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of organic semiconductor devices, and in particular relates to a method for predicting the performance of an organic photovoltaic system, which can be used to guide the screening and optimization of active layer material combinations. Background Art

[0002] Environmental and energy issues are major challenges facing the development of human society today. Fossil fuels represented by oil, coal, natural gas, etc. occupy a major share in the current energy structure of human society. However, fossil fuels and other energy sources have limited reserves, uneven distribution and are non-renewable. They will also cause serious environmental problems during use, which is not conducive to the sustainable development of society. Therefore, it is urgent to develop green renewable energy. As a widely distributed, inexhaustible, safe and harmless clean energy, solar energy is an excellent substitute for traditional fossil fuels. Solar cells, as a technology that directly converts solar energy into electrical energy, can achieve efficient utilization of solar energy. Among them, organic solar cells have excellent characteristics such as rich sources of photovoltaic materials, flexibility, and lightness, and have received widespread attention from scientists. At present, the conversion efficiency of organic solar cells has exceeded 19%, and the photoelectric conversion efficiency of stacked devices has exceeded 20%.

[0003] There are many kinds of materials for the active layer of organic solar cells, and they are still increasing. This leads to countless combinations of donor and acceptor materials in the active layer, but there are few high-performance combinations. In addition, the device performance of the same donor or acceptor material with different combinations often varies greatly. It is extremely important to be able to accurately predict the device performance of a material system, which can greatly promote the screening and development of high-performance material systems, avoid trial-and-error research, and guide the design and development of new materials. Summary of the invention

[0004] The present invention provides a method for predicting the performance of an organic photovoltaic system, which reflects the aggregation and stacking progress of the donor and acceptor materials through the change of the absorption peak position or absorption peak intensity of in-situ absorption. The performance of the device is evaluated by the speed of the accumulation of the donor and acceptor. This is because materials that aggregate quickly will dominate the morphological evolution of the active layer during the film formation process. For example, when the polymer donor aggregates quickly, a polymer network will be formed preferentially, thereby limiting the excessive aggregation of the acceptor and forming a suitable nanoscale phase separation. On the contrary, when the acceptor aggregates quickly, due to the strong crystallinity of the small molecules, it will tend to form large-scale aggregation, making it difficult to form nanoscale phase separation, which is not conducive to the diffusion dissociation of excitons and the transmission of carriers.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for predicting the performance of an organic photovoltaic system. The method tests the film-forming process of the active layer of an organic solar cell by an in-situ absorption method, calculates the aggregation degree of the material by using the changes in the absorption peak positions and absorption peak intensities of the respective donor and acceptor materials in the active layer, and predicts the performance of the organic solar cell by the aggregation degree.

[0007] The above-mentioned method for predicting the performance of the organic photovoltaic system comprises the following steps:

[0008] (1) Using in-situ absorption method to measure the donor and acceptor absorption peak intensity curves of the active layer of organic solar cells;

[0009] (2) Calculate the aggregation degree of the donor and the aggregation degree of the acceptor according to the absorption peak intensity curve, as follows:

[0010] according to Calculate the donor aggregation degree A Dt =5%, L Dt value;

[0011] The absorption peak intensity curve obtained in step (1) is used to obtain L Dt The time t corresponding to the value;

[0012] Then through Calculate the receptor aggregation degree A at time t At value;

[0013] Among them, L D It is the difference between the final state value and the minimum value of the donor absorption peak intensity or peak position;

[0014] L Dt It is the difference between the donor absorption peak intensity or peak position at time t and the minimum value;

[0015] A Dt is the aggregation degree of the donor at time t;

[0016] L A It is the difference between the final state value and the minimum value of the receptor absorption peak intensity or peak position;

[0017] L At It is the difference between the peak intensity or peak position of the receptor absorption at time t and the minimum value;

[0018] A At is the degree of receptor aggregation at time t.

[0019] The above-mentioned standard for evaluating the performance of the device is: the receptor aggregation at the time point when the donor aggregation reaches 5% is used as the standard for predicting the device parameters of the system. When the receptor aggregation is ≤20% at this time, the device performance is excellent; when the receptor aggregation is >20%, the device performance is poor.

[0020] Preferably, the donor material in the active layer is a wide bandgap polymer, and the acceptor material is a narrow bandgap non-fullerene small molecule acceptor and a polymer acceptor. Preferably, the donor material is a BDT-type conjugated polymer, and the acceptor material is an ADA-type non-fullerene small molecule acceptor.

[0021] The above organic solar cell structure is from bottom to top: transparent electrode, electron / hole transport layer, active layer, hole / electron transport layer, metal electrode. Preferably, the organic solar cell involved in the present invention is a positive structure, which is from bottom to top: transparent electrode, hole transport layer, active layer, electron transport layer, metal electrode.

[0022] In situ absorption Figure 1 The transmission mode is used to measure the time resolution of the spectrum up to 10ms. The present invention obtains the donor and acceptor absorption peak intensity curves simultaneously through in-situ absorption spectroscopy, thereby obtaining the aggregation degree of the donor and acceptor materials at each moment in the film forming process.

[0023] Compared with the prior art, the present invention has the following advantages

[0024] 1. Through in-situ absorption, the film formation kinetics of the active layer are quantitatively analyzed, and the aggregation characteristics are successfully correlated with the active layer morphology and the final efficiency of the device, realizing the predictive evaluation of the performance of the active layer system device.

[0025] 2. The present invention can quickly select the best combination for newly designed and synthesized materials, saving device optimization process and time.

[0026] 3. The present invention guides the design and synthesis of new materials, namely, improving the aggregation properties of polymer donors. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the in-situ absorption device used in the examples.

[0028] Figure 2 The figure is a typical in-situ absorption peak intensity curve measured in the examples.

[0029] Figure 3 Schematic diagram and steps of the prediction method of the present invention.

[0030] Figure 4 is the structural formula of each donor and acceptor material in the examples.

[0031] Figure 5 The in-situ absorption peak intensity of each system in Examples 1-8 changes with time.

[0032] Figure 6 The current-voltage characteristic curves of the organic solar cell devices prepared in Examples 1-8.

[0033] Figure 7 EQE curves of the organic solar cells prepared in Examples 1-8.

[0034] Figure 8 is the receptor aggregation, device filling factor FF and EQE maximum value EQE of each system in the embodiment max . DETAILED DESCRIPTION

[0035] The following is an explanation with reference to the embodiments, which involve the following organic semiconductor materials:

[0036] PBDB-T-SF: Poly[[4,8-bis[5-[(2-ethylhexyl)thio]-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c′]dibenzo-1,3-diyl]-2-thiophenediyl]

[0037] PBDE-TT: Poly[2-butyloctyl 5-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']thiophen-2-yl)-2-(5-(3-(((2-butyloctyl)oxy)carbonyl)thiophen-2-yl)thieno[3,2-b]thiophen-2-yl])thiophene-3-carboxylate]

[0038] PM6: Poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene])-alt-(5,5-(1',3'-di-2-thiophene-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)]

[0039] PDTB-EF-T: Poly[[4,8-bis[5-[(2-ethylhexyl)thio]-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3,3′-[(decyloxy)carbonyl][2,2′:5′,2′-terthiophene]-5,5′-diyl]]

[0040] IT-4Cl: 2,2′-[[6,6,12,12-tetrakis(4-hexylphenyl)-6,12-dihydrodithiophene[2,3-d:2′,3′-d′]-s-indeno[1,2-b:5,6-b′]dithiophene-2,8-diyl]bis[methyl(5,6-dichloro-3-oxo-1H-indene-2,1(3H)-diylidene)]][malononitrile]

[0041] Y6-HD:12,13-di(2-hexyldecyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazo[3,4-e]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-bis(5,6-difluoro-3-(dicyanomethylene)indene-1-one)

[0042] BTP-eC9:2,2'-[[12,13-bis(2-butyloctyl)-12,13-dihydro-3,9-dinonylbisthieno[2",3":4',5']thieno[2',3':4,5]pyrrolo[3,2-e:2',3'-g][2,1,3]benzothiadiazole-2,10-diyl]bis[methylmethylene(5,6-chloro-3-oxo-1H-indene-2,1(3H)-dimethylene)]]bis[malononitrile]

[0043] L8BO:2,2′-[[3,9-bis(2-butylbutyl)-12,13-bis(2-ethylhexyl)-12,12-dihydrobithiophene[2′,3′:4′,5′]thiophene[2′,3′:4,5]pyrrolo[3,2-2,2,3]benzothiazole-2,10-diyl]bis[methylaniline(5,6-difluoro-3-oxo-1H-indene-2,1(3H)-diylidene)]][malononitrile]

[0044] Y6: 12,13-di(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazo[3,4-e]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-bis(5,6-difluoro-3-(dicyanomethylene)indene-1-one)

[0045] For the convenience of description, the following are expressed in English abbreviations:

[0046] Example 1 takes the PBDB-T-SF:Y6 system as an example:

[0047] (1) The in-situ absorption test steps and analysis steps are as follows:

[0048] The test solution was consistent with the conditions used in device preparation.

[0049] The donor material PBDB-T-SF and the acceptor material Y6 were dissolved in chlorobenzene, and the mass ratio of the donor to the acceptor in the obtained donor-acceptor chlorobenzene solution was 1:1.2, and the total concentration was 16.5 mg / mL.

[0050] In situ absorption test device Figure 1 As shown, the spectrometer model used in the test is QEPro from Ocean Optics, the model of the white light source is EQ-99X-FC from Hamamatsu, and the substrate used in the test is a quartz wafer. The white light source is connected to the first collimator via an optical fiber, and the substrate and sample to be tested are placed between the first collimator and the second collimator. After collimation, the white light passes through the test substrate and sample, is collected by the second collimator, and is connected to the spectrometer via an optical fiber to collect the spectrum. During the test, the substrate is prepared, and the reference spectrum I0 is collected first; then the active layer is spin-coated. The spin-coating process is the same as the device preparation conditions. We define the moment when the spin coater starts to rotate as t=0s, and use the spectrometer to collect the transmission spectrum I at intervals of 10ms. T , and with the formula: The absorption spectrum A is calculated, and the obtained in-situ absorption data includes variables in three dimensions: time, wavelength, and intensity. The variation of the absorption peak intensity of the donor and acceptor extracted from the in-situ absorption with time is shown in Figure 5 shown.

[0051] The prediction process is as follows Figure 3 As shown:

[0052] In this example, we set the aggregation degree A of the donor during film formation Dt When the receptor aggregation reaches 5%, A At As a standard for predicting the device parameters of the system. At When the receptor aggregation degree A is less than 20%, the device performance is excellent; At When it is greater than 20%, the device performance is poor.

[0053] First, the absorption peak intensity curve was obtained through in-situ absorption test. The absorption peaks of PBDB-T-SF and Y6 are 623nm and 850nm respectively. The intensity changes of 623nm and 850nm wavelengths over time were extracted respectively; Figure 2 As shown in the figure, the minimum value of the intensity curve of PBDB-T-SF at 623 nm is 0.431 and the final value is 0.463, so L D =0.463-0.431=0.032, passed Calculate A Dt = L at 5% Dt =0.032×5%=0.0016, the corresponding intensity is 0.431+0.0016=0.433. From the curve, we know that the time t when the intensity is 0.433 is 6.02s. From the intensity curve of Y6 at 850nm, we know that the minimum value is 0.027, the final value is 0.449, and the value at t=6.02s is 0.033, so L A =0.449-0.027=0.422, L At=0.033-0.027=0.006, passed The calculation shows that at 6.02s, A At =0.006÷0.422×100%=1.42%.

[0054] The A of the PBDB-T-SF:Y6 system was calculated At =1.42%<20%, so this material system is a high-performance system.

[0055] (2) The steps for preparing the device are as follows:

[0056] The ITO glass was cleaned with detergent, ultrapure water, and anhydrous ethanol in turn. After oxygen plasma treatment for 10 minutes, a layer of PEDOT:PSS was spin-coated. After annealing at 150°C for 10 minutes, the substrate was transferred to a nitrogen atmosphere glove box, and then the active layer was spin-coated. The vacuum degree was less than 2×10 -4 The silver electrode was prepared by thermal evaporation under the condition of 1.54 Pa, and PDINN was used as the electron transport layer.

[0057] The organic solar cell adopts an upright structure, ITO / PEDOT:PSS / active layer / PDINN / Ag, where the active layer is a PBDB-T-SF:Y6 system.

[0058] The device was tested under a solar simulator AM1.5G (100mW / cm 2 ) light, and the current-voltage curves were measured in a nitrogen atmosphere.

[0059] The test results are shown in Table 1.

[0060] Through the device FF and EQE max To judge the performance of the active layer system, it is considered that FF is greater than 60 and EQE max Greater than 70% is excellent, otherwise it is inferior.

[0061] The FF of the PBDB-T-SF:Y6 system is 74.9% and the EQE max The prediction is correct at 83.9%.

[0062] Example 2 takes PM6:Y6-HD system as an example:

[0063] The donor material PM6 and the acceptor material Y6-HD were placed in chlorobenzene with a donor-acceptor mass ratio of 1:1.2 and a total concentration of 17.6 mg / ml.

[0064] The in-situ test and analysis and calculation steps are the same as in Example 1. The absorption peaks of PM6 and Y6-HD obtained by in-situ absorption are 626nm and 815nm respectively. The intensity changes of 626nm and 815nm wavelengths over time are extracted and analyzed and calculated. Dt =5%, A At It is 6.9%<20%. It is predicted that this material system is a high-performance system.

[0065] The device preparation steps are the same as in Example 1.

[0066] The device parameters are shown in Table 1. FF is 73.5%, EQE max The device performance is excellent and the prediction is accurate.

[0067] Example 3 takes PM6:L8BO system as an example:

[0068] The donor material PM6 and the acceptor material L8BO were dissolved in chloroform, the mass ratio of donor to acceptor was 1:1.2, and the total concentration was 17.6 mg / ml.

[0069] The in-situ test and analysis and calculation steps are the same as in Example 1. The absorption peaks of PM6 and L8BO obtained by in-situ absorption are 623nm and 791nm respectively. The intensity changes of 623nm and 791nm wavelengths over time are extracted and analyzed and calculated. Dt =5%, A At It is 11.2%<20%. It is predicted that this material system is a high-performance system.

[0070] The device preparation steps are the same as in Example 1.

[0071] The device parameters are shown in Table 1. FF is 78.3%, EQE max The device performance is excellent and the prediction is accurate.

[0072] Example 4 takes PM6:BTP-eC9 system as an example:

[0073] The donor material PM6 and the acceptor material BTP-eC9 were dissolved in chloroform, the mass ratio of donor to acceptor was 1:1.2, and the total concentration was 17.6 mg / ml.

[0074] The in-situ test and analysis and calculation steps are the same as in Example 1. The absorption peaks of PM6 and BTP-eC9 obtained by in-situ absorption are 626nm and 824nm respectively. The intensity changes of the wavelengths of 626nm and 824nm over time are extracted and analyzed and calculated. Dt =5%, A At It is 8.3%<20%. It is predicted that this material system is a high-performance system.

[0075] The device preparation steps are the same as in Example 1.

[0076] The device parameters are shown in Table 1. FF is 77.9%, EQE max The device performance is excellent and the prediction is accurate.

[0077] Example 5 takes the PBDE-TT:IT-4Cl system as an example:

[0078] The donor material PBDE-TT and the acceptor material IT-4Cl were dissolved in chloroform, the mass ratio of the donor to the acceptor was 1:1, and the total concentration was 16 mg / ml.

[0079] The in-situ test and analysis and calculation steps are the same as those in Example 1. The absorption peaks of PBDE-TT and IT-4Cl obtained by in-situ absorption are 541nm and 750nm respectively. The intensity changes of the wavelengths of 541nm and 750nm over time are respectively extracted and analyzed and calculated. Dt =5%, A At It is 16.6%<20%. It is predicted that this material system is a high-performance system.

[0080] The device preparation steps are the same as in Example 1.

[0081] The device parameters are shown in Table 1. FF is 63.2%, EQE max The device performance is excellent and the prediction is accurate.

[0082] Example 6 takes the PDTB-EF-T:Y6 system as an example:

[0083] The donor material PDTB-EF-T and the acceptor material Y6 were dissolved in chloroform, the mass ratio of donor to acceptor was 1:1.2, and the total concentration was 17.6 mg / ml.

[0084] The in-situ test and analysis and calculation steps are the same as in Example 1. The absorption peaks of PDTB-EF-T and Y6 obtained by in-situ absorption are 548nm and 850nm respectively. The intensity changes of 548nm and 850nm wavelengths over time are extracted and analyzed and calculated. Dt =5%, A At It is 27.1%>20%. It is predicted that this material system is a poor performance system.

[0085] The device preparation steps are the same as in Example 1.

[0086] The device parameters are shown in Table 1. FF is 57.8%, EQE max It is 52.9%, the device performance is poor, and the prediction is accurate.

[0087] Example 7 takes the PBDE-TT:L8BO system as an example:

[0088] The donor material PBDE-TT and the acceptor material L8BO were dissolved in chlorobenzene, with the mass ratio of donor to acceptor being 1:1.2 and the total concentration being 22 mg / ml.

[0089] The in-situ test and analysis and calculation steps are the same as those in Example 1. The absorption peaks of PBDE-TT and L8BO obtained by in-situ absorption are 541nm and 794nm respectively. The intensity changes of the wavelengths of 541nm and 794nm over time are respectively extracted and analyzed and calculated. Dt =5%, A At It is 34.9%>20%. It is predicted that this material system is a poor performance system.

[0090] The device preparation steps are the same as in Example 1.

[0091] The device parameters are shown in Table 1. FF is 49.8%, EQE max It is 62.4%, the device performance is poor, and the prediction is accurate.

[0092] Example 8 takes the PBDE-TT:Y6 system as an example:

[0093] The donor material PBDE-TT and the acceptor material Y6 were dissolved in chlorobenzene, the mass ratio of the donor to the acceptor was 1:1.2, and the total concentration was 22 mg / ml.

[0094] The in-situ test and analysis and calculation steps are the same as in Example 1. The absorption peaks of PBDE-TT and Y6 obtained by in-situ absorption are 540nm and 803nm respectively. The intensity changes of 540nm and 803nm wavelengths over time are extracted and analyzed and calculated. Dt =5%, A At It is 44.3%>20%. It is predicted that this material system is a poor performance system.

[0095] The device preparation steps are the same as in Example 1.

[0096] The device parameters are shown in Table 1. FF is 31.0%, EQE max It is 26.1%, the device performance is poor, and the prediction is accurate.

[0097] Therefore, PM6:Y6-HD, PM6:L8BO, PM6:BTP-eC9, PBDE-TT:IT-4Cl system A Dt =5%, A At All are lower than 20%, and are excellent active layer material systems, while PDTB-EF-T:Y6, PBDE-TT:L8BO, and PBDE-TT:Y6 are poor systems.

[0098] The device performance of Examples 1-8 is as follows Figure 6 , Figure 7 As shown in Table 1.

[0099] Table 1

[0100]

[0101]

Claims

1. A method for predicting the performance of an organic photovoltaic system, characterized in that This method tests the film formation process of the active layer of the organic solar cell by the in-situ absorption method, calculates the aggregation degree of the material by using the changes in the absorption peak position and absorption peak intensity of the donor and acceptor materials in the active layer, and predicts the performance of the organic solar cell by the aggregation degree.

2. The method for predicting the performance of an organic photovoltaic system according to claim 1, characterized in that The method comprises the following steps: (1) Using in-situ absorption method to measure the donor and acceptor absorption peak intensity curves of the active layer of organic solar cells; (2) Calculate the aggregation degree of the donor and the aggregation degree of the acceptor according to the absorption peak intensity curve, as follows: according to By L D Calculate the aggregation degree A Dt =5%, L Dt value; The absorption peak intensity curve of the donor obtained in step (1) is used to obtain L Dt The time t corresponding to the value; Then through Calculate the receptor aggregation degree A at time t according to the receptor absorption peak intensity curve At value; Among them, L D It is the difference between the final state value and the minimum value of the donor absorption peak intensity or peak position; L Dt It is the difference between the donor absorption peak intensity or peak position at time t and the minimum value; A Dt is the aggregation degree of the donor at time t; L A It is the difference between the final state value and the minimum value of the receptor absorption peak intensity or peak position; L At It is the difference between the peak intensity or peak position of the receptor absorption at time t and the minimum value; A At is the degree of receptor aggregation at time t.

3. The method for predicting the performance of an organic photovoltaic system according to claim 1, characterized in that The standard for evaluating device performance is: the receptor aggregation at the time point when the donor aggregation reaches 5% is used as the standard for predicting the device parameters of the system. When the receptor aggregation is ≤20% at this time, the device performance is excellent; when the receptor aggregation is >20%, the device performance is poor.

4. The prediction method according to claim 1, characterized in that The donor material in the active layer is a wide bandgap polymer, and the receptor material is a narrow bandgap non-fullerene small molecule receptor or a polymer receptor.

5. The prediction method according to claim 4, characterized in that The wide bandgap polymer in the active layer is a BDT-type conjugated polymer, and the narrow bandgap non-fullerene small molecule receptor is an ADA-type non-fullerene small molecule receptor.

6. The method for predicting the performance of an organic photovoltaic system according to claim 1, characterized in that The structure of the organic solar cell is, from bottom to top, a transparent electrode, an electron / hole transport layer, an active layer, a hole / electron transport layer, and a metal electrode.

7. The method for predicting the performance of an organic photovoltaic system according to claim 1, characterized in that The in-situ absorption is in transmission mode, and the time resolution of the spectrum is up to 10 ms.

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