阅读说明：本技术 一类a-d-d’-a型非对称有机光伏受体材料及其应用 (A-D-D' -A type asymmetric organic photovoltaic receptor material and application thereof ) 是由 朱卫国 朱佳宁 谭华 邵正勇 朱梦冰 王峻峰 于 2021-07-21 设计创作，主要内容包括：本发明属于有机光伏技术领域,特别涉及一类A-D-D’-A型非对称有机光伏受体材料及其应用。以烷氧基茚并噻吩和环戊二烯并二噻吩双电子给体(D-D’)单元共同构建含非共价键构型锁的骨架,并采用氟、氯原子取代的3-(二氰基亚甲基)茚-1-酮修饰其末端。仅包含简单稠环的受体具有共平面骨架、低能量无序度和J-聚集倾向等多方面优势,这类非对称的小分子受体光学带隙在1.30-1.45eV的范围内可控调节,能够与大多数给体材料组合,构建高效的本体异质结二元有机太阳能电池。当给体材料为聚合物PM6时,其二元OSCs器件能量转换效率高达13.67％,开路电压为0.85eV,E-(loss)仅为0.50V。(The invention belongs to the technical field of organic photovoltaics, and particularly relates to an A-D-D' -A type asymmetric organic photovoltaic receptor material and application thereof. The alkoxy indenothiophene and cyclopentadithiophene double electron donor (D-D') units are used for constructing a skeleton containing a non-covalent bond configuration lock, and the tail end of the skeleton is modified by 3- (dicyanomethylene) indene-1-ketone substituted by fluorine and chlorine atoms. The receptor only containing the simple condensed rings has various advantages of coplanar frameworks, low energy disorder degree, J-aggregation tendency and the like, the optical band gap of the asymmetric micromolecule receptor can be controllably adjusted within the range of 1.30-1.45eV, and the asymmetric micromolecule receptor can be combined with most of donor materials to construct a high-efficiency bulk heterojunction binary organic solar cell. When the donor material is polymer PM6, the energy conversion efficiency of the binary OSCs device is as high as 13.67%, and the open-circuit voltage is0.85eV，E loss Only 0.50V.)

1. A-D-D' -A type asymmetric organic photovoltaic acceptor material is characterized in that the asymmetric organic photovoltaic acceptor material has a structure shown in the following formula 1:

wherein R is¹，R²，R³Each being of atomic number C₁～C₂₀Linear or branched alkyl groups of (a);

x is H, F, Cl atom.

2. The a-D '-a type asymmetric organic photovoltaic acceptor material according to claim 1, characterized in that said a-D' -a type asymmetric organic photovoltaic acceptor material has the structure shown in formula 2 below:

3. the use of an asymmetric A-D-D '-A organic photovoltaic acceptor material according to claim 1, characterized in that said A-D-D' -A asymmetric organic photovoltaic acceptor material is used in organic solar cell photoactive layers.

4. The use of an A-D-D '-A type asymmetric organic photovoltaic acceptor material according to claim 3, characterized in that the A-D-D' -A type asymmetric organic photovoltaic acceptor material is blended with a polymer donor material to make a binary or ternary bulk heterojunction organic solar cell photoactive layer.

5. The use of an A-D-D '-A type asymmetric organic photovoltaic acceptor material according to claim 4 characterized in that the mass ratio of said A-D-D' -A type asymmetric organic photovoltaic acceptor material blended with the polymer donor material PM6 is 1: 1.5.

6. The use of the asymmetric A-D-D' -A organic photovoltaic acceptor material according to claim 4, characterized in that 1-Chloronaphthalene (CN) is used as solvent additive to make photoactive layer of binary bulk heterojunction organic solar cell.

Technical Field

The invention belongs to the technical field of organic photovoltaics, and particularly relates to an A-D-D' -A type asymmetric organic photovoltaic receptor material with a simple structure and application thereof in an organic solar cell.

Background

The development of the simple condensed ring type micromolecule receptor material (the number of condensed rings is less than or equal to 3) in the organic solar cell is obviously lagged behind that of the large condensed ring type micromolecule receptor material (the number of condensed rings is more than 3). Most reports of such materials are A-D-C-D-A type small molecules with a symmetrical structure, wherein the D unit is mainly Dithienocyclopentadiene (DTC). So far, binary solar cell device efficiencies based on such acceptor materials when mixed with polymer donors such as PBDB-T, PM6 or J52 are typically 10-14%. However, compounds containing DTC units are relatively expensive, have poor photostability, and the presence of a central core (C unit connected by a carbon-carbon single bond) tends to adversely affect photovoltaic performance (H-aggregation and electron mobility degradation).

Indenothiophene has coplanarity and good stability, but the research on constructing a small molecule receptor with a simple structure by using an asymmetric indenothiophene unit with a simple structure is very little, so how to construct a high-efficiency fused ring type small molecule receptor material with a simple structure by using an asymmetric indenothiophene unit is an important subject of the advanced research on small molecule receptor materials.

Disclosure of Invention

Aiming at the problems of low energy conversion efficiency and E existing in the existing micromolecular photovoltaic receptor material with simple structure_lossThe invention provides an A-D-D' -A type asymmetric small molecule receptor material with a simple structure.

The invention synthesizes the asymmetric A-D-D' -A type narrow band gap micromolecule receptor material with simple structure by a plane molecule design strategy of non-covalent bond configuration lock. The micromolecule receptor material is characterized in that alkoxy is introduced to a benzene ring of indenothiophene, and then forms a non-covalent bond conformation lock with a thiophene ring of DTC, so that the solubility of the material is ensured, the energy level and band gap fine adjustment can be carried out, the cold crystallization of the material is promoted, the photophysical, electrochemical and aggregation behaviors of the material are further regulated and controlled, and the performance of a photovoltaic device is improved. Because the benzene ring derivative has wide sources, a plurality of functional groups can be introduced simultaneously. Therefore, the asymmetric A-D-D' -A type small molecule acceptor material has great significance for developing low-cost and high-efficiency organic solar cells.

The A-D-D' -A type micromolecule receptor material based on the alkoxy indenothiophene provided by the invention has a structure shown in the following general formula 1:

wherein R is¹，R²，R³Each being of atomic number C₁～C₂₀Linear or branched alkyl groups of (a);

x is H, F, Cl atom.

The A-D-D' -A type small molecule receptor material SM1-4 is a structure shown in formula 2:

the alkoxy indenothiophene is prepared by the classical reactions of 2-bromo-4-methoxybenzoic acid, such as esterification reaction, suzuki coupling reaction, Friedel-crafts acylation reaction, Huang Minlon reduction reaction and the like.

The application of the invention is that: the designed and synthesized asymmetric A-D-D' -A type organic micromolecule material is used as a near infrared absorbent in a photoactive layer to manufacture a binary or ternary organic solar cell device.

The organic solar cell device comprises Indium Tin Oxide (ITO) conductive glass, an anode modification layer, a light active layer, a cathode modification layer and a cathode. The active layer material adopts the small molecule receptor material and the commercial polymer donor material (such as PM6) to be blended (the mass ratio of the two blending is 1:1.5), 1-chloronaphthalene is used as a solvent additive, and the thermal annealing and the CS are sequentially carried out₂And steam annealing is carried out, so that the preparation of the organic solar cell based on the simple and efficient micromolecular acceptor is realized.

The photovoltaic receptor material provided by the invention is an A-D-D' -A type micromolecule only containing a simple fused ring unit. Compared with the small molecule receptor materials reported currently, the small molecule receptor materials have the following characteristics: (1) compared with a large condensed ring small molecule receptor with a complex structure, the molecular structure is greatly simplified; (2) the asymmetric D-D' units are locked through non-covalent bond conformation, so that the coplanarity of molecular frameworks is maintained; (3) compared with an A-D-C-D-A type symmetrical small molecule receptor, the main advantages are that C-C single bonds among units are reduced, and the delocalization range of pi electrons is favorably expanded; (4) the asymmetric structure has certain advantages in the aspect of energy level matching of a donor/acceptor, and the balance of open-circuit voltage and short-circuit current is easier to achieve; (5) the small molecule receptor has the characteristics of simple synthesis and diversified structure.

Description of the drawings:

FIGS. 1.1 and 1.2 are UV-VIS absorption spectra of the small molecule acceptor materials of the present invention.

FIG. 2 is a cyclic voltammogram of a small molecule acceptor material of the invention.

FIG. 3 is a J-V curve of a PM6: SM4 organic solar cell device of the present invention.

FIG. 4 is the EQE curve of the PM6: SM4 organic solar cell device of the present invention.

Detailed Description

The following specific examples are intended to further illustrate the invention, but these specific embodiments do not limit the scope of the invention in any way.

Example 1

And (3) synthesis of an A-D-D' -A type small molecule receptor material based on alkoxy indenothiophene.

The synthetic route for SM1 is as follows:

1.1 Synthesis of Compound 1

In a 250mL single neck flask, 2-bromo-4-methoxybenzoic acid (25.0g,108mmol) and anhydrous methanol (120mL) were added. Stirring at room temperature, slowly adding concentrated sulfuric acid (30mL), heating to 80 deg.C, reacting for 5 hr, stopping reaction, cooling, pouring the reaction solution into 300mL water, and extracting with dichloromethaneAfter drying over anhydrous magnesium sulfate, the organic solvent was distilled off under reduced pressure and dried to obtain compound 1(26.1g, yield 98%) as an oily liquid.¹H NMR(400MHz,CDCl₃)δ7.86(d,J＝8.8Hz,1H),7.20(s,1H),6.86(d,J＝8.8Hz,1H),3.90(s,3H),3.85(s,3H)。

1.2 Synthesis of Compound 2

In a 250mL single-neck flask, compound 1(12.2g,50.0mmol), 2-thiopheneboronic acid pinacol ester (12.1g, 65mmol), Pd (dppf) Cl were added in this order₂(0.300g，0.401mmol)、CuI(0.10g)、30％K₂CO₃(30mL, 65mmol), ethanol (20mL) and THF (80 mL). Reacting under nitrogen protection at 80 deg.C for 6 hr, heating to 140 deg.C, evaporating to remove organic solvent, cooling, adding 30% NaOH (30mL) and 1, 4-dioxane (50mL), reacting at 120 deg.C for 3 hr, cooling to room temperature, pouring the reaction solution into a large amount of water, vacuum filtering, adding HCl into the filtrate, acidifying to pH<1 (a large amount of white solid is separated out), a large amount of precipitate is separated out, and then the precipitate is filtered and dried to obtain the compound 2(10.7g, the yield is 92%) as an off-white solid.¹H NMR(400MHz,DMSO-D6)δ12.66(s,1H),7.70(d,J＝8.4Hz,1H),7.58(d,J＝5.2Hz,1H),7.11(d,J＝3.2Hz,1H),7.10-7.08(t,J＝4.4Hz,1H),7.01(d,J＝8.8Hz,1H),6.95(d,1H)、3.83(s,3H)。

1.3 Synthesis of Compound 3

In a 250mL one-neck flask, Compound 2(4.68g,20.0mmol) is dissolved in DCM (120mL), stirred at 35 deg.C, and DMF (0.02mL), SOCl is added sequentially₂(11.9g,100mmol) and SnCl₂·2H₂O (0.450g,2.00mmol) and the reaction stirred for 1 h. Pouring into water, extracting with DCM, removing the solvent by rotary distillation, and performing column chromatography on the crude product by using petroleum ether and dichloromethane (1:1.5, v: v) as an eluent to obtain a yellow solid, namely the compound 3(2.75g, the yield is 64%).¹H NMR(400MHz,CDCl₃)δ7.41(d,J＝8.0Hz,1H),7.20(d,J＝4.8Hz,1H),7.12(d,J＝4.8Hz,1H),6.70(s,1H),6.57(d,J＝8.0Hz,1H),3.86(s,3H)。

1.4 Synthesis of Compound 4

In a 100mL two-neck flask, compound 3(2.5g,3.9mmol), hydrazine hydrate (2mL) and diethylene glycol (40mL) are added, and the mixture is reacted under the protection of nitrogen at 120 DEG CAfter 1h, NaOH (1g,25mmol) was added, the temperature was raised to 190 ℃ to react for 2h, after cooling, the mixture was poured into water, extracted with DCM, and the solvent was removed by rotary distillation. The brown liquid was dissolved in DMSO (60mL), 1-bromohexane (2.57g, 15.6mmol) was added, the mixture was stirred at 80 ℃ and potassium tert-butoxide (1.75g, 15.6mmol) was added slowly, reaction was continued for 12h, the reaction was poured into water, extracted with dichloromethane, and the organic phases were combined and dried over anhydrous magnesium sulfate. The organic solvent was removed by distillation under the reduced pressure, and column chromatography using petroleum ether and dichloromethane (8:1, v: v) as eluent gave compound 4(3.2g, yield 75%) as a yellowish oily liquid.¹H NMR(400MHz,CDCl₃)δ7.28(d,J＝4.8Hz,1H),7.14(d,J＝8.0Hz,1H)，6.95(s,1H)，6.94(d,J＝4.8Hz，1H),6.70(d,J＝8.0Hz，1H),3.85(s,3H),1.94-1.86(m,2H),1.84-1.76(m,2H),1.15-1.08(m,16H),0.80-0.77(t,J＝7.0Hz，6H)。

1.5 Synthesis of Compound 5

In a 100mL two-necked flask, compound 4(3.2g,8.65mmol) and anhydrous tetrahydrofuran (40mL) were added, 1.6M n-butyllithium (8.13mL, 13.0mmol) was slowly added dropwise at-78 ℃ under nitrogen protection, after 1h of reaction, DMF (1.14g, 1.56mmol) was injected, after returning to room temperature, the reaction was poured into water, acidified with hydrochloric acid (5mL), extracted three times with DCM, the organic phases combined and dried over anhydrous magnesium sulfate. The solvent was removed by rotary distillation and column chromatography using petroleum ether and dichloromethane (1:1, v: v) as eluent gave compound 5 as a yellowish viscous liquid (3.13g, 91% yield).¹H NMR(400MHz,CDCl₃)δ9.89(s,1H),7.61(s,1H),7.21(d,J＝8.4Hz，1H),7.07(s,1H),6.88(d,J＝8.4Hz,1H),3.88(s,3H),1.99-1.91(m,2H),1.87-1.79(m,2H)，1.18-1.08(m,16H),0.81-0.77(t，J＝7.0Hz，6H)。

1.6 Synthesis of Compound 6a

In a 250mL two-necked flask, compound 5(3.10g,7.79mmol) and DCM (100mL) were added, stirred at room temperature and methanesulfonic acid (0.822g, 8.57mmol) was added dropwise, followed by the slow addition of NBS (1.39g, 7.79 mmol). After 1h of reaction, the reaction was poured into water, extracted with DCM, the organic phases were combined and washed with K₂CO₃And (5) drying. Removing solvent by rotary distillation, and washing with petroleum ether and dichloromethane (1:1, v: v)The solvent was removed and column chromatography was used to isolate compound 6a as a yellowish viscous liquid (3.46g, 93% yield).¹H NMR(400MHz,CDCl₃)δ9.90(s,1H),7.61(s,1H),7.48(s,1H),7.06(s,1H),3.99(s,3H),1.99-1.91(m,2H),1.85-1.77(m,2H)，1.18-1.09(m,16H),0.82-0.78(t，J＝7.0Hz，6H)。

1.7 Synthesis of Compound 7a

4, 4-bis (2-ethylhexyl) -dithienocyclopentadiene (1.26g,3.00mmol) and anhydrous tetrahydrofuran (30mL) are added into a 100mL double-neck flask, the flask is cooled to-78 ℃ and kept at the constant temperature for 15min under the protection of nitrogen, 1.6M n-butyl carbonate (2.16mL, 3.45mmol) is added dropwise, after stirring for reaction for 1h, 1.0M trimethyltin chloride (4.00mL, 4.00mmol) is injected, and the flask is heated to 60 ℃ for further reaction for 2 h. The compound 6a (0.915g, 2.3mmol) and Pd₂(dba)₃(30mg) and P (o-toly)₃(40mg) was dissolved in toluene (20mL), added to the reaction, and the reaction was continued overnight after warming to 85 ℃. After cooling to room temperature, the solvent was removed by rotary distillation, and the mixture was separated by column chromatography using petroleum ether and dichloromethane (1:1, v: v) as eluent to give compound 7a as an orange-yellow viscous liquid (1.22g, 66% yield).¹H NMR(400MHz,CDCl₃)δ9.89(s,1H),7.62(s,1H),7.54(s,1H),7.44(t,J＝2.6Hz,1H),7.14(d,J＝4.8Hz，2H),7.13(s,1H),6.95(m，1H)，4.04(s，3H)，2.01-1.87(m,8H),1.17-1.11(m,16H),1.02-0.91(m，18H)，0.84-0.63(m，18H)。

1.7 Synthesis of Compound 8a

In a 100mL one-neck flask, DMF (0.912g, 12.5mmol) and DCM (30mL) were added, cooled in an ice-water bath and thermostated, and SOCl was slowly added dropwise₂(1.49g,12.5mmol) and after stirring for 1h, compound 7a (1.00g,1.25mmol) in DCM (5mL) was added and the reaction stirred at 45 ℃ for 3 h. Cooling and dropping to K₂CO₃To the solution, triethylamine (1mL) was added and stirred for 15 min. Extraction with DCM, separation of the organic layer, removal of the solvent by rotary distillation, and separation by column chromatography using petroleum ether chloroform (1:2, v: v) as eluent gave compound 8a as a red solid (0.522g, 51% yield).¹H NMR(400MHz,CDCl₃)δ9.91(s,1H),9.83(s,1H),7.64(s,1H),7.58(t,J＝4.0Hz,1H),7.56(s,1H)7.48(t,J＝2.2Hz,1H),,7.16(s,1H)，4.08(s,3H)，2.07-1.94(m,8H),1.17-1.12(m,16H),1.00-0.93(m，18H)，0.84-0.63(m，18H)。

1.9 Synthesis of SM1

In a 50mL two-necked flask, compound 8a (0.150g,0.181mmol), 5, 6-difluoro-1, 3-bis (dicyanomethylene) inden-1-one (0.146g,0.634mmol), THF (20mL) and pyridine (0.2mL) were added sequentially and the reaction was stirred at 65 ℃ for 3 h. Cooling to room temperature, pouring into 200mL of anhydrous methanol for precipitation, filtering, and separating the crude product by column chromatography with petroleum ether and chloroform (1:1, v: v) as eluent to obtain black solid powder SM1(0.172g, 76% yield).¹H NMR(400MHz,CDCl₃)δ8.98(s,1H),8.90(s,1H),8.56-8.53(m,2H),7.72-7.64(m,4H),7.64(s,1H),7.57(s,1H),7.30(s,1H)，4.12(s,3H),2.07-1.94(m,8H),1.18-1.13(m,16H),1.02-0.95(m，18H),0.81-0.63(m，18H)。

Example 2

Preparation of SM2 with reference to SM1, only the starting material (5, 6-difluoro-1, 3-bis (dicyanomethylene) inden-1-one) was replaced with 5, 6-dichloro-1, 3-bis (dicyanomethylene) inden-1-one.

Preparation of SM3 and SM4 referring to SM1 and SM2 respectively, compound 6a was simply replaced by compound 6b by the following synthetic procedure.

2.1 Synthesis of Compound 6b

In a 50mL two-necked flask, dissolve Compound 6a (3.20g,6.70mmol) in DCM (30mL) and slowly add BBr dropwise₃(1 mL). The reaction mixture was stirred at room temperature for 3 hours, then poured into 30ml of saturated aqueous sodium bicarbonate solution and stirring was continued for 10 minutes. Collecting Mg for organic phase₂SO₄Dried and then the solution removed by rotary evaporation. Mixing the brown liquid with K₂CO₃(1.85g,13.4mmol), KI (1.11g,6.70mmol), bromoisooctane (2.60g, 13.4mmol) and DMF (60mL) were mixed and stirred at 90 ℃ for 12 hours. Cooled to room temperature, poured into 150mL of water, extracted with DCM, the solvent evaporated to give a red liquid and the crude product isolated by column chromatography using petroleum ether, dichloromethane (1:1, v: v) as eluent to give yellowish liquid 6b (3.46g, 90%).¹H NMR(400MHz,CDCl₃)δ9.90(s,1H),7.61(s,1H),7.48(s,1H),7.06(s,1H),3.99(s,3H),1.99-1.91(m,2H),1.85-1.77(m,2H),1.18-1.09(m,16H),0.82-0.78(t,J＝7.0Hz,6H).

Example 3

Performance characterization of small molecule receptor materials and preparation and test of photovoltaic devices:

of all intermediates and small molecule receptor materials¹H NMR spectra were determined by Bruker Dex-400 NMR instrument, UV-vis absorption spectra by Shimadzu UV-2600 UV-vis spectrophotometer, cyclic voltammogram by CHI630E electrochemical analyzer in acetonitrile solution with 0.1M tetrabutylammonium hexafluorophosphate (Bu)₄NPF₆) As a supporting electrolyte.

The organic solar cell device based on the micromolecular acceptor material comprises an Indium Tin Oxide (ITO) conductive glass anode, an anode modification layer, a light active layer, a cathode modification layer and a cathode. The active layer is prepared from the micromolecular acceptor material and a commercially available polymer donor material, the blending weight ratio (D: A) of PM6: SM4 is 1:1.5, CN is added in a chloroform solvent with the volume fraction of 0.5%, and the active layer is subjected to thermal annealing at 100 ℃ and CS₂The binary photovoltaic device obtained an energy conversion efficiency of 13.67% with a solvent vapor annealing process.

3.1 measurement of photophysical Properties of organic Small molecule acceptor materials

FIG. 1 shows UV-visible absorption spectra of organic small molecule acceptor materials in chloroform solution and thin film state, and it can be seen from FIG. 1 that they have strong absorption in chloroform solution (ε ═ 1.6-2.0 × 10⁵) The absorption peak of the solid film is in the range of 650-900nm and can be attributed to Intramolecular Charge Transfer (ICT) effect. The film has a 100nm red shift relative to the absorption of the solution, the film of the small molecule receptor of the methoxy side chain shows a distinct shoulder, while the film of the small molecule receptor of the isooctoxy side chain is relatively red-shifted and has no sharp peak, because the larger alkyl chain volume hinders the formation of H aggregates, which enhances the J-aggregates. At the same time canThe measured optical band gaps of the small molecule acceptor materials are 1.38(SM1 and SM3) and 1.35eV (SM2 and SM4) (formula E)_g1240/λ, wherein E_gIs the optical bandgap, and λ is the initial absorption of the film).

3.2 electrochemical Performance testing of Small organic molecule receptors

Cyclic voltammograms of small organic molecule receptors SM1, SM2, SM3 and SM4 in solid films are shown in FIG. 2, according to the calculation formula E_HOMO＝-(E_ox+4.80) eV, giving rise to HOMO energy levels of SM1, SM2, SM3 and SM4 of-5.45, -5.46, -5.47 and-5.49 eV, respectively. According to the calculation formula E_LUMO＝-(E_red+4.80) eV, giving them LUMO levels of-3.95 eV, -3.96, -4.03 and-4.05 eV, respectively. The electrochemical band gaps of the small molecule acceptor materials were thus calculated to be 1.44eV (SM1 and SM3) and 1.46eV (SM2 and SM4), respectively.

3.3 photovoltaic Performance testing of organic Small molecule acceptor materials

Selecting designed and synthesized SM1 or SM4 as acceptor materials, respectively using commercially available polymer PM6 as donor materials to prepare a forward binary organic solar cell, and using the forward binary organic solar cell as a simulated sunlight light source (irradiance of 100 mW/cm)²) The J-V curve of the organic solar cell under irradiation was measured as shown in fig. 3. The test result shows that: the device structure is ITO/PEDOT: PSS/PM6: SM1/PFN-Br/Ag organic solar cell device short-circuit current (J)_sc) Is 20.35mA cm^-2Open circuit voltage (V)_oc) 0.83V, a Fill Factor (FF) of 70.11%, and an energy conversion efficiency (PCE) of 11.84%; j of organic solar cell device with ITO/PEDOT: PSS/PM6: SM4/PDIN/Ag structure_scIs 22.99mA cm^-2，V_oc0.85V, FF 70.19%, PCE as high as 13.67%.

The EQE curve for PM6: SM4 is shown in FIG. 4 under optimal conditions (1:5 w/w; CF; 0.5% CN, 100 ℃ thermal annealing and CS₂Steam annealing), the EQE response range is 300-900nm, the EQE response range reaches 70% in the range of 550-850nm, and the maximum EQE value reaches 76% at 690 nm.

While the present invention has been described in connection with the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. In light of the present inventive concept, those skilled in the art will recognize that certain changes may be made in the embodiments of the invention described herein, which are intended to be covered by the claims.