n-Doped Electrically Conductive Organic Materials
20220059769 · 2022-02-24
Assignee
Inventors
- Peter Kian-Hoon Ho (Singapore, SG)
- Lay-Lay Chua (Singapore, SG)
- Rui-Qi Png (Singapore, SG)
- Cindy Guan-Yu Tang (Singapore, SG)
Cpc classification
H10K85/111
ELECTRICITY
H10K85/113
ELECTRICITY
International classification
Abstract
A composition comprising: an organic semiconductor comprising one or more aromatic or heteroaromatic moieties; one or more cations covalently bonded to the organic semiconductor, or to a second material; and at least one anion donor selected from the class of divalent and higher valent anions; wherein the organic semiconductor has an electron affinity between 1.5 and 4.5 eV.
Claims
1. A composition comprising an organic semiconductor comprising one or more aromatic or heteroaromatic moieties; one or more cations covalently bonded to the organic semiconductor, or to a second material; and at least one anion donor selected from the class of divalent and higher valent anions; wherein the organic semiconductor has an electron affinity between 1.5 and 4.5 eV.
2. The composition according to claim 1, wherein the organic semiconductor has an electron affinity between 1.8 and 4.5 eV.
3. The composition according to claim 1, wherein the anion donor is capable of n-doping the composition to form an n-doped organic semiconductor having a work function between 1.5 eV and 4.8 eV.
4. The composition according to claim 1, wherein the at least one anion donor is ionically bound to the one or more cations.
5. The composition according to claim 1, wherein the organic semiconductor has a fully conjugated backbone; a partially conjugated backbone, or a non-conjugated backbone and a conjugated aromatic or heteroaromatic moiety therefrom.
6. The composition according to claim 1, wherein the organic semiconductor is a polymer.
7. The composition according to claim 1, wherein the cation is covalently bound to the organic semiconductor.
8. The composition according to claim 6, wherein the cation is a pendent group of a repeat unit of the polymer or wherein the cation is a substituent of a repeat unit of the polymer.
9. The composition according to claim 8, wherein the repeat unit comprises a plurality of cations pendent therefrom.
10. (canceled)
11. The composition according to claim 1, wherein the covalently bonded cations are selected from ammonium of formula R.sub.4N.sup.+, sulfonium R.sub.3S.sup.+, phosphonium R.sub.4P.sup.+, guanidinium (NR).sub.3C.sup.+, oxonium R.sub.3O, borinium R.sub.2B.sup.+, or a combination thereof, wherein R is selected from C.sub.1-12 alkyl, and optionally substituted phenyl.
12. The composition according to claim 1, further comprising untethered cationic groups, wherein a proportion of the untethered cationic groups relative to tethered cationic groups (cations covalently bonded to the organic semiconductor) is less than about 45%.
13. The composition according to claim 1, wherein the gas-phase electron donor level for the anion donor in a vacuum is shallower than the vacuum level.
14. The composition according to claim 1, wherein the anion donor is selected from the group consisting of oxalate, malonate, succinate, phosphate, phosphite, sulfate, sulfite, carbonate, ferrocyanide, ferricyanide, and their substituted analogues, or a combination thereof.
15. A composition according to claim 1 and a second material.
16. A formulation comprising a composition according to claim 1 dissolved or dispersed in a solvent comprising one or more solvent materials.
17. An organic electronic device comprising a layer of a composition according to claim 1, wherein the layer of composition is disposed between a first electrode and a second electrode.
18. (canceled)
19. The organic electronic device according to claim 17, wherein the organic electronic device is an organic light-emitting device; wherein the first electrode is an anode; the second electrode is a cathode; and further comprising a light-emitting layer disposed between the anode and the layer of composition.
20. The organic electronic device according to claim 17, wherein the layer of composition has an ohmic electron-injection or electron-extraction contact to an adjacent semiconductor layer having an electron affinity of up to about 1.8 eV.
21. The organic electronic device according to claim 17 wherein the layer comprising the n-doped organic semiconductor is an electron-injection layer or electron-extraction layer.
22. A method of forming an organic electronic device according to claim 17, the method comprising forming a layer comprising a composition comprising an organic semiconductor comprising one or more aromatic or heteroaromatic moieties; one or more cations covalently bonded to the organic semiconductor, or to a second material; and at least one anion donor selected from the class of divalent and higher valent anions, wherein the organic semiconductor has an electron affinity between 1.5 and 4.5 eV; and activating the anion donor to cause doping of the organic semiconductor.
23. The method according claim 22, wherein the layer comprising the composition is formed by depositing a formulation comprising the composition dissolved or dispersed in a solvent comprising one or more solvent materials, and evaporating the solvent.
24. The method according to claim 22, wherein the activation comprises reducing the water-: anion donor molar ratio of the layer comprising the composition.
25. The method according to claim 22, wherein the layer comprising the composition undergoes a treatment of one or more of heating, vacuum treatment and exposure to a dry atmosphere.
26. The method of forming an organic electronic device according to claim 22, wherein the n-doped organic semiconductor is formed by formation of a layer comprising the composition between the first and second electrodes and activation of the anion donor to cause the anion donor to dope the organic semiconductor.
27. A method of forming a compound comprising an organic semiconductor comprising one or more aromatic or heteroaromatic moieties; one or more cations covalently bonded to the organic semiconductor; and at least one anion donor selected from the class of divalent and higher valent anions, the method comprising exchanging at least one anion of a precursor compound with the donor anion.
28. The method according to claim 27, wherein the anion of the precursor compound is a monovalent anion.
Description
DESCRIPTION OF THE DRAWINGS
[0114] Scheme 1a. shows the synthesis route of poly(9,9′-bis(3-trimethylammoniopropyl)fluorenyl-2,7-diyl-1,4-phenylene-N-(p-sec-butylphenyl)imino-1,4-phenylene) triflate (F3NMe3-OTf-TFB)
[0115] Scheme 1b. shows the synthesis route of poly(9,9′-bis(3-trimethylammoniopropyl)fluorene-2,7-diyl) triflate (F3NMe3-OTf)
[0116] Scheme 1c. shows the synthesis route of poly(9,9′-bis(3-trimethylammoniopropyl)fluorenyl-2,7-diyl-benzothiadiazole-2,7-diyl) triflate (F3NMe3-OTf-BT)
[0117] Scheme 1d. shows the synthesis route of poly(9,9′-bis(3-(1-methyl)imidaziopropyl)fluorenyl-2,7) bromide (F3Im1-Br)
[0118] Scheme 1e. shows the synthesis route of poly(9,9′-bis(3-(1-ethyl)imidaziopropyl)fluorenyl-2,7-diyl-1,4-phenylene-N-(p-sec-butylphenyl)imino-1,4-phenylene) bromide (F3Im2-Br-TFB)
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[0120]
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[0122]
[0123]
[0124]
[0125]
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[0128]
EXAMPLES
Example 1: Synthesis
Example 1a. Synthesis of poly(9,9′-bis(3-trimethylammoniopropyl)fluorenyl-2,7-diyl-1,4-phenylene-N-(p-sec-butylphenyl)imino-1,4-phenylene) triflate (F3NMe3-OTf-TFB) (Scheme 1a)
[0129] 9,9′-bis(3-dimethylaminepropyl)fluorenyl-2,7-dibromo (diBr-F3NMe2) (1 equiv) and N,N-Bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-(p-isobutyl)aniline (diEs-TFB) (1 equiv) and [1,1′-bis(diphenylphosphino)ferrocene] dichloropalladium(II) (Pd(dppf)Cl.sub.2) (2 mol %) were added to a microwave vial and purged with argon 3 times. Degassed tetrahydrofuran (THF): dimethylformamide (DMF) (2:1) (25 mg/ml) was added to the microwave vial to dissolve the reactants. Degassed 200 mg/ml sodium carbonate (Na.sub.2CO.sub.3) (5 equiv) in H.sub.2O was added to the microwave vial. The reaction mixture was degassed and stirred for an additional 15 min. The vial was then irradiated by microwave (130° C., 15 min).
[0130] The reaction mixture in the microwave vial was dried under vacuum. The resultant solid was dissolved in dichloromethane (DCM) and washed with water. The DCM layer was isolated, and dried under vacuum. The resultant solid was redissolved in THF. The polymer solution was centrifuged and filtered. Sodium diethyldithiocarbamate (70 equiv of Pd(dppf)Cl.sub.2) in THF was added to the polymer solution. The polymer poly(9,9′-bis(3-trimethylaminepropyl)fluorenyl-2,7-diyl-1,4-phenylene-N-(p-sec-butylphenyl)imino-1,4-phenylene) (F3NMe2-TFB) solution was filtered and precipitated in diethyl ether (DEE).
[0131] F3NMe2-TFB (1 equiv) was added to a one neck round-bottomed flask and purged with argon 3 times. Anhydrous chloroform (CHCl.sub.3) was added to dissolve F3NMe2-TFB (20 mg/ml). Methyl trifluoromethanesulfonate (MeOTf) (2.5 equiv) added dropwise to the polymer solution. Precipitation of polymer is observed immediately during addition. The mixture was stirred for 3 hr.
[0132] The precipitated polymer was collected by filtration. The precipitate was dissolve in acetonitrile (ACN) and precipitate in toluene. Precipitate was redissolve in ACN to undergo dialysis in ACN. After dialysis, the polymer solution was concentrated before preciptation in DEE to yield off-white F3NMe3-OTf-TFB.
Example 1b. Synthesis of poly(9,9′-bis(3-trimethylammoniopropyl)fluorene-2,7-diyl) triflate (F3NMe3-OTf) (Scheme 1b)
[0133] diBr-F3NMe2 (1 equiv) and 2,2′-(9,9-bis(3-dimethylaminopropyl)-9H-fluorene-2,7-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (diEs-F3NMe2) (1 equiv) and Pd(dppf)Cl.sub.2 (3 mol %) were added to a microwave vial and purged with argon 3 times. Degassed THF:DMF (2:1) (50 mg/ml) was added to the microwave vial to dissolve the reactants. Degassed 200 mg/ml Na.sub.2CO.sub.3 (5 equiv) in H.sub.2O was added to the microwave vial. The reaction mixture was degassed and stirred for an additional 15 min. The vial was then irradiated by microwave (130° C., 15 min).
[0134] The reaction mixture in the microwave vial was precipitated in water. The precipitate was redissolved in methanol (MeOH) and sodium diethyldithiocarbamate (70 equiv of Pd(dppf)Cl.sub.2) in MeOH was added. The reaction mixture was filtered and the polymer poly(9,9′-bis(3-trimethylaminepropyl)fluorene-2,7-diyl) (F3NMe2) was precipitated in water.
[0135] F3NMe2 (1 equiv) was added to a one neck round-bottomed flask and purged with argon 3 times. Anhydrous CHCl.sub.3 (20 mg of F.sub.3NMe.sub.2/ml) was added to dissolve the F3NMe2. MeOTf (2.5 equiv) was added dropwise to the polymer solution. Precipitation of polymer is observed immediately during addition. The mixture was stirred for 3 hr.
[0136] The precipitated polymer was collected by filtration. The precipitate was dissolved in ACN and precipitated in toluene. The precipitate was redissolved in ACN to undergo dialysis in ACN. After dialysis, the polymer solution was concentrated before precipitation in DEE to yield white F3NMe3-OTf solids.
Example 1c. Synthesis of Poly(9,9′-Bis(3-Trimethylammoniopropyl)Fluorenyl-2,7-Diyl-Benzothiadiazole-2,7-Diyl) Triflate (F3NMe3-OTf-BT) (Scheme 1c)
[0137] 4,7-Dibromobenzo[c]-1,2,5-thiadiazole (diBr-BT) (1 equiv) and diEs-F3NMe2 (1 equiv) and Pd(dppf)Cl.sub.2 (3 mol %) were added to a microwave vial and purged with argon 3 times. Degassed THF:DMF (2:1) (25 mg/ml) was added to the microwave vial to dissolve the reactants. Degassed 200 mg/ml Na.sub.2CO.sub.3 (5 equiv) in H.sub.2O was added to the microwave vial. The reaction mixture was degassed and stirred for an additional 15 min. The vial was then irradiated by microwave (130° C., 15 min).
[0138] The reaction mixture in the microwave vial was dried under vacuum. The solid was dissolved in DCM and washed with water. The DCM layer was isolated, and dried under vacuum. The resultant solid was redissolved in THF. The polymer solution was centrifuged and filtered. Sodium diethyldithiocarbamate (70 equiv of Pd(dppf)Cl.sub.2) in THF was added to the polymer solution. The polymer poly(9,9′-bis(3-dimethylaminepropyl)fluorenyl-2,7-diyl-benzothiadiazole-2,7-diyl) (F3NMe2-BT) solution was filtered and precipitated in DEE.
[0139] F3NMe2-BT (1 equiv) was added to a one neck round-bottomed flask and purged with argon 3 times. Anhydrous CHCl.sub.3 was added to dissolve F3NMe2-BT (20 mg/ml). MeOTf (2.5 equiv) added dropwise to the polymer solution. Precipitation of polymer is observed immediately during addition. The mixture was stirred at room temperature for 3 hr.
[0140] The precipitated polymer was collected by filtration. The polymer was dissolved in MeOH and precipitated in toluene. The precipitate was redissolved in MeOH to undergo dialysis in MeOH. After dialysis, the polymer solution was concentrated before precitation in DEE to yield orange F3NMe3-OTf-BT solids.
Example 1d. Synthesis of poly(9,9′-bis(3-(1-methyl)imidaziopropyl)fluorenyl-2,7) bromide (F3Im1-Br) (Scheme 1d)
[0141] 1-Methyl-imidazole (10 equiv) was added to a solution of 9,9′-bis(3-bromo)fluorenyl-2,7-dibromo (diBr-F3Br) (1 equiv) dissolved in THF (50 mg/ml). The resulting reaction mixture was stirred at 70° C. for two days. After evaporation of the solvent, the crude product was washed with ethyl acetate and DEE to yield 9,9′-bis(3-(1-methyl)imidaziopropyl)fluorenyl-2,7-dibromo bromide.
[0142] 9,9′-bis(3-(1-methyl)imidaziopropyl)fluorenyl-2,7-dibromo bromide (1 equiv), 2,2′-bipyridine (2.5 equiv), bis(cyclooctadiene)nickel(0) (Ni(COD).sub.2) catalyst (2.5 equiv) and cyclooctadiene (COD) (2.5 equiv) were added to a microwave vial. 50 mg/mL of dry DMF was added to microwave vial to dissolve reaction content and then irradiated by microwave (200° C., 60 min). After completion of the reaction, the solution in the vial was filtered and precipitated in DEE and dried under vacuum to yield a dark brown solid. The solid was dissolved in MeOH to undergo dialysis in MeOH to yield F3Im1-Br solids.
Example 1e. Synthesis of poly(9,9′-bis(3-(1-ethyl)imidaziopropyl)fluorenyl-2,7-diyl-1,4-phenylene-N-(p-sec-butylphenyl)imino-1,4-phenylene) bromide (F3Im2-Br-TFB) (Scheme 1e)
[0143] 1-ethyl-imidazole (10 equiv)(light sensitive) was added to a solution of diBr-F3Br (1 equiv) dissolved in THE (50 mg/ml). The resulting reaction mixture was stirred at 70° C. for two days in the dark. After evaporation of the solvent, the crude product was washed with ethyl acetate and DEE to yield 9,9′-bis(3-(1-ethyl)imidaziopropyl)fluorenyl-2,7-dibromo bromide.
[0144] 9,9′-bis(3-(1-ethyl)imidaziopropyl)fluorenyl-2,7-dibromo bromide (1 equiv) and diEs-TFB (1 equiv) and Pd(dppf)Cl.sub.2 (3 mol %) were added to a microwave vial. Degassed THF:DMF (2:1) was added to the microwave vial. Degassed 0.6M Na.sub.2CO.sub.3 (5 equiv) in H.sub.2O was added to the microwave vial. The reaction mixture was degassed and stirred for an additional 15 min. The vial was then irradiated by microwave (130° C., 15 min).
[0145] The solid in the microwave vial was dissolved in DMF and precipitated in DEE. The precipitate was redissolved in MeOH and sodium diethyldithiocarbamate (20 equiv of Pd(dppf)Cl.sub.2) in MeOH was added. The reaction mixture was filtered and precipitated in DEE to yield F3Im2-Br-TFB solids.
Example 2. Ion Exchange
Example 2a. Preparation of poly(9,9′-bis(3-trimethylammoniopropyl)fluorene-2,7-diyl) oxalate (F3NMe3-Ox) by Acid-Based Ion-Exchange
[0146] F3NMe3-OTf was dissolved in 2,2,2-trifluoroethanol (TFE) at 20 mg/mL and added into 10 equiv of hydroxide resin (pre-conditioned in TFE). The vial was left on a roller for 3 hours. The polymer solution was then filtered through 0.45 μm polypropylene (PP) filter and concentrated with a rotary evaporator. The polymer was dissolved in a minimal amount of MeOH and precipitated in toluene. This was repeated once more. The poly(9,9′-bis(3-trimethylammoniopropyl)fluorene-2,7-diyl) hydroxide (F3NMe3-OH) solids were subsequently washed with DEE, then dried under vacuum for an hour. Oxalic acid (1.2 equiv), dissolved in MeOH at 0.1 M, was added into F3NMe3-OH solids which gradually dissolved. More MeOH was added if there are any undissolved solids, up to 30 mg/mL. The solution was left to stir for 5 min. After evaporation of the solvent, the solids were redissolved in water at 10 mg/mL and dialysed. Water was removed via rotavap and the resultant solids were washed with DEE. The polymer was dried in vacuum for 30 min and redissolved in MeOH or 2,2,3,3,4,4,5,5-octafluoro-1-pentanol (OFP) at 20 mg/mL.
Example 2b. Preparation of poly(9,9′-bis(3-trimethylammonioethyl)fluorenyl-2,7-diyl-1,4-phenylene) (F2NMe3-X-Ph) by Acid-Based Ion-Exchange, where X is an Anion
[0147] Where X is an oxalate (Ox)(F2NMe3-Ox-Ph): poly(9,9′-bis(3-trimethylammonioethyl)fluorenyl-2,7-diyl-1,4-phenylene) iodide (F2NMe3-I-Ph) was dissolved in TFE at 20 mg/mL and was added into 10 equiv of hydroxide resin (pre-conditioned in TFE). The vial was left on a roller for 3 hours. The polymer solution was then filtered through 0.45 μm PP filter and concentrated with a rotary evaporator. The polymer was dissolved in minimal amount of MeOH and precipitated in toluene twice, before it was washed with DEE. The poly(9,9′-bis(3-trimethylammonioethyl)fluorenyl-2,7-diyl-1,4-phenylene) hydroxide (F2NMe3-OH-Ph) solids dried under vacuum for 1h. Oxalic acid (1.2 equiv), dissolved in MeOH at 0.1M, was added into F2NMe3-OH-Ph solids which gradually dissolves. More MeOH was added, up to ca. 30 mg/ml, if there were any polymer solids that remained undissolved after adding oxalic acid. The solution was left to stir for 5 more mins. The solution was dried. The solids were suspended and stirred vigorously in water at ca. 4 mg/ml before filtering the supernatant to obtain the solids. This was repeated 5 times. Solids were washed with DEE twice. The polymer was dried in vacuum for 30 mins and re-dissolved in MeOH or OFP at 20 mg/mL.
[0148] Where X is triflate (OTf) (F2NMe3-OTf-Ph): Triflic acid (1.2 equiv), dissolved in MeOH at 0.1 mmol/mL, was added into F2NMe3-OH-Ph solids which gradually dissolves. More MeOH was added, up to ca. 30 mg/ml, if there were any polymer solids that remained undissolved after adding triflic acid. The solution was left to stir for 5 min. The solution was dried. The solids were suspended and stirred vigorously in water at ca. 4 mg/ml before filtering the supernatant to obtain the solids. This was repeated 5 times. Solids were washed with DEE twice. The polymer was dried in vacuum for 30 min and re-dissolved in MeOH or OFP at 20 mg/mL.
[0149] Where X is 1:1 Ox:OTf (F2NMe3-Ox:OTf-Ph). F2NMe3-Ox:OTf-Ph with 1:1 Ox:OTf was prepared by mixing 1:1 F2NMe3-Ox-Ph: F2NMe3-OTf-Ph.
[0150] Alternatively F2NMe3-Ox:OTf-Ph with 1:1 Ox:OTf can be prepared by adding stoichiometric amount of 1:1 oxalic acid: triflic acid to F2NMe3-OH-Ph for acid-base reaction.
Example 2c. Preparation of F3NMe3-SO.SUB.4.-TFB by Ion-Exchange Resins
[0151] Clean hydroxide resins were conditioned with sodium sulfate (Na.sub.2SO.sub.4) solution and rinsed with water, followed by 1:1 MeOH: ACN. F3NMe3-OTf-TFB was dissolved in MeOH:ACN (1:1) at 10 mg/mL and added into 10 equiv of Na.sub.2SO.sub.4 conditioned resin and rolled overnight. The polymer solution was concentrated and precipitated in toluene and washed in DEE. The polymer solid was washed with water, followed by DEE. The polymer solids were dried under vacuum. F3NMe3-OTF:SO.sub.4-TFB is soluble in a MeOH: ACN mixture but not MeOH or ACN only.
Example 2d. Preparation of poly(9,9′-bis(3-trimethylammonioethyl)fluorene-2,7-diyl-9,9-dioctylfluorene-2,7-diyl) (F2NMe3-X-F8) by Contact-Exchange, where X is an Anion
[0152] poly(9,9′-bis(3-trimethylammonioethyl)fluorene-2,7-diyl-9,9-dioctylfluorene-2,7-diyl) triflate (F2NMe3-OTf-F8) was dissolved in OFP to give 5 mg/mL solution. The solution was spin-cast on O.sub.2-plasma cleaned quartz substrates to give 10-nm-thick films. The films were contacted with 80 mM salt solution of X in water or other solvents or solvent mixtures then spin off. This was followed by a spin-wash step with water or other solvents or solvent mixtures.
Example 3: UV-Vis n-Doped Spectra
Example 3a: Optical spectra of n-doped poly[N,N-bis(3-trimethylammoniopropyl)-1,4,5,8-napthalenedicarboximide-2,6-diyl]-alt-5,5′-(thieno[3,2-b]thiophene) oxalate (NDI-TT-Ox) and sulfite (NDI-TT-SO.SUB.3.)
[0153] poly[N,N-bis(3-trimethylammoniopropyl)-1,4,5,8-napthalenedicarboximide-2,6-diyl]-alt-5,5′-(thieno[3,2-b]thiophene) triflate (NDI-TT-OTf) was dissolved in TFE to give 10 mg/mL solution. The solution was spin-cast in the ambient on an 02-plasma cleaned quartz substrate to give a 37-nm-thick film. The film was then brought into a N.sub.2 glovebag at 47% relative humidity (RH) for UV-Vis measurement. The film was subsequently brought out into the ambient and contacted with 80 mM sodium oxalate solution in water, in air, then spin off. This was followed by a spin-wash step with water. UV-Vis measurement of the NDI-TT-Ox film was performed, in N.sub.2 glovebag at 47% RH, after the contact-exchange. The film was then brought into a N.sub.2 glovebox, <1% RH, for a subsequent UV-Vis measurement.
[0154]
[0155] NDI-TT-OTf was dissolved in TFE to give 10 mg/mL solution. The solution was spin-cast on a O.sub.2-plasma cleaned quartz substrate to give a 37-nm-thick film. The film was then brought into a N.sub.2 glovebox, <1% RH, for UV-Vis measurement. The film was then contacted with 80 mM sodium sulfite solution in water, in the N.sub.2 glovebox, then spin off. This was followed by a spin-wash step with water. UV-Vis measurement of the NDI-TT-SO.sub.3 film was performed, in N.sub.2 glovebox, after the contact-exchange.
[0156]
[0157] The figure illustrates one mode of in situ activation of the electron doping for the donor anions, providing ground-state electron doping of organic semiconductors upon dehydration. When the films were transferred into a N.sub.2 chamber with 47% RH (regulated by saturated salt solutions), the film turns brown and its optical spectrum reveals spontaneous n-doping. As the RH is further decreased towards 0% (pH.sub.2O<300 ppm), n-doping becomes complete.
Example 3b: Optical Spectra of n-Doped F2NMe3-Ox-F8 and F3NMe3-Ox-BT
[0158] F2NMe3-OTf-F8 was dissolved in OFP to give 20 mg/mL solution. The solution was spin-cast in the ambient on O.sub.2-plasma cleaned quartz substrates to give 260-nm-thick films. Subsequently, the film was contacted with 80 mM sodium oxalate solution, dissolved in 1:4 MeOH:H.sub.2O, in the dark then spin off. This was followed by a spin-wash step with water. The poly(9,9′-bis(3-trimethylammonioethyl)fluorene-2,7-diyl-9,9-dioctylfluorene-2,7-diyl) oxalate (F2NMe3-Ox-F8) film was then transferred into a vacuum chamber and pumped up to 10.sup.−6 mbar for UV-Vis measurement.
[0159]
[0160] The figure illustrates electron doping for the oxalate anion, providing ground-state electron doping of polyfluorene core upon dehydration. Spontaneous electron doping occurs only under high vacuum conditions.
[0161] F3NMe3-OTf-BT was dissolved in OFP to give 5 mg/mL solution. The solution was spin-cast in the ambient on 02-plasma cleaned quartz substrates to give 19-nm-thick film. The film was then transferred into a vacuum chamber fitted with quartz window for UV-Vis measurement in air. Subsequently, the films was contacted with 80 mM sodium oxalate solution, dissolved in 1:4 MeOH:H.sub.2O, in the dark then spin off. This was followed by a spin-wash step with water. The film was then transferred into a vacuum chamber and pumped up to 10.sup.−6 mbar for UV-Vis measurement.
[0162]
Example 4. FTIR Spectra of Dehydration-Induced n-Doped F2NMe3-Ox-F8
[0163] F2NMe3-OTf-F8 was dissolved in OFP to give 20 mg/mL solution. The solution was drop-cast in the ambient on 02-plasma cleaned intrinsic silicon substrates to give 1.2-μm-thick films. The film was then transferred into a N.sub.2-filled vacuum chamber fitted with potassium bromide (KBr) windows for FTIR measurement and pumped up to 10.sup.−6 mbar for FTIR measurements.
[0164]
Example 5. Improved Device Performances
[0165] Examples are outlined below to illustrate the improvements in electron-injection performance.
Example 5a. Electron Injection from Ag Through F2NMe3-X-F8, where X=Donor Anions
[0166] 30-nm-thick poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDT:PSSH) (1:6) polymer films were spun in air on O.sub.2 plasma-cleaned ITO substrates and annealed (140° C., 15 min) in a N.sub.2 glovebox. 100-nm-thick host material poly(9,9-bis(4-octylphenyl)fluorene-2,7-diyl) (PFOP) from toluene was then spin-cast over the PEDT:PSSH film. 10-nm-thick F2NMe3-OTf-F8 electron injection layer (EIL) was spin-cast on PFOP and contact-exchanged to oxalate (Ox.sup.2−), sulfite (SO.sub.3.sup.2−), sulfate (SO.sub.4.sup.2−), carbonate (CO.sub.3.sup.2−), or phosphate (PO.sub.4.sup.3−) anion as described in Example 2d. Devices were completed with the evaporation of a silver cathode.
[0167]
Example 5b. Electron Space-Charge-Limited-Current (SCLC) in PFOP with F3NMe3-Ox-TFB
[0168] 20-nm-thick poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) polymers with mixed caesium and hydrogen cations (PEDT:PSSCsH) (1:6) polymer films were spun in air on O.sub.2 plasma-cleaned ITO substrates and annealed (140° C., 15 min) in a N.sub.2 glovebox. Variable thicknesses of host material poly(9,9-bis(4-octylphenyl)fluorene-2,7-diyl) (PFOP) from toluene was then spin-cast over the PEDT:PSSCsH film. 10-nm-thick F3NMe3-OTf-TFB electron injection layer (EIL) was spin-cast on PFOP and contact-exchanged to oxalate (Ox.sup.2−) as described in Example 2d. Devices were completed with the evaporation of a silver cathode.
[0169] PEDT:PSSCsH, with an even lower work function than PEDT:PSSH, was used as electron exit contact to further reduce the hole current contribution into PFOP.
[0170]
Example 5c. Electron Injection from F3NMe3-Ox-TFB Capped with Ag or Al
[0171] 30-nm-thick PEDT:PSSH (1:6) polymer films were spun in air on 02 plasma-cleaned ITO substrates and annealed (140° C., 15 min) in N.sub.2 glovebox. 90-nm-thick host material PFOP from toluene was then spin-cast over the PEDT:PSSH film. 10-nm-thick F3NMe3-OTf-TFB film was spin-cast on PFOP and contact-exchanged to oxalate anion. An example of the contact-exchange procedure is described in Example 2d. Devices were completed with the evaporation of Ag or Al.
[0172] Device without EIL capped with Ca/Al was fabricated as reference.
[0173] F3NMe3-Ox-TFB capped with Ag give electron current density similar to the reference (
[0174] F3NMe3Ox-TFB capped with Al give electron current density similar to the reference (
[0175] Calcium of the reference device has a work function much closer to the LUMO of PFOP than that of silver or aluminium, however the use of an electron-injection layer formed from the oxalate-containing polymer has a similar current density to the calcium-containing device.
Example 5d. Electron Injection from Deep Work Function Ag Through Thick n-Doped EIL
[0176] 30-nm-thick PEDT:PSSH (1:6) polymer films were spun in air on O.sub.2 plasma-cleaned ITO substrates and annealed (140° C., 15 min) in N.sub.2 glovebox. 90-nm-thick host material PFOP from toluene was then spin-cast over the PEDT:PSSH film. 5, 10, 30 and 50-nm-thick F2NMe3-OTf-F8 films were spin-cast on PFOP and contact-exchanged to oxalate anion as described in Example 2d. Devices were completed with the evaporation of Ag.
[0177] EIL with increase thickness up to 50 nm gave similar current density. (
Example 5e. Effective Work Function of F3NMe3-Ox-TFB in Device
[0178] 30-nm-thick PEDT:PSSH (1:6) polymer films were spun in air on O.sub.2 plasma-cleaned ITO substrates and annealed (140° C., 15 min) in N.sub.2 glovebox. 100-nm-thick host material poly[2,7-(9,9-di-n-octylfluorenediyl)-alt-(1,4-phenylene-(4-sec-butylphenylimino)-1,4-phenylene)] (TFB) from toluene was then spin-cast over the PEDT:PSSH film. 10-nm-thick F3NMe3-OTf-TFB EIL was spin-cast on PFOP and contact-exchanged to oxalate (Ox.sup.2−) as described in Example 2d. Devices were completed with the evaporation of a silver cathode.
[0179] Device without EIL capped with Ag was fabricated as references.
[0180]
Example 5f. Electron Extraction with F3NMe3-Ox-BT
[0181] Conventional cells. Self-compensated hole-doped triarylamine-fluorene copolymer films as a hole extraction layer (HEL) were spun on O.sub.2 plasma-cleaned ITO substrates in N.sub.2 glovebox. 100-nm-thick 1:1.2 poly([2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]{3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}): 2,2′-[[6,6,12,12-Tetrakis(4-hexylphenyl)-6,12-dihydrodithieno[2,3-d:2′,3‘-d’]-s-indaceno[1,2-b:5,6-b′]dithiophene-2,8-diyl]bis[methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]] bis[propanedinitrile] (PTB7-Th:ITIC) photoactive layer (PAL) from dichlorobenzene was then spin-cast over the PEDT:PSSH film. 20-nm-thick F3NMe3-OTf-BT film was spin-cast on the PAL and contact-exchanged to oxalate anion as described in Example 2d. Devices were completed with the evaporation of Ag.
[0182] Control device with PEDT:PSSH as HCL and Ca/Al as electron contact was fabricated.
[0183] Inverted cells. 20-nm-thick F3NMe3-OTf-BT film was spin-cast in air on 02 plasma-cleaned ITO substrates in N.sub.2 glovebox and contact-exchanged to oxalate anion as described in Example 2d. 100-nm-thick 1:1.2 PTB7-Th:ITIC PAL from dichlorobenzene was then spin-cast over the EIL film. Self-compensated hole-doped triarylamine-fluorene copolymer films were spin-cast on PAL. Devices were completed with the evaporation of Ag.
[0184] All devices were measured under 100 mW cm.sup.−2 illumination with the simulated AM1.5 spectral output on an Oriel Sol2A solar simulator.
[0185]
[0186] The ITO/HEL/PAL/F3NMe3-OTf-BT/Ag device clear shows superior performance than the reference ITO/PEDT:PSSH/PAL/Ca/Al device. The improved fill factor is a signature of reduced contact resistance in highly ohmic contacts. The advantage of solution-processability of the HEL and F3NMe3-OTf-BT allows for solar cells to be fabricated in both conventional and inverted structures.
Example 6. Raman Spectra of Electroactivated n-Doped F2NMe3-Ox-F8 in Device
[0187] 10-nm-thick F2NMe3-OTf-F8 film was spin-cast in air on O.sub.2 plasma-cleaned ITO substrates and contact-exchanged to either oxalate or carbonate anion. An example of the contact-exchange procedure is described in Example 2d. 60-nm-thick host material PFOP from toluene was then spin-cast over the F2NMe3-X-F8film, where X=Ox.sup.2− or CO.sub.3.sup.2−, in a N.sub.2 glovebox. Devices were completed with the evaporation of 5-nm-thick molybdenum oxide (MoOx) and capped with Ag.
[0188] A voltage bias on the ITO, 0V.fwdarw.8V.fwdarw.−3V.fwdarw.0V over a period of 8s, was performed twice on one of the pixel from each device in the N.sub.2 glovebox. The devices were subsequently encapsulated in N.sub.2 for Raman measurements.
[0189] Two 120-nm-thick F2NMe3-OTf-F8 films were spin-cast in air on O.sub.2 plasma-cleaned quartz substrates and contact-exchanged to oxalate anion. An example of the contact-exchange procedure is described in Example 2d. One of the films was loaded into a vacuum chamber for Raman measurement. The other film was evaporated with Ag at a base pressure of 10.sup.−6 torr, followed by encapsulation in N.sub.2 to give a n-doped F2NMe3-OTf-F8 film.
[0190] Unpolarised Raman spectra of a driven and an undriven pixel from each device, an undoped F2NMe3-Ox-F8 film (vacuum 10.sup.−4 mbar), and a n-doped F2NMe3-OTf-F8 film were collected using back-scattered geometry with 633 nm excitation source focused through a glass correctional objective lens (numerical aperture 0.70, 63×).
[0191]
Schemes
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