WO2019145025A1

WO2019145025A1 - Covalent polymer network semiconducting thin-films and method for producing thereof

Info

Publication number: WO2019145025A1
Application number: PCT/EP2018/051640
Authority: WO
Inventors: Liang YAO; Kevin SIVULA
Original assignee: Ecole Polytechnique Federale De Lausanne (Epfl)
Priority date: 2018-01-24
Filing date: 2018-01-24
Publication date: 2019-08-01

Abstract

A method for manufacturing a semiconducting, organic, covalent polymer network thin film is disclosed, said method comprising the steps of deposing a solution comprising azide- containing monomers and electron-deficient alkyne-containing monomers onto a receiving substrate to prepare a film of monomers, and subsequently providing a thermal trigger to the deposed film of monomers to allow a 1,3-dipolar cycloaddition polymerization reaction to occur between azide-containing monomers and alkyne-containing monomers, thereby forming said covalent polymer network thin film on said receiving substrate. The obtainable thin film has optoelectronic and/or semiconductor properties and can be used for the manufacturing of e.g. solar cells, transistors, light-emitting diodes or organic electronic devices.

Description

Covalent polymer network semiconducting thin-films and method for producing thereof

Technical Field

[0001] The present invention lies in the field of optoelectronics, semiconductor devices and solar cells, particularly to a method for preparing an organic covalent polymer network thin film having semiconductor properties.

Background of the Invention

[0002] Solution-processable semiconducting organic polymers have revolutionized the field of organic electronics by enabling the scalable roll-to-roll fabrication of solar cells, light emitting diodes, and transistors. However, improving the robustness of these materials is required for viable commercial application. A relatively new class of materials, organic covalent polymer networks (CPNs), possess attractive advantages over traditional linear polymers such as superior chemical stability, solvent resistance, and mechanical robustness due to their interconnected molecular structure (E. Blasco, M. Wegener, C. Barner-Kowollik, Adv. Mater. 2017, 29, 1604005).

[0003] While a wide variety of CPNs have been demonstrated as promising materials for gas separation, storage, and other fields, employing CPNs in organic electronic devices is still relatively unexplored. Although the excellent robustness of CPNs is potentially attractive for enhancing the stability of organic semiconductor devices, and their solvent resistance could also facilitate the fabrication of solution-processable multi-layer devices, the poor processibility of CPNs has severely limited their application.

[0004] Indeed, typical CPN preparation routes lead to insoluble and intractable powders. While spin-coating powder dispersions has been described (see for instance J. Guo et al. , Nat. Commun. 2013, 4, 2736), such an approach does not offer high quality, continuous large-area thin films. Chemical bath deposition and (gas/liquid) interfacial film growth have also been recently reported, leading to initial device demonstrations with CPNs. However, these synthesis routes are slow— on the order of tens of hours— which seriously diminishes the potential for scalability. While electro- polymerization has also been considered as an alternative method for CRN thin film fabrication (H. Ma et al., Adv. Funct. Mater. 2016, 26 \ 2025), this method is limited to a small subset of monomers (containing carbazole, thiophene, or triphenylamine groups with sufficient electron-donating character). In addition, a non-negligible amount of electrolyte remains in the film, which can be detrimental to optoelectronic performance.

[0005] US patent US7772358 B2 describes a process for synthesizing in bulk hyperbranched polytriazoles, linear and hyperbranched poly(aroyltriazoles) by Huisgen 1 ,3-dipolar cycloaddition. These polytriazoles are synthesized in the absence of metal catalysts and with a thermal refluxing up to 72 hours in organic solvents. The resulting hyperbranched polytriazoles are still soluble in organic solvents, indicating that the polymerization extent is not high enough such that polymer networks containing numerous interconnections between polymer chains are not obtained. Although light emissive properties are exhibited, a semiconducting behavior of these polytriazoles is not revealed.

[0006] In order to advance the application of CPNs in solution-processed organic electronic devices, a rapid and direct film fabrication approach that combines simplicity with high quality film formation and tunable optoelectronic performance is urgently needed.

Summary of Invention

[0007] Provided herein is a method for manufacturing a semiconducting, organic, covalent polymer network thin film, said method comprising the steps of:

[0008] i) providing a solution comprising azide-containing monomers and electron- deficient alkyne-containing monomers;

[0009] ii) deposing said solution onto a receiving substrate to prepare a film of monomers; and

[0010] ill) providing a thermal trigger to the deposed film of monomers to allow a 1 ,3-dipolar cycloaddition polymerization reaction to occur between azide- containing monomers and alkyne-containing monomers, thereby forming said covalent polymer network thin film on said receiving substrate. [0011] Another aspect of the subject-matter described in the present specification relates to a semiconducting, organic, covalent polymer network thin film obtainable by a method as previously described.

[0012] Still another aspect of the subject-matter described in the present specification relates to the use of the organic covalent polymer network thin film as previously described for the manufacturing of solar cells, transistors, light-emitting diodes or organic electronic devices.

[0013] Still another aspect of the subject-matter described in the present specification relates to a solid substrate comprising the organic covalent polymer network thin film of the invention.

[0014] Still a further aspect of the subject-matter described in the present specification relates to the use of said solid substrate for manufacturing of solar cells, transistors, light-emitting diodes or organic electronic devices.

[0015] Still a further aspect of the subject-matter described in the present specification relates to a solar cell comprising an organic covalent polymer network thin film of the invention or a solid substrate according to the invention.

[0016] Still a further aspect of the subject-matter described in the present specification relates to an azide-containing monomer selected from a list consisting of the following monomers:

[0017] Preferably, the R groups are independently selected from the group consisting of -H, a heteroatom, branched or unbranched alkyl or substituted alkyl, branched or unbranched alkenyl or substituted alkenyl, alkynyl, phenyl, benzyl, aryl, heteroaryl or substituted heteroaryl, aroyl, aryloxy, carboxy, ester, carboxamide, carbamoyl, oligopeptidyl, amine, halo, hydroxyl, mercapto, acryloyl, methacryloyl, styryl, isocyanate, sulfonyl hydroxide, phosphono or its derivatives, phosphate or its derivatives, oxiranyl, trihalosilyl, and trialkoxysilyl.

[0018] Still a further aspect of the subject-matter described in the present specification relates to an alkyne-containing monomer selected from a list consisting of the following monomers:

[0019] The above and other objects, features and advantages of the herein presented subject-matter will become more apparent from a study of the following description with reference to the attached drawings.

Brief description of drawings

[0020] Figure 1 shows a) Molecular structure of the PDI-DA and Triazine-TA monomers and b) a schematic representation of the CRN synthesis;

[0021] Figure 2 shows thermogravimetric analysis (TGA) curves of PDI-DA and Triazine-TA;

[0022] Figure 3 shows ¹H NMR spectra of (a) PDI-DA and (b) Triazine-TA before and after heating at 180 C for 30 min. The star label in the figure represents solvent signal;

[0023] Figure 4 shows an optical microscope image of the blend film prepared from solvent evaporation. The blend of 5 mg PDI-DA and 1.62 mg Triazine-TA was dissolved in 1 mL chloroform; [0024] Figure 5 shows (a) FT-IR spectra of PDI-DA and insoluble CRN powder (with asterisk indicating C0₂ stretch); (b) ¹³C solid-state MAS-NMR of the as-cast blend and insoluble CRN powder and a schematic of the assigned peaks;

[0025] Figure 6 shows ¹³C solid-state MAS-NMR of Triazine-TA and PDI-DA;

[0026] Figure 7 shows mass spectra of the soluble products obtained by the in-situ TAAC reaction. The top figure shows the experimental results, and the bottom figure gives the theoretical values. The solid state mixture of PDI- DA and Triazine-TA was heated at 180° C for 1 h. After the reaction, the soluble products were extracted by chloroform. A3 and B2 in the figure represents Triazine-TA and PDI-DA, respectively;

[0027] Figure 8 shows optical microscope images of the spin-coating films (35 nm).

(a) Chloroform as processing solvent; (b) chlorobenzene as processing solvent. The blend solution of 3 mg mL·¹ PDI-DA and 0.97 mg mL·¹ Triazine- TA dissolved in chloroform or chlorobenzene was spin coated on glass substrate. Chloroform enables a smooth and homogenous film (a). Micrometer-scale phase segregation was observed in the film processed from chlorobenzene solution (b), which is induced by the slow evaporation of chlorobenzene;

[0028] Figure 9 shows an optical microscope image of the PDI-DA and Triazine- TA blend film after heating at 180° C for 30 min. The smooth morphology is still kept after heating;

[0029] Figure 10 shows (a) UV-vis spectra of (top) the blend thin film heated at 180 °C for different times and (bottom) the PDI-DA solution (10^~5 mol Lr¹ in THF);

(b) The absorption ratio (i.e. the ratio of UV-vis absorption at 570 nm after washing the film with CB to before washing) as a function of thermal treatment (T™ for 10 min). The inset figure shows the UV-vis spectra of the blend film treated at various T™ for 10 min and after washing in CB for the 180 °C film;

[0030] Figure 11 shows (a) Absorption spectra of PDI-DA in thin film and solution;

(b) Absorption spectra of Triazine-TA in thin film and solution. PDI-DA exhibits a sharp absorption with the peak at 556 nm in diluted solution (10-⁵ mol L·¹ in THF). In thin film, the absorption spectra is broadened, and the absorption peak is shifted to 654 nm and 491 nm, which is caused by the tt-p stacking of PDI-DA. The UV spectra of Triazine-TA show the maximum absorption peak at 305 nm, indicating that Triazine-TA has a very wide band-gap;

[0031] Figure 12 shows UV spectra of the polymer network films before and after washing by chlorobenzene (CB). Different heating temperatures are compared. The heating time for all the films was 10 mins. It can be seen that for the films heated at the temperature higher than 120° C, the absorption keeps the same after washing by CB. The result implies that appreciable reaction extent can be achieved at the heating temperature higher than 120° C;

[0032] Figure 13 shows the resistance of the CRN film for common organic solvents. The CRN film was prepared from heating the blend film at 180° C for 10 min. THF: tetrahydrofuran, DMF: dimethylformamide, DCB: dichlorobenzene, ACE: acetonitrile, EA: ethyl acetate, Tol: toluene, CF: chloroform, CB: chlorobenzene;

[0033] Figure 14 shows (a) AFM images of the as-cast film and the CRN film obtained after 10 min annealing at 180° C; (b) image of the CRN free- standing film (left) with the thickness of 35 nm delaminated from an ITO substrate. A TEM image (right) of the folded edge of the free-standing film is also shown;

[0034] Figure 15 shows atomic force microscopy (AFM) images of the as cast film and the films heated at different temperature for 10 min;

[0035] Figure 16 shows (a) GIWAXS out-of-plane line-cuts of as cast film and heated films (120° C or 180° C); (b) GIWAXS out-of-plane line-cuts of as cast film, PDI-DA and Triazine-TA. The blend film was prepared by drop casting. The as cast blend film contained the scattering peaks of both PDI- DA and Triazine-TA. After heating, it can be observed that some peaks are less pronounced. The heating time for the TAAC reaction was 30 min;

[0036] Figure 17 shows AFM images of the films heated at different temperature for 2 hours;

[0037] Figure 18 shows an optical microscope image of the free-standing CRN film supported by a glass substrate. The scale bar is 200 pm; [0038] Figure 19 shows (a) the average p_sat of CRN films as a function of TVxn and time; (b) the average p_sat of a CRN film (T_ran = 150° C) as a function of CB soaking time. The inset image displays the transistors based on as-cast blend and CRN films in CB after soaking for 2 h;

[0039] Figure 20 shows transfer curves of the transistors. The heating time was 10 min. The source-drain voltage of 80 V was applied;

[0040] Figure 21 shows additional transfer curve of the transistors: (a) CRN film transistor before and after 2 hour CB soaking; (b) as cast film transistor before and after 5 min CB soaking. CRN film is obtained after heating at 150° C for 10 min. The source-drain voltage of 80 V was applied;

[0041] Figure 22 shows (a) the molecular structure of polymer donor and planar heterojunction (PHJ) and planar-mixed heterojunction (PM-HJ) device configurations; (b) J-V characteristics of the optimized CPN/PTB7 and CPN/P3HT PHJ devices; (c) J-V characteristics of the hybrid planar-mixed heterojunction (PM-HJ) devices with or without CRN processed at T_ran = 120° C. The dashed curves represent P3HT:PC_6iBM bulk heterojunction (BHJ) devices, and the solid curves represent PTB7:PC7iBM BHJ devices;

[0042] Figure 23 shows (a) CV curve of the PDI-DA and Triazine-TA blend. The film after heating at 180° C for 20 min exhibits the identical onset reduction and oxidation potential with the as cast film. The HOMO and LUMO levels are estimated as -5.9 eV and -3.7 eV, respectively. The result indicates the heating temperature of TAAC reaction has insignificant effect on the energy levels of the films; (b) Energy level alignment of CRN, P3HT and PTB7;

[0043] Figure 24 shows the EQE curve of the optimal a) CPN/PTB7 and b) CPN/P3HT PHJ devices. The bottom figure shows the absorption spectra of PTB7, P3HT and CRN film. The CRN film was prepared from heating at 150° C for 10 min;

[0044] Figure 25 shows J-V characteristics of a) CPN/PTB7:PCyiBM and b) CPN/P3HT:PC₆I BM PM-HJ devices;

[0045] Figure 26 shows examples of possible azide-containing monomers (26a) and electron-deficient alkyne-containing monomers (26b). R is a general group improving or facilitating solubility of the monomers depending on the solvent used; for instance, R can be a polar group facilitating solubilization of monomers into aqueous solutions, or R can be a non-polar group such as an alkyl chain facilitating solubilization of monomers into organic solutions.

Detailed description of the invention

[0046] The subject-matter herein described will be clarified in the following by means of the following description of those aspects which are depicted in the drawings. It is however to be understood that the subject matter described in this specification is not limited to the aspects described in the following and depicted in the drawings; to the contrary, the scope of the invention is defined by the claims. Moreover, it is to be understood that the specific conditions or parameters described and/or shown in the following are not limiting of the subject-matter herein described, and that the terminology used herein is for the purpose of describing particular aspects by way of example only and is not intended to be limiting of the invention as claimed.

[0047] As used herein and in the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

[0048] Also, the use of "or" means "and/or" unless stated otherwise.

[0049] Similarly, "comprise", "comprises", "comprising", "include", "includes" and "including" are interchangeable and not intended to be limiting. It is to be further understood that where descriptions of various aspects use the term "comprising", those skilled in the art would understand that in some specific instances, an aspect can be alternatively described using language "consisting essentially of " or "consisting of'.

[0050] Further, for the sake of clarity, the use of the term“about” is herein intended to encompass a variation of +/- 10% of a given value.

[0051] In view of the limitations and the drawbacks of the previous approaches to overcome the challenge of CRN film fabrication, the inventors have conceived a novel manufacturing method that is realized by the use of a catalyst-free thermal alkyne-azide cycloaddition (TAAC) reaction. The CRN thin films are rapidly obtained through the in-situ heat treatment of a blend film containing alkyne- and azide-based monomers, and since the TAAC reaction affords site-specific bond-formation in the absence of catalyst or additional solvent, the method enables a“pure” and well-defined CPN thin film. Compared to the known strategy of cross-linking linear polymers, the approach demonstrated by the present invention offers the advantages of synthetic simplicity and less batch-to-batch variation as only small-molecule precursors are used.

[0052] In addition, the polymer cross-linking approach frequently requires the addition of initiator and exhibits a non-specific reaction mechanism, which has a negative impact on the optoelectronic performance. The presently invented method possess a high specificity, which clearly provides a major advantage. Moreover, the method of the invention enables the fabrication of smooth CPN films with thermally stable homogenous morphology, favorable solvent resistance, and tunable optoelectronic properties directly on a wide variety of substrates. In an implemented aspect of the invention, the application of these robust CPN films in solution-processed multilayer organic solar cells has been demonstrated, where introducing CPN films is shown to be a versatile method to improve the solar energy conversion efficiency.

[0053] The invention provides for a new method for manufacturing a semiconducting, organic, covalent polymer network thin film. A“covalent polymeric network”, also referred to herein as“CPN”, is a highly dense macromolecule, in which essentially each constituting unit is connected to other constituting unit and possibly to the macroscopic phase boundary by permanent covalent bonding sites throughout the macromolecule. Covalently crosslinked networks typically yield materials with desirable properties such as improved strength, flexibility, and durability. Covalent crosslinks can be formed by a large number of chemical reactions, which are initiated by heat, pressure, changes in pH or light.

[0054] Generally speaking, a“thin film” as used herein relates to a film or layer of a material having a thickness much smaller than the other dimensions, e.g. at least one fifth compared to the other dimensions. Typically, a thin film is a solid layer having an upper surface and a bottom surface, with any suitable shape, and a thickness generally in the order of nanometers or even micrometers, depending on the needs and circumstances, e.g. the manufacturing steps used to produce it. However, the film of the invention can even be a so called“single layered film” or“monolayer”, a substantially two-dimensional layer of covalently-bonded monomers. As used herein, a “two-dimensional” layer or film is a sheet-like macromolecule consisting of interconnected repeat units having a thickness in the order of a single molecule (monomolecular). In some aspects, the film according to the invention has a thickness comprised between about 1 and 1000 nanometers, such as for instance between about 10 and 800 nanometers, between about 50 and 500 nanometers, between about 100 and 600 nanometers, between about 200 and 500 nanometers or between about 300 and 500 nanometers.

[0055] In a first step of the method of the invention, a solution comprising azide- containing monomers and electron-deficient alkyne-containing monomers is deposited onto a receiving substrate to prepare a film of monomers. In this first phase, the monomers are brought into tight contact between them by depositing the same onto a substrate, while being however still not covalently connected. The solution can be deposited onto the receiving substrate by methods known in the art such as spin coating, chemical or physical vapour deposition, spraying, painting, doctor blading, draw coating, dip coating or inkjet printing. The best choice for the depositing method within the frame of the present invention can be easily assessed by a person skilled in the art depending on the needs and circumstances; for instance, in order to obtain very thin film of monomers (in the order of few nanometers), spin coating or vapour deposition techniques are highly advantageous. Furthermore, the thickness of the film can be optimized by changing some parameters such as for instance the concentration of the starting solution or the spin rate in case spin coating is used.

[0056] For“azide-containing monomers”, it is herein meant organic monomers comprising the azide group N₃. Advantageously, azide-containing monomers (as well as, mutatis mutandis, electron-deficient alkyne- containing monomers) have multiple functional azide groups such that a network polymer will form upon polymerization with electron-deficient alkyne-containing monomers counterparts. Therefore, in many advantageous aspects according to the present disclosure, the azide monomers are selected from diazides, including conjugated and non- conju gated diazides, triazides including conjugated and non-conjugated triazides, as well as metal containing diazides/triazides derivatives.

[0057] For“electron-deficient alkyne-containing monomers” it is herein meant organic monomers comprising acetylene functional groups connected with electron-withdrawing groups. Electron deficiency occurs when a compound has too few valence electrons for the connections between atoms to be described as covalent bonds. Electron deficient bonds are often better described as 3-center-2-electron bonds. The term electron-deficient is also used in a more general way in organic chemistry, to indicate a pi -system such as an alkene or arene that has electron-withdrawing groups attached, as found in nitrobenzene or acrylonitrile. Accordingly, preferred electron- deficient alkyne-containing monomers have terminal alkynes and comprises monomers selected from a non-limiting group comprising a diacetylene, an aromatic diacetylene, a triyne, an aromatic triyne, or an aroyldiacetylene having adjacent electron withdrawing groups such as trihalides, cyano groups, sulfonic groups, nitro groups, ketones, aldehydes, amides, esters such as the benzoate group, carboxylic groups, carboxylate esters and the like.

[0058] Moreover, preferably both the electron-deficient alkyne-containing monomers and the azide-containing monomers have features allowing to form a semiconducting polymeric network. In some aspects, the azide- containing monomers for use according to the method herein presented are selected from a list comprising or consisting of the following monomers, (further shown in Figure 26A):

[0059] In some aspects, the R groups are independently selected from the group consisting of -H, a heteroatom (i.e. an atom other than carbon, for example boron, nitrogen, oxygen, phosphorous, sulfur, silicon or germanium), branched or unbranched alkyl or substituted alkyl, branched or unbranched alkenyl or substituted alkenyl, alkynyl, phenyl, benzyl, aryl, heteroaryl or substituted heteroaryl, aroyl, aryloxy, carboxy, ester, carboxamide, carbamoyl, oligopeptidyl, amine, halo (i.e. fluoro, chloro, bromo or iodo), hydroxyl, mercapto, acryloyl, methacryloyl, styryl, isocyanate, sulfonyl hydroxide, phosphono or its derivatives, phosphate or its derivatives, oxiranyl, trihalosilyl, and trialkoxysilyl.

[0060] In some aspects, the electron-deficient alkyne-containing monomers for use according to the method herein presented are selected from a list comprising or consisting of the following monomers (further shown in Figure 26B):

[0061] Preferably, and within the scope of the present disclosure, the molar ratio (in the solution and resulting blend film) between azide groups from the azide-containing monomers and acetylene groups from the electron- deficient alkyne-containing monomers is selected according to the Carothers equation to form a network polymer. As it is known to a person skilled in the relevant art, monomers should have multiple functional (for example, azide/alkyne in the present case) groups such that a network polymer will form. The functionality of a monomer molecule is the number of functional groups which participate in the polymerization. Monomers with functionality greater than two will introduce branching into a polymer, and the degree of polymerization will depend on the average functionality per monomer unit, and the molar ratio of functional groups present in the mixture of monomers. This is defined by the Carothers equation as any system with an average monomer functionality of greater than 2. As a way of example, when using a stoichiometric mixture (based on functional groups) of a monomer with 2 azide functionalities and a monomer with 3 alkyne functional groups, an average functionality of 2.4 is obtained. As it will be evident for a skilled person, other (non-stoichiometric or functional-number) combinations are possible.

[0062] The solution comprising azide-containing monomers and electron-deficient alkyne-containing monomers can comprise either an aqueous solvent or an organic solvent (i.e., can be an aqueous solution or an organic solution). The choice of the solvent is dictated by several different factors such as the used monomers, the decomposition temperature of these latter or the receiving substrate just to cite a few. Generally speaking, any solvent that is capable to dissolve the used monomers, and which has a sufficient vapour pressure to allow the deposition of a film, can be considered as suitable within the scope of the invention.

[0063] As used herein, an“aqueous solution” is a solution in which the solvent is substantially made of water. In the frame of the present disclosure, the term “aqueous” means pertaining to, related to, similar to, or dissolved in water.

[0064] An“organic solution” or“non-polar solution” is a solution in which the solvent is a non-polar compound. Non-polar solvents are intended to be compounds having low dielectric constants and that are barely or not miscible with water. Organic solutions can comprise for example solutions comprising oils, benzene, carbon tetrachloride, diethyl ether, isooctane, ethanol, heptanol, cyclohexane, hexadecane, n-octane and the like. In a preferred aspect, organic solutions according to the subject-matter of the present disclosure comprise chloroform, dichloromethane, tetrahydrofuran, chlorobenzene, toluene, dimethyl sulfoxide, dimethyl formamide, xylene, as well as mixture thereof.

[0065] The receiving substrate can be variable in nature, and its choice is not limiting as long as this is not soluble in the solvent used to process the film. For instance, the receiving substrate can be selected from a non-limiting group comprising silicon dioxide, glass, quartz, aluminium oxide, in particular sapphire, indium tin oxide, ceramics, mica, brass, non-noble metals such as aluminium, steel, iron, tin, solder, titanium, magnesium, zinc, chrome, copper, nickel, silicon, cobalt, tantalum, zirconium and oxides thereof, noble metals such as silver, gold, platinum, palladium, osmium, and alloys thereof, silver oxide, polymers such as epoxy resins, polyesters, polyethylene terephthalate), polyethylene naphthalate), poly(lactic acid), polyamides, polyurethanes, poly(vinylic) polymers, poly(vinyl alcohol), poly(vinyl acetate), poly(vinylidene chloride), polyolefins, poly(isoprene), poly(methacrylate)s, polyecrylate)s or combinations of the foregoing.

[0066] In a second step according to the method herein presented, a thermal trigger is provided to the deposed film of monomers in order to allow a 1 ,3- dipolar cycloaddition polymerization reaction to occur between azide- containing monomers and alkyne-containing monomers, thereby forming said covalent polymer network thin film on said receiving substrate. A thermal trigger according to the subject-matter of this disclosure can be provided in a variety of forms, such as for instance as heating, electromagnetic irradiation, ultrasonication as well as suitable combinations of the foregoing. Importantly, the temperature at which said heating must be conducted should be comprised between room temperature (about 25°C) and the thermal decomposition temperature of the used monomers. As it will be evident, the choice of the temperature range is linked to the need to obtain a suitable film of monomers on a receiving substrate without decomposing the azide-containing and alkyne-containing monomers, and it is therefore associated to the chemical nature of these latter. The decomposition temperature of the used azide-containing and alkyne- containing monomers can obviously be variable; therefore, the temperature at which the 1 ,3-dipolar cycloaddition polymerization reaction is performed is selected accordingly. Typically, for the majority of the azide-containing monomers and electron-deficient alkyne-containing monomers having semiconducting properties according to the invention, said temperature is comprised between about 25°C and 1000°C, usually between about 50°C and 800°C such as between about 50°C and 600°C, between about 50°C and 500°C, as between about 50°C and 400°C, between about 50°C and 350°C, preferably between about 100°C and 300°C, still preferably between about 100°C and 250°C or between about 120°C and 200°C such as at 120°C, 150°C, 180°C or 200°G.

[0067] Generally speaking, the rate of 1 ,3-dipolar cycloaddition polymerization is drastically increased in the presence of an appropriate catalyst such as transition-metal ions, but the inclusion of e.g. copper ions to drive the reaction could result detrimental for optoelectronic properties and performance of a semiconducting thin film. One of the main advantage of the method herein described lies in the possibility to use a starting solution which is free of metal catalyst(s), thus rendering the method environmental friendly, less costly and without any catalyst residues left inside the polymer. Additionally, the cycloaddition crosslinking reaction requires a short reaction time, thus favouring up-scalability of the process. In some aspects, the reaction is favoured by providing a thermal trigger for about 10 seconds to few minutes such as 10 or 30 minutes, up to about several hours, such as for instance 1 , 2, 3, 5, 10 or 24 hours. The time range is decided depending on the needs and circumstances, and shall be sufficiently long to drive the reaction up to the production of an insoluble, non-re-dissolvable covalent polymer network.

[0068] In alternative aspects according to the subject-matter herein described, the method further comprises an additional step of depositing an additional solid substrate on said semiconducting organic covalent polymer network thin film, or otherwise removing said semiconducting organic covalent polymer network thin film from said receiving substrate. Those further steps are advantageous in scenarios wherein optoelectronic devices, solar cells, transistors or organic electronic devices have to be fabricated. These steps can be performed by means of methods known in the art such as spin coating, vapour depositions, doctor blading and the like.

[0069] As it will be evident, another aspect of the subject-matter described in the present specification relates to a semiconducting, organic, covalent polymer network thin film obtainable by a method as previously described. In one aspect, the polymerized semiconducting organic covalent polymer network thin film has a thickness comprised between 1 nm and 1000 nm, such as for instance between about 10 and 800 nanometers, between about 50 and 500 nanometers, between about 100 and 600 nanometers, between about 200 and 500 nanometers or between about 300 and 500 nanometers, and in preferred aspects with a smooth appearance of the upper surface (i.e., the surface not in direct contact with the receiving substrate); in particular, the semiconducting organic covalent polymer network thin film can have a root mean square roughness of less than 5 nm, as detectable by atomic force microscopy. Advantageously, in the most preferred aspects, the semiconducting organic covalent polymer network thin film is characterized in that it has optoelectronic and/or semiconductor properties.

[0070] Additionally, another aspect of the disclosure herein described relates to the use of the semiconducting organic covalent polymer network thin film as previously described for the manufacturing of solar cells, transistors, light- emitting diodes or organic electronic devices, a solid substrate comprising the semiconducting organic covalent polymer network thin film, the use of said solid substrate for manufacturing of solar cells, transistors, light- emitting diodes or organic electronic devices as well as solar cells comprising a semiconducting organic covalent polymer network thin film as herein described and a solid substrate according to the present disclosure.

EXAMPLES

[0071] To describe and illustrate more clearly the subject matter of the present disclosure, the following examples are provided in detail, which however are not intended to be limiting of the invention.

[0072] 1. Catalyst- and Solvent- free synthesis of CP Ns

[0073] To demonstrate the TAAC-based CRN formation, two monomers, Perylenediimide diazide (PDI-DA) and Triazine trialkyne (Triazine-TA; Figure 1 a), were rationally designed and prepared. Perylenediimide (PDI) was chosen as it is an extensively investigated building block for organic n- type materials. Azidoethyl groups were included at the imide position of PDI for the TAAC reaction and 4-(octyloxy)phenoxy groups at the bay positions to increase solubility. For Triazine-TA, electron-withdrawing alkynes were selected to accelerate the TAAC reaction rate. Before running the TAAC reaction (shown schematically in Figure 1 b), the thermal stability of the two monomers was evaluated using thermogravimetric analysis (TGA; Figure 2), and ¹H NMR (Figure 3), which indicated monomer stability to 200 °C.

[0074] To test the TAAC solid state reaction, the two monomers were first dissolved in chloroform at a 1 :1 molar ratio of azide to alkyne, and the solid-state mixture was prepared by evaporating the chloroform. The mixture was heated at a reaction temperature, T™, of 180 °C for 1 hour under argon and insoluble CPN powder was formed implying the TAAC reaction occurs at temperatures below decomposition. The reaction yield was estimated from the mass of insoluble powders and the mass of the monomers before the TAAC reaction. A low mass yield (47%) was found under this condition, which is attributed to a pm-scale phase segregation between monomers in the evaporated mixture as shown by optical microscopy (Figure 4). For the insoluble CPN powder, the intensity of the PDI-DA azide group IR stretch at 2103 cm-¹ is significantly suppressed (Figure 5a). In the solid-state MAS ¹³C NMR spectra (Figure 5b, see reference in Figure 6), the alkynyl carbon signals (marked b, c) of Triazine-TA (at 80.2 and 77.4 ppm) are diminished in the CPN powder. Notably, the Triazine-TA methylene signal (marked a) shifts from 55.4 ppm to 61.1 ppm in the CPN powder, ascribed to the formation of triazole. In addition, the formed triazole also induces the ¹³C signal shift of methylene in PDI-DA (marked d). The mass spectra of the soluble products (Figure 7) indicates a mixture of oligomers with observed molecular weights matching well with predicted values, suggesting no unknown side reactions occur. Overall these characterization results confirm the success and specificity of the solid-state TAAC reaction between PDI-DA and Triazine-TA.

[0075] 2, Morphology of the CPN thin films

[0076] To obtain CPN thin films, blend solutions of PDI-DA and Triazine-TA were spin-coated onto glass or ITO substrates. The type of the used solvent was found to be critical for the film formation. While processing from chlorobenzene (CB) led to pm-scale phase separation (Figure 8), chloroform (CF) gave smooth and homogeneous films with no detectable phase separation, even after treating at T™ = 180 °C (Figure 9). Varying the concentration of the CF solution allowed a tunable film thickness between 10-100 nm without changing the film homogeneity. UV-vis spectra of thin- films after heating for different times (Figure 10a) give insight into the progress of the CPN film formation. The as-cast blend film of monomers displayed a broad absorption with peaks at 670 nm and 494 nm attributed to TT-TT stacking of PDI-DA (the peak at 305 nm is due to Triazine-TA, see Figure 11). Heating at 180 °C causes the peak at 670 nm to decrease while a new absorption band appears at 570 nm. This new band has nearly the same position as PDI-DA in dilute solution (Figure 10a bottom), suggesting that the tt-p stacking is progressively disrupted as the TAAC reaction occurs, as expected from the covalent bonding between PDI and triazine. The formation of the CPN films is very rapid: a clear change of absorption is observed after heating for only 10 s, and no change is seen after 10 min.

[0077] Varying the reaction temperature, T™, from 90-180 °C (10 min heating, Figure 10b inset) showed a similar effect on the UV-vis spectra compared to varying heating time at 180 °C and the extent of the TAAC reaction could be further probed by assessing the solvent resistance of the resulting CPN film (by washing with CB). For films treated at 180° for 10 min there was no change in the UV-vis spectra after washing (Figure 10b inset). The ratio of the UV-vis absorption after/before CB washing as a function of T™ is shown in Figure 10b (see also Figure 12) and suggests that 10 min heating at 120 °C is sufficient to prepare a robust insoluble CRN film. Interestingly, while films treated at T_rx_n of 120-180 °C all exhibit robust insoluble CRN film formation, they significantly differ in UV-vis spectra, implying a tunable tt-p stacking and self-assembly that reasonably should influence the charge carrier transport in the CRN film. In addition to solvent resistance in CB, the CRN films possess solvent resistance for many other common organic solvents, i.e. it is insoluble in organic solvents upon polymerization (Figure 13).

[0078] Morphological characterization of the thin films prepared by spin-coating from CF solutions showed homogeneity from the nm to mm length scales. Atomic force microscopy (AFM, Figure 14a) showed that an as-cast blend film is smooth (RMS roughness of 4.2 nm) with granular domains less than 100 nm in lateral dimension. After heating for 10 min, the domain boundaries are softened, and the RMS roughness decreases to 3.6 nm (120 °C), 3.3 nm (150 °C) and 2.7 nm (180 °C) (see Figure 15). This smoothing of the topography is consistent with the formation of fewer PDI aggregates as suggested by the UV-vis data. A decrease in crystallinity as a result of the CRN formation is further supported by grazing incident wide angle X-ray scattering (GIWAXS). Out-of-plane scans (Figure 16), show that the scattering peaks of the as-cast film become less pronounced after heating, in good agreement with the UV-vis spectra and AFM data. Notably, the film morphology remains unchanged after heating for 2 hours at T_rx_n = 120°C or 180 °C (Figure 17) indicating excellent thermal stability of the CRN films.

[0079] The robustness of the CRN films are further demonstrated by delaminating a 35 nm thick CRN film from an ITO substrate (via dilute HCI etching). The resulting free-standing film (ca. 0.4 cm² see Figure 14b) retains mechanical integrity and can be easily transferred to any substrate. Transmission electron microscopy (Figure 14b) and optical microscopy (Figure 18) further confirm that the free-standing CRN film is homogeneous over pm to mm length scales. [0080] 3. Electron mobility of the CPN films

[0081] As the optoelectronic performance of the CPN is of particular interest, thin films were next investigated as active layers in organic field effect transistors (OFETs). Bottom-gate bottom-contact devices were fabricated as described in the experimental section and the extracted saturation-regime electron mobility, p_sat, as a function of 1™ and heating time is shown in Figure 19a (for transfer curves see Figure 20). The as -cast film of monomers exhibited P_sat = 1.1 *10^~5 cm² V ¹ S^“1. This relatively low electron mobility is likely due to the bulky substituents on the PDI bay-region, which affect the planarity of PDI and negatively impact the intermolecular charge transport. This issue could be resolved by further optimization of molecular structure. After heating the blend film for 10 min, p_sat slightly increased when Trxn = 90 °C, and decreased for films treated at higher Trxn (when CPN formation occurs) consistent with the decrease in film crystallinity and loss of aggregation observed in the UV-vis results. This observation further validates the ability to tune the optoelectronic performance of the CPN film. Importantly, heating at 120 °C or 150 °C reduced p_sat by less than factor of 10 while still forming a robust CPN. In fact, p_sat remained essentially constant over a 2-hour heating period (Figure 19a) indicating thermal stability, and solvent resistance (tested by soaking CPN transistors prepared at 150 °C in CB and retesting repeatedly over 2 hours) was further verified by exhibiting an insignificant effect on p_sat after a small initial decrease (Figure 19b). In contrast, the as-cast blend film of PDI-DA and Triazine-TA completely loses electrical signal after 5 min soaking in CB (Figure 21) due to the dissolution of the film in the CB (see photograph of soaking solution Figure 19b inset).

[0082] 4. The application of the CPN films in solar cells

[0083] The tunability and robustness of the CPN electronic properties even under solvent soaking suggests their effectiveness in applications that require solvent-tolerance, such as solution-processed multilayer device fabrication. To demonstrate this, planar heterojunction (PHJ) organic photovoltaic devices (OPVs) were studied using CPN films as the acceptor layer, and common linear polymers P3HT or PTB7 as the donor (See molecular structures Figure 22a). Firstly, we established the HOMO/LUMO levels the CPN film at -5.9 eV and -3.7 eV, respectively (Figure 23a), and found these levels to be invariant with T™. Since this energy level alignment is suitable for exciton dissociation at the CPN/PTB7 or CPN/P3HT interface (Figure 23b), inventors next fabricated inverted PHJ OPVs (active areas of 16 mm²) with the configuration of ITO/ZnO/CPN/(PTB7 or P3HT)/Mo03/Ag (see schematic Figure 22a) by directly spin coating PTB7 or P3HT on the formed CPN. Device fabrication conditions were optimized (e.g. CPN film thickness and T_rx_n, see Table 1), and the current density-voltage (J-V) curves of the optimized devices are shown in Figure 22b. The average power conversion efficiency (PCE) of the CPN/PTB7 PHJ devices at optimized conditions is 0.53% with an open-circuit voltage (V_oc) of 0.73 V, a short circuit current (Js_c) of 1.65 mA cm^-2, and a fill factor (FF) of 45%. The CPN/P3HT PHJ device exhibits a V_oc of 0.53 V, a J_sc of 1.73 mA cm-², a FF of 53% and an average PCE of 0.52%. The external quantum efficiency (EQE) spectra of the optimized PHJ devices are displayed in Figure 24 and photons absorbed by the CPN layer actively contribute to photocurrent for both CPN/PTB7 and CPN/P3HT devices. Notably, the CPN/P3HT PHJ device achieved a comparable performance with reported bulk heterojunction (BHJ) devices based on mono PDI acceptors and P3HT (See Table 2) although it is well known that the performance of PHJs are inferior to that BHJs due to a limited donor-acceptor interfacial area. Nevertheless the PHJ device results confirm the promising potential of CPN films in the construction of solution- processed multi-layer optoelectronic devices.

[0084] The suitability of our CPN preparation for robust optoelectronic application was further demonstrated by employing films as interfacial layers in PTB7:PC₇I BM or P3HT:PCeiBM BHJ OPVs by coating the BHJ on top of the CPN film giving a planar-mixed heterojunction (PM-HJ) OPV with a final configuration of ITO/ZnO/CPN/(PTB7:PC_7iBM or P3HT:PC_6iBM)/Mo0₃/Ag (See device schematic Figure 22a). The J-V curves of optimized devices are shown in Figure 22c, and the device metrics are summarized in Table 3. The control PTB7:PC₇I BM BHJ device without a CPN layer shows an average PCE of 6.95% with a V_oc of 0.73 V, a J_sc of 14.9 mA cm-², and a FF of 0.67. When adding a CPN layer prepared at T™ = 120 °C an enhanced V_oc of 0.75 V and J_sc of 16.7 mA cm-² is observed leading to an average PCE of 7.94% (highest PCE of 8.19%). The improvement in both the V₀₀ and the J_sc suggest a reduced recombination at the electron-collecting cathode interface due to the presence of the CPN. Similarly, the PCE of P3HT:PCeiBM PM-HJ device is improved from 3.34% to 4.17%. It is noted that the PM-HJ devices with Trxn = 150 °C and 180 °C show a slightly reduced PCE compared to T™ = 120 °C (Figure 25), likely due to the lower electron mobility of the CPN film prepared at these condition.

[0085] Table 1. Photovoltaic parameters of the PHJ devices. The results are average values calculated from 6 cells.

Jsc

CPN film Polymer

PCEavg(max)

Polymer [mA cnrf FF

O nm — - P3HT 60 nm 0.25 0.46 0.31 0.04 (0.07)

20 nm 120 °C P3HT 60 nm 0.46 1.88 0.42 0.40 (0.45)

20 nm 150 °C P3HT 60 nm 0.53 1.73 0.53 0.52 (0.56)

20 nm 180 °C P3HT 60 nm 0.45 1.58 0.46 0.35 (0.35)

50 nm 150 °C P3HT 60 nm 0.59 0.26 0.25 0.04 (0.05)

20 nm 150 °C P3HT 40 nm 0.49 1.80 0.47 0.46 (0.49)

20 nm 150 °C P3HT 90 nm 0.51 1.31 0.48 0.34 (0.36)

0.013

O nm — PTB7 45 nm 0.08 0.74 0.25

(0.025)

20 nm 120 °C PTB7 45 nm 0.75 1.14 0.40 0.34 (0.35)

20 nm 150 °C PTB7 45 nm 0.73 1.65 0.45 0.53 (0.57) 20 nm 180 °C PTB7 45 nm 0.70 1.32 0.44 0.40 (0.46) 20 nm 150 °C PTB7 60 nm 0.72 1.45 0.40 0.41 (0.43) 20 nm 150 °C PTB7 85 nm 0.78 0.91 0.47 0.33 (0.36)

[0086] Table 2. The reported photovoltaic parameters of bulk heterojunction OPV devices utilized mono PDI as acceptor and P3HT as donor. The molecular structure are displayed below.

PCE

Acceptor Donor Reference

PDI-1 P3HT 0.01 Adv. Energy Mater.2011, 1, 297-302

PDI-2 P3HT 0.25 Thin Solid Films 2009, 517, 4654-4657

PDI-3 P3HT 0.29 Chem. Sci.2013, 4, 4389-4394

PDI-4 P3HT 0.50 Adv. Energy Mater.2011, 1, 297-302

J. Am. Chem. Soc.2014, 136, 16345-

PDI-5 P3HT 0.65

16356

PDI-4 PD1-5

[0087] Table 3. Photovoltaic parameters of PM-HJ devices. The results are average values calculated from 6 cells.

)

10 nm 120 °C P3HT:PC₆IBM 0.55 13.03 0.57 4.17 (4.40) 10 nm 150 °C P3HT:PC₆IBM 0.55 12.88 0.56 4.07 (4.26) 10 nm 180 °C P3HT:PCeiBM 0.54 11.34 0.48 3.33 (3.55)

20 nm 150 °C P3HT:PCeiBM 0.54 12.08 0.50 3.47 (3.55)

0 nm —- PTB7:PC₇IBM 073 14.93 0.67 6.95 (7.01)

10 nm 120 °C PTB7:PC₇IBM 0.75 16.65 0.65 7.94 (8.19) 10 nm 150 °C PTB7:PC₇IBM 0.75 16.12 0.65 7.58 (7.79) 10 nm 180 °C PTB7:PC_7iBM 0.75 15.15 0.65 7.13 (7.37) 20 nm 150 °C PTB7:PC₇iBM 0.75 17.23 0.60 7.54(7.59)

35 nm 150 °C PTB7:PCnBM 0.75 14.88 0.32 3.47 (3.67)

[0088] Experimental Section

[0089] General measurement Liquid NMR experiments were performed on Bruker AVANCEIII-400 spectrometer. Tetramethylsilane (TMS) was used as the internal standard. For solid state NMR measurements, the two monomers and their blend were filled in 2.5 mm Zr0₂ rotor, and measured with a standard triple channel (H, X, Y) 2.5 mm MAS probe in a 400 MHz Bruker instrument. The method was ¹H-¹³C CP-MAS and the spinning speed 15 kHz. The insoluble CPN powder was filled in a 1.3 mm Zr0₂ rotor and measured with a standard triple channel (¹H, ¹³C, ¹⁵N) 1.3 mm MAS probe in an 800 MHz Bruker instrument. The method was ¹H-¹³C CP-MAS and the spinning speed 40 kHz. Mass spectra were recorded on AutoFlex speed MALDI-TOF mass spectrometer (Bruker), using a-cyano-4- hydroxycinnamic (CHCA) as matrix. TGA curves were performed on TGA 4000 from Perkin Elmer. The TGA measurement was carried out under nitrogen, and the heating rate is 10 °C min-¹. FT-IR spectra were recorded in transmission mode using Perkin Elmer Frontier FT-IR spectrometer. KBr pellets contained the samples were performed for the measurement. The absorption spectra of the thin films and solutions were tested by Shimazu UV 3600 spectrometer. The AFM images were recorded on Cypher S AFM from Asylum Research. The polymer network films were spin coated on silica wafer substrates. The spin-coating speed is 1000 rpm min-¹. Chloroform was utilized to dissolve PDI-DA and Triazine-TA with the concentration of 3 mg mL·¹ and 0.97 mg L·¹ (the molar ratio between azide and alkyne is 1 :1), respectively.

[0090] Transistor device and characterization: Bottom gate bottom contact transistor substrates were purchased from Fraunhofer Institute for Photonic Microsystems. The n-doped silicon wafer is used as bottom gate electrode, and a 230 nm Si0₂ is applied for dielectric layer. Au is used for source and drain electrodes, which is the most commonly used metal for source and drain electrodes in n-type OFETs because of its environmental stability, although its high work function may lead to a decrease of measured electron mobility. The thickness of Au is 30 nm, and 10 nm high work function ITO is used as the adhesion layer. The channel length (L) and width (W) are 2.5 pm and 10 mm, respectively. The substrates were successively cleaned by water, isopropanol, and acetone. After dried by argon, a 35 nm organic layer was spin coated on the substrates at 1000 rpm. The blend of PDI-DA and Triazine-TA were dissolved in chloroform with the concentration of 3 mg mL· 1 and 0.97 mg mL·¹, respectively. The transistors were annealed in argon glovebox at specified temperature and time. For the chlorobenzene soaking measurement, the transistor was immersed in clean chlorobenzene for specified time. After the transistor was taken out from the chlorobenzene solution, it was dried by argon gun and then subjected to a thermal annealing at 80 °C for 10 min in order to remove the remaining chlorobenzene in the film. The current-voltage (l-V) characteristics of the transistors were measured in nitrogen glovebox using a custom-built probe station and a Keithley 2612A dual-channel source measure unit. The electron mobility of the transistors was extracted from saturation regime according to the equation:

[0091] Where L and W are the channel length and width, respectively. ID is the current between source and drain electrode, and VGS is the gate voltage. Q (1.4x10 ⁸ F cm-²) is the capacity of the dielectric layer. [0092] Solar cell fabrication and characterization. P3HT was purchased from Aldrich, and RObiBM and PC_7-1BM from Ossila. PTB7 was synthesized according to the literature.!⁴¹! Pre-patterned ITO was cleaned by sequential sonication in water, isopropanol and acetone for 30 min each, and dried by argon. ZnO (20 nm) was utilized for the electron transport layer in the inverted solar cells. The ZnO precursor solution, which contains 0.5 M zinc acetate dehydrate and 0.5 M monoethanolamine in 2-methoxyethanol, was stirred under 60 °C for overnight. The ZnO electron transport layer was deposited on the clean ITO substrates by spin-coating the precursor solution with the spin rate of 5000 rpm. After cleaning the electrical contacts, the substrates were annealed at 200 °C in air for 30 min. The blend solution of PDI-DA and Triazine-TA was prepared in chloroform with the 1 :1 molar ratio of azide and alkyne. The thickness of the CPN films was optimized by changing the concentration of the blend solution and spin rate. Basically, a 20 nm film can be obtained from spin-coating the solution contained 3 mg mL·¹ PDI-DA and 0.97 mg mL·¹ Triazine-TA at 2000 rpm. The CPN films were obtained by heating the substrates for 10 min at different temperatures, and the heating process was carried out in argon glovebox. For planar heterojunction, P3HT was dissolved in chlorobenzene at the concentration of 7 mg mL·¹, 10 mg mL·¹ and 15 mg mL·¹. The P3HT solution was spin coated on CPN at 1000 rpm, which produced the P3HT layer with the thickness of 40 nm, 60 nm and 90 nm, respectively. PTB7 was dissolved in chlorobenzene at the concentration of 10 mg mL·¹, 13 mg mL·¹ and 18 mg mL·¹. The PTB7 layer with the thickness of 45 nm, 60 nm and 85 nm was deposited on CPN films by spin coating PTB7 solution at 1000 rpm min- 1. For hybrid planar mixed heterojunction (PM-H J), P3HT and PCeiBM with the mass ratio of 1 :0.7 were dissolved in dichlorobenzene contained 1 % DIO (v/v), and the concentration was 30 mg mL·¹. The P3HT:PC6iBM blend solution was spin coated on the CPN films at 800 rpm for 90 s, which produced a 200 nm P3HT:PC_6iBM blend layer. PTB7:PC_7iBM was blended with the weight ratio of 1 :1.5 and spin-casted from chlorobenzene with 3% 1 ,8-diiodoctane (v/v). The concentration of PTB7 is 10 mg mL·¹. The PTB7: PC71BM film was prepared from spin coating the blend solution at 1000 rpm min-¹ for 120 s. Finally, the substrates were transferred to the vacuum chamber, and 10 nm M0O3 and 100 nm Ag were evaporated at ~10-⁶ mbar through a shadow mask. The active area of the solar cells was 16 mm². The thickness of the solution processed films was determined by Bruker DektakXT profilometer. Current density-voltage (J-V) characteristics of the devices were tested under simulated AM1.5G irradiation from a 300 W Xe arc lamp set to 100 mW cm-² with a calibrated Si photodiode. Electronic characterization was measured by Keithley 2400 source measure unit. The external quantum efficiency (EQE) of the devices was characterized by illumination from a Tunable PowerArc illuminator (Optical Building Blocks Corporation). A calibrated photodiode was employed to measure the incident photon number at each wavelength.

Claims

Claim 1. A method for manufacturing a semiconducting, organic, covalent polymer network thin film comprising the steps of:

i) providing a solution comprising azide-containing monomers and electron- deficient alkyne-containing monomers;

ii) deposing said solution onto a receiving substrate to prepare a film of monomers; and

iii) providing a thermal trigger to the deposed film of monomers to allow a 1 ,3- dipolar cycloaddition polymerization reaction to occur between azide-containing monomers and alkyne-containing monomers, thereby forming said covalent polymer network thin film on said receiving substrate.

Claim 2. The method of claim 1 , wherein said thermal trigger comprises heating, electromagnetic irradiation and/or ultrasonication.

Claim 3. The method of claim 2, wherein said heating is conducted at a temperature comprised between 25°C and the thermal decomposition temperature of the monomers.

Claim 4. The method of any previous claim, wherein said azide-containing monomers comprise the following monomers:

wherein the R groups are independently selected from the group consisting of - H, a heteroatom, branched or unbranched alkyl or substituted alkyl, branched or unbranched alkenyi or substituted alkenyl, alkynyl, phenyl, benzyl, aryl, heteroaryl or substituted heteroaryl, aroyl, aryloxy, carboxy, ester, carboxamide, carbamoyl, oligopeptidyl, amine, halo, hydroxyl, mercapto, acryloyl, methacryloyl, styryl, isocyanate, sulfonyl hydroxide, phosphono or its derivatives, phosphate or its derivatives, oxiranyl, trihalosilyl, and trialkoxysilyl.

Claim 5. The method of any previous claim, wherein said alkyne-containing monomers comprise the following monomers:

Claim 6. The method of any previous claim, wherein organic solution is devoid of any chemical catalyst such as a metal catalyst(s).

Claim 7. The method of any previous claim, wherein deposing a solution to a receiving substrate comprises spin coating, vapour deposition, spraying, painting, doctor blading, draw coating, dip coating or inkjet printing.

Claim 8. The method of any previous claim, wherein the molar ratio between azide groups from the azide-containing monomers and acetylene groups from the electron-deficient alkyne-containing monomers is selected according to the Carothers equation to form a network polymer.

Claim 9. The method of any previous claim, wherein the solution comprises a solvent selected from a non-limiting group comprising chloroform, dichloromethane, tetrahydrofuran, chlorobenzene, toluene, dimethyl sulfoxide dimethyl formamide, xylene, and mixture thereof.

Claim 10. The method of any previous claim, wherein said thermal trigger is provided for about 10 seconds to about 1 hour.

Claim 11. The method of any previous claim further comprising an additional step of depositing an additional solid substrate on said semiconducting organic covalent polymer network thin film.

Claim 12. The method of claims 1 to 10, further comprising an additional step of removing said semiconducting organic covalent polymer network thin film from said receiving substrate.

Claim 13. A semiconducting organic covalent polymer network thin film obtainable by a method according to anyone of claims 1 to 12.

Claim 14. The semiconducting organic covalent polymer network thin film of claim 13 having a thickness comprised between 1 nm and 1000 nm.

Claim 15. The semiconducting organic covalent polymer network thin film of claims 13 or 14, characterized in that it has optoelectronic and/or semiconductor properties.

Claim 16. Use of the semiconducting organic covalent polymer network thin film of claims 13 to 15 for manufacturing of solar cells, transistors, light-emitting diodes or organic electronic devices.

Claim 17. A solid substrate comprising the semiconducting organic covalent polymer network thin film of claims 13 to 15.

Claim 18. Use of the solid substrate of claim 17 for manufacturing of solar cells, transistors, light-emitting diodes or organic electronic devices.

Claim 19. A solar cell comprising a semiconducting organic covalent polymer network thin film according to claims 13 to 15 or a solid substrate according to claim 17.

Claim 20. An azide-containing monomer selected from a list consisting of the following monomers:

wherein the R groups are independently selected from the group consisting of - H, a heteroatom, branched or unbranched alkyl or substituted alkyl, branched or unbranched alkenyl or substituted alkenyl, alkynyl, phenyl, benzyl, aryl, heteroaryl or substituted heteroaryl, aroyl, aryloxy, carboxy, ester, carboxamide, carbamoyl, oligopeptidyl, amine, halo, hydroxyl, mercapto, acryloyl, methacryloyl, styryl, isocyanate, sulfonyl hydroxide, phosphono or its derivatives, phosphate or its derivatives, oxiranyl, trihalosilyl, and tria!koxysilyl.

Claim 21. An alkyne-containing monomer selected from a list consisting of the following monomers: