Self-healing coating material

Abstract

Composite materials comprising a thermosetting resin together with a compatibilizer and polyethylene glycol, showing self-repairing properties to be used as coating materials for covering solar cells are disclosed, together with the method for their preparation and the method for coating solar cells.

Description

[0001] SELF-HEALING COATING MATERIAL

[0002] Field of the Invention

[0003] The present invention regards the field of chemistry and in particular composite materials with self-repairing properties to be used as coating materials in the solar energy field, in particular for covering perovskite solar cells.

[0004] State of the art

[0005] Self-healing epoxy resins (ER) based on diglycidyl ether of bisphenol A (DGEBA) are known as promising materials for the encapsulation of perovskite-based solar cells (PSCs) and show the ability to partially repair cracks after 4 hours of heating [Yan Jiang et al., Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation, Nature Energy volume 4, pages585-593 (2019), doi: https: / / doi.org / 10.1038 / s41560-019-0406-2]. Polyethylene glycol (PEG), when used as a templating agent for perovskite crystals, exhibit self-healing properties within 30 seconds when exposed to sunlight and its self-healing ability is only shown following exposure to solar radiation and not heating [Yicheng Zhao et al., A polymer scaffold for self-healing perovskite solar cells, Nature Communications volume 7, Article number: 10228 (2016), doi: 10.1038 / ncommsl0228].

[0006] The scientific publication Baoji Hu et al., Multi-stimuli temperature, reusable, recyclable, and healable shape-memory epoxy-PEG multifunctional films by regulating polyethylene glycol, Progress in Organic Coatings 174 (2023) 107309, doi: https: / / doi

[0007] ,org / 10.1016 / j.porgcoat.2022.107309 describes the self-repair capacity of a mixture of epoxy resin with polyethylene glycol, but not for use as an encapsulating agent for solar cells, the selfrepair times include conditioning for 8 hours at temperature environment, which represents a decidedly long time if used to limit the dispersion of lead.

[0008] It is known that mixing epoxy resin with polyethylene glycol produces a material with self-healing ability that has properties of a phase change material and possesses heat absorption properties [Yutang Fang et al., Study on polyethylene glycol / epoxy resin composite as a form-stable phase change material, Energy Conversion and Management 51 (2010) 2757-2761, doi: https: / / doi.Org / 10.1016 / j.enconman.2010.06.012],

[0009] A mixture of epoxy resin with photo-hardening polyethylene glycol used as a coating for perovskite-based solar cells (PSC) with Phase Change Materials PCM properties which produces a coating capable of extending the life of the solar cell, but without any self-healing ability is reported [Nasibeh Mansour Rezaei Fumani et al., Prolonged Lifetime of Perovskite Solar Cells Using a Moisture-Blocked and Temperature-Controlled Encapsulation System Comprising a Phase Change Material as a Cooling Agent, ACS Omega 2020, 5, 7106-7114, doi:https: / / dx.doi.org / 10.1021 / acsomega.9b03407]. US patent n. US 8 722 798 discloses a thermosettable composition comprising (DGEBA), -methyl tetrahydrophthalic anhydride as hardener, PEG and a copolymer PEO-PBO-PEO being a compatibilizer.

[0010] Technical problem

[0011] In recent years Perovskite-based solar cells (PSCs) have attracted much attention due to their high efficiency and low cost. Practical applications are limited by susceptibility to humidity and temperature changes. Furthermore, accidental breakages of the cell and atmospheric phenomena such as rain, hail and humidity can cause the dispersion of lead into the environment; this risk further limits its applications. Solar cell encapsulation is a widely used tool to overcome these drawbacks and the use of polymers capable of autonomously repairing damage (self-healing) represents a promising strategy to improve the stability and longevity of perovskite-based solar cells. Polymers with self-healing properties act as a barrier against environmental factors, improve the mechanical stability of perovskite-based solar cells, and a coating prepared using this class of polymers is more resistant to external stresses, prolongs durability of PSCs and reduces lead losses.

[0012] The aim of the present invention is to identify a new composite material based on thermosetting epoxy resin and polyethylene glycol having self-healing properties which is activated following heating of the material to a temperature higher than its glass transition temperature (Tg).

[0013] Has been designed a specific coating being a composite material based on thermosetting epoxy resin (ER) and polyethylene glycol (PEG) with improved self-repairing properties, at the operating temperature of the solar cells which should be coated, so as to reduce repairing time and extending their lifespan. Furthermore, the coating can be applied at temperatures suitable for use on perovskite-based solar cells (PSCs), thus avoiding the degradation of perovskites and simplifying the production process.

[0014] The composite material of the present invention has a triple function: to protect the perovskitebased solar cells from environmental conditions, water and humidity; minimize or prevent the release of lead into the environment; preserve perovskite C-based solar cells from temperature fluctuations.

[0015] The thermosetting epoxy resin (ER) was identified by a purposive selection based on the self- healing capacity activated by heating the material above its glass transition temperature (Tg). Thermoset epoxy resin (ER) is combined with polyethylene glycol (PEG) to create a versatile and adaptable encapsulation composite material that provides mechanical reinforcement and also enhances self-healing properties, crucial for maintaining the integrity of the encapsulation layer.

[0016] The composite material of the present invention represents an improvement over the prior art.

[0017] The composite material disclosed in US patent n. US 8 722 798 is designed to have temperature resistance and mechanical properties but does not shows any self-healing and thermal mitigation properties, as it is used in casting, potting, and encapsulation, such as electrical and electronics applications. The encapsulation system for Perovskite Solar Cells comprising poly(ethylene glycol) (PEG) and epoxy resin disclosed in Nasibeh Mansour Rezaei Fumani et al., Prolonged Lifetime of Perovskite Solar Cells Using a Moisture-Blocked and Temperature-Controlled Encapsulation System Comprising a Phase Change Material as a Cooling Agent, ACS Omega 2020, 5, 7106-7114, doi:https: / / dx.doi.org / 10.1021 / acsomega.9b03407 uses use a photo-curing resin, instead of a thermo-curing resin, in order to preserve the perovskite solar cell, which acts as a cooling agent (or temperature mitigator) without having self-healing functions.

[0018] Comparing the composite material of the present invention with the formulation reported in Yan Jiang et al., Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation, Nature Energy volume 4, pages585-593 (2019), doi: https: / / doi.org / 10.1038 / s41560-019-0406-2, the improvement lies in the implementation of PEG within the formulation. Under the same self-healing conditions, the formulation reported in Yan Jiang et al., shows a repair efficiency of 35% after 8 hours of treatment, while the material of the present invention has an efficiency of self-healing of 100%, in a time ranging from 5 minutes to one hour at a temperature of 85°C. Shortening the timing of the self-healing process allows you to reduce the risk of infiltration of harmful agents such as water and humidity, which could reduce the functionality of the solar cell and cause the lead present in the photoactive layer to dissolve, dispersing it into the environment. The reduction of cross-linking temperatures also resolves the operational complexity of deposition of the coating on the cell, allowing operation at temperatures at which the photoactivity of the perovskite layer is not compromised. Photo-degradative instability of the epoxy-resins is reported in Rauf Mahmudzade et al., Photodegradation mechanisms and physico-chemical properties of EPON-IPD epoxy-based polymers, Reactive and Functional Polymers Volume 178, 105351 (2022), doi: https: / / doi.Org / 10.1016 / j.reactfunctpolym.2022.105351 [2], which however depend on the particular formulation. The polymeric material of the present invention does not show to date degradation upon short observation times.

[0019] Object of the invention

[0020] The technical problem is therefore solved by providing a composite material comprising: i) A thermosetting resin of formula (I): wherein

[0021] Y is a cross-linking agent selected from the group consisting of benzylalkylamine, secondary amine , tertiary amine, anhydrides. m and n are integers with the proviso that 3<n / m<5

[0022] X is a monomer of formula (II) wherein

[0023] R and R', the same or different, are: CH2CHCH2O, CH2CHOHCH3

[0024] R" and R'", the same or different, are H, CH3,CH2CH3 ii) a compatibilizer iii) Polyethylene glycol iv) an UV adsorber.

[0025] Another object of the present invention is the use of the above composite material for coating solar cells.

[0026] Are also another object of the present invention solar cells characterised in having a coating made of the above composite material.

[0027] Another object of the present invention is the method for the preparation of the above composite material.

[0028] It is also an object of the present invention a method for coating solar cells with the above composite material.

[0029] Further features of the present invention would be clear from the following detailed description with reference to the experimental results provided and the attached drawings.

[0030] Brief description of figures

[0031] Figure 1 reports SEM picture shows damage repair (self-healing capacity) analysing the morphology of the material and the extent of damage for a maximum of 4 hours. Figure 2 report in graphs phase changing material tests carried out on the material vs reference material.

[0032] Figure 3 illustrates the efficiency evolution over time, extracted from J-V curves, for the three device types, under continuous ambient light, room temperature, and 40% relative humidity (RH).

[0033] Detailed description of the invention

[0034] Within the meaning of the present invention the composite material is in the form of a physical mixture meaning a mixture wherein the constituents are not chemically combined but are intimately mingled as to be impossible to be separate by mechanical means.

[0035] Within the meaning of the present invention compatibilizer means an agent improving stability and mechanical properties of a mixture comprising polymers.

[0036] Within the meaning of the present invention cross linking agent means an agent allowing the creation of chemical bonds between molecules.

[0037] Within the meaning of the present invention UV adsorber means a compound that added to the composite material intercepting UV radiation prevents and avoid degradation of the polymers due to UV radiations.

[0038] Within the meaning of the present invention glovebox means a closed chamber with sealed-in gloves for handling hazardous material or materials that have to be protected from the environment, in particular oxygen.

[0039] Within the meaning of the present invention conditioning a glove box for the production of Perovskite solar cells means creating a controlled environment within the glove box to ensures optimal conditions for the manufacturing and coating process minimizing contamination of the system, wherein all the contaminants, such as oxygen, moisture and any atmospheric contaminants are removed from the glove-box, by purging an inert gas, such as N2 or Ar, within the box. During all the experiments, the box has to be purged with inert gas to ensure a controlled environment.

[0040] The main object of the present invention is composite material comprising: i) A thermosetting resin of formula (I):

[0041] wherein

[0042] Y is a cross-linking agent selected from the group consisting of: benzylalkylamine, secondary and tertiary amine, anhydrides. m and n are integers with the proviso that 3<n / m<5

[0043] X is a monomer of formula (II) wherein

[0044] R and R', the same or different, are: CH2CHCH2O, CH2CHOHCH3

[0045] R" and R'", the same or different, are H, CH3, CH2CH3 ii) a compatibilizer iii) polyethylene glycol iv) an UV adsorber.

[0046] Preferably the cross-linking agent is N,N dimethylethanolamine or m-xylylendiamine.

[0047] Preferably the compatibilizer is octylamine.

[0048] Preferably R and R', the same or different, are isopropyl, methyl epoxyethane, more preferably they are the same.

[0049] Preferably R" and R'" are the same and are CH3. More preferably the monomer of formula (II) is Diglycidyl Ether of Bisphenol A or Bisphenol A propoxylated.

[0050] Preferably Polyethylene glycol has a molecular weight ranging from 1000 Da to 4000 Da.

[0051] Preferably in the composite material (physical mixture) the final molar ratio monomer of formula (II): compatibilizing agent: cross-linking agent is between 3:2:1 and 5:2:1, more preferably 4:2:1.

[0052] Preferably the UV adsorber is selected from the group consisting of: quercetin, dioxybenzone, and thymol, more preferably is quercetin.

[0053] A further object of the present invention is the method for the preparation of the composite material mixture of the present invention providing the following steps: a) Heating the monomer of formula (II) at a temperature ranging from 45°C and 80°C, b) Heating polyethylene glycol at a temperature ranging from 45°C and 80°C, c) Mixing under stirring the monomer as obtained at the end of step a) with a compatibilizer to obtain a mixture at a temperature ranging from 45°C and 80°C, d) Adding to polyethylene glycol as obtained at the end of step b) the mixture as obtained at the end of step c) to obtain a mixture at a temperature ranging from 45°C and 80°C, e) Adding to the mixture as obtained at the end of step d) a crosslinker agent until the complete polymerization of the polymeric material to obtain (I) the UV adsorber is added at the end of step a).

[0054] Preferably in step c) stirring rate is between 100 and 600 rpm.

[0055] Preferably in step c) stirring is carried out for 3 minutes.

[0056] Preferably in step d) mixing is under stirring and at a stirring rate between 100 and 600 rpm) for a time between 30 and 60 minutes.

[0057] The composite material comprising: i) A thermosetting resin of formula (I): wherein

[0058] Y is a cross-linking agent selected from the group consisting of: benzylalkylamine, secondary and tertiary amine, anhydrides. m and n are integers with the proviso that 3<n / m<5

[0059] X is a monomer of formula (II) wherein

[0060] R and R', the same or different, are: CH2CHCH2O, CH2CHOHCH3

[0061] R" and R'", the same or different, are H, CH3, CH2CH3 ii) a compatibilizer iii) polyethylene glycol iv) a UV adsorber is used for coating solar cells, preferably perovskite solar cells.

[0062] Another object of the present invention is a solar cell, preferably A perovskite solar cell, coated with a composite material comprising: i) A thermosetting resin of formula (I): wherein

[0063] Y is a cross-linking agent selected from the group consisting of: benzylalkylamine, secondary and tertiary amine, and anhydrides. m and n are integers with the proviso that 3<n / m<5

[0064] X is a monomer of formula (II) wherein

[0065] R and R', the same or different, are: CH2CHCH2O, CH2CHOHCH3

[0066] R" and R'", the same or different, are H, CH3, CH2CH3 ii) a compatibilizer iii) polyethylene glycol iv) a UV adsorber.

[0067] It is also an object of the present invention a method for coating solar cells with the composite material comprising: i) A thermosetting resin of formula (I): wherein

[0068] Y is a cross-linking agent selected from the group consisting of: benzylalkylamine, secondary and tertiary amine, anhydrides. m and n are integers with the proviso that 3<n / m<5

[0069] X is a monomer of formula (II) wherein

[0070] R and R', the same or different, are: CH2CHCH2O, CH2CHOHCH3

[0071] R" and R'", the same or different, are H, CH3, CH2CH3 ii) a compatibilizer iii) polyethylene glycol iv) a UV adsorber. comprising the following steps: a) embedding a solar cell in a frame, wherein said frame acts as a mould and protects the electrical connections of the solar cell, b) drop casting the composite material on the solar cell embedded in a frame as obtained in step a) until a plain coating is obtained, c) heating the coated solar cell as obtained at the end of step b) until complete polymerization.

[0072] Preferably the steps from a) to c) are carried out in a glove-box, wherein said glove-box is conditioned in an inert atmosphere before step a).

[0073] Preferably, in step c) heating is carried out at a temperature of 55°C and overnight.

[0074] It is also an object of the present invention a solar cell coated with the composite material comprising:

[0075] A thermosetting resin of formula (I):

[0076] wherein

[0077] Y is a cross-linking agent selected from the group consisting of: benzylalkylamine, secondary amine , tertiary amine, anhydrides. m and n are integers with the proviso that 3<n / m<5

[0078] X is a monomer of formula (II) wherein

[0079] R and R', the same or different, are: CH2CHCH2O, CH2CHOHCH3

[0080] R" and R'", the same or different, are H, CH3, CH2CH3 ii) a compatibilizer iii) polyethylene glycol iv) an UV adsorber wherein the coated solar cell is obtained by: a) embedding a solar cell in a frame, wherein said frame acts as a mould and protects the electrical connections of the solar cell, b) drop casting the composite material on the solar cell embedded in a frame as obtained in step a) until a plain coating is obtained, c) heating the coated solar cell as obtained at the end of step b) until complete polymerization.

[0081] Wherein optionally and preferably the steps from a) to c) are carried out in a glove-box, wherein said glove-box is conditioned in an inert atmosphere before step a), and preferably, in step c) heating is carried out at a temperature of 55°C and overnight.

[0082] Examples

[0083] Synthesis of the resin lg of PEG and 1.36g Diglycidyl Ether of Bisphenol A (DGEBA) are melted on a heating plate at a temperature of 45°C. 330 pl of Octylamine (Oct) are added as a compatibilizer to melted DGEBA and mixed for 3 minutes. The blend DGEBA-Oct is added to the melted PEG and stirred to complete mixing for 30 minutes at 45°C. Finally, the crosslinker agent, 136 pl of m-xylylendiamine (Xyl), is added to the blend DGEBA-Oct-PEG and mixed for 2 minutes. The ratios DGEBA:Oct:Xyl were 4:2:1 as reported in Yan Jiang et al., Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation, Nature Energy volume 4, pages585-593 (2019), doi: https: / / doi.org / 10.1038 / s41560-019-0406-2. The resin is drop casted in a mold with a diameter of 43mm to obtain a sample with a thickness of 1.2mm. The mold is transferred in a preheated vacuum oven and kept at isothermal temperature; two different cross-linking temperatures were used, 70°C for 4 hours or 55°C for the whole night. The possibility of cross-linking the resin at a temperature of 55°C is a key feature of the material presented here. At 55°C, in fact, the perovskite is stable in its photoactive crystalline state, and the risk of it degrading by passing into its inactive state, in which it is inefficient from an energy point of view, is avoided. The production of the coating is, thus, compatible with the PSCs technology.

[0084] Synthesis of the resin lg of PEG and 1.36g Diglycidyl Ether of Bisphenol A (DGEBA) are melted on a heating plate at a temperature of 80°C. 330 pl of Octylamine (Oct) are added as a compatibilizer to melted DGEBA and mixed for 3 minutes. The blend DGEBA-Oct is added to the melted PEG and stirred to complete mixing for 40 minutes at 80°C. Finally, the crosslinker agent, 136 pl of m-xylylendiamine (Xyl), is added to the blend DGEBA-Oct-PEG and mixed for 2 minutes. The ratios DGEBA:Oct:Xyl were 4:2:1 as reported in Yan Jiang et al., Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation, Nature Energy volume 4, pages585-593 (2019), doi: https: / / doi.org / 10.1038 / s41560-019-0406-2. The resin is drop casted in a mold with a diameter of 43mm to obtain a sample with a thickness of 1.2mm. The mold is transferred in a preheated vacuum oven and kept at isothermal temperature; two different cross-linking temperatures were used, 70°C for 4 hours or 55°C for the whole night. The possibility of cross-linking the resin at a temperature of 55°C is a key feature of the material presented here. At 55°C, in fact, the perovskite is stable in its photoactive crystalline state, and the risk of it degrading by passing into its inactive state, in which it is inefficient from an energy point of view, is avoided. The production of the coating is, thus, compatible with the PSCs technology. Synthesis of the resin lg of PEG and 1.36g Diglycidyl Ether of Bisphenol A (DGEBA) are melted on a heating plate at a temperature of 45°C. 33 pl of Octylamine (Oct) are added as a compatibilizer to melted DGEBA and mixed for 3 minutes. The blend DGEBA-Oct is added to the melted PEG and stirred to complete mixing for 30 minutes at 45°C. Finally the crosslinker agent, 100 pl of N,N- dimetylethanolamine (DMA), is added to the blend DGEBA-Oct-PEG and mixed for 2 minutes. The ratios DGEBA:Oct:DMA were 4:2:l.The resin is drop casted in a mold with a diameter of 43mm to obtain a sample with a thickness of 1.2mm. The mold is transferred in a preheated vacuum oven and kept at isothermal temperature; two different cross-linking temperatures were used, 70°C for 4 hours or 55°C for the whole night. The possibility of cross-linking the resin at a temperature of 55°C is a key feature of the material presented here. At 55°C, in fact, the perovskite is stable in its photoactive crystalline state, and the risk of it degrading by passing into its inactive state, in which it is inefficient from an energy point of view, is avoided. The production of the coating is, thus, compatible with the PSCs technology.

[0085] Characterization and self-healing tests

[0086] Thermogravimetry (TGA) shows that the material is thermally stable up to a temperature of 278°C, at which PEG degradation begins. The analysis of the thermal properties of the composite materials by the DSC technique proves that the procedure used for the resin cross-linking step allows to obtain a completely cross-linked material. In fact, the persistence of an unpolymerized fraction of the resin after cross-linking should manifest itself through the presence of an exothermic peak in the DSC curves of the samples, as the polymerization process is intrinsically exothermic. In the case of the materials presented here, both resins cured at 55°C and 70°C show only the endothermic peak associated with the melting of PEG.

[0087] To confirm, the transmittance of the coating at the working wavelength of PSCs, UV-Vis absorption of the materials was tested. The material results as completely transparent to visible wavelength, and display an absorption band in the UV wavelength range. This proves the efficiency of the coating in transmitting visible light, making it suitable for the particular application selected. Moreover, since UV radiation could enhance perovskite degradation, the ability of the coating in absorbing UV light could improve PSCs durability

[0088] Electron microscopy was used to study the self-healing properties of the composite materials. The morphology of undamaged resin was firstly observed. Subsequently, the material was cut with a razor blade, to obtain incisions approximately 100 pm wide. The damaged samples are observed using SEM to study the morphology of the cuts and then transferred to a laboratory oven at a constant temperature of 60°C. At regular intervals of one hour, the samples are again observed via SEM to evaluate the self-healing capacity, analysing the morphology of the material and the extent of damage for a maximum of 4 hours. Figure 1 shows an example of damage repair.

[0089] The results of the self-healing tests show how resins cross-linked at 70°C have the ability to heal the damage by 100% in just one hour, while resins cross-linked at 55°C have an efficiency of 90% damage repair, which rises to 100% after 10 minutes of treatment at 60°C. Method for coating

[0090] The cell is embedded in a frame designed to act as a mould for the production of a plain coating and to shield from the coating the electrical connections on the edges of the PSC.

[0091] The coating prepared as previously reported, is transferred in a glove-box pre-conditioned in inert atmosphere and the coating is drop casted on the surface of the cell embedded in the frame. The system is transferred on a heating plate at a temperature of 55°C and the casting is cured overnight.

[0092] Phase Changing Material Tests

[0093] To test the ability in reducing the temperature fluctuations, the heating of the coating material has been registered by means of an infrared thermocamera. The coating object of the invention and the reference material as reported in Yan Jiang et al., Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation, Nature Energy volume 4, pages585-593 (2019), doi: https: / / doi.org / 10.1038 / s41560-019-0406- 2) were placed on a heating plate and the temperature raise of the materials has been registered.

[0094] As shown in figure 2, the coating object of the invention has a warming rate lower than that of the reference material and, at the same time, the highest temperature reached is 10°C lower than that of the reference material, resulting in a phase changing material able to mitigate temperature fluctuations.

[0095] Efficiency

[0096] To verify the effect of the coating material on the PSC's efficiency, three device AVA-MAPbl3carbon-based perovskite solar cells (PSCs)

[0097] (ref.https: / / onlinelibrary.wiley.com / doi / 10.1002 / solr.202300944) were encapsulated using self- healing coating material with different PEG weights (1000, 2000, and 4000) and an interlayer of Kapton tape, as described in (ref.https: / / pubs.acs.org / doi / 10.1021 / acsaem.4c02572).

[0098] Figure 1 illustrates the efficiency evolution over time, extracted from J-V curves, for the three device types, under continuous ambient light, room temperature, and 40% relative humidity (RH). The results indicate that all compositions effectively preserve the MAPbl3photoactive phase from the degradation inducted by ambient moisture, maintaining the initial efficiency with a slight increase for up to 3000h.

Claims

CLAIMS1. Composite material comprising: i) A thermosetting resin of formula (I):whereinY is a cross-linking agent selected from the group consisting of: benzylalkylamine, secondary amine, tertiary amine, and anhydrides. m and n are integers with the proviso that 3<n / m<5X is a monomer of formula (II)whereinR and R', the same or different, are: CH2CHCH2O, CH2CHOHCH3R" and R'", the same or different, are H, CH3, CH2CH3 ii) a compatibilizer iii) polyethylene glycol iv) a UV adsorber.

2. Composite material of claim 1 wherein the cross-linking agent is N,N dimethylethanolamine or m-xylylendiamine.

3. Composite material of claim 1 wherein the compatibilizer is octylamine.

4. Composite material of claim 1 wherein R and R', the same or different, are isopropyl, methyl epoxyethane.

5. Composite material of claim 5 wherein R and R' are the same.

6. Composite material of claim 6 wherein R and R' are the same and are methyl epoxyethane.

7. Composite material of claim 1 wherein R" and R'" are the same and are CH3.

8. Composite material of claim 1 wherein the monomer of formula (II) is Diglycidyl Ether of Bisphenol A or Bisphenol A propoxylated.

9. Composite material of claim 1 wherein Polyethylene glycol has a molecular weight ranging from 1000 Da to 4000 Da.

10. Composite material of claim 1 wherein the final molar ratio monomer of formula(ll):compatibilizing agent: cross-linking agent is between 3:2:1 and 5:2:1.

11. Composite material of claim 10 wherein the final molar ratio monomer of formula(ll):compatibilizing agent: cross-linking agent is 4:2:1.

12. Composite material of claim 1 wherein UV adsorber is selected from the group consisting of: quercetin, dioxybenzone and thymol.

13. Composite material of claim 12 wherein UV adsorber is quercetin.

14. Method for the preparation of the composite material of anyone of claims 1-13 providing the following steps: a) Heating the monomer of formula (II) at a temperature ranging from 45°C and 80°C, b) Heating polyethylene glycol at a temperature ranging from 45°C and 80°C, c) Mixing under stirring the monomer as obtained at the end of step a) with a compatibilizer to obtain a mixture at a temperature ranging from 45°C and 80°C, d) Adding to polyethylene glycol as obtained at the end of step b) the mixture as obtained at the end of step c) to obtain a mixture at a temperature ranging from 45°C and 80°C, e) Adding to the mixture as obtained at the end of step d) a crosslinker agent until the complete polymerization of the polymeric material to obtain (I). wherein the UV adsorber is added at the end of step a).

15. Method of claim 14 wherein in step c) stirring rate is between 100 and 600 rpm.

16. Method of claim 14 wherein in step c) stirring is carried out for 3 minutes.

17. Method of claim 14 wherein in step d) mixing is under stirring and at a stirring rate between 100 and 600 rpm) for a time between 30 and 60 minutes.

18. Composite material according to anyone of claims 1-13 for coating solar cells.

19. Composite material for use according to claim 18 wherein solar cells are perovskite solar cells.

20. Solar cell coated with the composite material according to anyone of claims 1-13.

21. Solar cell according to claim 20 being a perovskite solar cell.

22. Method for coating solar cells of with the composite material with the composite material according to anyone of claims 1-13 comprising the following steps:a) embedding a solar cell in a frame, wherein said frame acts as a mould and protects the electrical connections of the solar cell, b) drop casting the composite material on the solar cell embedded in a frame as obtained in step a) until a plain coating is obtained, c) heating the coated solar cell as obtained at the end of step b) until complete polymerization.

23. Method according to claim 22 wherein steps from a) to c) are carried out in a glove-box conditioned in an inert atmosphere before step a).

24. Method according to claim 22 wherein in step c) heating is carried out at a temperature of 55°C and overnight.

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