Polymeric LED-type devices with a fixed active layer, method for producing polymeric LED-type devices emitting various colors, and use of the devices.

Abstract

polymeric LED devices with a fixed active layer, production method of polymeric LED devices that emit different colors, and use of the devices The present invention refers to light-emitting diodes (LEDs), obtained from electronic devices based on in conjugated polymers, as well as production methods and their use. in the aforementioned polymeric LEDs, the active layer is maintained, however, the wavelength of light emitted can be easily tuned, using an external filter that converts the radiation emitted by the device.

Description

Polymeric LED-type devices with a fixed active layer, method for producing polymeric LED-type devices emitting various colors, and use of the devices. FIELD OF THE INVENTION

[001] The present invention falls within the area of ​​Organic Electronics, particularly in the field of light-emitting diodes (LEDs) obtained from electronic devices based on conjugated polymers, as well as the methods of production thereof and their use. BACKGROUND OF THE INVENTION

[002] Polymer light-emitting devices have been extensively studied and developed over the past 25 years, and much progress has been made since their initial proposal in 1990. The construction of a polymer light-emitting diode basically involves using a transparent electrode, usually Indium-doped Tin Oxide or Poly(3,4-ethylenedioxythiophene), whose abbreviations are ITO and PEDOT, respectively. The active layer of the light-emitting polymer material, with a thickness ranging from tens to hundreds of nanometers, is deposited onto these layers. The device is finalized by evaporating metallic contacts, usually Calcium and Aluminum, whose thickness can vary from 30 to 120 nm.

[003] Due to the chemical characteristics of polymeric materials, the emitted wavelength range is fixed and dictated by the energy difference between its conduction and valence bands. Therefore, polymer light-emitting diodes cannot be tuned, and a given device will always emit the same color. Given this, Petition 870210044159, dated 05 / 14 / 2021, p. 6 / 34 2 / 23 Low-cost applications involving selectivity in emission color encounter difficulties when using polymer LEDs, unless multiple devices with different active layers are used, which makes the product more expensive and more complex to produce.

[004] At this point, the present invention will use only a polymer light-emitting diode, typically at higher energy wavelengths (bluish tones), and filters, also polymeric, which will convert part of the higher energy radiation emitted by the device into different color tones. The final color obtained will depend on the energy characteristics of the material to be used as a filter and will be composed from the addition of the transmitted blue color to that absorbed and subsequently re-emitted by the filter.

[005] A very convenient application for the present invention is in lighting equipment used in nightclubs and music shows, where the emitted wavelength changes constantly. In the case of current equipment, there are several independent monochromatic sources that turn on and off, depending on a switching electronics. In the case of using the present invention, the light source would be unique and would remain lit all the time, requiring only a stepper motor to select the different filters for radiation conversion.

[006] Another possible application of the present invention that deserves highlighting is that for generating white light in polymeric LEDs. The optimization and proposition of new methods for obtaining white light in electroluminescent polymeric devices has been the focus of much research. Petition 870210044159, dated 05 / 14 / 2021, page 7 / 34 3 / 23 current in organic electronics (see references). Currently, there are basically three methods used to obtain white light from this technology: the use of polymer blends, the use of multilayer devices, and the production of single molecules that emit white light.

[007] In the use of polymer blends, two or more emitting polymers are mixed in order to electrically excite them. The composition of their emissions must cover the entire visible spectrum, thus forming white light. However, the difficulty in this process lies in finding the correct weight ratio of the materials to be mixed, so that the proportion of each emission is correct to compose white light. Furthermore, polymeric materials with distinct chemical compositions tend to separate (phase separation), which can induce non-homogeneous emissions throughout the film, as well as problems with the film's morphology.

[008] In the multi-layered device method, the strategy employed is to deposit several active layers with different emissions, one on top of the other. The idea is to electroluminesce them simultaneously, with the light composition being white. However, the fabrication of these devices is challenging, since layers to be deposited usually dissolve previously deposited layers (polymeric materials, for the most part, are soluble in similar solvents). In this process, methods to stabilize the layers are necessary, increasing the manufacturing steps and increasing production costs.

[009] The production of unique light-emitting molecules Petition 870210044159, dated 05 / 14 / 2021, page 8 / 34 White light production involves the chemical synthesis of new molecules with various emitters to obtain white light. However, such molecules are extremely complex and difficult to design and synthesize. Furthermore, the synthesis of complex molecules involves a series of chemical routines, usually of low efficiency, which increases the production cost.

[010] As discussed above, each methodology has certain disadvantages, which can influence costs and speed of production. Therefore, there is a need for process optimization in order to enable large-scale industrial production. State of the Art Documents

[011] There is great motivation in the pursuit of developing white light-emitting polymer diodes, since their applicability in the electronics and lighting industries is quite vast and important. An important point in the development of such devices is the search for simple manufacturing methods, since this implies cost reduction and increased production rate. Because of this, there are several works that show the preparation of white light-emitting diodes using different configurations and / or materials.

[012] As an example, we can cite the following documents: a) EP1753048-A1; US2007035236-A1; JP2007053089A; EP1753048-B1; DE502005005126-G; US7589463-B2 (“Top emitting unit eg white organic light emitting diode, for eg display, has surface structure defining reflection of light at base electrode of layer arrangement, where surface structure is formed by mechanical molding “); b) TW201023674 Petition 870210044159, dated 05 / 14 / 2021, page 9 / 34 5 / 23 The invention ("Organic light emitting diode (OLED) color tuning layer includes external color tuning layer (ECTL) on the out coupling side of the device producing a WOLED"). In these inventions, only small electroluminescent organic molecules, such as dyes, are used. The use of small molecules implies high cost due to the need for thermal evaporation of these species for the formation of the active layer of the diode.

[013] In the device of the present invention, we employ only conjugated polymers, which can be processed in solution and the films are formed by fast processability and low cost techniques, such as spin-coating and inkjet printing. The thickness of the outer photoluminescent layer was also made using a photoluminescent polymer and it is easily controlled by the rotation speed and time in the film deposition process (also deposited by the spin-coating technique).

[014] Next, the present invention is compared with some prior inventions: “Red-Green-Blue light emission from a thin film electroluminescence device based on parahexaphenyl” (authors: Stefan Tasch, Christoph Brandstatter, Farideh Meghdadi, Giinther Leising, Gerard Froyer, Laurence Athouel; Journal: Advanced Materials, Year: 1997, Volume: 9, Page: 33).

[015] In the aforementioned document, small organic molecules were used as the active layer of an organic light-emitting diode. The layer used was based on the dye parahexaphenyl. The authors showed that an outer photoluminescent layer is capable of absorbing part of the radiation from the electroluminescent diode, however they were unable to Petition 870210044159, dated 05 / 14 / 2021, page 10 / 34 6 / 23 produce white light. On the other hand, in the present invention, in addition to the use of polymeric materials instead of small molecules, the production of white light is successfully achieved.

[016] The study “Top-emitting white organic lightemitting devices with down-conversion phosphors: Theory and experiment” (authors: Wenyu Ji, Letian Zhang, Ruixue Gao, Liming Zhang, Wenfa Xie, Hanzhuang Zhang, Bin Li; Journal: Optics Express, Year: 2008, Volume: 16, Page: 15489).

[017] In this document, the authors employ small organic molecules and the emission of white light was only achieved when the angle used to record the emission was 60°. It is important to emphasize that even at this angle, the ideal white emission color (CIE x = 0.35 ey = 0.35) was not observed. Again, in the present invention, in addition to achieving white emission in either direction, the technology used was based on conjugated polymers, and not on small molecules.

[018] In the study “Top-emitting white organic lightemitting diodes with a color conversion cap layer” (authors: Shuming Chen, Hoi-Sing Kwok; Organic Electronics Journal, Year: 2011, Volume: 12, Page: 677) the authors again used an organic dye as an electroluminescent active layer, based on small molecules. The method of obtaining the layer was thermal evaporation, which is expensive and slow.

[019] In our case, the technology is based on polymeric materials, which can be processed in solution, facilitating and simplifying production methods.

[020] In view of the patents and articles shown above Petition 870210044159, dated 05 / 14 / 2021, page 11 / 34 7 / 23 It is important to emphasize that the present invention is the first to utilize only polymeric systems, both with electroluminescent and photoluminescent properties. In this case, the EL (Electroluminescent) diode is separated by an external barrier from the PL (Photoluminescent) film. This avoids problems such as non-radiative energy transfer by the Forster mechanism (FRET), as observed in blends of polymeric systems. This FRET process compromises the device's performance and hinders the preparation of diodes capable of emitting white light. Another problem associated when different polymers are in the same active layer of the diode is the morphological complications due to phase separation processes of the polymeric blend components, making diode reproducibility difficult.

[021] Therefore, the present invention presents a quick and easy way to prepare white emission, eliminating the problems mentioned above. In the developed methodology, the EL and PL layers are all processed in solution and the films can be deposited by various low-cost techniques, such as spin-coating, inkjet printing, silkscreening, etc., thus avoiding the use of thermal evaporators and high vacuum for the deposition of the active layers on the diodes. It is also worth highlighting that this methodology is not limited to white light, as it can be applied to the production of polymeric light-emitting devices with different colors in both the visible and infrared regions. Industrial Applicability

[022] The industrial applicability of this invention encompasses the interior and exterior lighting industries, Petition 870210044159, dated 05 / 14 / 2021, page 12 / 34 8 / 23 LCD display industry, as backlight, and / or for any other application that involves the need to use light, preferably white light, such as: in children's toys, watch faces, and even lighting systems used in nightclubs, among others. Advantages of the invention

[023] The invention described here is very effective for producing white light at low cost. It is sufficient to produce a polymer LED with blue-green emission and place a red filter with the appropriate characteristics. In this case, we would need 50% of the blue-green radiation from the device to be transmitted by the external filter and 50% absorbed and re-emitted in red. This transmission / absorption percentage can be easily adjusted by controlling the thickness of the external filter. Finally, the final light produced by such a device is the combination of the transmitted blue-green light and the red light re-emitted by the filter. It is known that the combination of blue, green, and red generates white light. In fact, we have carried out such an application, the data of which, being merely illustrative, will be presented in the following section. BRIEF DESCRIPTION OF THE INVENTION

[024] The present invention relates to the construction of polymer LEDs where the active layer is maintained, however, the wavelength of emitted light can be easily tuned using an external filter that converts the radiation emitted by the device. The invention also relates to the use of said polymer light-emitting devices.

[025] The invention has several applications, including Petition 870210044159, dated 05 / 14 / 2021, p. 13 / 34 9 / 23 which we can highlight in lighting since it is quite simplified compared to current methods of manufacturing polymeric LEDs, especially in relation to white light emitters.

[026] Obviously, this proposal is not limited to the production of polymer LEDs for lighting only, but the technique allows for the conversion of radiation in any range of the visible and infrared spectrum, provided that certain criteria detailed later are respected. BRIEF DESCRIPTION OF THE FIGURES

[027] Figure 1a refers to an illustrative diagram of the device constructed and the scheme used for generating white light.

[028] Figure 1b is a representation of the molecular structure of poly[(9,9-dioctylfluorene-2,7-diyl)-alt-co(9,9-di-{5'-pentanyl}-fluorene-2,7-diyl)] (PFP).

[029] Figure 1c is a representation of the molecular structure of poly[2-methoxy-5(3,,7,-dimethyloctyloxy)1-4-phenylenevinylene] (MDMO-PPV).

[030] Figure 2a refers to the representation of the electrical performance illustrated by the Current and Luminance curve as a function of Voltage of the ITO / PEDOTPPS / PFP / Ca / Al device.

[031] Figure 2b is an electroluminescence spectrum of the ITO / PEDOT-PPS / PFP / Ca / Al diode (blue graph), absorption spectrum of the MDMO-PPV (dashed black line), and photoluminescence spectrum of the MDMO excited at 500 nm (red line with circles).

[032] Figure 3 is a final emission spectrum of the proposed structure, formed by the ITO / PEDOT diode. Petition 870210044159, dated 05 / 14 / 2021, p. 14 / 34 10 / 23 PPS / PFP / Ca / Al and the quartz substrate with the deposited MDMO (the combination of colors generating white light, with CIE chromaticity coordinates (x = 0.35 and y = 0.35)). DETAILED DESCRIPTION OF THE INVENTION

[033] The present invention relates to the construction of polymer LED type devices with a fixed active layer, and with easy tuning of the emitted light wavelength, using an external filter that converts the radiation emitted by the device. The invention also relates to the use of said diodes (polymer LEDs).

[034] The preferred embodiment of the invention relates to the production of white light, as exemplified below. However, it is not limited to obtaining only white light, and can be used to tune the emission of any other wavelength, simply by using the material whose absorption and emission is appropriate for the application. Polymeric LED-type devices with a fixed active layer

[035] Polymer LED devices with a fixed active layer are detailed below in terms of their construction.

[036] This is a device made using a substrate (glass, quartz and / or any type of flexible substrate, such as polyethylene terephthalate PET). On this substrate there must be a transparent conductive electrode, which can be obtained by evaporating conductive oxides, such as indium tin oxide (ITO). The surface resistivity of this conductive layer must be between 1 and 50 Ω / cm2.

[037] A layer is normally deposited under the oxide. Petition 870210044159, dated 05 / 14 / 2021, page 15 / 34 11 / 23 hole injector and electron blocker, which must have its valence band between the work function of the conducting oxide and the valence band of the active semiconductor, which will emit light. To block the passage of electrons, its conduction band must be energetically positioned above the conduction band of the emissive material. An example of a material that satisfies these characteristics is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), known as PEDOT:PSS, and is widely used in the field of organic electronics. The thickness of this layer should be between 30 and 200 nm. The deposition of this layer can be carried out using various processes, such as thermal evaporation and / or any low-cost method, such as spin-coating deposition, inkjet printing, silkscreening, and spray deposition.

[038] The electroluminescent material is deposited on top of this last layer. This layer can be deposited using various processes, such as spin-coating and / or any low-cost method, such as inkjet printing, silkscreening, and spray deposition.

[039] Under the active light-emitting layer, electrodes were deposited that will serve as cathodes, which are normally metallic (calcium, aluminum, silver, etc.), but can also be made of any other conductive material that exhibits good electron injection into the active layer. For this, its work function must be energetically aligned with the Conduction Band of the electroluminescent material.

[040] To achieve the radiation conversion claimed in this invention, an extra layer of photoluminescent polymeric material was added to the outer side of the substrate. Petition 870210044159, dated 05 / 14 / 2021, page 16 / 34 12 / 23 (glass, quartz and / or any type of flexible substrate) (referred to as a filter). For radiation conversion to occur, the material composing this filter must have an absorption spectrum within the wavelength range emitted by the active electroluminescent material of the device. In this case, a basic optical characterization of the materials to be used is necessary. Another important parameter of this outer layer is its thickness. This is because the molar absorption coefficient is proportional to the exponential of the sample thickness. Thus, the thicker the outer layer, the greater the percentage of light absorbed. In practical terms, the thickness of this layer should be between 10 and 1000 nm.

[041] By absorbing part of the radiation emitted by the light-emitting device, the material will be excited and consequently decay radiatively, emitting light in its emission spectrum. This light emitted by the filter will combine with the light from the LED transmitted through the filter, converting the final output radiation of the LED. To prove this concept, a white light-emitting polymeric LED was developed, which will be detailed below. Polymer LED type devices emitting white light.

[042] The invention is based on a diode that emits electroluminescent (EL) light, as described in the previous item, and an external filter for radiation conversion.

[043] This is a device made using a substrate (glass, quartz and / or any type of flexible substrate, such as polyethylene terephthalate PET). On this substrate we must have a conductive and transparent electrode, which can be obtained through the evaporation of Petition 870210044159, dated 05 / 14 / 2021, p. 17 / 34 13 / 23 conductive oxides, such as indium-doped tin oxide (ITO). The surface resistivity of this conductive layer should be between 1 and 50 Ω / οπι2.

[044] A hole-injecting and electron-blocking layer is normally deposited under the oxide, which must have its valence band between the work function of the conducting oxide and the valence band of the active semiconductor, which will emit light. To block the passage of electrons, its conduction band must be energetically positioned above the conduction band of the emissive material. An example of a material that satisfies these characteristics is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), known as PEDOT:PSS, and is widely used in the field of organic electronics. The thickness of this layer should be between 30 and 200 nm. The deposition of this layer can be carried out using various processes, such as thermal evaporation and / or any low-cost method, such as spin-coating deposition, inkjet printing, silkscreening, and spray deposition.

[045] The electroluminescent material is deposited on top of this last layer. The present invention relates to polymeric devices, therefore, such material must belong to the class of Conjugated Polymers, and present a Band-Gap within the visible range of the electromagnetic spectrum (3.5 to 1.8 eV). The deposition of this layer can be carried out using various processes, such as spin-coating deposition and / or any low-cost method, such as inkjet printing, silkscreening and spray deposition.

[046] Beneath the active light-emitting layer, electrodes were Petition 870210044159, dated 05 / 14 / 2021, page 18 / 34 14 / 23 deposits that will serve as cathodes, which are normally metallic (calcium, aluminum, silver, etc.), but can also be any other conductive material that exhibits good electron injection into the active layer. For this, its work function must be energetically aligned with the conduction band of the electroluminescent material.

[047] To achieve the radiation conversion claimed in this invention, an extra layer of photoluminescent polymeric material was added to the outer side of the substrate (glass, quartz and / or any type of flexible substrate) (referred to as a filter). For radiation conversion to occur, the material comprising this filter must have an absorption spectrum that is within the wavelength range emitted by the active electroluminescent material of the device. In this case, a basic optical characterization of the materials to be used is necessary. Another important parameter of this outer layer is its thickness. This is because the absorption coefficient is proportional to the exponential of the sample thickness. Thus, the thicker the outer layer, the greater the percentage of light absorbed. In practical terms, the thickness of this extra layer should be between 10 and 1000 pm.

[048] By absorbing part of the radiation emitted by the light-emitting device, the material will be excited and consequently decay radiatively, emitting light in its emission spectrum. This light emitted by the filter will combine with the light from the LED transmitted through the filter, converting the final output radiation of the LED.

[049] In the case of application to white light, the electroluminescent film of the device must emit in the color Blue Petition 870210044159, dated 05 / 14 / 2021, p. 19 / 34 15 / 23 and / or Blue-Green (wavelength between 380 and 550 nm), since white light is composed of the combination of wavelengths (colors) of the visible spectrum. Therefore, the presence of more energetic wavelengths is necessary.

[050] To obtain less energetic wavelengths, i.e., colors between orange and red (560 nm to 670 nm), a filter based on luminescent conjugated polymers is used, whose absorption is contained within the emission of the electroluminescent material and which presents emission complementary to the electroluminescence of the active layer of the device. Thus, half of the electroluminescent radiation is transmitted and the other half is absorbed by the filter and re-emitted radiatively. The final composition is an output light composed of all wavelengths of the visible spectrum, thus producing white light. Production Method for Polymer LED Devices Emitting Various Colors

[051] The method can be extended to produce any desired wavelength. The method for tuning the output colors of polymer light-emitting diodes comprises the following steps: a) Construction of a fixed-layer light-emitting device, as detailed in the previous item. The choice of active material will depend on the desired output color; however, the invention will always function using materials with higher energy emissions (200-500 nm), since the technique is based on external radiation conversion through filters, which will need to be excited to decay radiatively. Petition 870210044159, dated 05 / 14 / 2021, page 20 / 34 16 / 23 b) Definition of parameters and material related to the deposition of the layer used as a filter: The material to be used as a filter will also depend on the desired output color and must necessarily have its absorption spectrum contained within that of the electroluminescent emission spectrum of the active layer of the device. Its thickness must be controlled via the relationship between the absorption coefficient of the material and the thickness of the film, which is given by: Iabs = ke“L (1)

[052] Where, IABS is the intensity of radiation absorbed by the filter, I0 is the intensity of the incident light, α is the absorption coefficient of the material used as a filter, and L is its thickness. This means that the thicker the film, the greater the percentage of absorption of the light pumped by the device. Therefore, the output color will approximate the original emission color of the polymer used as a filter.

[053] To make applications more flexible, materials with more energetic color emissions (blue tones) are chosen, given the ease of transforming them into less energetic radiations. There are several polymers with blue light emission, mainly those of the polyfluorene family, preferably and more specifically poly[(9,9-di-noctyl-2,7-fluorene)] (PFO), poly[(9,9-diheptylfluorene)] (PF7) and poly[(9,9-dioctylfluorene-2,7-diyl)-alt-co-(9,9di-{5'-pentanyl}-fluorene-2,7-diyl)] (PFP), used here in the present invention as an electroluminescent active layer. c) Conversion of the radiation emitted by this device using a suitable external filter. The material and characteristics of this film should be chosen depending Petition 870210044159, dated 05 / 14 / 2021, page 21 / 34 17 / 23 of the desired application criteria: white light or polychromatic light.

[054] The aforementioned method uses only one electroluminescent layer, making production easier and reducing costs.

[055] The method is flexible, since the external radiation conversion material can be chosen to emit at any wavelength, making it possible to produce various colors in the visible spectrum, such as white light, and also in the infrared. Use

[056] Both the device and the method may have application in lighting (especially white light emitting devices) as it is quite simplified compared to current methods of manufacturing polymer LEDs, especially when dealing with white light emitters.

[057] Obviously, this proposal is not limited to the production of polymeric LEDs for lighting only, but the technique allows for the conversion of radiation in any range of the visible and infrared spectrum, provided that the criteria presented here are respected or that there are evident variations from them. Example of Implementation of the Invention

[058] White light-emitting diodes were produced by way of example and not limitation, using the methods for external radiation conversion described above. The original polymer LED emitted blue-green light. The outer layer partially absorbed this radiation and re-emitted it in red. The combination of colors generated white light, with CIE chromaticity coordinates (x = 0.35 ey Petition 870210044159, dated 05 / 14 / 2021, page 22 / 34 18 / 23 = 0.35).

[059] The polymer light-emitting diode was manufactured using traditional techniques, already widely disseminated in the specialized literature and which will be detailed below: I) Deposition of PEDOT:PSS film - poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) - onto commercial ITO sheets, with a sheet strength of 20-40 Ω / cm2. The deposition is done either by the "spin-coating" method, silkscreening or by printing methods and must have a thickness of tens to hundreds of nanometers. II) Heat treatment of the PEDOT:PSS layer for 5 to 10 minutes at 100-110°C. III) Production of the polymer solution in a suitable organic solvent (chloroform, xylene, toluene, dichlorobenzene, tetrahydrofuran, etc.), with a weight ratio of 0.05 to 10% for the solution. IV) Deposition of the active layer (light-emitting polymer, which may belong to the polyparaphenylene and polyfluorene families), with a thickness of tens to hundreds of nanometers. This deposition can be done using the "spin-coating" method, silkscreening, or printing methods. V) Heat treatment of the active layer to remove the organic solvent. The temperature and treatment time will depend on the type of solvent used (as each has a different boiling point). VI) Deposition of suitable cathodes. This step can be performed using conductive polymeric materials (e.g., conductive PEDOT) and / or any electron-injecting metallic contact (e.g., calcium, silver, aluminum, fluoride). Petition 870210044159, dated 05 / 14 / 2021, page 23 / 34 19 / 23 Lithium). Both can be deposited by thermal evaporation, silkscreening, or printing methods. VII) Production of the polymer solution in a suitable organic solvent (chloroform, xylene, toluene, dichlorobenzene, tetrahydrofuran, etc.), with a weight ratio of 0.05 to 10%, which will be used as an external filter for radiation conversion. VIII) Fabrication of the external radiation conversion filter. The choice of material will depend on the intended application, but it should be a conjugated polymer, mainly from the polyparaphenylene, polyfluorene, and polythiophene families. Deposition can be done by spin-coating, thermal evaporation, silkscreening, or printing methods, and its thickness will depend on the application, since the thickness will control the amount of light that will be transmitted / absorbed by the external filter.

[060] Next, we will detail the steps for producing a white light-emitting polymer LED using the technique proposed here.

[061] The configuration of our light emitting diode for application in white light emitting polymer LED, see Figure 1a, was ITO(E) / PEDOT:PSS(D) / Polymer(C) / Calcium(B) / Aluminum(A), where ITO stands for Indium-doped Tin Oxide, PEDOT:PSS is a hole-injecting material, called poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate).

[062] The polymeric material used was poly[(9,9-dioctylfluorene-2,7-diyl)-alt-co-(9,9-di-{5'-pentanyl}fluorene-2,7-diyl)], hereinafter referred to as PFP. This polymer is commercially available from several companies. Petition 870210044159, dated 05 / 14 / 2021, page 24 / 34 20 / 23 chemical plants, such as the American Dye Source (Quebec, Canada), and exhibit a blue-green emission.

[063] The fabrication began with steps I and II, which is the deposition of an 80 nm PEDOT:PSS film onto the ITO substrates (25 Ω / cm-2 obtained from Delta Tecnologia), and drying the film for 5 minutes at 100°C. Subsequently, we carried out steps III, IV and V, which is the deposition of a 90 nm active layer of PFP material using the spincoating method, from a THF solution (1% by weight), in a nitrogen atmosphere, and then heated for 15 minutes at 60°C.

[064] Finally, step VI was completed by thermally evaporating the electrodes, which were a calcium film with a thickness of 30 nm and an aluminum film with a thickness of 100 nm under a pressure of 0.0001 pascal (equivalent to 10-6 mbar). The final structure of the device is shown schematically in Figure 1a. This device exhibits blue-green emission, as shown in the emission spectrum illustrated in Figure 2. Figure 3a illustrates the electrical characterization of the device, where an operating voltage of 3 volts and a brightness of approximately 500 cd / m2 at 8 volts are observed.

[065] The major innovation achieved relates to the transformation of the blue-green light emitted by a single layer of PFP into white light, which is accomplished by steps VII and VIII. This was achieved by adding to the reverse side of the PFP-based device, i.e., where the light is transmitted, a thin film of a red-emitting polymeric film, called poly[2-methoxy-5(3,7'-dimethyloctyloxy)1-4-phenylenevinylene], hereinafter referred to as MDMO-PPV - see illustration in Figure 1a. Petition 870210044159, dated 05 / 14 / 2021, page 25 / 34 21 / 23

[066] The colored filter containing the thin film (100 nm thick) of the red-emitting polymer, MDMO-PPV, was deposited by the spincoating method (500 rpm, 1 minute) using a THF solution (1 wt%) on a clean quartz substrate. This film was placed under the light-emitting device. The MDMO-PPV material exhibits an absorption peak around 500 nm, its band being completely superimposed by the electroluminescent emission of the aforementioned device, see Figure 3b. This is a requirement of the technique: the absorption spectrum of the polymer to be used as a filter must overlap with the emission spectrum of the polymer used as the active layer in the light-emitting diode. Thus, the light emitted by the device excites the filter molecules, which decay radiatively, emitting light in the color dictated by their electronic structure.

[067] In the case of the application for white light, the thickness of the MDMO-PPV film was chosen such that it absorbs half and transmits half of the radiation emitted by the device. By absorbing half of the incident radiation, the MDMO-PPV material decays radiatively, emitting red light (photoluminescence).

[068] The final composition of transmitted electroluminescence and fluorescent radiative decay of MDMOPPV covers the entire visible spectrum region, thus generating white light. The final emission spectrum is shown in Figure 3. The chromaticity coordinate of the obtained white light was x = 0.35 and y = 0.35.

[069] This example demonstrates the feasibility of the proposed invention, the methodology being simple and low cost, in addition Petition 870210044159, dated 05 / 14 / 2021, page 26 / 34 22 / 23 brings considerable flexibility to applications, as it is not limited to the production of white light, but to the conversion of radiation in any part of the spectrum, provided that the physical and chemical conditions mentioned above are respected.

[070] Although the invention has been extensively described, it is obvious to those skilled in the art that various alterations and modifications may be made with a view to improving the design without such alterations not being covered by the scope of the invention. References

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[078] B. W. D’Andrade, S. R. Forrest, White Organic Light-Emitting Devices for Solid-State Lighting. Adv. Mater., 204, 18, 1585.

Claims

1. Polymer LED-type devices with a fixed active layer, comprising: - a glass, quartz and / or flexible substrate, such as polyethylene terephthalate (PET), and on this - a transparent conductive electrode obtained by evaporation of conductive oxides, such as indium-doped tin oxide (ITO); - a hole-injecting and electron-blocking layer with a thickness between 30 and 200 nm, which has a valence band between the work function of the conductive oxide and the valence band of the active semiconductor to emit light, energetically positioned above the conduction band of the emitting material poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS); - an electroluminescent material belonging to the class of conjugated polymers and having a band gap within the visible range of the electromagnetic spectrum from 3.5 to 1.8 eV, deposited on top of the hole-injecting and electron-blocking layer; - electrodes, wherein the device is based on poly[(9,9dioctylfluorene-2,7-diyl)-alt-co-(9,9-di-{5'pentanyl}fluorene-2,7-diyl)] (PFP) and wherein the devices are characterized by the fact that they have an extra layer of photoluminescent polymeric material added to the outer side of the substrate.

2. Polymer LED-type devices with a fixed active layer, according to claim 1, characterized by the fact that the surface resistivity of the conductive layer is between 1 and 50 Ω / cm2.

3. Polymer LED-type devices with a fixed active layer, according to any one of claims 1 to 2, characterized in that the deposition of the hole-injecting and electron-blocking layer is carried out using processes selected from the group consisting of spin-coating deposition and / or other low-cost methods, such as inkjet printing, silkscreening, and spray deposition.

4. Polymer LED-type devices with a fixed active layer, according to claim 1, characterized in that the thickness of the extra layer is between 10 and 1000 μm.

5. Polymer LED-type devices with a fixed active layer, according to claim 1, characterized in that, for radiation conversion to occur, the material comprising said substrate must have an absorption spectrum that is within the wavelength range emitted by the active electroluminescent material of the device.

6. Polymer LED-type devices with a fixed active layer, according to claim 1, characterized in that, in the case of white light, the electroluminescent material of the device emits in blue and / or blue-green color.

7. Polymer LED-type devices with a fixed active layer, according to claim 6, characterized in that the blue and / or blue-green color has a wavelength between 380 and 550 nm. Petition 870260039109, dated 04 / 27 / 2026, p. 8 / 19 3 / 4 8. Polymer LED-type devices with a fixed active layer, according to any one of claims 6 or 7, characterized in that the blue-green light is transformed into white light by adding to the reverse side of the device a thin film of a red-emitting polymer film based on poly[2-methoxy5(3',7'dimethyloctyloxy)1-4-phenylenevinylene].

9. Method for producing polymeric LED-type devices emitting various colors, as defined in claims 1 to 8, characterized by comprising the following steps: a) making a fixed-layer light-emitting device as defined in any of claims 1 to 8; and b) defining the parameters and material related to the deposition of the layer used as a filter; and c) converting the emitted radiation using a suitable external filter.

10. Method, according to claim 9, characterized by the fact that materials with more energetic color emissions in blue tones are chosen.

11. Method according to claim 10, characterized in that the materials emitting more energetic colors in blue tones are polymers belonging to the polyfluorene family, preferably and more specifically poly[(9,9-di-n-octyl-2,7-fluorene)] (PFO), poly[(9,9-diheptylfluorene)] (PF7) and poly[(9,9-dioctylfluorene-2,7-diyl)-alt-co-(9,9-di-{5'pentanyl}fluorene-2,7-diyl)] (PFP). Petition 870260039109, dated 04 / 27 / 2026, page 9 / 19 4 / 4 12. Method, according to any one of claims 9 to 11, characterized in that it uses only one electroluminescent layer.

13. Use of the devices as defined in any of claims 1 to 8, characterized by the fact that it is for lighting purposes.

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