Thermoelectric micro column array device, methods and uses thereof

Abstract

The present disclosure relates to a thermoelectric device for thermal energy harvesting and method to obtain said device, where the thermoelectric device comprises: a substrate; a bottom electrically conductive layer deposited on the substrate; a top electrically conductive layer; a plurality of columns of a thermoelectric semiconductor material; an electrically and thermally insulating layer surrounding the plurality of columns; wherein the electrically and thermally insulating layer, and the thermoelectric material are between the bottom electrically conductive layer and the top electrically conductive layer.

Description

D E S C R I P T I O NTHERMOELECTRIC MICRO COLUMN ARRAY DEVICE, METHODS AND USES THEREOFTECH NICAL FIELD

[0001] The present disclosure relates to a device for the conversion of thermal heat into electricity. The present disclosure relates to a heterostructured thermoelectric device for windows, touch-displays, photovoltaic panels, and thermal solar panels for harvesting thermal heat and converting it into electricity.BACKGROUND

[0002] About 60% of the energy that is produced in the world is wasted due to transport losses, in particular energy loss in the form of heat. Thermoelectric materials can reduce this energy loss by converting thermal energy into electricity. For example, it is well known that most of the windowpanes in buildings are not efficient in inhibiting thermal losses in either interior cooling or heating environments. The range of values for the thermal conductivity of most glasses at room temperature ranges from 0.5 W-m-1-K1(high lead-containing glasses) to about 1.4 W-m^-K1(pure quartz glass). Commonly used silicate glasses have thermal conductivities that vary between 0.9 and 1.2 W-m-1-K-1. Hence, albeit these values being small in comparison to most metal structures, there is still energy loss.

[0003] The thermoelectric (TE) effect is historically known as the direct conversion of temperature differences on a material to an electric voltage. Thermoelectric materials have been explored for many years. The first were thermocouples, two dissimilar electrical conductors forming an electrical junction, and this discovery was made in 1794 by Alessandro Volta, followed by the works of Thomas Johann Seebeck, who in 1821 independently rediscovered it, and from which the thermoelectric effect is generally known as the Seebeck effect. More recent thermoelectric materials are based on metals and semiconductors, such as zinc, lead, antimony, bismuth, copper and different constituent alloys, among many other more complex systems that were developed throughout the years, such as ceramics, polymers and composites. Most of these materials have a high Seebeck coefficient (S), which is theproduced electromotive force (AV) divided by the thermal difference across the material (AT). An optimized thermoelectric material must have a high electrical conductivity (G) and a low thermal conductivity (K) to attain a high figure of merit (ZT=S2G / K-T) at a specific temperature (T) and a resulting high-power factor (PF=S2G). However, the aforementioned materials cannot be applied on glass if optical transparency is required. To circumvent this issue, research on transparent thermoelectric materials evolved, particularly with transparent metal oxide coatings. However, so far, these metal oxide coatings were designed to harvest thermal heat across their surface, which is not suitable for applications such as touch displays or windowpanes.

[0004] The state-of-the-art of thermoelectric generator devices is extensive, with different solutions and applications being presented.

[0005] Starting with non-transparent devices, Boukai et al [1] report an efficient thermoelectric performance from the single-component system of silicon (Si) nanowires for cross-sectional areas of 10 nm x 20 nm and 20 nm x 20 nm. By varying the nanowire size and impurity doping levels, ZT values representing an approximately 100-fold improvement over bulk Si are achieved, over a broad temperature range, including ZT < 1 at 200 K. Hochbaum et al [2] report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20-300 nm in diameter with a figure of merit ZT = 0.6 at room temperature. Because thermoelectric (TE) modules consist of complementary p- and n-type materials wired in series, the generality and scalability of this synthesis are promising for the fabrication of Si-based devices. Zhou and co-workers [3] also report the use of nanowires to continuously convert body heat into electrical power that can be applied to portable / wearable electronic devices. However, despite the previously mentioned good thermoelectric properties of silicon nanowires, these nanowires are not optically transparent, only if applied as a mesh on the substrate surface, with the inevitable loss of transparency for the windowpane or touch display. Another flexible thermoelectric generator (TEG) was presented by Kim et al [4] for harvesting thermal energy from human skin. This TEG consists of an n-type ( BizTea) and a p-type (SbzTes) material, with a weight surface density of 0.13 g / cm2. Tan et al [5] report the study of the growth mechanism of the hierarchical pillar arrays and the ordinary SbzTes film. The p-type antimony telluride pillar arrays with hierarchical architecture were selfassembled on a large scale by a simple vacuum thermal evaporation technique. Thehierarchical film consists of well-oriented pillar arrays perpendicular to the substrate. Another work reports [6] n-BizTez.zSeo.s pillar array legs micro-device with layered silver (Ag) electrode fabricated using magnetron sputtering and mask-assisted deposition technology. These last two solutions are the most similar to the present disclosure, with the main difference, being the vertical pillars addressed. While these solutions focus on how the thin film grows, the proposed disclosure concerns the geometry of the thin film. Nevertheless, these STEGs are not optically transparent, hindering applications in structures where transparency is an issue. Moreover, the microfabrication steps to produce transparent thermoelectric micro arrays in the present disclosure are different.

[0006] Proceeding to semi-transparent devices, Wang et al [7] report a flexible TEG module based on a polymer composite, PEDOT:PSS, consisting of 16 legs and being able to output a stable TE voltage of 4.6 mV in response to the heat of a human body. The results demonstrate a great potential in the mass production of thermoelectric polymers for industrial applications, although still with deficiencies in optical transparency, with relatively high absorption in the visible spectrum. Klochko [8] reports a new design of a semi-transparent solar thermoelectric nanogenerator (n-TEG) based on the pulsed electro-deposited array of zinc oxide (ZnO) nanorods on a transparent conducting fluorine-doped tin oxide (FTO) substrate. The solar n- TEG design combines the benefits of low thermal emittance of FTO and ZnO coatings with TE technology for the harvesting of photo-thermal energy from outdoor sunlight by the windows themselves, and thus to produce electricity, having also high transparency in infra-red. However promising, the TE applications fail on optical transparency in the visible part of the electromagnetic spectrum, with the highest transmittance generally smaller than 20-30%, and below 5% in the blue-green region.

[0007] Regarding transparent TEGs, Faustino et al [9] report p-type thermoelectric thin films of copper iodide (Cui) developed by three different methods to maximise optical transparency (>70% in the visible range), electrical conductivity (o=l.lxl0-4S-m1) and thermoelectric properties (ZT=0.22 at 300K). However, these planar transparent p-n type TE modules are tailored for harvesting in-plane thermal differences. Chen and co-workers

[0010] present the design, simulation and fabrication of an innovative transparent micro-thermoelectric generator (p-TEG), also in the form of planar p-n type TE modules for solar energy conversion applications, by using the surface micromachining technology of microelectromechanicalsystems (MEMS) technology. This results in a transparent p-TEG with suspending bridge-type polysilicon Peltier elements and transparent conductive indium tin oxide (ITO) thin films as the hot side and cold side electrodes fabricated on a glass or quartz wafer, designed for harvesting in-plane thermal differences. In some cases, these transparent thermoelectric devices can be manufactured as stretchable and transparent ionogels, according to Fan et al

[0011] , The report from Ferreira and co-workers

[0012] shows the TE properties of tin oxide (SnOz) produced by RF sputtering technique, with and without post-deposition annealing in air at atmospheric pressure, and compares its performance with other potential eco-friendly metal oxide materials. It is shown that when annealing the thinner planar films (250 nm) up to 500 °C, the absolute Seebeck coefficient increases monotonically from 150 to 250 pV / K at room temperature. In 2019, Coroa et al

[0013] reported the first highly transparent and flexible p-n thermoelectric generator, comprising 17 p-n modules electrically and thermally connected in series and in parallel. This device was successfully constructed and tested for temperature inplane thermal differences up to 30 °C. The reported ZT values of copper iodide (Cui) and gallium-doped zinc oxide (GZO) are 0.29 and 0.07, respectively, and the Seebeck coefficient for Cui (p-type) and GZO (n-type) are 206 pV / K and -60 pV / K, respectively. However, it was observed that the thin films of Cui were electrically unstable at temperatures beyond 80 °C. Ishibe et al

[0014] reported a uni-leg type (n-type) film TEG composed of domain-engineered SnOz film, which generates a maximum power density of ~ 54 pW-rrr2when applying an inplane thermal difference of 20 K, which is sufficient to run some internet of things sensors. The samples exhibited a maximum power factor of ~ 0.04 pW-m ^l2at room temperature and a high optical transmittance of >80% in the visible region. Another n-type thermoelectric material with huge potential is niobium-doped titanium dioxide (TiO2:Nb), where according to Ribeiro et al

[0015] , a nanometric junction less thermoelectric element was built, consisting of a thin layer of TiO2:Nb film deposited onto a borosilicate glass substrate, with a thickness of 120- 300 nm, maximum average optical transmittance in the visible range of 73 %, n-type electrical resistivity of 0.05 Q-cm, thermal conductivity of 1.7 W-m ^-K1and an absolute Seebeck coefficient greater than 220 pV / K. The resulting maximum thermoelectric power factor is 60 pW-rn ^K’2, and the maximum thermoelectric figure of merit is 0.014. The patent document PT110639 was filed for the latter thermoelectric n-type coating

[0016] , which harvests heat in the in-plane direction.

[0008] Table 1 summarises the previously presented TEG devices: their application, the types of materials being used and how they are built.

[0009] Following this, the prospects for using thermoelectric coatings in windowpanes, touch displays, photovoltaic panels, among other types of structures and devices, are enticing to convert thermal heat into electricity and, in particular cases, to render the devices more energetically sustainable.

[0010] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.GENERAL DESCRIPTION

[0011] The present disclosure relates to a heterostructured thermoelectric device capable of converting thermal heat into electricity with high efficiency. The device comprises a series of heterostructured layers that enhance thermoelectric performance by optimizing the Seebeck coefficient and electrical conductivity while minimizing thermal conductivity. This device can be integrated into various applications such as windows, touch-displays, photovoltaic panels, and thermal solar panels, enabling them to harvest thermal energy and convert it into electricity.

[0012] The heterostructured thermoelectric device of the present disclosure relates to a layered structure, combining the structure, materials and thickness of the layer which significantly enhances the efficiency of thermal to electrical energy conversion compared to conventional thermoelectric devices. The present invention incorporates a combination of thermoelectric material layers and interface layers that enhance material bonding and device stability, and conductive layers (electrodes) that provide efficient electrical pathways. This synergistic combination results in superior thermoelectric properties, enabling the device to be effectively integrated into a variety of applications such as windows, touch-displays, photovoltaic panels, and thermal solar panels. This integration capability allows for versatile harvesting of thermal energy from different sources, addressing a significant gap in the field of energy conversion technologies. Moreover, depending on the chosen substrate, this heterostructured device can be rigid (when using glass as a substrate) or flexible (when using a polymer as a substrate)

[0013] The present disclosure relates to a heterostructured material, particularly a matrix of micro-arrays of pillars or columns with thermoelectric properties for thermal energy harvesting that flows perpendicular to the outer and inner surfaces (in the out-of-plane direction) and that are optically transparent in the visible range, with the proposed set of incorporated functions. The present disclosure is intended for application in structures presenting thermal differences between two surfaces, normally between an internal and external surface, to harvest heat from the hotter surface and, in case there is a thermal difference, to convert it into electric energy.

[0014] This effect is designated as the Seebeck effect and can be expressed as the absolute voltage, or electrical potential difference, produced between the hot and cold electrodes of the thermoelectric material divided by the temperature difference through the material.

[0015] Currently, several transparent thermoelectric coatings are designed to harvest heat differences on the surface (in-plane) of a material but not across it (out-of-plane), being the latter the case of thermal difference across the section of the windowpane. The prior art does not disclose micro-arrays of pillars or columns arranged in a matrix with thermoelectric properties for thermal energy harvesting that flows perpendicular to the outer and inner surfaces (in the out-of-plane direction), and that are optically transparent in the visible range, with the proposed set of incorporated functions.

[0016] An aspect of the present disclosure relates to a thermoelectric device comprising: a substrate; a bottom electrically conductive layer deposited on the substrate; a top electrically conductive layer; a plurality of columns of a thermoelectric semiconductor material, between the top electrically conductive layer and the bottom electrically conductive layer; an electrically and thermally insulating layer [between the top electrically conductive layer and the bottom electrically conductive layer] and surrounding each of the plurality of columns; wherein the electrically and thermally insulating layer is transparent to visible light, wherein each cylindrical column of the plurality of cylindrical columns has a diameter from 50 nm to 500 .m; wherein the plurality of columns of a thermoelectric semiconductor material generates an electric potential difference when the bottom electrically conductive layer and the top electrically conductive layer are subjected to a thermal difference.

[0017] In an embodiment, the heterostructured material comprises a transparent thermoelectric micro pillar or columns array that are etched into a glass substrate or structure, along its thickness, which includes a transparent bottom and top electrically conductive layer (electrodes), a patterned transparent and electrically insulator glass matrix with wells and a thermoelectric semiconductor material deposited in these wells.

[0018] In an embodiment, the heterostructured material comprises a transparent thermoelectric micro pillar or columns array that are etched into a polymer substrate, along its thickness, which includes a transparent bottom and top electrically conductive layer (electrodes), a patterned transparent and electrically insulator polymeric matrix with wells and a thermoelectric semiconductor material deposited in these wells, rendering a flexible and transparent device.

[0019] In an embodiment, a transparent matrix comprising cylindrical thermoelectric pillars or columns generates an electric potential difference when the top and bottom electrodes aresubjected to a thermal difference. The electric current that is generated from these pillars or columns is summed to provide an output direct current that may, for example, charge a battery, or be transformed to alternating current.

[0020] Thus, the heterostructured material allows thermal heat recovery from surfaces, where normally it is wasted, and its conversion into electric energy. Preferably, all layers, pillars or columns, and electrodes are optically transparent in the visible part of the electromagnetic spectrum. Furthermore, the top and bottom electrodes, made from a transparent and conductive oxide (TCO) material, such as fluorine-doped tin oxide (FTO), or indium-tin oxide (ITO), or indium-, aluminium- and / or gallium-doped zin oxide (IZO, AZO, GZO), for example, besides being transparent, have an electrical conductivity greater than lxlO4S / cm and have good adhesion to the glass substrate. The range of thickness for the electrodes is 50-300 nm. The electrical insulating matrix can be made from a transparent electrically and thermally insulating oxide material, such as silicon or aluminium oxide, for example, with a thickness between 200 and 2000 nm. The thermoelectric pillars or columns should be made from a transparent semiconductor material, n- or p-type, or a combination of both, with high electrical conductivity, preferably larger than lxlO4S / cm, low thermal conductivity, preferably smaller than 2 W-m-1-K-1, preferably from doped metal oxides, such as doped zinc oxide, copper oxide or doped titanium dioxide. To avoid transmittance losses through the heterostructured material on the glass, its total thickness should be preferably lower than 3 .m, however in the range of 3 to 30 pm it should also have an average transmittance of about 80% in the visible region.

[0021] In an embodiment, the present disclosure is applied in the glass and civil engineering industry, namely, in windowpanes. These glass structures can be functionalized with the heterostructured material to harvest heat from either side of the glass, depending on the atmospheric conditions. For example, during summer, the outer surface of the windowpane should be much hotter than the inner surface and, in the winter / cold days, the opposite is expected.

[0022] In an embodiment, a glass structure, covered with a TCO electrode layer on both surfaces, can be etched across its total thickness with a matrix of micro-arrays of wells onto which the thermoelectric material can be deposited, to harvest heat from either side of the glass surface.

[0023] In an embodiment, a polymer substrate, covered with a TCO electrode layer on both surfaces, can be etched across its total thickness with a matrix of micro-arrays of wells onto which the thermoelectric material can be deposited, to harvest heat from either side of the polymer surface.

[0024] Since this heterostructured material comprises an array of thermoelectric pillars or columns, the thermal difference will originate an electric potential difference between the outer and inner surfaces of the windowpane. The same concept can be applied to other devices such as touch-displays, photovoltaic panels, thermal solar panels or similar structures / surfaces. Thus, the present disclosure can additionally be of interest to the electronic components industry, amongst others.

[0025] It is disclosed a thermoelectric device for harvesting thermal energy and convert into energy, comprising: a substrate; a bottom electrically conductive layer deposited on the substrate; a top electrically conductive layer; a plurality of columns of a thermoelectric semiconductor material; an electrically and thermally insulating layer surrounding the plurality of columns; wherein the electrically and thermally insulating layer, and the thermoelectric material are between the bottom electrically conductive layer and the top electrically conductive layer.

[0026] In an embodiment, each column is spaced from the following column by the electrically and thermally insulating layer.

[0027] In an embodiment, each column is spaced from the following column by the glass structure into which the columns are etched.

[0028] In an embodiment, each column is spaced from the following column by the polymer substrate into which the columns are etched.

[0029] In an embodiment, the electrically and thermally insulating layer is transparent to visible light.

[0030] In an embodiment, wherein the material of the transparent electrically and thermally insulating layer is selected from a list consisting of: glass, a polymer or combinations thereof.

[0031] In an embodiment, each column is cylindrical or cuboid, preferably cylindrical.

[0032] In an embodiment, each column of the plurality of columns has a diameter from 50 nm to 500 .m, preferably 50 pm to 200 pm.

[0033] In an embodiment, each column of the plurality of columns has a pitch from 50 nm to 500 pm, preferably from 50 pm to 200 pm.

[0034] In an embodiment, each column of the plurality of columns has a height from 50 nm to 500 pm, preferably from 0.5 pm to 1 pm.

[0035] In an embodiment, the bottom electrically conductive layer and the top electrically conductive are transparent to light, preferably visible light.

[0036] In an embodiment, the top and bottom conductive layers are made of a transparent electrical conductive metal oxide layer with a conductivity larger than 1000 S / cm. The ionic conductivity can be measured by standard methods, namely by Electrochemical Impedance Spectroscopy (EIS) at 300 K.

[0037] In an embodiment, the top and bottom conductive layers are made of a material selected from a list comprising: fluorine-doped tin oxide, indium-tin oxide, aluminium-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, or mixtures thereof.

[0038] In an embodiment, each of the top and bottom electrically conductive layers have a thickness from 50 nm to 500 nm, preferably from 100 nm to 300 nm.

[0039] In an embodiment, the electrically and thermally insulating matrix layer is made from a metal oxide.

[0040] In an embodiment, the electrically and thermally insulating matrix layer is made from glass and / or a polymer; preferably a film.

[0041] In an embodiment, the electrically and thermally insulating layer is made of a material selected from a list comprising: silicon oxide, bismuth oxide, titanium oxide, vanadium oxide, chromium oxide, tantalum oxide or zinc oxide, hafnium oxide, aluminium oxide, copper oxide, zirconium oxide, aluminium oxide or mixtures thereof.

[0042] In an embodiment, the electrically and thermally insulating layer is made of a polymer selected from a list comprising: polyethylene terephthalate, polyethylene, polyvinyl chloride, polypropylene, polystyrene, poly(methyl acrylate), SU-8, cellulose acetate, polyamide.

[0043] In an embodiment, the electrically and thermally insulating layer in the form of a film has a thickness from 50 nm to 500 .m, preferably from 0.5 pm to 1 pm.

[0044] In an embodiment, the electrically and thermally insulating layer in the form of a polymer has a thickness from 10 pm to 10 mm, preferably from 20 pm to 1 mm.

[0045] In an embodiment, the electrically and thermally insulating layer in the form of a glass has a thickness from 1 mm to 10 mm, preferably from 2 mm to 4 mm.

[0046] In an embodiment, the thermoelectric semiconductor material is transparent to light, preferably to visible light.

[0047] In an embodiment, the thermoelectric semiconductor material is a metal oxide doped with a cation or an anion.

[0048] In an embodiment, the thermoelectric semiconductor material is a doped or undoped carbon material selected from a list of carbon materials such as carbon nanowires, carbon nanofibers or carbon nanotubes.

[0049] In an embodiment, the thermoelectric semiconductor material is undoped titanium oxide or titanium oxide doped with an element selected from the following list: niobium, aluminum, gallium, molybdenum, iron, antimony, bismuth, vanadium, tantalum, nitrogen, phosphor, arsenic, indium, sulphur, carbon, or mixtures thereof.

[0050] In an embodiment, the thermoelectric semiconductor material is undoped zinc oxide or zinc oxide doped with an element selected from the following list: niobium, aluminum, gallium, molybdenum, iron, antimony, bismuth, vanadium, tantalum, nitrogen, phosphor, arsenic, indium, sulphur, carbon, or mixtures thereof.

[0051] In an embodiment, the thermoelectric semiconductor material is undoped copper oxide or copper oxide doped with an element selected from the following list: niobium, aluminum, gallium, molybdenum, iron, antimony, bismuth, vanadium, tantalum, nitrogen, phosphor, arsenic, indium, sulphur, carbon, or mixtures thereof.

[0052] In an embodiment, the substrate is glass or polymer.

[0053] In an embodiment, the plurality of columns is a microarray.

[0054] In an embodiment, the bottom electrically conductive layer is an anode or cathode and the top electrically conductive layer is a cathode or an anode.

[0055] It is also disclosed a process to obtain the thermoelectric device comprising the following steps sequentially: depositing a bottom electrically conductive layer on a substrate; depositing an electrically and thermally insulating layer on a surface of the bottom electrically conductive layer; coating the electrically and thermally insulating layer with a photoresist layer; patterning a matrix of wells onto the photoresist layer until it reaches the electrically and thermally insulating layer through optical lithography or laser direct-writing; etching with reactive ions the electrically and thermally insulating layer not coated (i.e. uncoated) with the photoresist layer until it reaches the bottom electrically conductive layer; depositing a thermoelectric material; removing the thermoelectric material that is surplus, i.e. that is above the surface of the photoresist layer, keeping the thermoelectric semiconductor material that is inside the wells to form the plurality of columns of thermoelectric semiconductor material; removing the photoresist layer; depositing a top electrically conductive layer.

[0056] In an embodiment, the bottom electrically conductive layer and the top electrically conductive layer are deposited by physical vapour deposition, chemical vapour deposition, atomic layer deposition, wet chemistry, including sol-gel, electrodeposition, molecular beam epitaxy, pulsed laser sintering, pulsed laser deposition, or arc plating.

[0057] In an embodiment, the electrically and thermally insulating matrix layer is deposited by physical or chemical vapour deposition, spin-coating, or wet chemistry method.

[0058] In an embodiment, the electrically and thermally insulating matrix layer is deposited by physical vapour deposition, chemical vapour deposition, atomic layer deposition, wet chemistry, including sol-gel, electrodeposition, spin-coating, molecular beam epitaxy, pulsed laser sintering, pulsed laser deposition, or arc plating.

[0059] In an embodiment, the deposition of the thermoelectric material is made by physical vapour deposition, chemical vapour deposition, atomic layer deposition, electrodeposition,wet chemistry, such as sol-gel, molecular beam epitaxy, pulsed laser sintering, pulsed laser deposition, or arc plating.

[0060] In an embodiment, the bottom conductive electrode is an anode or cathode and the top conductive electrode is a cathode or an anode, for n-type or p-type semiconductor thermoelectric material, respectively.

[0061] It is also disclosed the use of the device for harvesting thermal energy from windows.BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The following figures provide preferred embodiments for illustrating the disclosure and should not be seen as limiting the scope of invention.

[0063] Figure 1: Schematic representation of an embodiment of a cross-section of the microfabrication steps required to obtain the thermoelectric transparent micro-arrays, being represented the steps of a) starting with a glass substrate; b) deposition of the bottom electrode; c) deposition of a SiCh insulating matrix layer; d) coating with a photoresist layer; e) definition of the micro-pillar arrays or micro-columns arrays; f) etching of the insulation matrix layer; g) deposition of the thermoelectric pillars or columns; h) removal of wanted material; and, finally i) deposition of the top electrode.

[0064] Figure 2: Schematic representation of the heterostructured thermoelectric material and experimental setup to determine the Seebeck coefficient and output electric current. Figure 2 presents the heterostructured material viewed from multiple perspectives; Figure 2a shows the cross-section of the heterostructured material; Figure 2b presents the heterostructured material from two perspectives, where the location of the bottom and top electrodes are identified; in Figure 2c, the device is vertically separated into its constituent layers; Figure 2d illustrates the setup to perform the thermoelectric experiment, including the two Peltiers, sample and heat dissipator, and electrical connections; Figure 2e and Figure 2f illustrate the Peltiers for cooling and heating, respectively, without the heterostructured material; Figure 2g presents another view of the experimental setup with the leads for electric current and voltage measurement.DETAILED DESCRIPTION

[0065] The present disclosure relates to an optically transparent thermoelectric heterostructured semiconductor material that can harvest thermal heat, for example, through a glass windowpane, in case there is a thermal difference between the outside and inside faces of this windowpane, independently of which one is hotter. This effect, the Seebeck effect is not new; however, the heterostructured material and his architecture that produces this thermoelectric effect are. The novelty is in the architecture of the heterostructured layer, which can be efficiently applied in glass windows, tactile screens, photovoltaics, architectural structures, etc. Currently, there are several transparent thermoelectric coatings applied to glass surfaces, for example, that produce a thermoelectric voltage if there is a heat difference across the surface (in-plane), but not across it (out-of-plane), because the whole coating is thermalized by being on one of the sides of the glass, either inner or outer side. The present disclosure provides a transparent matrix comprising cylindrical thermoelectric pillars or columns with low thermal conductivity that generate an electric potential difference when the top and bottom electrodes of this matrix are subjected to a thermal difference. The electric current that is generated from these pillars or columns is summed to provide an output direct current that may, for example, charge a battery, or be transformed to alternating current. Similarly, for other devices, such as touch-displays, photovoltaic panels, thermo solar panels, the same heterostructured thermoelectric device can be applied to harvest thermal heat and convert it to electricity, thus rendering the device more sustainable.

[0066] The disclosed heterostructured thermoelectric material is intended for application in structures presenting thermal differences between two surfaces, normally an internal and external surface, where the heat flows perpendicular to these surfaces, converting it into electric energy. An embodiment comprises a transparent thermoelectric micro column array, which includes transparent bottom and top electrically conductive layers (electrodes), a patterned transparent insulating matrix with wells and a thermoelectric n- or p-type semiconductor material deposited in these wells.

[0067] In one embodiment, the transparent bottom and top electrically conductive layers (electrodes) are made of fluorine-doped tin oxide (FTO), indium-tin oxide (ITO), aluminium- doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), or any combination of mixtures or alloys of these materials, as well as other transparent conductive metal oxides with an electrical conductivity greater than 1000 S / cm.

[0068] In one embodiment, the transparent bottom and top electrically conductive layers have a thickness from 50 to 300 nm.

[0069] In one embodiment, the patterned transparent matrix with empty wells, being the well the space for receiving the pillars or columns, is made of silicon dioxide (SiOz), aluminium oxide (AI2O3), titanium oxides (TiO, TiCh, TizCh), copper oxides (CuO, CuC>2, CU2O), zirconium oxide (ZrCh), bismuth oxides (BiO, Bi2C>3, Bi20s), hafnium oxide (HfCh), vanadium oxide (VO, VO2), tantalum oxide (Ta2O3), iron oxides (Fe2O3, FesC ), chromium oxide (( 203), zinc oxide (ZnO), or any combination of mixtures or alloys of these metal oxides, or transparent electrical insulating metal oxides.

[0070] In one embodiment, the patterned transparent matrix with empty wells is an electrically and thermally insulator material, that can be in the form of a glass and / or polymeric film.

[0071] In one embodiment, the patterned transparent matrix has a thickness ranging from 50 nm to 500 .m, but greater thickness may also be considered. These ranges of thickness correspond to the depth of the wells.

[0072] In one embodiment, the patterned transparent matrix has cylindrical or rectangular wells with a diameter or size ranging from 50 nm to 500 .m. Preferably, the columns or pillars of thermoelectric semiconductor material may be cylindrical or rectangular.

[0073] In one embodiment, the patterned transparent matrix has wells with a pitch ranging from 50 nm to 500 .m.

[0074] In one embodiment, the thermoelectric semiconductor material deposited in the wells, forming the columns or pillars, is a semiconductor metal oxide, preferably titanium dioxide (TiC>2), zinc oxide (ZnO), or any combination of mixtures or alloys of these oxides, or any other transparent n-type or p-type metal oxide with good thermoelectric properties, such as based on copper oxides, or transparent doped or undoped carbon materials, such as carbon nanowires, carbon nanofibers or carbon nanotubes.

[0075] In one embodiment, the thermoelectric semiconductor material deposited in the wells is n-type or p-type doped with an element, cation or anion, from the following list: niobium, aluminium, gallium, molybdenum, iron, antimony, bismuth, vanadium, tantalum, nitrogen, phosphor, arsenic, indium, or any combinations and mixtures of the above.

[0076] In one embodiment, the thermoelectric material is deposited by physical vapour deposition, chemical vapour deposition, atomic layer deposition, wet chemistry, including solgel, electrodeposition, molecular beam epitaxy, pulsed laser sintering, pulsed laser deposition, arc plating, amongst other common deposition techniques.

[0077] In an embodiment, the microfabrication process required to obtain the thermoelectric transparent micro-arrays consists of a series of steps: starting with a glass substrate (Fig.la); deposition of the bottom electrode (Fig.lb); deposition of an insulating matrix layer (Fig.lc); coating with a photoresist layer (Fig.ld); definition of the micro-pillar arrays (Fig.le); etching of the insulating matrix layer (Fig.lf); deposition of the thermoelectric material pillars (Fig.lg); removal of unwanted material (Fig.lh); and, finally, deposition of the top electrode (Fig.li).

[0078] In an embodiment, Figure 1 shows: 1 the substrate, 2 the bottom electrically conductive layer, 3 the electrically and thermally insulating layer, 4 the photoresist material, 5 thermoelectric semiconductor material and 6 is the top electrically conductive layer.

[0079] Figure 2 represents the heterostructured material and experimental setup to measure the Seebeck coefficient and output electric current.

[0080] Figure 2 presents the heterostructured material viewed from multiple perspectives. Figure 2a) shows the cross-section of the heterostructured material. The multiple layers constituting the heterostructured material are deposited on a glass substrate covered with a transparent conductive layer. During the entire fabrication process, the edges of the samples are protected to allow access to the bottom electrode, obtaining, as a result, a design similar to the one represented in Figure 2b). In Figure 2b), the heterostructured material can be seen from two perspectives, where the location of the bottom and top electrodes is viewed. In Figure 2c), the device is separated into its constituent layers.

[0081] Considering the arrangement of the micro-pillars or micro-arrays of columns, the temperature difference must be applied across all layers. Figure 2d) illustrates the setup built to perform thermoelectric measurements, where the heterostructured material is "sandwiched" by two Peltier modules to generate a temperature difference. As for each Peltier module, one of the sides heats 8a, and the other cools 8b. A temperature sink is attached to the side of the Peltier that is not used, to give greater emphasis to the side that really matters to produce the temperature difference. 7 represents the heat sinks. Figures 2e)and 2f) illustrate the disassembled device without the heterostructured material and show the two Peltier stages, for heating 8a and cooling 8b, with thermocouples for temperature measurement. Figure 2g) presents another view of the experimental setup with the leads for electric current and voltage measurement.

[0082] The generated output potential difference and electric current are measured by, for example, an Agilent 34401A high precision multimeter. Thermocouples are used to accurately measure the temperature on the top and bottom electrodes. The Peltier modules are controlled by a power supply, taking special care never to exceed the maximum voltage and current values of these modules. With this setup it is possible to measure the electric potential, and the output electric current (sum of all currents flowing from each pillar / column) between the top and bottom electrodes when a thermal difference is applied in between them.

[0083] As illustrated in Figure 2, the Peltier modules create a temperature difference across the heterostructured material, which is monitored by the thermocouples. This difference is responsible for generating the potential difference between top and bottom electrodes, producing an electrical current through the thermoelectric pillars / columns, being these two quantities measured through the electrodes implemented in the setup.

[0084] In one embodiment, the heterostructured material can be applied to windowpanes. Depending on the atmospheric conditions, these structures can be functionalized with the heterostructured material to harvest heat from either side of the glass structure. For example, during summer, the outer surface of the windowpane should be much hotter than the inner surface, and in the winter / cold days, the opposite is expected.

[0085] In an embodiment, the fabrication process required to obtain the thermoelectric transparent micro-arrays consists of a series of steps, starting, in this example, with a sodalime glass (SLG) substrate or other types of commercial glass used in windowpanes, used for transparency (Fig. la). A fluorine-doped tin oxide (FTO) thin-film is then deposited on the glass substrate, to work as the bottom electrode (anode, for n-type semiconductor thermoelectric material), due to its transparency and good conductivity, both thermal and electrical (Fig.lb). Alternatively, other transparent and conductive metal oxide materials (TCO), such as aluminium-doped zinc oxide (ZnO:AI or AZO), gallium-doped zinc oxide (ZnO:Ga or GZO) and indium-tin oxide (ITO) films can also be used to coat the glass. These TCO films can bedeposited by physical vapour deposition, including thermal evaporation, sputtering, preferably, or by chemical vapour deposition, including atomic layer deposition, or by wet chemistry, such as sol-gel, amongst other deposition techniques. The FTO-coated glass can also be used as the base material.

[0086] The next step is the deposition of an electrically and thermally insulating matrix layer (Fig.lc), preferably made of silicon oxide (SiOz) or aluminium oxide (AI2O3). This electrical and thermal insulating film can be deposited by chemical vapour deposition (CVD), preferably, or by atomic layer deposition (ALD), wet chemical deposition (for example sol-gel) or physical vapour deposition (PVD, sputtering, thermal evaporation), amongst other deposition techniques. This layer will insulate the thermoelectric pillars or columns created in the next steps.

[0087] The electrically and thermally insulating matrix layer is then coated with a photoresist, or another type of masking material, by lithography or another templating method (Fig.ld). Through lithography: laser direct - writing, the micro-pillar array (or micro column array) is defined to obtain the desired pattern (Fig.le).

[0088] In an embodiment, the desired pattern comprises columns with spaces between the columns, forming arrays of wells with a diameter ranging from 50 nm to 500 p.m, a pitch from 50 nm to 500 pm and a depth from 50 nm to 500 pm.

[0089] After imprinting the pattern onto the photoresist layer, reactive ion etching is used to etch the insulating matrix layer that is not covered by the photoresist (Fig.lf). This will result in an insulating matrix with cylindrical wells where the thermoelectric material will be deposited.

[0090] In the next step, the thermoelectric material, TiO2:Nb as an example of n-type semiconductor, is deposited by sputtering, preferably via PVD (sputtering, evaporation), CVD or ALD, or wet chemistry, such as sol-gel, or by electrodeposition, amongst other deposition techniques (Fig.lg). Once the TiO2:Nb pillars are manufactured, the excess material which is on top of the photoresist is removed. By using the resist lift-off technique, excess TiO2:Nb is eliminated and, consequently, the remaining photoresist (Fig.lh).

[0091] Finally, the entire device is covered with the top contact layer, preferably the top electrically conductive layer, that works as the top electrode (cathode, for n-typethermoelectric material) (Fig.li). This layer is made of FTO, or other transparent and conductive metal oxide materials (TCO), such as aluminium-doped zinc oxide (ZnO:AI or AZO), gallium-doped zinc oxide (ZnO:Ga or GZO) and indium-tin oxide (ITO) films can also be used to coat the glass.

[0092] During the entire fabrication process, the edges of the samples are protected to allow access to the bottom electrode, obtaining as a result a design similar to the one represented in Figure 2b.

[0093] In an embodiment, the device is a thermoelectric and transparent micro array heterostructure deposited onto a transparent substrate. Preferably, transparent substrate is glass or polymer.

[0094] In an embodiment, the top and bottom electrodes are made from a transparent electrically conductive metal oxide layer. Preferably, fluorine-doped tin oxide. In an embodiment, the transparent electrically conductive layer consists in doped tin oxide, doped titanium oxides, or doped zinc oxides.

[0095] In an embodiment, the transparent electrically conductive layer consists in fluorine- doped tin oxide or indium-tin oxide.

[0096] In an embodiment, the transparent electrically conductive layer consists in aluminium oxide doped with gallium and / or bismuth and / or indium and / or aluminium.

[0097] In an embodiment, the transparent electrically conductive layer has a thickness ranging from 50 nm to 500 .m.

[0098] In an embodiment, the transparent electrically conductive layer is deposited by physical or chemical vapour deposition.

[0099] In an embodiment, a transparent electrically and thermally insulating layer is deposited onto the bottom electrode.

[0100] In an embodiment, the transparent electrically and thermally insulating layer has a thickness ranging from 50 nm to 500 .m.

[0101] In an embodiment, the transparent electrically and thermally insulating layer is made from a metal oxide.

[0102] In an embodiment, where the material of the transparent electrically and thermally insulating is glass, a polymer or combinations thereof.

[0103] In an embodiment, the transparent electrically and thermally insulating layer film is chosen from silicon oxide, bismuth oxide, titanium oxide, vanadium oxide, chromium oxide, tantalum oxide or zinc oxide, hafnium oxide, aluminium oxide, copper oxide, zirconium oxide or any combination of mixtures or alloys of these metal oxides, or transparent metal oxides.

[0104] In an embodiment, the transparent electrically and thermally insulating layer is deposited by physical or chemical vapour deposition, or from a wet chemical synthesis.

[0105] In an embodiment, the transparent electrically and thermally insulating layer is etched with cylindrical wells along its thickness, with diameters in the range of from 50 nm to 500 .m. In an embodiment, the transparent electrically and thermally insulating layer is etched with cylindrical wells along its thickness, with a pitch in the range of from 50 nm to 500 .m. In an embodiment, the transparent electrically and thermally insulating layer is etched with cylindrical wells along its thickness, with a depth in the range of from 50 nm to 500 .m.

[0106] In an embodiment, the transparent electrically and thermally insulating layer is a polymer and is etched with cylindrical wells along its thickness, with diameters in the range of from 50 nm to 500 .m.

[0107] In an embodiment, the transparent electrically and thermally insulating layer is etched with cylindrical wells along the polymer thickness, with a pitch in the range of from 50 nm to 500 .m.

[0108] In an embodiment, the transparent electrically and thermally insulating layer is etched with cylindrical wells along its thickness, with a depth in the range of from 100 nm to 10 mm.

[0109] In an embodiment, the transparent electrically and thermally insulating layer is a polymer and is etched with cylindrical wells along its thickness, with diameters in the range of from 50 nm to 500 .m.

[0110] In an embodiment, the transparent electrically and thermally insulating layer is etched with cylindrical wells along the glass thickness, with a pitch in the range of from 50 nm to 500 .m.

[0111] In an embodiment, the transparent electrically and thermally insulating layer is etched with cylindrical wells along its thickness, with a depth in the range of from 2 mm to 4 mm.

[0112] In an embodiment, a transparent thermoelectric material is deposited into the cylindrical wells of the transparent electrical and thermal insulating layer matrix.

[0113] In an embodiment, the transparent thermoelectric material that fills the matrix cylindrical wells is a semiconductor n-type metal oxide.

[0114] In an embodiment, the transparent thermoelectric material that fills the matrix cylindrical wells is a semiconductor p-type metal oxide.

[0115] In an embodiment, the transparent thermoelectric material that fills the matrix cylindrical wells is a combination of n-typt and p-type metal oxide semiconductors.

[0116] In an embodiment, the transparent thermoelectric material is a metal oxide doped with a cation.

[0117] In an embodiment, the transparent thermoelectric material is a metal oxide doped with an anion.

[0118] In an embodiment, the transparent thermoelectric material is a doped or undoped carbon material, such as carbon nanowires, carbon nanofibers or carbon nanotubes.

[0119] In an embodiment, the transparent thermoelectric material is undoped titanium oxide or titanium oxide doped with an element from the following list: niobium, aluminum, gallium, molybdenum, iron, antimony, bismuth, vanadium, tantalum, nitrogen, phosphor, arsenic, indium, or any combinations and mixtures of the above.

[0120] In an embodiment, the transparent thermoelectric material is undoped zinc oxide or zinc oxide doped with an element from the following list: niobium, aluminum, gallium, molybdenum, iron, antimony, bismuth, vanadium, tantalum, nitrogen, phosphor, arsenic, indium, or any combinations and mixtures of the above.

[0121] In an embodiment, the transparent thermoelectric material is undoped copper oxide or copper oxide doped with an element from the following list: niobium, aluminum, gallium, molybdenum, iron, antimony, bismuth, vanadium, tantalum, nitrogen, phosphor, arsenic, indium, or any combinations and mixtures of the above.

[0122] In an embodiment, the transparent electrical and thermal insulating layer is deposited from the following list of techniques: physical vapour deposition, chemical vapour deposition, atomic layer deposition, wet chemistry, including sol-gel, electrodeposition, molecular beam epitaxy, pulsed laser sintering, pulsed laser deposition, arc plating, amongst other common deposition techniques.

[0123] In an embodiment, a top electrically conductive layer as an electrode is deposited onto the previous matrix composed of thermoelectric pillar / columns arrays.

[0124] The term "comprising" whenever used in this document, is intended to indicate the presence of stated features, integers, steps, components but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0125] The disclosure should not be seen in any way restricted to the embodiments described, and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above-described embodiments are combinable.

[0126] The following claims further set out particular embodiments of the disclosure.References:[1] A. I. Boukai, Y. Bunimovich, J. Tahir-Kheli, J.K. Yu, W.A. Goddard, J. R. Heath, Silicon nanowires as efficient thermoelectric materials, Nature. 451 (2008) 168-171. https: / / doi.org / 10.1038 / nature06458.[2] A. I. Hochbaum, R. Chen, R.D. Delgado, W. Liang, E.C. Garnett, M. Najarian, A. Majumdar, P. Yang, Enhanced thermoelectric performance of rough silicon nanowires, Nature. 451 (2008) 163-167. https: / / doi.org / 10.1038 / nature06381.[3] C. Zhou, C. Dun, Q. Wang, K. Wang, Z. Shi, D.L. Carroll, G. Liu, G. Qiao, Nanowires as Building Blocks to Fabricate Flexible Thermoelectric Fabric: The Case of Copper Telluride Nanowires, ACS Appl Mater Interfaces. 7 (2015) 21015-21020. https: / / doi.org / 10.1021 / acsami.5b07144.[4] SJ. Kim, J.H. We, BJ. Cho, A wearable thermoelectric generator fabricated on a glass fabric, Energy Environ Sci. 7 (2014) 1959-1965. https: / / doi.org / 10.1039 / c4ee00242c.[5] M. Tan, Y. Deng, Y. Wang, Unique hierarchical structure and high thermoelectric properties of antimony telluride pillar arrays, Journal of Nanoparticle Research. 14 (2012). https: / / doi.org / 10.1007 / sll051-012-1204-y.[6] M. Tan, Y. Deng, Y. Hao, Synergistic effect between ordered Bi2Te2.7Se0.3 pillar array and layered Ag electrode for remarkably enhancing thermoelectric device performance, Energy. 77 (2014) 591-596. https: / / doi.Org / 10.1016 / j.energy.2014.09.041.[7] C. Wang, K. Sun, J. Fu, R. Chen, M. Li, Z. Zang, X. Liu, B. Li, H. Gong, J. Ouyang, Enhancement of Conductivity and Thermoelectric Property of PEDOT:PSS via Acid Doping and Single Post-Treatment for Flexible Power Generator, Adv Sustain Syst. 2 (2018). https: / / doi.org / 10.1002 / adsu.201800085.[8] N.P. Klochko, K.S. Klepikova, V.R. Kopach, 1.1. Tyukhov, . v. Starikov, D.S. Sofronov, I. v. Khrypunova, D.O. Zhadan, S.l. Petrushenko, S. v. Dukarov, V.M. Lyubov, M. v. Kirichenko, A.L. Khrypunova, Development of semi-transparent ZnO / FTO solar thermoelectric nanogenerator for energy efficient glazing, Solar Energy. 184 (2019) 230-239. https: / / doi.Org / 10.1016 / j.solener.2019.04.002.[9] B.M.M. Faustino, D. Gomes, J. Faria, T. Juntunen, G. Gaspar, C. Bianchi, A. Almeida, A. Marques, I. Tittonen, I. Ferreira, Cui p-type thin films for highly transparent thermoelectric p-n modules, Sci Rep. 8 (2018). https: / / doi.org / 10.1038 / s41598-018-25106-3.

[0010] G.-M. Chen, L.-Y. Ma, l.-Y. Huang, T.-E. Wu, Development of a novel transparent micro-thermoelectric generator for solar energy conversion, in: 2011 6th IEEE International Conference on Nano / Micro Engineered and Molecular Systems, IEEE, 2011: pp. 976-979. https: / / doi.org / 10.1109 / NEMS.2011.6017518.

[0011] Y. Fang, H. Cheng, H. He, S. Wang, J. Li, S. Yue, L. Zhang, Z. Du, J. Ouyang, Stretchable and Transparent lonogels with High Thermoelectric Properties, Adv Funct Mater. (2020). https: / / doi.org / 10.1002 / adfm.202004699.

[0012] M. Ferreira, J. Loureiro, A. Nogueira, A. Rodrigues, R. Martins, I. Ferreira, SnO2 thin Film Oxides Produced by rf Sputtering for Transparent Thermoelectric Devices, in: Mater Today Proc, Elsevier Ltd, 2015: pp. 647-653. https: / / doi.Org / 10.1016 / j.matpr.2015.05.090.

[0013] J. Coroa, B.M. Morais Faustino, A. Marques, C. Bianchi, T. Koskinen, T. Juntunen, I. Tittonen, I. Ferreira, Highly transparent copper iodide thin film thermoelectric generator on a flexible substrate, RSC Adv. 9 (2019) 35384-35391. https: / / doi.org / 10.1039 / c9ra07309d.

[0014] T. Ishibe, A. Tomeda, Y. Komatsubara, R. Kitaura, M. Uenuma, Y. Uraoka, Y. Yamashita, Y. Nakamura, Carrier and phonon transport control by domain engineering for high-performance transparent thin film thermoelectric generator, Appl Phys Lett. 118 (2021). https: / / doi.Org / 10.1063 / 5.0048577.

[0015] J.M. Ribeiro, F.C. Correia, FJ. Rodrigues, J. S. Reparaz, A.R. Goni, CJ. Tavares, Transparent niobium-doped titanium dioxide thin films with high Seebeck coefficient for thermoelectric applications, Surface & Coatings Technology 425 (2021) 127724. https: / / doi.Org / 10.1016 / i.surfcost.2021.127724

[0016] THERMOELECTRIC TRANSPARENT THIN FILM AND METHOD THEREOF, Carlos Jose Tavares, Joana Ribeiro, Filipe Correia Costa - Portuguese Patent PT 110639.

Claims

C L A I M S1. A thermoelectric device comprising: a substrate; a bottom electrically conductive layer deposited on the substrate; a top electrically conductive layer; a plurality of columns of a thermoelectric semiconductor material; an electrically and thermally insulating layer and surrounding each of the plurality of columns; wherein the electrically and thermally insulating layer is transparent to visible light; wherein each cylindrical column of the plurality of cylindrical columns has a diameter from 50 nm to 500 .m; wherein the plurality of columns of a thermoelectric semiconductor material generates an electric potential difference when the bottom electrically conductive layer and the top electrically conductive layer are subjected to a thermal difference.

2. Device according to the previous claim wherein the material of the transparent electrically and thermally insulating is glass, a polymer or combinations thereof; preferably a film.

3. Device according to any of the previous claims wherein the electrically and thermally insulating layer has a thickness lower than 30 .m.

4. Device according to any of the previous claims wherein the electrically and thermally insulating polymer layer has a thickness lower than 10mm; preferably lower than 5 mm; more preferably lower than 1 mm.

5. Device according to any of the previous claims wherein the electrically and thermally insulating glass layer has a thickness lower than 10 mm; preferably lower than 5 mm; more preferably lower than 4 mm.

6. Device according to any of the previous claims wherein the electrically and thermally insulating layer has a thickness lower than 1 mm, more preferably lower than 15 .m.

7. Device according to any of the previous claims wherein the electrically and thermally insulating layer has a thickness lower than 5 .m, preferably more preferably lower than 3 .m.

8. Device according to any of the previous claims wherein each column is cylindrical or cuboid, preferably cylindrical.

9. Device according to the previous claim wherein each cylindrical column of the plurality of cylindrical columns has a diameter from 50 nm to 500 .m, preferably from 50 pm to 200 pm.

10. Device according to any of the previous claims wherein each column of the plurality of columns has a pitch from 50 nm to 500 pm, preferably from 50 pm to 200 pm.

11. Device according to any of the previous claims wherein each column of the plurality of columns has a height from 50 nm to 500 pm, preferably from 0.5 pm to 1 pm.

12. Device according to any of the previous claims wherein the bottom electrically conductive layer and the top electrically conductive are transparent to light, preferably visible light.

13. Device according to any of the previous claims, where the top and bottom conductive layers are made of a transparent electrical conductive metal oxide layer with a conductivity larger than 1000 S / cm.

14. Device according to any of the previous claims, wherein the top and bottom conductive layer are made of a material selected from a list comprising: fluorine-doped tin oxide, indium-tin oxide, aluminium-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, or mixtures thereof.

15. Device according to any of the previous claims wherein each of the top and bottom electrically conductive layers has a thickness from 50 to 500 nm, preferably from 100 nm to 300 nm.

16. Device according to any of the previous claims, wherein the electrically and thermally insulating matrix layer is made from a metal oxide.

17. Device according to any of the previous claims, wherein the electrically and thermally insulating layer is made from a material selected from a list of: silicon oxide, bismuth oxide, titanium oxide, vanadium oxide, chromium oxide, tantalum oxide or zinc oxide, hafnium oxide, aluminium oxide, copper oxide, zirconium oxide, aluminium oxide or mixtures thereof.

18. Device according to any of the previous claims, wherein the electrically and thermally insulating layer has a thickness from 50 nm to 500 .m, preferably from 0.5 pm to 1 pm.

19. Device according to any of the previous claims, wherein the thermoelectric semiconductor material is transparent to light, preferably to visible light.

20. Device according to any of the previous claims, wherein the thermoelectric semiconductor material is a metal oxide doped with a cation or an anion.

21. Device according to any of the previous claims, wherein the thermoelectric semiconductor material is a doped or undoped carbon material selected from a list of: carbon nanowires, carbon nanofibers or carbon nanotubes.

22. Device according to any of the previous claims, wherein the thermoelectric semiconductor material is undoped titanium oxide or titanium oxide doped with an element selected from the following list: niobium, aluminum, gallium, molybdenum, iron, antimony, bismuth, vanadium, tantalum, nitrogen, phosphor, arsenic, indium, sulphur, carbon, or mixtures thereof.

23. Device according to any of the previous claims, wherein the thermoelectric semiconductor material is undoped zinc oxide or zinc oxide doped with an element selected from the following list: niobium, aluminum, gallium, molybdenum, iron, antimony, bismuth, vanadium, tantalum, nitrogen, phosphor, arsenic, indium, sulphur, carbon, or mixtures thereof.

24. Device according to any of the previous claims, wherein the thermoelectric semiconductor material is undoped copper oxide or copper oxide doped with an element selected from the following list: niobium, aluminum, gallium, molybdenum, iron, antimony, bismuth, vanadium, tantalum, nitrogen, phosphor, arsenic, indium, sulphur, carbon, or mixtures thereof.

25. Device according to any of the previous claims, wherein the substrate is glass or polymer.

26. Device according to any of the previous claims wherein the plurality of columns is a micro array.

27. Device according to any of the previous claims wherein the bottom electrically conductive layer is an anode or cathode and the top electrically conductive layer is a cathode or an anode.

28. Process to obtain the thermoelectric device according to any of the previous claims comprising the following steps: depositing a bottom electrically conductive layer on a substrate; depositing an electrically and thermally insulating layer on a surface of the bottom electrically conductive layer; coating the electrically and thermally insulating matrix layer with a photoresist layer; patterning a matrix of wells onto the photoresist layer through optical lithography or laser direct-writing until it reaches the electrically and thermally insulating layer; etching with reactive ions the electrically and thermally insulating layer not coated with the photoresist layer, until it reaches the bottom electrically conductive layer; depositing a thermoelectric semiconductor material;removing the thermoelectric semiconductor material that is surplus, keeping the thermoelectric semiconductor material that is filling the wells and forming a plurality of columns; removing the photoresist layer; depositing a top electrically conductive layer.

29. Process according to claim 27 wherein the bottom electrically conductive layer and top electrically conductive layer are deposited by physical vapour deposition, chemical vapour deposition, atomic layer deposition, wet chemistry, including sol-gel, electrodeposition, molecular beam epitaxy, pulsed laser sintering, pulsed laser deposition, or arc plating.

30. Process according to any of the previous claims 27 to 28 wherein the electrically and thermally insulating matrix layer is deposited by physical or chemical vapour deposition, spin coating or wet chemistry method.

31. Process according to any of the previous claims 27 to 29, wherein the electrically and thermally insulating matrix layer is deposited by physical vapour deposition, chemical vapour deposition, atomic layer deposition, spin coating, wet chemistry, including sol-gel, electrodeposition, molecular beam epitaxy, pulsed laser sintering, pulsed laser deposition, or arc plating.

32. Process according to any of the previous claims 27 to 30 wherein the deposition of the thermoelectric material is made by physical vapour deposition, chemical vapour deposition, atomic layer deposition, electrodeposition, wet chemistry, such as sol-gel, molecular beam epitaxy, pulsed laser sintering, pulsed laser deposition, or arc plating.

33. Use of the device according to any of the previous claims 1 to 26 for harvest thermal energy from a window and convert into energy.

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