ULTRAVIOLET EMITTING OPTICAL DEVICE AND OPERATING METHOD THEREOF

Provided are an ultraviolet emitting optical device and an operating method thereof. The ultraviolet emitting optical device includes a substrate, a first encapsulation layer, an active layer and a second encapsulation layer sequentially stacked on the substrate, a first electrode layer between the first encapsulation layer and the active layer, a second electrode layer between the active layer and the second encapsulation layer, and color centers provided in the active layer, wherein the active layer includes hexagonal boron nitride (hBN), wherein the color centers are configured to emit light in an ultraviolet wavelength range.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application claims priority under 35 U.S.C. § 119 of Korean Patent Application No. 10-2021-0083673, filed on Jun. 28, 2021, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The present disclosure herein relates to an ultraviolet emitting optical device, and more particularly, to an ultraviolet emitting optical device using hexagonal boron nitride (hBN) and an operating method thereof.

Various optical elements using photonics technology are generally fabricated based on a silicon-on-insulator (SOI) wafer. These optical elements include a light source, a photodetector, an optical modulator, a photodiode, a polarization rotator, a polarization splitter, a wavelength division multiplexer, a wavelength division demultiplexer, an optical power splitter, and the like.

On the other hand, currently used ultraviolet light sources include mercury lamps, UV LEDs, deuterium lamps, and the like. Among them, the mercury lamp emits light in the deep UV region, but when the lamp is heated after several tens of seconds, the light in the deep UV region is weakened and light in the visible region appears. In addition, because of the use of mercury, its use in lighting is banned in many countries. In addition, UV LEDs use semiconductor materials with wide bandgap energy (e.g., AlGaN, AlGaInN, etc.), and these semiconductor materials are difficult to synthesize and require epitaxial growth to generate heterojunction structures or multi-quantum well structures. In addition, since the deuterium lamp operates at a temperature of about 300 degrees, requires preheating, and emits light through arc discharge, it requires a high voltage of about 200 V or more. Accordingly, research on a new UV light source is being actively conducted.

SUMMARY

The present disclosure provides an ultraviolet emitting optical device using hexagonal boron nitride (hBN) and an operating method thereof.

An embodiment of the inventive concept provides an ultraviolet emitting optical device including: a substrate; a first encapsulation layer, an active layer and a second encapsulation layer sequentially stacked on the substrate; a first electrode layer between the first encapsulation layer and the active layer; a second electrode layer between the active layer and the second encapsulation layer; and color centers provided in the active layer, wherein the active layer includes hexagonal boron nitride (hBN), wherein the color centers are configured to emit light in an ultraviolet wavelength range.

In an embodiment, the color centers may be formed when a crystal structure of a partial region of the active layer is modified or some of atoms constituting the first and second electrode layers are implanted into a crystal structure of a partial region of the active layer.

In an embodiment, a partial region of the active layer overlapping the first electrode layer and the second electrode layer in a vertical direction may be defined as a crossing region, wherein the color centers may be provided at positions overlapping an edge of the second electrode layer in the vertical direction in the crossing region.

In an embodiment, a band gap energy of each of the color centers may be 3.3 eV to 6.5 eV.

In an embodiment, the first electrode layer and the second electrode layer may include at least one of graphene, elements such as silicon (Si), magnesium (Mg), carbon (C), and gallium (Ga), metal elements, and transition metal dichalcogenides (TMDC).

In an embodiment, the first encapsulation layer and the second encapsulation layer may include hexagonal boron nitride.

In an embodiment, each of junctions of the first and second electrode layers and the active layer may be a van der Waals heterostructure.

In an embodiment, the first electrode layer may extend in a first direction parallel to an upper surface of the substrate, wherein the second electrode layer may be parallel to an upper surface of the substrate and extend in a second direction intersecting the first direction.

In an embodiment, at least a portion of a side surface of the second electrode layer may have a geometric pattern such as a wave pattern or a sawtooth pattern or a curved shape.

In an embodiment, the first electrode layer may include a first portion extending in a first direction parallel to the upper surface of the substrate and a second portion connected to an end of the first portion, wherein the second electrode layer may include a first portion extending in the first direction and a second portion overlapping the first electrode layer in a vertical direction, wherein the first portion of the first electrode layer may not overlap the first portion of the second electrode layer in the vertical direction.

In an embodiment, the active layer may include a first active layer on the first electrode layer and a second active layer between the first active layer and the second electrode layer, and may further include a third electrode layer between the first active layer and the second active layer.

In an embodiment, the active layer may include first to third active layers sequentially stacked on the first encapsulation layer between the first electrode layer and the second electrode layer, wherein a crystal structure of each of the first to third active layers may extend in different directions.

In an embodiment, the first electrode layer may be provided in plurality, and each of the plurality of first electrode layers may extend in a first direction parallel to an upper surface of the substrate, wherein the second electrode layer may be provided in plurality, and each of the plurality of second electrode layers may extend in a second direction parallel to the upper surface of the substrate and intersecting the first direction, wherein the plurality of first electrode layers may be spaced apart from each other in the second direction at regular intervals, wherein the plurality of second electrode layers may be spaced apart from each other in the first direction at regular intervals.

In an embodiment of the inventive concept, an operating method of an ultraviolet emitting optical device including a substrate, a first encapsulation layer, an active layer and a second encapsulation layer sequentially stacked on the substrate, a first electrode layer between the first encapsulation layer and the active layer, and a second electrode layer between the active layer and the second encapsulation layer includes: applying a first electric field between the first electrode layer and the second electrode layer to form color centers within the active layer; and applying a second electric field between the first electrode layer and the second electrode layer to excite the color centers, wherein the active layer includes hexagonal boron nitride (hBN), wherein the excited color centers emit light in an ultraviolet wavelength range.

In an embodiment, the method may further include controlling an intensity and direction of the second electric field, wherein an intensity of the emitted light may be controlled through controlling the intensity of the second electric field, wherein an emission wavelength may be controlled through controlling the direction of the second electric field.

In an embodiment, controlling the direction of the second electric field may change the direction of the second electric field applied between the first electrode layer and the second electrode layer, wherein changing the direction of the second electric field may change a state in which the first electrode layer is grounded and a voltage is applied to the second electrode layer to a state in which a voltage is applied to the first electrode layer and the second electrode layer is grounded, or vice versa.

In an embodiment, a wavelength change according to changing the direction of the second electric field may be 10 nm to 50 nm.

In an embodiment, a partial region of the active layer overlapping the first electrode layer and the second electrode layer in a vertical direction may be defined as a crossing region, wherein the color centers may be generated at positions overlapping an edge of the second electrode layer in the vertical direction in the crossing region.

In an embodiment, the color centers may be generated at predetermined positions according to a shape and positional relationship of the first electrode layer and the second electrode layer.

In an embodiment, the active layer may include a first active layer on the first electrode layer and a second active layer between the first active layer and the second electrode layer, wherein the ultraviolet emitting optical device may further include a third electrode layer between the first active layer and the second active layer, wherein applying the first electric field or applying the second electric field may be applying a voltage different from that of the third electrode layer to each of the first and second electrode layers.

DETAILED DESCRIPTION

In order to fully understand the configuration and effects of the inventive concept, preferred embodiments of the inventive concept will be described in detail with reference to the accompanying drawings.

The inventive concept is not limited to the embodiments disclosed below, but may be implemented in various forms, and various modifications and changes may be added. However, it is provided to completely disclose the technical idea of the inventive concept through the description of the present embodiments, and to fully inform a person of ordinary skill in the art to which the inventive concept belongs. In the accompanying drawings, for convenience of description, the ratio of each component may be exaggerated or reduced.

The terms used in this specification are for describing embodiments and are not intended to limit the inventive concept. In addition, terms used in the present specification may be interpreted as meanings commonly known to those of ordinary skill in the art, unless otherwise defined.

In this specification, the singular form also includes the plural form unless specifically stated in the phrase. As used in the specification, in relation to ‘comprises’ and/or ‘comprising’, the mentioned elements, steps, operations and/or elements do not exclude the presence or addition of one or more other elements, steps, operations and/or elements.

In this specification, terms such as first and second are used to describe various areas, directions, shapes, etc., but these areas, directions, and shapes should not be limited by these terms. These terms are only used to distinguish one area, direction, or shape from another area, direction, or shape. Accordingly, a portion referred to as a first portion in one embodiment may be referred to as a second portion in another embodiment. The embodiments described and illustrated herein also include complementary embodiments thereof. Like reference numerals refer to like elements throughout the specification.

Hereinafter, an ultraviolet emitting optical device and an operating method thereof according to embodiments of the inventive concept will be described in detail with reference to the drawings.

FIG.1Ais a perspective view illustrating an ultraviolet emitting optical device according to embodiments of the inventive concept.FIG.1Bis a cross-sectional view for explaining an ultraviolet emitting optical device according to embodiments of the inventive concept, and corresponds to a cross-sectional view taken along line I-I′ ofFIG.1A.

Referring toFIGS.1A and1B, the ultraviolet emitting optical device according to the inventive concept may include a substrate100, a first encapsulation layer110, an active layer130and a second encapsulation layer150stacked sequentially on the substrate100, a first electrode layer GL1between the first encapsulation layer110and the active layer130, and a second electrode layer GL2between the active layer130and the second encapsulation layer150.

The substrate100may be, for example, a semiconductor substrate including silicon or a silicon-on-insulator (SOI) substrate including silicon oxide. The substrate100may have an upper surface that is parallel to the first direction D1and the second direction D2intersecting the first direction D1and is perpendicular to the third direction D3. The first to third directions D1, D2, and D3may be, for example, directions orthogonal to each other.

The thickness of the active layer130in the third direction D3may be different from the thickness of each of the first encapsulation layer110and the second encapsulation layer150in the third direction D3. More specifically, the thickness in the third direction D3of the active layer130may be smaller than the thickness in the third direction D3of each of the first encapsulation layer110and the second encapsulation layer150.

The first encapsulation layer110, the active layer130, and the second encapsulation layer150may include, for example, the same material. For example, the first encapsulation layer110, the active layer130, and the second encapsulation layer150may include hexagonal boron nitride (hBN). Hexagonal boron nitride (hBN) is an isostructural two-dimensional material having a structure equivalent to that of graphene, and is a material that is stable at high temperatures and has an excellent encapsulation effect. As another example, the first encapsulation layer110and the second encapsulation layer150may include a material different from that of the active layer130. For example, the active layer130may include hexagonal boron nitride (hBN), and the first encapsulation layer110and the second encapsulation layer150may include a different oxide or nitride.

A thickness of each of the first electrode layer GL1and the second electrode layer GL2in the third direction D3may be smaller than a thickness of the active layer130in the third direction D3. The first electrode layer GL1and the second electrode layer GL2may have a substantially two-dimensional structure. Each of the junctions of the first and second electrode layers GL1and GL2and the active layer130may be a van der Waals heterostructure causing strong light-material interaction at the interface thereof.

The first electrode layer GL1may extend in a first direction D1parallel to the upper surface of the substrate100. The first electrode layer GL1may contact the lower surface of the active layer130. The first encapsulation layer110may cover a lower surface of the first electrode layer GL1.

The second electrode layer GL2may extend in a second direction D2that is parallel to the upper surface of the substrate100and intersects the first direction D1. However, this is merely exemplary, and the inventive concept is not limited thereto, and as described with reference toFIGS.7B,7C, and7D, the second electrode layer GL2may extend in the same direction as the first electrode layer GL1. The second electrode layer GL2may contact the upper surface of the active layer130. The second encapsulation layer150may cover an upper surface of the second electrode layer GL2.

A wiring configured to apply a voltage to each of the first electrode layer GL1and the second electrode layer GL2may be connected. Although it is shown inFIG.1Athat the first electrode layer GL1is grounded and the voltage V is applied to the second electrode layer GL2, this is just an example, and according to the operating method of the ultraviolet emitting optical device according to the inventive concept, conversely, the voltage V may be applied to the first electrode layer GL1and the second electrode layer GL2may be grounded.

The first electrode layer GL1and the second electrode layer GL2may extend beyond the sidewall of the active layer130. In other words, a length of the first electrode layer GL1in the first direction D1may be greater than a width of the active layer130in the first direction D1, and a length of the second electrode layer GL2in the second direction D2may be greater than a width of the active layer130in the second direction D2. However, this is merely exemplary, and the inventive concept is not limited thereto, and the first electrode layer GL1and the second electrode layer GL2may be locally provided on the upper surface of the active layer130. In other words, a length of the first electrode layer GL1in the first direction D1may be substantially the same as a width of the active layer130in the first direction D1, and a length of the second electrode layer GL2in the second direction D2may be substantially the same as a width of the active layer130in the second direction D2. When the first electrode layer GL1and the second electrode layer GL2are locally provided on the upper surface of the active layer130, wiring adjacent to the sidewall of the active layer130may be connected to each of the first electrode layer GL1and the second electrode layer GL2.

For example, the first electrode layer GL1and the second electrode layer GL2may include at least one of graphene, elements such as silicon (Si), magnesium (Mg), carbon (C), gallium (Ga), and the like, a metal element, and a transition metal dichalcogenide (TMDC).

FIGS.2A and2Bare flowcharts illustrating a method of operating an ultraviolet emitting optical device according to embodiments of the inventive concept. Hereinafter, a method of operating an ultraviolet emitting optical device according to the inventive concept will be described in detail.

Referring toFIG.2A, a method of operating an ultraviolet emitting optical device according to the inventive concept may include forming color centers in the active layer130by applying a first electric field between the first electrode layer GL1and the second electrode layer GL2(S100), and applying a second electric field between the first electrode layer GL1and the second electrode layer GL2to excite the color centers (S200). Excited color centers may emit light in the ultraviolet wavelength range.

In this case, the color center means a defect state generated in the active layer130by the first electric field between the first electrode layer GL1and the second electrode layer GL2. A defect state inside the active layer130may be due to the facts that the crystal structure of the active layer130is deformed and/or some of the atoms (e.g., carbon) constituting the first and second electrode layers GL1and GL2are injected into the crystal structure of the active layer130. Each of the defect states may have a band gap energy capable of emitting light in the ultraviolet wavelength range. The band gap energy of the defect states (i.e., the band gap energy of the color centers) may be, for example, about 3.3 eV to about 6.5 eV. More specifically, the band gap energy of the defect states may be about 3.37 eV, about 4.09 eV, or about 4.62 eV.

Referring toFIG.2B, a method of operating an ultraviolet emitting optical device according to the inventive concept may include forming color centers in the active layer130by applying a first electric field between the first electrode layer GL1and the second electrode layer GL2(S100), applying a second electric field between the first electrode layer GL1and the second electrode layer GL2to excite the color centers (S200), and controlling the intensity and direction of the second electric field (S300).

In the method of operating an ultraviolet emitting optical device according to the inventive concept, the intensity and emission wavelength of the emitted light may be controlled through the controlling of the intensity and direction of the second electric field (S300). More specifically, the intensity of the emitted light may be controlled by controlling the intensity of the second electric field, and the emission wavelength may be controlled by controlling the direction of the second electric field. The controlling of the direction of the second electric field means changing the direction of the second electric field applied between the first electrode layer GL1and the second electrode layer GL2. More specifically, changing the direction of the second electric field applied between the first electrode layer GL1and the second electrode layer GL2means changing a state in which the first electrode layer GL1is grounded and a voltage is applied to the second electrode layer GL2(a forward voltage applied state) into a state in which a voltage is applied to the first electrode layer GL1and the second electrode layer GL2is grounded (reverse voltage applied state) or vice versa.

FIGS.3A and3Bare simulation results illustrating an internal electric field state of an ultraviolet emitting optical device according to embodiments of the inventive concept.

More specifically,FIG.3Ashows an electric field state in a cross-section taken along line II-IT ofFIG.1A, andFIG.3Bshows an electric field state viewed from a vertical direction inFIG.1A. Referring toFIGS.3A and3B, x represents the distance in the first direction D1based on the center of the active layer130, y represents the distance in the second direction D2based on the center of the active layer130, and z represents a distance in the third direction D3with respect to the center of the active layer130. Units of x and y are μm, and units of z are nm. InFIGS.3A and3B, the spectrum on the right shows the magnitude of a normalized electric field.

Referring toFIGS.3A and3B, an electric field applied to the active layer130between the first electrode layer GL1and the second electrode layer GL2is illustrated. In particular, referring toFIG.3B, a strong electric field is applied to the crossing region CA where the first electrode layer GL1and the second electrode layer GL2cross (i.e., overlap each other). In addition, an electric field stronger than the center of the crossing region CA is applied to a position in the crossing region CA that overlaps the edge of the second electrode layer GL2in the vertical direction. Accordingly, color centers may be locally generated at a position in the crossing region CA that overlaps the edge of the second electrode layer GL2in the vertical direction. That is, according to the inventive concept, color centers may be generated at predetermined (or desired) locations.

FIGS.4A to4Hare graphs illustrating emission spectra of an ultraviolet emitting optical device according to embodiments of the inventive concept.

More specifically,FIGS.4A and4Bshow the magnitude of electro-luminescence (EL) with respect to a wavelength when a forward voltage is applied. In this case, referring toFIG.1A, the forward voltage application means that the first electrode layer GL1is grounded and the voltage V is applied to the second electrode layer GL2. The emission spectra are measured when the voltage V applied to the second electrode layer GL2is 19 V, 21 V, and 23 V, respectively.

FIGS.4C and4Dshow the magnitude of the electro-luminescence (EL) with respect to the wavelength when a reverse voltage is applied. At this time, referring toFIG.1A, the reverse voltage application means that the voltage V is applied to the first electrode layer GL1and the second electrode layer GL2is grounded as opposed to when the forward voltage is applied. The emission spectra are measured when the voltage V applied to the first electrode layer GL1is 16 V, 18 V, and 20 V, respectively.

FIGS.4E,4F, and4Gshow the magnitude of normalized electro-luminescence (EL) with respect to wavelength when a forward voltage is applied and when a reverse voltage is applied.FIG.4Eshows the normalized electro-luminescence (EL) size for a wavelength range of about 200 nm to about 450 nm, andFIGS.4F and4Gshow the normalized electro-luminescence (EL) magnitudes for a portion (FIG.4fis about 200 nm to about 275 nm, andFIG.4gis about 275 nm to about 450 nm) of the wavelength range ofFIG.4e, respectively.

Referring toFIGS.4A to4G, when a forward voltage is applied, the emission spectrum includes emission peaks of about 215 nm, about 225 nm, about 303 nm, about 317 nm, and about 333 nm, and when a reverse voltage is applied, the emission spectrum includes emission peaks of about 215 nm, about 245 nm, about 303 nm, about 317 nm, and about 375 nm. The emission peaks are located within the ultraviolet wavelength range. At this time, the 215 nm peak and the peaks within the wavelength range of about 220 nm to about 250 nm correspond to the band gap energy of hexagonal boron nitride (hBN), and the 303 nm peak, the 317 nm peak, and the 333 nm peak correspond to the band gap energies of the color centers.

When changing from a forward voltage application to a reverse voltage application (i.e., changing the direction of the electric field), the 225 nm peak changes to a 245 nm peak (Δ=20 nm). However, this is an example, and when changing from a forward voltage application to a reverse voltage application, the change in wavelength may be about 10 nm to about 50 nm.

Referring toFIGS.4B and4Dby comparison, when changing from a forward voltage application to a reverse voltage application, in the wavelength range of about 300 nm to about 350 nm, the magnitude of electro-luminescence (EL) (i.e., luminous efficiency (or quantum efficiency)) increases by about 10 times or more.

FIG.4Hshows the emission spectrum and the current density of the tunneling current according to the magnitude of the applied electric field. Graphs of emission spectra and current density of tunneling current were measured when the magnitude of the applied electric field was about 1.2 V/nm, about 1.3 V/nm, about 1.36 V/nm, and about 1.46 V/nm, respectively At this time, the measurement is performed while gradually increasing the magnitude of the electric field. At this time, the unit of the magnitude of the electric field is V/nm, and the unit of the current density is A/μm2.

Referring toFIG.4H, emission is observed in a wavelength range of about 400 nm to about 450 nm when the magnitude of the electric field is about 1.3 V/nm. Although not shown in the drawing, the tunneling current starts to increase when the electric field is about 0.7 V/nm.

When the magnitude of the electric field is about 1.36 V/nm, emission peaks are observed in the emission spectrum. The emission peaks mean that color centers are generated in the active layer130(refer toFIG.1A).

When the magnitude of the electric field is about 1.46 V/nm, light emission is observed in a wavelength range of about 300 nm to 350 nm, and although not shown in the drawing, when an electric field greater than 1.46 V/nm is applied, emission is observed in the wavelength range of about 215 nm and about 225 nm to about 245 nm. In the above, the graphs described with reference toFIGS.4A to4Gare measured when the first electrode layer GL1and the second electrode layer GL2include graphene. However, this is only an example, and the first electrode layer GL1and the second electrode layer GL2may include an element such as silicon (Si), magnesium (Mg), carbon (C), gallium (Ga), and the like, a metal element, or a transition metal dichalcogenide (TMDC). For example, when the first electrode layer GL1and the second electrode layer GL2include a metal element or a transition metal dichalcogenide (TMDC), the emission peaks may be located within a wavelength range of about 210 nm to about 250 nm. As another example, when the first electrode layer GL1and the second electrode layer GL2include carbon (C), they may have an emission peak of about 303 nm. As another example, when the first electrode layer GL1and the second electrode layer GL2include gallium (Ga), they may have an emission peak of about 280 nm.

Since the ultraviolet emitting optical device according to the inventive concept emits ultraviolet light in the UVC region (wavelength range of about 200 nm to about 280 nm), it may be used in an ultraviolet sterilizer.

FIGS.5A and5Bare graphs illustrating emission spectra of an ultraviolet emitting optical device according to other embodiments of the inventive concept.

More specifically,FIG.5Ashow the magnitude of electro-luminescence (EL) with respect to a wavelength when a forward voltage is applied. The emission spectra are measured when the voltage V applied to the second electrode layer GL2is 28 V, 30 V, and 32 V, respectively.FIG.5Bshow the magnitude of normalized electro-luminescence (EL) with respect to wavelength when a forward voltage is applied and when a reverse voltage is applied.FIG.5Bshows the normalized electro-luminescence (EL) size for a wavelength range of about 200 nm to about 260 nm.

Referring toFIGS.5A and5B, when a forward voltage is applied, the emission spectrum includes emission peaks of about 208 nm, about 215 nm, about 218 nm, and about 225 nm, and when a reverse voltage is applied, the emission spectrum includes emission peaks of about 215 nm, and about 235 nm. The emission peaks are located within the ultraviolet wavelength range. At this time, the peaks within the wavelength range of about 200 nm to about 240 nm correspond to the band gap energy of hexagonal boron nitride (hBN). The 215 nm peak may have greater intensity than other peaks. Electrons and holes may be injected into the hBN by graphene, and thus, the 215 nm peak corresponding to the optical bandgap energy of the hBN may be relatively strong.

FIGS.6A and6Bare plan views illustrating a crossing region of first and second electrode layers of an ultraviolet emitting optical device according to embodiments of the inventive concept, andFIG.6Bcorresponds to part A ofFIG.6A.

Referring toFIGS.6A and6B, at least a portion of a side surface of the second electrode layer GL2may have a geometric pattern such as a wave pattern or a sawtooth (wheel) pattern. The geometric pattern of the side surface of the second electrode layer GL2may be provided at a position overlapping the first electrode layer GL1in the third direction D3. For example, the first surface GL2aof the second electrode layer GL2may have a wave pattern, and the second surface GL2bof the second electrode layer GL2may have a sawtooth pattern, but this is merely exemplary, and the inventive concept is not limited thereto. As another example, both of the first and second surfaces GL2aand GL2bmay have a wave pattern, or both of the first and second surfaces GL2aand GL2bmay have a sawtooth pattern. Each of the first and second surfaces GL2aand GL2bis not limited to what is illustrated and/or described and may have various patterns other than straight lines.

Referring toFIG.3Btogether, as a part of the side surface of the second electrode layer GL2has various patterns, compared to a case where the side surface of the second electrode layer GL2has a straight profile, the number of color centers generated at a position vertically overlapping with the edge of the second electrode layer GL2may be increased in the crossing region CA.

FIGS.7A to7Eare plan views illustrating shapes of first and second electrode layers of an ultraviolet emitting optical device according to embodiments of the inventive concept.

Referring toFIG.7A, the first electrode layer GL1may include first portions P11having a constant width in the second direction D2and a second portion P12vertically overlapping with the second electrode layer GL2. The second electrode layer GL2may include first portions P21having a constant width in the first direction D1and a second portion P22vertically overlapping with the first electrode layer GL1. The first portions P11of the first electrode layer GL1may extend from both sides of the second portion P12in the first direction D1. The first portions P21of the second electrode layer GL2may extend from both sides of the second portion P22in the second direction D2. Each side surface of the second portion P12of the first electrode layer GL1and the second portion P22of the second electrode layer GL2may have a curved shape. When an electric field is applied between the first electrode layer GL1and the second electrode layer GL2, the color centers may be formed at positions overlapping the side surface of the second portion P22of the second electrode layer GL2in the vertical direction.

Referring toFIG.7B, the first electrode layer GL1may include a first portion P11extending in the first direction D1and having a constant width in the second direction D2and a second portion P12connected to an end of the first portion P11and having a circular shape. The second electrode layer GL2may include a first portion P21extending in the first direction D1and having a constant width in the second direction D2and a second portion P22connected to an end of the first portion P21and having a circular shape. The first portion P11of the first electrode layer GL1and the first portion P21of the second electrode layer GL2may extend in the same direction, but may not overlap each other in a vertical direction. A diameter of the second portion P12of the first electrode layer GL1may be greater than a diameter of the second portion P22of the second electrode layer GL2. The second portion P22of the second electrode layer GL2may vertically overlap the second portion P12of the first electrode layer GL1. When an electric field is applied between the first electrode layer GL1and the second electrode layer GL2, the color centers may be formed at positions overlapping the circumference of the second portion P22of the second electrode layer GL2in the vertical direction.

Referring toFIG.7C, the first electrode layer GL1may include a first portion P11extending in the first direction D1and a second portion P12connected to an end of the first portion P11and having a rectangular shape. A width of the second portion P12of the first electrode layer GL1in the second direction D2may be greater than a width of the first portion P11in the second direction D2. The second electrode layer GL2may include a first portion P21extending in a first direction D1, a plurality of second portions P22vertically overlapping the first electrode layer GL1and extending in the first direction D1, and a third portion P23vertically overlapping with the first electrode layer GL1and extending in the second direction D2. The first portion P11of the first electrode layer GL1and the first portion P21of the second electrode layer GL2may extend in the same direction, but may not overlap each other in a vertical direction. The third portion P23of the second electrode layer GL2may be provided between the first portion P21and the second portions P22, and may connect the first portion P21and the second portions P22. The second portions P22and the third portion P23of the second electrode layer GL2may form a comb shape. When an electric field is applied between the first electrode layer GL1and the second electrode layer GL2, color centers may be formed at positions vertically overlapping side surfaces of the second portions P22and the third portion P23of the second electrode layer GL2.

Referring toFIG.7D, the first electrode layer GL1may include a first portion P11extending in the first direction D1and a second portion P12connected to an end of the first portion P11and having a rectangular shape. A width of the second portion P12of the first electrode layer GL1in the second direction D2may be greater than a width of the first portion P11in the second direction D2. The second electrode layer GL2may include a first portion P21extending in a first direction D1, a second portion P22connected to an end of the first portion P21and extending in the first direction D1, and a plurality of third portions P23protruding from the second portion P22in the second direction D2. A width of the second portion P22of the second electrode layer GL2in the second direction D2may be smaller than a width of the first portion P21in the second direction D2. The second portion P22and the third portions P23of the second electrode layer GL2may vertically overlap the first electrode layer GL1. Although the third portions P23of the second electrode layer GL2are illustrated to have a triangular shape, this is merely exemplary and the inventive concept is not limited thereto, and the third portions P23may have various shapes. When an electric field is applied between the first electrode layer GL1and the second electrode layer GL2, color centers may be formed at positions overlapping side surfaces of the third portions P23of the second electrode layer GL2in a vertical direction.

Referring toFIG.7E, the first electrode layer GL1may extend in the first direction D2. The second electrode layer GL2may include a first portion P21extending in the second direction D2; and a second portion P22connected to an end of the first portion P21and overlapping the first electrode layer GL1in a vertical direction. The second portion P22may have, for example, a triangular shape in which the vertex Vx is positioned on the first electrode layer GL1. However, this is merely exemplary, and the inventive concept is not limited thereto, and the second portion P22may have various shapes such as an ellipse or a polygon other than a triangle. When an electric field is applied between the first electrode layer GL1and the second electrode layer GL2, color centers may be formed at positions, particularly near the vertices Vx, overlapping the side surfaces of the second portion P22of the second electrode layer GL2in the vertical direction.

What has been described with reference toFIGS.7A to7Eis exemplary only, and the inventive concept is not limited thereto, and by variously setting the shape and positional relationship of the first electrode layer GL1and the second electrode layer GL2as described above, it is possible to widen the area in which the color centers are created, and further generate the color centers at a predetermined (or desired) location.

FIG.8is a cross-sectional view for explaining an ultraviolet emitting optical device according to embodiments of the inventive concept, and corresponds to a cross-sectional view taken along line I-I′ ofFIG.1A. Hereinafter, for convenience of explanation, descriptions of substantially the same matters as those described with reference toFIGS.1A and1Bwill be omitted, and differences will be described in detail.

Referring toFIG.8, the active layer130may include a first active layer131and a second active layer132. The first active layer131may be in contact with the upper surface of the first encapsulation layer110and/or the upper surface of the first electrode layer GL1. The second active layer132may be in contact with a lower surface of the second encapsulation layer150and/or a lower surface of the second electrode layer GL2. The first active layer131may be provided between the second active layer132and the first encapsulation layer110. The second active layer132may be provided between the first active layer131and the second encapsulation layer150.

The ultraviolet emitting optical device according to the inventive concept may further include a third electrode layer GL3between the first active layer131and the second active layer132. The third electrode layer GL3may include substantially the same material as the first and second electrode layers GL1and GL2. When a voltage different from that of the third electrode layer GL3is applied to each of the first and second electrode layers GL1and GL2, electro-luminescence may occur in both the first active layer131and the second active layer132.

Referring toFIG.1Aagain, for example, the first electrode layer GL1may extend in the first direction D1, the second electrode layer GL2may extend in the second direction D2, and the third electrode layer GL3may extend in a horizontal direction crossing each of the first direction D1and the second direction D2. As another example, the first electrode layer GL1and the second electrode layer GL2may extend in the first direction D1, and the third electrode layer GL3may extend in the second direction D2.

FIG.9Ais a cross-sectional view for explaining an ultraviolet emitting optical device according to embodiments of the inventive concept, and corresponds to a cross-sectional view taken along line I-I′ ofFIG.1A.FIG.9Bis a perspective view illustrating an active layer of the ultraviolet emitting optical device ofFIG.9A. Hereinafter, for convenience of explanation, descriptions of substantially the same matters as those described with reference toFIGS.1A and1Bwill be omitted, and differences will be described in detail.

Referring toFIG.9A, the active layer130may include a first active layer141, a second active layer142, and a third active layer143sequentially stacked on the first encapsulation layer110between the first electrode layer GL1and the second electrode layer GL2. The first active layer141may be in contact with the upper surface of the first encapsulation layer110and/or the upper surface of the first electrode layer GL1. The second active layer142may be provided between the first active layer141and the third active layer143. The third active layer143may be in contact with a lower surface of the second encapsulation layer150and/or a lower surface of the second electrode layer GL2.

Referring toFIG.9B, crystal structures of the first to third active layers141,142, and143may extend in different directions. Specifically, the direction in which the crystal structure of the first active layer141extends may form a predetermined angle with the direction in which the crystal structure of the second active layer142extends, and the direction in which the crystal structure of the second active layer142extends may form a predetermined angle with the direction in which the crystal structure of the third active layer143extends.

The first active layer141in contact with the first electrode layer GL1and the third active layer143in contact with the second electrode layer GL2may help inject electrons or holes into the second active layer142, so that the luminous efficiency of the ultraviolet emitting optical device according to the inventive concept may be improved.

FIG.10Ais a perspective view illustrating an ultraviolet emitting optical device according to embodiments of the inventive concept.FIG.10Bis a plan view illustrating a crossing region of first and second electrode layers of the ultraviolet emitting optical device ofFIG.10A. Hereinafter, for convenience of explanation, descriptions of substantially the same matters as those described with reference toFIGS.1A and1Bwill be omitted, and differences will be described in detail.

Referring toFIGS.10A and10B, a plurality of first electrode layers GL1extending in the first direction D1between the first encapsulation layer110and the active layer130may be provided. The plurality of first electrode layers GL1may extend in parallel in the first direction D1and may be spaced apart from each other in the second direction D2at regular intervals. A plurality of second electrode layers GL2extending in the second direction D2between the second encapsulation layer150and the active layer130may be provided. The plurality of second electrode layers GL2may extend in parallel in the second direction D2and may be spaced apart from each other in the first direction D1at regular intervals. Although the number of the first electrode layers GL1and the number of the second electrode layers GL2are each shown to be three, this is merely exemplary and the inventive concept is not limited thereto.

Regions where the first electrode layers GL1and the second electrode layers GL2overlap in the third direction D3may be referred to as first to ninth crossing regions CA1to CA9. When a voltage is respectively applied to any one of the first electrode layers GL1and the second electrode layers GL2, electro-luminescence may occur at any one of the first to ninth crossing regions CA1to CA9.

The ultraviolet emitting optical device according to the inventive concept may be applied to a display element. In this case, each of the first to ninth crossing regions CA1to CA9may correspond to a pixel of the display element. In this case, the size of the pixel may be controlled by the width and/or spacing of each of the first and second electrode layers GL1and GL2, and thus the size may be reduced more easily than other display elements. That is, the ultraviolet emitting optical device according to the inventive concept may be applied to a high-resolution display element including pixels having a high degree of integration.

In addition, when using a material capable of converting light in the ultraviolet wavelength range into light in the visible wavelength range, the ultraviolet emitting optical device according to the inventive concept may be applied to a display element including RGB sub-pixels. In addition, the ultraviolet emitting optical device according to the inventive concept may be applied to a transparent and flexible display element due to material properties such as hexagonal boron nitride (hBN) and graphene.

Since the ultraviolet emitting optical device according to embodiments of the inventive concept uses a commercially available material, it is easy to manufacture and operates regardless of temperature, so that the ultraviolet emitting optical device may not require preheating and may be operated at a voltage as low as several tens of V. In addition, since the ultraviolet emitting optical device according to embodiments of the inventive concept emits ultraviolet light in the UVC region (wavelength range of about 200 nm to about 280 nm), it may be used in an ultraviolet sterilizer.

In addition, according to an ultraviolet emitting optical device and an operating method thereof according to embodiments of the inventive concept, color centers serving as light sources may be generated at predetermined (or desired) locations, and the intensity and emission wavelength of the emitted light may be controlled by controlling the intensity and direction of the electric field. The ultraviolet emitting optical device according to embodiments of the inventive concept may be applied to a display element. More specifically, the ultraviolet emitting optical device according to embodiments of the inventive concept may be applied to a high-resolution display element including pixels having a high degree of integration.

In addition, when using a material capable of converting light in the ultraviolet wavelength range into light in the visible wavelength range, the ultraviolet emitting optical device according to the inventive concept may be applied to a display element including RGB sub-pixels. In addition, the ultraviolet emitting optical device according to the inventive concept may be applied to a transparent and flexible display element due to material properties such as hexagonal boron nitride (hBN) and graphene.

Although the embodiments of the inventive concept have been described, it is understood that the inventive concept should not be limited to these embodiments but various changes and modifications may be made by one ordinary skilled in the art within the spirit and scope of the inventive concept as hereinafter claimed.