Patent Application
20130106294
Optoelectronic devices such as organic light emitting diodes (OLEDs) are being increasingly employed for lighting and display applications. The OLED includes a stack of thin organic layers sandwiched between two charged electrodes (anode and cathode). The organic layers may include a hole injection layer, a hole transport layer, an emissive layer, an electron transport layer, and an electron injection layer. Upon application of an appropriate voltage to the OLED lighting device, the injected positive and negative charges recombine in the emissive layer to produce light.
OLED devices have been increasingly employed for lighting applications in part because an OLED device may emit a similar amount of luminescence compared to an incandescent light device with significantly less energy. Due to the efficient nature of typical OLED devices, an OLED device may by powered by a relatively low voltage or low current battery for a relatively long period of operation. Furthermore, OLED devices may be fabricated on either a rigid substrate, such as glass, or on a flexible substrate such as polyethylene naphthalate (PEN) or polyethylene terephthalate (PET). Flexible substrates in particular may be efficiently produced using high-volume roll-to-roll production techniques and may result in a more flexible OLED device. Generally, flexible polymers used as substrates for OLED devices are coated with barrier materials which prevent and/or slow the ingress of water vapor, oxygen, and other environmental agents which may degrade the organic materials in an OLED device, resulting in efficiency loss and visual defects.
While OLED devices may be advantageously used in various lighting applications, different types of light sources may sometimes be preferred. For example, existing light fixtures may be configured to power a fluorescent light source, and the cost for rewiring a building and/or the light fixtures to power OLED devices may be higher than the immediate cost savings of converting to OLED devices. Furthermore, certain lighting characteristics from various types of light sources may be suitable for lighting different environments.
In one embodiment, a light emitting module is provided. The light emitting module includes a reflective light source having one or more organic light emitting diode (OLED) devices. The reflective light source is configured to reflect light from a different light source and configured to emit light based on the light reflected from the different light source.
In another embodiment, a lighting system is provided. The lighting system includes a primary light source, a secondary light source, control circuitry, and a secondary power source. The secondary light source includes one or more organic light emitting diode (OLED) devices. The primary light source is configured to emit light when powered by a primary power supply. The control circuitry is configured to determine whether the primary light source is powered and power the secondary light source using the secondary power source when the primary light source is determined to not be powered.
Yet another embodiment involves a method of operating a light module. The method includes monitoring a primary light source in the light module to determine whether the primary light source is emitting light and whether the primary light source is switched to an on state. The method also includes activating a secondary light source in the light module when the primary light source is not emitting light while switched to the on state. The secondary light source comprises one or more organic light emitting diode (OLED) devices.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Organic materials are becoming increasingly utilized in circuit and lighting area technology due to the low cost and high performance offered by organic electronic devices and optoelectronic devices. For example, optoelectronic devices such as organic light emitting diodes (OLEDs) may be employed for lighting and display applications. One or more embodiments of the present disclosure involve utilizing an OLED device having one or more OLEDs as a secondary light source in a light module. In some embodiments, the light module may include a primary light source including any suitable light source (e.g., linear fluorescent lights, compact fluorescent lights, incandescent lights, daylight, etc.) and a secondary light source including the OLED device.
In some embodiments, the OLED device may include reflective areas or surfaces and may be configured to reflect a portion of light illuminated by the primary light source, thereby increasing the amount of light emitted from the light module to a lit area (e.g., in a downward direction from a ceiling-mounted light module). For example, in some embodiments, the reflective area or surface on the OLED device may include an electrode of the OLED. Furthermore, the OLED device may be activated when illumination by the primary light source is interrupted. For example, an interruption of illumination from the primary light source may result from a power outage or an electrical or mechanical failure of the primary light source. As the OLED device may be relatively power efficient, the OLED device may provide illumination using an uninterruptible power supply, such as a battery, when the primary light source fails, such as due to lack of power. Therefore, the light module may provide light substantially continuously even if illumination from the primary light source is interrupted.
Referring to
In some embodiments, the anode 14 may include a substantially transparent doped thin metal oxide film, such as indium tin oxide (ITO), tin oxide, indium oxide, zinc oxide, indium zinc oxide, zinc indium tin oxide, antimony oxide, and mixtures thereof. The thickness of the anode 14 may range from approximately 10 nm to 200 nm, though other thicknesses are also contemplated.
Examples of materials suitable for the hole injection layer 26 disposed over the anode 14 may include proton-doped (i.e., “p-doped”) conducting polymers, such as p-doped polythiophene or polyaniline, and p-doped organic semiconductors, such as tetrafluorotetracyanoquinodimethane (F4-TCQN), doped organic and polymeric semiconductors, and triarylamine-containing compounds and polymers.
The hole transport layer 24 disposed over the hole injection layer 26 may include, for example, triaryldiamines, tetraphenyldiamines, aromatic tertiary amines, hydrazone derivatives, carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives including an amino group, polythiophenes, and like materials. Non-limiting examples of materials suitable for a hole transport layer 24 may include poly N-vinyl carbazole, and like materials.
The emissive layer 22 may include any electroluminescent organic materials that emit radiation in the visible spectrum upon electrical stimulation. In some embodiments, such materials may include electroluminescent organic materials which emit light in a determined wavelength range. For example, the electroluminescent organic materials in the emissive layer 22 may include small molecules, oligomers, polymers, copolymers, or a mixture thereof. For example, suitable electroluminescent organic materials 28 may include Tris(8-hydroxyquinolinato)aluminium (Alq3) and its derivatives; poly N-vinylcarbazole (PVK) and its derivatives; polyfluorene and its derivatives, such as polyalkylfluorene, for example poly-9,9-dihexylfluorene, polydioctylfluorene, or poly-9,9-bis-3,6-dioxaheptyl-fluorene-2,7-diyl; polypara-phenylene and its derivatives, such as poly-2-decyloxy-1,4-phenylene or poly-2,5-diheptyl-1,4-phenylene; polyp-phenylene vinylene and its derivatives, such as dialkoxy-substituted PPV and cyano-substituted PPV; polythiophene and its derivatives, such as poly-3-alkylthiophene, poly-4,4′-dialkyl-2,2′-bithiophene, poly-2,5-thienylene vinylene; polypyridine vinylene and its derivatives; polyquinoxaline and its derivatives; and polyquinoline and its derivatives. In one embodiment, a suitable electroluminescent material is poly-9,9-dioctylfluorenyl-2,7-diyl end capped with N,N-bis4-methylphenyl-4-aniline. Mixtures of these polymers or copolymers based on one or more of these polymers may be used. Other suitable materials may include polysilanes, or linear polymers having a silicon-backbone substituted with an alkyl and/or aryl side groups. Polysilanes are quasi one-dimensional materials with delocalized sigma-conjugated electrons along polymer backbone chains. Examples of polysilanes include poly di-n-butylsilane, poly di-n-pentylsilane, poly di-n-hexylsilane, polymethyl phenylsilane, and poly bis p-butyl phenylsilane.
The electron transport layer 20 disposed over the emissive layer 22 may include small molecules or low-to-intermediate molecular weight organic polymers, for example, organic polymers having weight average molecular weights of less than about 200,000 grams per mole as determined using polystyrene standards. Such polymers may include, for example, poly-3,4-ethylene dioxy thiophene (PDOT), polyaniline, poly-3,4-propylene dioxythiophene (PPropOT), polystyrene sulfonate (PSS), polyvinyl carbazole (PVK), and other like materials. The electron injection layer 18 disposed over the electron transport layer 20 may include, for example, sodium fluoride or potassium fluoride, or other like materials.
The cathode 12 may include a vapor-deposited metal layer having a thickness of approximately 100 nm to 1000 nm. The cathode 12 may include conductive, reflective materials such as aluminum, silver, indium, tin, zinc, other suitable metals, and combinations thereof. In some embodiments, the cathode 12 may also be relatively thin (e.g., about 30 nm) and may be transparent. The cathode 12 may be deposited over the electron injection layer 18 by, for example, physical vapor deposition, chemical vapor deposition, sputtering or liquid coating.
In some embodiments, the OLED stack 10 may also include different or additional non-emissive materials which may improve the performance or lifespan of the electroluminescent materials in the emissive layer 22. For example, in addition to the hole injection layer 26, the hole transport layer 24, the electron transport layer 20 and the electron injection layer 18, the stack 10 may also include layers such as a hole injection enhancement layer, an electron injection enhancement layer, getter materials, or any combinations thereof. Furthermore, in some embodiments, the layers of the OLED stack 10 may be arranged in different orders or in different combinations, and additional layers may be disposed between the layers illustrated in
During operation of an optoelectronic device, a voltage may be applied across the OLED stack 10. The voltage may charge the anode 14 to a positive charge and the cathode 12 to a negative charge, and electrons may flow through the stack 10 from the negatively charged cathode 12 to the positively charged anode 14. More specifically, electrons may be withdrawn from the organic materials adjacent to the anode 14 and injected to the organic materials adjacent to the cathode 12. The process of withdrawing electrons from the anode-side organic materials may also be referred to as hole injection and hole transport, and the process of injecting the electrons to the cathode-side organic materials may also be referred to as electron transport and electron injection. During the process of hole and electron transport/injection, electrons are withdrawn from the hole injection layer 26, transported through the hole transport layer 24 and the electron transport layer 20, and injected to the electron injection layer 18. Electrostatic forces may combine the electrons and holes in the emissive layer 22 to form an excited bound state (i.e., an excitation) which upon de-excitation, emits radiation having frequencies in the visible region of the electromagnetic spectrum (e.g., visible light). The frequency of the emitted radiation and the colors and/or characteristics of visible light may vary in different embodiments depending on the properties of the particular materials used in the OLED stack 10.
In some embodiments, the visible light emitted by the emissive layer 22 may be transmitted (as indicated by the arrow 30) through the organic layers 24 and 26 and through the transparent anode 14 and substrate 28 and out of the stack 10. In such OLED configurations, referred to as bottom emission OLEDs, the light which travels from the emissive layer 22 may also travel through the organic layers 20 and 18. In some embodiments, the cathode 12 may be reflective, and the light which travels away from the substrate 28 may be reflected (as indicated by the arrow 32) by the reflective cathode 12 and transmitted out through the substrate 28 and out of the stack 10.
Furthermore, in some embodiments, the visible light emitted by the emissive layer 22 may be transmitted (as indicated by the arrow 34) through the organic layers 20 and 18 and through a transparent cathode 12 and out of the stack 10. In such OLED configurations, referred to as top emission OLEDs, light may also travel through organic layers 24 and 26 in such devices. The substrate 28 and/or the anode 14 may be reflective in some embodiments, or alternatively, the stack 10 may include an additional reflective layer, such that light that travels away from the cathode 12 in top emission OLEDs may be reflected (as indicated by the arrow 36) and transmitted out through the cathode 12 and out of the stack 10. The light transmitted out of the stack 10 may be perceived as visible light which may illuminate out of an optoelectronic device.
Generally, a bottom emission OLED may have an anode 14 that is transparent to light and a cathode 12 that is reflective to light to increase light extraction of the OLED device. A top emission OLED may have an anode 14 that is reflective to light to increase the light extraction out of the OLED device. Reflective electrodes (e.g., a reflective cathode 12 or a reflective anode 14) may be produced using a vapor deposition techniques (e.g., physical vapor deposition, chemical vapor deposition, sputtering or liquid coating), and the thickness of the layer may be between 10 nm to 1000 nm. Suitable metals may include, for example, aluminum, silver, indium, tin, zinc, or other suitable metals and combinations thereof which increase the reflectivity and electrical efficiency of the OLED device. In some embodiments, a reflective cathode 12 or a reflective anode 14 may have a mirror-like appearance.
With the foregoing discussion of OLED devices and their operation in mind, one or more embodiments of the present disclosure involve utilizing a light-emissive OLED device having at least one reflective layer in a light module (e.g., a light fixture). One embodiment of a light module which utilizes an OLED device having a reflective layer as a secondary light source is illustrated in perspective view of
The light module 40 may include a primary light source 42 (such as the depicted linear fluorescent lamp), a secondary light source 44 (here depicted as OLED devices), and a power supply and controller 46 which directs and/or supplies power to the primary light source 42 and/or the secondary light source 44. The secondary light source 44 may include a plurality of separate OLED substrates, a single OLED substrate with multiple OLED pixels, or a combination thereof. As illustrated in
In accordance with the present disclosure, the secondary light source 44 may be configured to reflect a portion of light from the primary light source 42 in a direction out of the light module 40, such as toward the diffuser 50. In some embodiments, a reflective layer of the secondary light source 44 may improve the efficacy of the light module 40 by reflecting the light from the primary light source 42 out of the light module 40. In some embodiments, the secondary light source 44 may also be configured to activate in response to an interruption in the operation of the primary light source 42. Furthermore, in some embodiments, the secondary light source 44 may include various configurations of OLED devices. For example, the OLED devices 52 may be arranged in one continuous sheet, or several separate OLED devices 52 may be arranged in the secondary light source 44, as illustrated in
The primary light source 42 may include any suitable light source, such as linear fluorescent lamps, compact fluorescent lamps, incandescent light bulbs, etc. The primary light source 42 may also include daylight, as will be further discussed with respect to
The secondary light source 44 may include one or more OLED devices 52, each having a configuration similar to the OLED stack 10 illustrated in
The cathode 12 may be encapsulated by a barrier layer 62 which may protect the OLED device 52 from degradation by water, oxygen, or other environmental reactants. The barrier layer 62 may include, for example, substantially impermeable material such as an insulator-coated metal foil.
The substrate 28 may include a transparent plastic coated with a conductive layer, such as metal oxide or a nano-array with conductive polymers. In some embodiments, the substrate 28 may be coated with barrier layers and/or light extraction films. For example, the substrate 28 may include barrier layers such as a graded structure which oscillates between organic rich and inorganic rich zones. The light extraction films may include surface-textured film or volumetric light scattering composites. For example, volumetric light scattering composites may include embedded particles (e.g., zirconia particles, phosphorescent scattering particles such as fluoro-chloro apatite or persistent luminescent materials such as SrAl2O4:Eu2, Dy3, etc.) in a suitable host material (e.g., polymethyl methacrylate matrix).
In some embodiments, the substrate 28, as well as other layers in the device 52, may be substantially flexible, such that the secondary light source 44 may be arranged in an angle or arc. In some embodiments, the secondary light source 44 may be arranged in an angle or arc with respect to an axial direction of the primary light source 42. For example, the secondary light source 44 may be trough shaped and may have a parabolic cross section. The primary light source 42 may be placed near the position of the focal point of the parabola in some embodiments. Arranging the secondary light source in an angle or arc may increase the diffuse reflection of light emitted by the OLED devices 52, as well as portions of light emitted by the primary light source 42. In some embodiments, as the OLED devices 52 may be reflective, the OLED devices 52 may be angled or arced such that the diffuse reflection is at least 50% in the visible region. In some embodiments, the OLED devices 52 may be angled or arced such that the diffuse reflection is at least 80% in the visible region.
Furthermore, the substrate 28 may be coated with reflective materials. As depicted in
Due to the reflectivity of the substrate 28, the secondary light source 44 may reflect a portion of light illuminated by the primary light source 42. For example, as illustrated in
In some embodiments, the OLED devices 52 may be configured to activate (i.e., turn ‘on’ or emit light) in response to an interruption in the operation of the primary light source 42. For example, the control circuitry 60 may be suitable for detecting such an interruption of the primary light source 42 when the primary light source 42 is otherwise supposed to be active. An interruption of the primary light source 42 may refer to a situation where the primary light source 42 is not emitting light. In some embodiments, an interruption of the primary light source 42 may refer to a situation where the primary light source 42 is not emitting light while the primary light source is switched to an on state. For instance, such situations may occur if the primary light source 42 is turned on (e.g., switched on by a wall switch), but is not emitting light due to an interruption of the power supply (e.g., power outage). Interruptions of the primary light source 42 may also refer to electrical or mechanical failures of one or more components of the light module 40 (e.g., a broken primary light source 42, disconnected power supplies, etc.).
The control circuitry 60 may be connected to a sense wire 76 which is connected to a power supply lead 56 of the primary light source 42. The control circuitry 60 may sense whether power is supplied to the primary power source 42 through the sense wire 76. In some embodiments, other sensing mechanisms may be used. For example, the control circuitry 60 may include a light sensor 78 configured to sense whether light is or is not emitted by the primary light source 42. In some embodiments, the control circuitry 60 may receive an output signal of the light sensor 78 and determine whether the primary light source 42 is emitting light, at least based on the output signal of the light sensor 78. For example, in some instances, the primary light source 42 may be switched on and may be receiving power. However, due to a failure of the primary light source bulb, the primary light source 42 does not emit light. In such situations, the control circuitry 60 may determine that the primary light source 42 has been interrupted based on the switched state (i.e., on) of the primary light and the output of the light sensor 78 (i.e., not emitting light).
In response to sensing an interruption of the primary light source 42, the control circuitry 60 may control the activation of the secondary light source 44 by supplying power to the secondary light source 44 from an uninterruptable power supply 64. The uninterruptible power supply 64 may refer to any suitable power supply that is separate and distinct from the power supply that powers the primary light source 42. In some embodiments, the uninterruptible power supply 64 may be connected to one or more capacitors or batteries and may be connected to the secondary light source 44 at a cathode connection point 66 and an anode connection point 68. In response to a voltage driven through the OLED device 52 between the cathode and anode connection points 66 and 68, the organic layers 16 may emit light. Therefore, the light module 40 may provide light substantially continuously through the secondary light source 44 even if illumination from the primary light source 42 is interrupted.
In some embodiments, the control circuitry 60 may maintain a charge stored in the uninterruptible power supple 64 when the light module 40 is operating normally (i.e., the primary light source 42 is emitting light). The control circuitry 60 may also activate the uninterruptible power supple 64 when the control circuitry 60 senses an interruption of the primary light source 42. Furthermore, in some embodiments, the control circuitry 60 may meter the power supplied to the secondary light source 44. In some embodiments, the control circuitry 60 may include one or more power converters (e.g., AC-DC converter), integrated battery charging circuitry (e.g., bq24022, from Texas Instruments®), a lithium battery, and digital logic circuitry for enabling activation of the secondary light source 44. In some embodiments, the control circuitry 60 may include digital logic circuitry which measures the output of the integrated battery charging circuitry to detect the presence of a line input power, such that the secondary light source 44 may operate only when the primary light source 42 is not powered.
In some embodiments, the light that is emitted by the primary light source 42, emitted by the secondary light source 44, and/or reflected by the secondary light source 44 may travel out of the diffuser 50. The diffuser 50 may spread or scatter light traveling out of the light module 40. For example, spreading or scattering the light traveling out of the light module 40 may improve certain characteristics of the light.
In some embodiments, a light module 40 utilizing an OLED device with a reflective layer as a secondary light source 44 may be utilized to reflect direct sunlight or diffuse daylight to be emitted out of the light module. In such embodiments, the direct sunlight or the diffuse daylight may be the primary light source, and the OLED device having a reflective layer may be the secondary light source. As used herein, sunlight or daylight may refer to light sources such as light from the sun or any ambient light in an environment. In embodiments where the primary light source includes daylight, the secondary light source may be configured to reflect diffuse daylight and/or direct sunlight for purposes of daylighting. Daylighting may refer to applications in which natural daylight and/or direct sunlight is redirected into commercial or residential buildings or other terrestrial or maritime structures such as ships, trains, or aircrafts, and the amount of usable daylight in the structure may be increased when compared to conventional window openings, skylights, etc. In some embodiments, a secondary light source suitable for daylighting may include reflective surfaces which divert light from an incident angle towards a different area in the building and/or redirect light to pass through an opening, such as a window or skylight, which the light would otherwise not have passed through. The secondary light source may also include an OLED device in the lighting module which may emit light when there is little or no available daylight or sunlight.
An illustration of an embodiment using daylight as a primary light source and an OLED device with a reflective layer as a secondary light source is provided in
The secondary light source 44a may also emit light rays 110 into the interior space 98. In some embodiments, the secondary light source 44a may include control circuitry (e.g., control circuitry 60 from
The control circuitry 60 may further be suitable for determining an amount of light directed out of the secondary light source 44a as reflected light rays 112 and powering the OLED device 52 to emit light rays 110 to compensate for any insufficiency in the reflected light rays 112. For example, the control circuitry 60 may determine the intensity of the reflected light rays 112. As the intensity of the reflected light rays 112 gradually decreases (e.g., while the sun sets or as the sun moves), the control circuitry 60 may gradually increase the brightness of the emitted light rays 110 to compensate for the decrease of the reflected light rays 112. As such, the secondary light source 44a may reflect light rays 112 and emit light rays 110 concurrently such that a substantially consistent amount of light is directed into the interior space 98 at or above a threshold intensity.
Another embodiment of a secondary light source including an OLED device and a reflective layer is illustrated in
In one embodiment, the secondary light source 44b may be arranged to be substantially perpendicularly with respect to the plane of the window 120. For example, the secondary light source 44b may be arranged horizontally with respect to a vertical pane of the window 120. The secondary light source 44b may be contained within a width of the window 120 (e.g., within the width of the window ledge) in some embodiments, or may extend beyond the width of the window 120 into the interior space 98. The secondary light source 44b may include one or more OLED devices 52. The secondary light source 44b may also include at least one reflective layer and may be substantially mirror-like. Diffuse daylight 104 or direct sunlight 102 which travel to the reflective surface of the secondary light source 44b may be reflected into the interior space 98.
In some embodiments, the reflective surface of the secondary light source 44b may be on the upper surface of the secondary light source 44b, such that diffuse daylight 104 or direct sunlight 102 which impinges the upper surface of the secondary light source 44b may be reflected upwards towards a ceiling of the interior space 98. The surface area of the secondary light source 44b may be curved or arced or flat in various embodiments to increase or maximize the amount of light rays reflected from the exterior environment 122 into the interior space 98. In some embodiments, the secondary light source 44b may also emit light 110 when activated, and may concurrently emit light 110 into the interior space 98 while reflecting light 112 into the interior space 98 and/or ceiling of the interior space 98. For example, the secondary light source 44b may reflect and/or emit an intensity of light which reaches or surpasses a threshold light intensity. In some embodiments, the secondary light source 44c may include an OLED device 52 and a reflective layer, and the secondary light source 44c may be substantially mirror-like. The light 112 reflected upwards by the secondary light source 44b may be reflected downwards towards in the interior space 98 by the secondary light source 44c.
In some embodiments, each or either of the secondary light sources 44b and/or 44c may include control circuitry (e.g., control circuitry 60 as in
Furthermore, in some embodiments, the reflective layers in the secondary light sources may be flat or curved or arced. In some embodiments, the secondary light sources 44b and/or 44c may be trough shaped and may have a parabolic cross section. The edges of the secondary light sources 44b and/or 44c may be straight or curved depending on functional, architectural, or aesthetic preferences. In various embodiments, the secondary light sources 44b and/or 44c may include a single OLED device 52 or multiple OLED devices 52 which are connected in series or in a parallel electrical string configuration.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
