Patent Application
20090159677
The invention relates generally to electrical powering of optoelectronic semiconductor devices. The invention more particularly relates to the contactless transfer of electrical power or information to or from optoelectronic semiconductor devices.
Optoelectronic semiconductor devices, especially devices based on organic materials are known to degrade rapidly when exposed to moisture and oxygen. Moisture and oxygen are often viewed as major extrinsic degradation factors, limiting the device lifetime. Typical large area devices such as organic light emitting devices (OLEDs) are fabricated, either in batch or roll-to-roll, using a hermetic packaging scheme so that the OLED is protected from harmful ambient. Typically, glass, metal foil (both inherently excellent barriers) and plastic films with a thin film barrier are used as substrate and/or superstrate depending on the device structure. A thin film barrier can also be applied as top encapsulation for an optoelectronic semiconductor device built on any of these aforementioned materials used as substrates. However, there are still parts or areas of the device where encapsulation is not applied or disrupted, such as portions of contact pads and power leads connecting the encapsulated device interior with the outside power sources. Unencapsulated power leads can prematurely corrode, delaminate or otherwise degrade providing a fast pathway for water vapor and oxygen ingress, compromising encapsulation.
A common method to test the barrier properties is to monitor the encapsulated device performance while it is exposed to a harsh environment such as 60° C./90% Relative Humidity (RH.). It is often observed with OLEDs, where part of the metal cathode contact reaches outside of the encapsulation, this contact delaminates, cracks and/or corrodes very rapidly (within hours) forming fast permeation pathway for water and oxygen thus causes premature device failure. Also, photovoltaic devices such as CIGS (copper indium gallium selenide) based devices on molybdenum substrate are also known to deteriorate due to water vapor and oxygen penetration.
Therefore, it is highly desirable to find a method to power such devices where aforementioned premature failure mechanisms are eliminated. Additional advantage of contactless power/data transfer is in potential cost savings achieved by elimination of multiple conductive interconnects, as, for example, required by such devices as displays and detector arrays.
One embodiment disclosed herein is a system including an encapsulated optoelectronic semiconductor device at least partly disposed within a barrier encapsulation, and a contactless power transfer system configured to transfer at least one of power and data across the barrier encapsulation.
Another embodiment disclosed herein is a system including an encapsulated optoelectronic planar semiconductor device, at least partly disposed within a barrier encapsulation, and a contactless power transfer system configured to transfer at least one of power and data across the barrier encapsulation.
Still another embodiment disclosed herein is a method of manufacturing an integrated contactless powered system. The method includes providing a device over a substrate, providing a first contactless power transfer element operably electrically coupled to the device, providing a barrier encapsulation surrounding the device and the first contactless power transfer element, and providing a second contactless power transfer element operably electrically coupled to a power source, external to the barrier encapsulation, and across from the first contactless power transfer element to form an integrated system.
Another embodiment disclosed herein is a method of manufacturing a contactless power transfer optoelectronic semiconductor device system. The method includes providing a first contactless power transfer element integrated with the optoelectronic semiconductor device and disposed internal to a barrier encapsulation, and providing a second contactless power transfer element disposed on a substrate and positioned external to the barrier encapsulation and disposed separately from the optoelectronic semiconductor device.
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:
Embodiments of the present invention disclose systems and methods for contactless power transfer. In one embodiment, electrical power is transferred through an insulating barrier with time varying fields, either magnetic or electric, i.e. via inductive or capacitive coupling.
In the following specification and the claims that follow, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. As used herein, the term “device” refers to an optoelectronic semiconductor device and/or to a plurality of optoelectronic semiconductor devices, the functionality of the device being based on the quantum mechanical effects of light in semiconducting materials. Non-limiting examples of such devices include light emitting diodes and photo diodes.
In one embodiment of the present invention, is a system including an encapsulated device and a contactless power transfer system. At least part of the device is enclosed within a barrier encapsulation. Non-limiting examples of devices, which may be advantageously encapsulated, are organic light emitting devices, organic photovoltaic devices, thin-film inorganic photovoltaic devices, detector arrays and displays. The contactless power transfer system is configured to couple power and/or data into or out of the encapsulated device, across the barrier encapsulation. In some embodiments, the device is wholly encapsulated.
A first part of the contactless power transfer system may be disposed internal to the encapsulation and a second part of the contactless power transfer system may be disposed external to the encapsulation, with the first part not in wired contact with the second part, and the first part and second part configured to transfer energy and/or data across the barrier encapsulation. In one embodiment, the distance between the first part and the second part is in the order of centimeters or less.
In some embodiments, the contactless power transfer system is an inductive power transfer system including at least one pair of transformer coils disposed across the barrier encapsulation. In one example, the barrier encapsulation is substantially transparent to magnetic field. In one embodiment, substantially transparent refers to at least 10% transparency to the magnetic field. In a further embodiment, substantially transparent refers to at least 50% transparency to the magnetic field.
In an alternate embodiment, the contactless power transfer system is a capacitive power transfer system. The capacitive power transfer system includes at least one pair of power transfer capacitors. The plates (first plate and second plate) of each capacitor is disposed on either side of the barrier encapsulation, with the barrier encapsulation positioned to act as a dielectric spacer between the first plate and the second plate of each capacitor of the at least one pair of capacitors.
In the illustrated embodiment of
In some embodiments, the inverter or the DC source may be controlled to control the current through the light emitting optoelectronic semiconductor devices, and thus their light output. Furthermore, commonly used resonant inverter circuits may be configured to function as current sources, so that large changes in the light emitting device voltage result in minimal changes in device current. The devices themselves may be used as rectifiers or as part of a rectifier circuit.
The inductor coils in power transfer system may have the same number of turns or different number of turns. When the coils have different turns, the transformer may be used in a step-up voltage configuration or a step-down voltage configuration. In one embodiment, the transformer may be a variable transformer having an adjustable turn ratio, where at least one of the coils has an adjustable turn control. Therefore, the energy transfer across the barrier encapsulation can also be varied.
In one embodiment, one or more magnetic core layers may be disposed adjacent to the primary and/or secondary inductor coil. In the illustrated embodiment of
In one embodiment, the magnetic core layer 76 is a divided layer. Since many magnetic materials are also electrically conductive, eddy current losses may occur in the core layers. The losses may be reduced by dividing the magnetic core layer into sections as seen in the illustrated embodiment of
For example, say power is transferred through a planar transformer without magnetic core at a level of 24 W/cm2 at a frequency of 6 MHz with a coupling efficiency >90%. A frequency of 600 kHz then would allow approximately 0.24 W/cm2 with comparable efficiency. The addition of a magnetic core on one side of the magnetic coupling can allow a further reduction of 15-30% in frequency for comparable efficiency if the core losses are kept low. The addition of core layers on both sides is expected to provide a 5×-10× improvement in the efficiency compared to when operated without a magnetic core.
As the operating frequency is increased, it is expected that the efficiency of energy transfer will also be increased. In one embodiment, a high frequency generator is powered by the primary source and the high frequency output from the high frequency generator is used to power the primary inductor coil.
In alternate embodiments to the embodiments illustrated in
In the illustrated embodiment of
In a non-limiting example, for capacitive contactless power transfer, for a 50-micrometer thick polymer barrier encapsulation, a total series capacitance is expected to be in the order of 7.5 pF-10 pF (series combination of C1A and C1B) per cm2. A 100 kHz frequency would allow approximately 50 mA of current with about 200 VRMS across the barrier. In capacitive power transfer, it is advantageous to reduce the current required for a given power by using an increased number of smaller devices in series. Capacitive energy transfer can be improved by reducing the insulating barrier thickness, increasing its dielectric constant, or by increasing the operating frequency.
As the operating frequency is increased, efficiency of energy transfer is increased. In capacitive power transfer, for a given current, the voltage across the barrier increases in inverse proportion to the frequency, so that at low frequencies, the voltage can break down the barrier. Therefore, in one embodiment of a capacitive contactless power transfer system, a frequency generator is used to power the capacitors. In a non-limiting example the applied frequencies are in a range from about 50 kHz to about 1 MHz.
For both inductive and capacitive embodiments of the power transfer system, a large area transfer element may be replaced with a plurality of smaller area elements. So a plurality of transformers may be used to transfer power across the encapsulation. Alternatively, a plurality of pairs of capacitors may be used to transfer power across the encapsulation. This may allow the reduction of peak stray field strength for a given total energy transfer, and thus reduce the generation of and the susceptibility to electromagnetic interference (EMI).
Embodiments of encapsulated contactless powered systems include lighting devices such as organic light emitting devices and display devices. In one embodiment, the contactless powered systems are configured for continuous powering, for example for powering for several hours continuously. Other examples of encapsulated contactless power or data transfer devices include encapsulated detector arrays, data from which can be contactlessly transferred to outside the encapsulated detector array. Examples of such detector array include CCD devices. In one embodiment the device is an encapsulated optoelectronic planar semiconductor device. In a further embodiment, the planar semiconductor device may be a flexible device capable of being rolled into a shape.
In one embodiment, a barrier encapsulation material may include an organic material, an inorganic material or combinations thereof. The barrier encapsulations reduces exposure of the device to deleterious materials such as but not limited to water vapor and oxygen. Non-limiting examples of barrier encapsulation material include glass, polymer, metal and combinations thereof. In some examples, the barrier encapsulation may be in the form of a metal foil. In some embodiments, a multilayer encapsulation including one or more barrier materials may be used. In one embodiment, the barrier encapsulation acts as a barrier against oxygen and/or water vapor penetration into the device. Examples of organic-inorganic barrier coatings are described in many references including U.S. Pat. No. 6,746,782 and U.S. Pat. No. 7,015,640. For example, such barrier encapsulation may provide water vapor transmission rates below 0.1 g/m2/day and oxygen transmission rate below 1 g/m2/day.
In one embodiment, the contactless power transfer system is a contactless data transfer system. In a non-limiting example, data can be sent to a modulator so that it can be carried on a high frequency carrier across the insulating barrier, where the signal is demodulated and sent on to additional control circuitry. This control circuitry could be used to control one or more devices. In particular, this control could be used to control displays, e.g. computer monitors or video displays. Such an approach could be used to eliminate hundreds, thousands, or greater numbers of conductive interconnects currently used, with the possibility of greatly reducing cost and increasing reliability of such displays. This could be applied to any optoelectronic semiconductor device system, including for example light emitting displays and liquid crystal displays, where the individual devices (or pixels) may be required to be sealed against the atmosphere or other ambient conditions.
In one embodiment, the system transfers both power and data. Inductive or capacitive coupling can be used to transfer data in addition to power. For example, it is possible to use an inverter as a modulator, so that it can transfer both power and data. Furthermore, a modulated data signal may be generated, combined with the power transfer waveform, and sent across the same contactless link. Alternatively, data signal may be transferred through a separate contactless link.
In a further embodiment of the invention is a method of manufacturing an integrated contactless powered optoelectronic semiconductor device system. The method includes the steps of providing an optoelectronic semiconductor device over a substrate and providing a first contactless power transfer element operably electrically coupled to the optoelectronic semiconductor device. The optoelectronic semiconductor device may be fabricated using techniques known to the skilled in the art. A dielectric barrier encapsulation is disposed surrounding the device and the first contactless power transfer element. A second contactless power transfer element operably electrically coupled to a power source, external to the barrier encapsulation, and across from the first contactless power transfer element to form an integrated device. In one embodiment, the first and second contactless power transfer elements are inductors, for example, thin film inductors. In an alternate embodiment, the contactless power transfer elements are plates of a capacitor, such as a thin film capacitor. The thin film capacitors or inductors can be manufactured by a variety of methods, as known to the skilled in the art. In a further alternate embodiment, of the invention is a method of manufacturing a contactless powered optoelectronic semiconductor device system, where the second power transfer element, electrically coupled to a power source, is disposed on a substrate of its own and possibly electrically isolated from the environment, providing a fixture part of the system. First power transfer element, optoelectronic semiconductor device and barrier encapsulation are fabricated on a separate substrate, providing a replaceable component of the system.
Although all the above described embodiments of the invention teach contactless transfer of power into an encapsulated optoelectronic semiconductor device, the invention is not limited to systems where power is transferred into an encapsulated optoelectronic semiconductor device. Contactless power transfer systems where power is transferred out of an encapsulated optoelectronic semiconductor device, also falls within the scope of this invention. For example, the contactless power transfer system may include an encapsulated photovoltaic device from which energy is transferred out.
One such example is illustrated in
In a first example of contactless powering 170, a 500 ohm load 172 was powered in a contactless mode. A low frequency or line frequency AC source 174 was used to power a high frequency generator 176 as illustrated in
The results summarized in Tables 1 and 2 indicate that at higher frequencies the efficiency of contactless power transfer is greater.
The contactless powering circuit of Example 1 was used to power an encapsulated OLED (organic light emitting device) device fabricated as illustrated in
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
