Sublimation unit with temporal stability of output vapor pressure

Abstract

The present application relates to a sublimation cell with temporal stability of output vapor pressure. The present invention provides designs and arrangements for a sublimation cell enriched with an inert carrier gas having organic vapor such that the partial pressure of the organic vapor is highly stable in time. Stability can be achieved by controlling the local evaporation rate along the solid-gas interface via one or more crucibles, thereby reducing the effects of larger headspace and reduced interface area due to resource exhaustion. The local evaporation rate can also be controlled using a temperature profile or a convective flow field.

Description

[0001] This application is a divisional application of an application with an application date of May 28, 2018, application number 201810520555.7, and invention name “Sublimation unit with time stability of output vapor pressure”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application is a non-provisional application of, and claims the benefit of priority to, U.S. Provisional Patent Application No. 62 / 511,728, filed on May 26, 2017, the entire contents of which are incorporated herein by reference. Technical Field

[0004] The present invention relates to a sublimation unit with a time-stable output vapor pressure for use in device manufacturing techniques such as OVJP, techniques for using the same, and devices manufactured therefrom. Background Art

[0005] Optoelectronic devices utilizing organic materials are becoming increasingly popular for a variety of reasons. Many of the materials used to make the devices are relatively inexpensive, so organic optoelectronic devices have the potential to have cost advantages over inorganic devices. In addition, the inherent properties of organic materials (e.g., their flexibility) can make them more suitable for specific applications, such as manufacturing on flexible substrates. Examples of organic optoelectronic devices include organic light emitting diodes / devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, organic materials can have performance advantages over conventional materials. For example, the wavelength of light emitted by the organic emissive layer can generally be easily adjusted with appropriate dopants.

[0006] OLEDs utilize organic thin films that emit light when voltage is applied to the device. OLEDs are becoming an increasingly popular technology for applications such as flat panel displays, lighting, and backlighting. Several OLED materials and configurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety.

[0007] One application of phosphorescent emitting molecules is full-color displays. Industry standards for such displays require pixels that are suitable for emitting specific colors (called "saturated" colors). Specifically, these standards require saturated red, green, and blue pixels. Alternatively, OLEDs can be designed to emit white light. In conventional liquid crystal displays, an absorption filter is used to filter the emission from a white backlight to produce red, green, and blue emissions. The same technology can also be used for OLEDs. White OLEDs can be single EML devices or stacked structures. Color can be measured using CIE coordinates well known in the art.

[0008] As used herein, the term "organic" includes polymeric materials and small molecule organic materials that can be used to make organic optoelectronic devices. "Small molecule" refers to any organic material that is not a polymer, and a "small molecule" may actually be quite large. In some cases, a small molecule may include a repeating unit. For example, the use of a long chain alkyl group as a substituent does not remove a molecule from the "small molecule" category. Small molecules can also be incorporated into polymers, for example as a side group on a polymer backbone or as part of a backbone. Small molecules can also serve as the core portion of a dendritic polymer, which consists of a series of chemical shells built on the core portion. The core portion of a dendritic polymer can be a fluorescent or phosphorescent small molecule emitter. A dendritic polymer can be a "small molecule", and all dendritic polymers currently used in the field of OLEDs are considered to be small molecules.

[0009] As used herein, "top" means farthest from the substrate, while "bottom" means closest to the substrate. Where a first layer is described as being "disposed "above" a second layer, the first layer is disposed farther from the substrate. Unless it is specified that the first layer is "in contact with" the second layer, there may be other layers between the first and second layers. For example, a cathode may be described as being "disposed "above" an anode even though various organic layers are present between the cathode and the anode.

[0010] As used herein, "solution processable" means capable of being dissolved, dispersed or transported in and / or deposited from a liquid medium in the form of a solution or suspension.

[0011] When a ligand is believed to directly contribute to the photosensitive property of an emissive material, the ligand may be referred to as "photosensitive." When a ligand is believed not to contribute to the photosensitive property of an emissive material, the ligand may be referred to as "ancillary," but the ancillary ligand may alter the properties of the photosensitive ligand.

[0012] As used herein, and as will be generally understood by one skilled in the art, a first "Highest Occupied Molecular Orbital" (HOMO) or "Lowest Unoccupied Molecular Orbital" (LUMO) energy level is "greater than" or "higher than" a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Since the ionization potential (IP) is measured as a negative energy relative to the vacuum energy level, a higher HOMO energy level corresponds to an IP with a smaller absolute value (a less negative IP). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) with a smaller absolute value (a less negative EA). On a conventional energy level diagram with the vacuum energy level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. A "higher" HOMO or LUMO energy level appears closer to the top of this diagram than a "lower" HOMO or LUMO energy level.

[0013] As used herein, and as one skilled in the art would generally understand, a first work function is "greater than" or "higher than" a second work function if the first work function has a higher absolute value. Because work functions are typically measured as negative numbers relative to the vacuum level, this means that a "higher" work function is more negative. On a conventional energy level diagram with the vacuum level at the top, a "higher" work function is illustrated as being farther away from the vacuum level in a downward direction. Thus, the definition of HOMO and LUMO energy levels follows different rules than work functions.

[0014] More details regarding OLEDs and the definitions set forth above can be found in U.S. Patent No. 7,279,704, which is incorporated herein by reference in its entirety. Summary of the invention

[0015] According to one embodiment, an organic light emitting diode / device (OLED) is also provided. The OLED may include an anode, a cathode, and an organic layer disposed between the anode and the cathode. According to one embodiment, the organic light emitting device is incorporated into one or more devices selected from the following: a consumer product, an electronic component module, and / or a lighting panel.

[0016] Embodiments disclosed herein provide an evaporation source unit for providing a material to be deposited via vapor deposition, and a method of operating the same by providing a carrier gas through the source unit. In one embodiment, the source unit includes: a first material crucible having a first material to be deposited via vapor deposition; a first heater configured to set the temperature of the first material crucible; and a second material crucible disposed downstream of the first material crucible. The second material crucible may include: a recess for holding the second material to be deposited via vapor deposition; a first exhaust hole in fluid communication with the first material crucible; and a second heater configured to set the temperature of the second material crucible independently of the temperature of the first material crucible. More generally, the source unit may include any number of material crucibles, each of which may be heated independently of each other crucible in the source unit. For example, in one embodiment, the source unit may include: a third material crucible disposed downstream of the second material crucible, the third material crucible having the same general configuration as the first and second units; and a third heater configured to set the temperature of the third material crucible independently of the temperatures of the first and second material crucibles.

[0017] The source unit may also include materials to be deposited using the unit, such as first, second, and third materials. Each unit may include the same material, or different units may include the same and / or different materials. The material may be any suitable material to be deposited using the evaporation unit, such as one or more organic emissive materials or other materials suitable for manufacturing OLEDs and devices containing OLEDs as disclosed herein. The unit and / or exhaust port between the crucibles may include one or more reverse connections between adjacent crucibles, such as the first and second crucibles or the second and third crucibles. The crucibles may be arranged in a superimposed, parallel, or any other physical arrangement. During operation of the source unit, the source unit may be configured to maintain the temperature of the first crucible at a temperature lower than that of the second crucible. Similarly, the source unit may be configured to maintain the temperature of the second crucible at a temperature lower than that of the third crucible. The crucible temperature may also be changed over time.

[0018] In one embodiment, a vaporization source unit is provided, comprising: a plurality of carrier gas injection ports arranged around a central interior region of the unit and a material charge carrier containing a source of vaporizable material; wherein the carrier gas injection ports are directed toward the material charge carrier at an angle sufficient to form a vortex of carrier gas above the material charge carrier during operation of the vaporization source unit. The unit may also include a separator disposed within the central interior region of the unit to increase the path length of the streamlines within the vortex of the carrier gas. A central flue may allow the carrier gas to exit the vaporization source unit after contacting the vaporizable material during operation of the vaporization source unit. The unit may include a carrier gas source in fluid communication with the plurality of carrier gas injection ports, and / or a vacuum source in fluid communication with the flue. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Organic light emitting devices that can be fabricated using the embodiments disclosed herein are shown.

[0020] Figure 2 It is demonstrated that an inverse organic light-emitting device that can be fabricated using the embodiments disclosed herein does not have a separate electron transport layer.

[0021] Figure 3 A schematic diagram showing the evaporation source unit.

[0022] Figure 4A Cross-sectional view showing a fully loaded evaporation source tray.

[0023] Figure 4B Showing the evaporation rate relative to Figure 4A The curve of the source disk position is shown.

[0024] Figure 5A Cross-sectional view showing a partially depleted evaporation source disk.

[0025] Figure 5B Showing the evaporation rate relative to Figure 5A The curve of the source disk position is shown.

[0026] Figure 6 A graph showing the saturation of organic vapor in the exhaust gas from the evaporator as a function of time for a constant temperature source.

[0027] Fig. 7A and 7B Curves for different temperature distributions along the evaporation source disk and the resulting maps of the organic vapor flux are shown, respectively.

[0028] Figure 8 A graph showing the saturation of organic vapor in the exhaust gas from the evaporator as a function of time for sources with various temperature profiles.

[0029] Fig.9A The design of a modular multi-tray sublimation source according to embodiments disclosed herein is presented, where the temperature of the individual trays can be controlled individually.

[0030] Fig. 9B Showing the separation of the spacer region according to the embodiments disclosed herein Fig.9A Stack of discs shown.

[0031] Fig. 10A An example of a flow path through a multi-disc sublimation source mixing a thin layer of fluid contacting a charge of material is shown according to embodiments disclosed herein.

[0032] Fig. 10B Demonstrating the embodiment according to the present disclosure Fig. 10ACurve of the evaporation rate in the source shown in .

[0033] Fig.11 The design of a source unit designed to generate a carrier gas vortex according to embodiments disclosed herein is shown.

[0034] Fig. 12A and 12B The local evaporation rate in the crucible and the flow pattern through the crucible of a source unit with carrier gas swirl according to embodiments disclosed herein are shown, respectively.

[0035] Fig.13 The partial pressure of vapor and the motion of a carrier gas in a vortex evaporation source normal to the plane of the crucible lip are shown according to embodiments disclosed herein.

[0036] Fig.14 Graphs showing saturation of organic vapor in exhaust gas from an evaporation source as a function of time for swirling and non-swirling carrier gas flows according to embodiments disclosed herein.

[0037] Fig.15 Graphs showing vapor saturation in exhaust gas from a vortex evaporation source as a function of time for various siphon designs according to embodiments disclosed herein.

[0038] Fig.16 Graphs showing vapor saturation in exhaust gas from a vortex evaporation source as a function of time for moving and stationary siphons according to embodiments disclosed herein. DETAILED DESCRIPTION

[0039] In general, an OLED comprises at least one organic layer disposed between and electrically connected to an anode and a cathode. When an electric current is applied, the anode injects holes and the cathode injects electrons into the organic layer. The injected holes and electrons each migrate toward the oppositely charged electrode. When electrons and holes are localized on the same molecule, an "exciton" is formed, which is a localized electron-hole pair with an excited energy state. When the exciton relaxes through a light emission mechanism, light is emitted. In some cases, the exciton can be localized on an excimer or an excited complex. Non-radiative mechanisms (such as thermal relaxation) may also occur, but are generally considered undesirable.

[0040] The first OLEDs used emissive molecules that emitted light from a singlet state ("fluorescence"), as disclosed, for example, in US Pat. No. 4,769,292, which is incorporated by reference in its entirety. Fluorescence emission typically occurs in a time frame of less than 10 nanoseconds.

[0041] Recently, OLEDs with emissive materials that emit light from triplet states ("phosphorescence") have been demonstrated. Baldo et al., "Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices", Nature, Vol. 395, 151-154, 1998 ("Baldo-I"); and Baldo et al., "Very high-efficiency green organic light-emitting devices based on electrophosphorescence", Appl. Phys. Lett., Vol. 75, Nos. 3, 4-6 (1999) ("Baldo-II"), which are incorporated by reference in their entirety. Phosphorescence is described in more detail in U.S. Pat. No. 7,279,704, Columns 5-6, which is incorporated by reference.

[0042] Figure 1 An organic light-emitting device 100 is shown. The figure is not necessarily drawn to scale. The device 100 may include a substrate 110, an anode 115, a hole injection layer 120, a hole transport layer 125, an electron blocking layer 130, an emission layer 135, a hole blocking layer 140, an electron transport layer 145, an electron injection layer 150, a protective layer 155, a cathode 160, and a blocking layer 170. The cathode 160 is a composite cathode having a first conductive layer 162 and a second conductive layer 164. The device 100 can be manufactured by depositing the layers in sequence. The properties and functions of these various layers and example materials are described in more detail in US 7,279,704, columns 6-10, which are incorporated by reference.

[0043] More examples of each of these layers are available. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Patent No. 5,844,363, which is incorporated by reference in its entirety. An example of a p-doped hole transport layer is m-MTDATA doped with F4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003 / 0230980, which is incorporated by reference in its entirety. Examples of luminescent and host materials are disclosed in U.S. Patent No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety. An example of an n-doped electron transport layer is BPhen doped with Li at a molar ratio of 1:1, as disclosed in U.S. Patent Application Publication No. 2003 / 0230980, which is incorporated by reference in its entirety. U.S. Patent Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entirety, disclose examples of cathodes comprising a composite cathode having a thin layer of a metal (e.g., Mg:Ag) with an overlying transparent, conductive, sputter-deposited ITO layer. The theory and use of barrier layers are described in more detail in U.S. Patent No. 6,097,147 and U.S. Patent Application Publication No. 2003 / 0230980, which are incorporated by reference in their entirety. Examples of injection layers are provided in U.S. Patent Application Publication No. 2004 / 0174116, which is incorporated by reference in its entirety. A description of protective layers can be found in U.S. Patent Application Publication No. 2004 / 0174116, which is incorporated by reference in its entirety.

[0044] Figure 2 An inverted OLED 200 is shown. The device includes a substrate 210, a cathode 215, an emissive layer 220, a hole transport layer 225, and an anode 230. Device 200 can be manufactured by depositing the layers in order. Because the most common OLED configuration has a cathode disposed above the anode, and device 200 has cathode 215 disposed below anode 230, device 200 can be referred to as an "inverted" OLED. Materials similar to those described with respect to device 100 can be used in the corresponding layers of device 200. Figure 2 An example is provided of how some layers may be omitted from the structure of device 100 .

[0045] Figure 1 and 2The simple layered structures described in are provided by way of non-limiting examples, and it should be understood that embodiments of the present invention may be used in conjunction with various other structures. The specific materials and structures described are exemplary in nature, and other materials and structures may be used. Functional OLEDs may be obtained by combining the various layers described in different ways, or the layers may be omitted entirely based on design, performance, and cost factors. Other layers not specifically described may also be included. Materials other than the specifically described materials may be used. Although many of the examples provided herein describe the various layers as comprising a single material, it should be understood that a combination of materials may be used, such as a mixture of a host and a dopant, or more generally, a mixture. In addition, the layers may have various sublayers. The names given to the various layers herein are not intended to be strictly limiting. For example, in device 200, hole transport layer 225 transports holes and injects holes into emissive layer 220, and may be described as a hole transport layer or a hole injection layer. In one embodiment, the OLED may be described as having an "organic layer" disposed between a cathode and an anode. This organic layer may include a single layer, or may further include, for example, Figure 1 and 2 Multiple layers of said different organic materials.

[0046] Structures and materials not specifically described may also be used, such as OLEDs containing polymeric materials (PLEDs), such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety. By way of another example, an OLED having a single organic layer may be used. OLEDs may be stacked, such as described in U.S. Pat. No. 5,707,745 to Forrest et al., which is incorporated by reference in its entirety. OLED structures may deviate from Figure 1 and 2 For example, the substrate may include angled reflective surfaces to improve out-coupling, such as a mesa structure as described in U.S. Pat. No. 6,091,195 to Forrest et al., and / or a pit structure as described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entirety.

[0047] Unless otherwise specified, any of the layers of the various embodiments may be deposited by any suitable method. For organic layers, preferred methods include thermal evaporation, inkjet (as described in U.S. Pat. Nos. 6,013,982 and 6,087,196, incorporated by reference in their entirety), organic vapor phase deposition (OVPD) (as described in U.S. Pat. No. 6,337,102 to Forrest et al., incorporated by reference in their entirety), and deposition by organic vapor jet printing (OVJP) (as described in U.S. Pat. No. 7,431,968, incorporated by reference in their entirety). Other suitable deposition methods include spin coating and other solution-based processes. Solution-based processes are preferably carried out in nitrogen or an inert atmosphere. For other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding (as described in U.S. Pat. Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entirety), and patterning associated with some of the deposition methods such as inkjet and OVJD. Other methods may also be used. The material to be deposited may be modified to make it compatible with a specific deposition method. For example, branched or unbranched substituents such as alkyl and aryl groups, preferably containing at least 3 carbons, may be used in small molecules to enhance their ability to withstand solution processing. Substituents having 20 or more carbons may be used, and 3 to 20 carbons are a preferred range. Materials having asymmetric structures may have better solution processability than materials having symmetric structures because asymmetric materials may have a lower tendency to recrystallize. Dendritic polymer substituents may be used to enhance the ability of small molecules to withstand solution processing.

[0048] The device manufactured according to the embodiment of the present invention may further optionally include a barrier layer. One purpose of the barrier layer is to protect the electrode and the organic layer from exposure to harmful substances in an environment including moisture, steam and / or gas. The barrier layer can be deposited on a substrate, an electrode, under a substrate, an electrode, or beside a substrate, an electrode, or on any other part (including the edge) of the device. The barrier layer may include a single layer or multiple layers. The barrier layer may be formed by various known chemical vapor deposition techniques, and may include a composition having a single phase and a composition having multiple phases. Any suitable material or material combination may be used for the barrier layer. The barrier layer may be combined with an inorganic compound or an organic compound or both. A preferred barrier layer includes a mixture of a polymeric material and a non-polymeric material, as described in U.S. Patent No. 7,968,146, PCT Patent Application No. PCT / US2007 / 023098, and No. PCT / US2009 / 042829, which are incorporated herein by reference in their entirety. In order to be considered a "mixture", the aforementioned polymeric material and non-polymeric material constituting the barrier layer should be deposited under the same reaction conditions and / or deposited simultaneously. The weight ratio of polymeric material to non-polymeric material can be in the range of 95:5 to 5:95. The polymeric material and non-polymeric material can be produced from the same precursor material. In one example, the mixture of polymeric material and non-polymeric material consists essentially of polymeric silicon and inorganic silicon.

[0049] Devices manufactured according to embodiments of the present invention may be incorporated into a wide variety of electronic component modules (or units), which may be incorporated into a variety of electronic products or intermediate components. Examples of electronic products or intermediate components include display screens, lighting devices (such as discrete light source devices or lighting panels), etc. that can be utilized by end-user product manufacturers. The electronic component module may optionally include drive electronics and / or a power supply. Devices manufactured according to embodiments of the present invention may be incorporated into a wide variety of consumer products, which have one or more electronic component modules (or units) incorporated therein. A consumer product comprising an OLED is disclosed, wherein the OLED includes a compound of the present disclosure in an organic layer in the OLED. The consumer product should include any kind of product containing one or more light sources and / or a certain type of visual display. Some examples of such consumer products include flat panel displays, computer monitors, medical monitors, televisions, billboards, lights for interior or exterior lighting and / or signaling, heads-up displays, fully or partially transparent displays, flexible displays, laser printers, telephones, cell phones, tablet computers, phablets, personal digital assistants (PDAs), wearable devices, laptop computers, digital cameras, video cameras, viewfinders, microdisplays (displays with a diagonal of less than 2 inches), 3-D displays, virtual reality or augmented reality displays, vehicles, video walls comprising multiple displays tiled together, theater or stadium screens, and signage. Various control mechanisms may be used to control devices made according to the present invention, including passive matrices and active matrices. Many of the devices are intended to be used in a temperature range comfortable for humans, such as 18° C. to 30° C., and more preferably at room temperature (20-25° C.), but may be used outside this temperature range (e.g., −40° C. to 80° C.).

[0050] The materials and structures described herein can be applied to devices other than OLEDs. For example, other optoelectronic devices such as organic solar cells and organic photodetectors can employ the materials and structures. More generally, organic devices such as organic transistors can employ the materials and structures.

[0051] [Insert description of OLED embodiment here.]

[0052] In some embodiments, the OLED has one or more features selected from the group consisting of: flexible, rollable, foldable, stretchable, and bendable. In some embodiments, the OLED is transparent or translucent. In some embodiments, the OLED further comprises a layer comprising carbon nanotubes.

[0053] In some embodiments, the OLED further comprises a layer comprising a delayed fluorescent emitter. In some embodiments, the OLED comprises an RGB pixel arrangement or a white plus color filter pixel arrangement. In some embodiments, the OLED is a mobile device, a handheld device, or a wearable device. In some embodiments, the OLED is a display panel having a diagonal of less than 10 inches or an area of ​​less than 50 square inches. In some embodiments, the OLED is a display panel having a diagonal of at least 10 inches or an area of ​​at least 50 square inches. In some embodiments, the OLED is a lighting panel.

[0054] In some embodiments of the emission region, the emission region further comprises a body.

[0055] In some embodiments, the compound can be an emissive dopant. In some embodiments, the compound can generate emission via phosphorescence, fluorescence, thermally activated delayed fluorescence (ie, TADF, also known as E-type delayed fluorescence), triplet-triplet annihilation, or a combination of these processes.

[0056] The OLEDs disclosed herein may be incorporated into one or more of consumer products, electronic component modules, and lighting panels.The organic layer may be an emissive layer, and the compound may be an emissive dopant in some embodiments, while the compound may be a non-emissive dopant in other embodiments.

[0057] The organic layer may also include a host. In some embodiments, two or more hosts are preferred. In some embodiments, the host used may be a) bipolar, b) electron transport, c) hole transport, or d) wide bandgap material that plays a minimal role in charge transport. In some embodiments, the host may include a metal complex. The host may be an inorganic compound.

[0058] Combination with other materials

[0059] The materials described herein as being suitable for use in a particular layer in an organic light-emitting device can be used in combination with a variety of other materials present in the device. For example, the emissive dopants disclosed herein can be used in combination with a wide variety of hosts, transport layers, barrier layers, injection layers, electrodes, and other layers that may be present. The materials described or mentioned below are non-limiting examples of materials that can be used in combination with the compounds disclosed herein, and those skilled in the art can readily consult the literature to identify other materials that can be used in combination.

[0060] Different emissive and non-emissive layers and arrangements disclosed herein may use different materials. Examples of suitable materials are disclosed in U.S. Patent Application Publication No. 2017 / 0229663, which is incorporated by reference in its entirety.

[0061] Conductive dopants:

[0062] The charge transport layer can be doped with a conductivity dopant to substantially change its charge carrier density, which in turn will change its conductivity. The conductivity is increased by generating charge carriers in the matrix material, and depending on the type of dopant, a change in the Fermi level of the semiconductor can also be achieved. The hole transport layer can be doped with a p-type conductivity dopant, and an n-type conductivity dopant is used in the electron transport layer.

[0063] HIL / HTL:

[0064] The hole injection / transport material used in the present invention is not particularly limited, and any compound may be used as long as the compound is generally used as a hole injection / transport material.

[0065] EBL:

[0066] An electron blocking layer (EBL) can be used to reduce the number of electrons and / or excitons that leave the emissive layer. The presence of such a blocking layer in a device can result in substantially higher efficiency and / or longer lifetime than a similar device lacking a blocking layer. In addition, a blocking layer can be used to confine emission to desired areas of the OLED. In some embodiments, the EBL material has a higher LUMO (closer to the vacuum level) and / or a higher triplet energy than the emitter closest to the EBL interface. In some embodiments, the EBL material has a higher LUMO (closer to the vacuum level) and / or a higher triplet energy than one or more of the hosts closest to the EBL interface. In one aspect, the compound used in the EBL contains the same molecule or the same functional group as used in one of the hosts described below.

[0067] main body:

[0068] The light-emitting layer of the organic EL device of the present invention preferably contains at least a metal complex as a light-emitting material, and may contain a host material using the metal complex as a dopant material. Examples of the host material are not particularly limited, and any metal complex or organic compound may be used as long as the triplet energy of the host is greater than the triplet energy of the dopant. Any host material may be used with any dopant as long as the triplet criterion is satisfied.

[0069] HBL:

[0070] A hole blocking layer (HBL) can be used to reduce the number of holes and / or excitons that leave the emissive layer. The presence of such a blocking layer in a device can result in substantially higher efficiency and / or longer lifetime than a similar device lacking a blocking layer. In addition, a blocking layer can be used to confine emission to a desired area of ​​the OLED. In some embodiments, the HBL material has a lower HOMO (further from the vacuum level) and / or a higher triplet energy than the emitter closest to the HBL interface. In some embodiments, the HBL material has a lower HOMO (further from the vacuum level) and / or a higher triplet energy than one or more of the hosts closest to the HBL interface.

[0071] ETL:

[0072] The electron transport layer (ETL) may include a material capable of transporting electrons. The electron transport layer may be intrinsic (undoped) or doped. Doping may be used to enhance conductivity. Examples of ETL materials are not particularly limited, and any metal complex or organic compound may be used as long as it is generally used to transport electrons.

[0073] Charge Generation Layer (CGL)

[0074] In a tandem or stacked OLED, the CGL plays a fundamental role in the performance and consists of an n-doped layer and a p-doped layer for injecting electrons and holes, respectively. Electrons and holes are supplied by the CGL and electrodes. The electrons and holes consumed in the CGL are refilled by electrons and holes injected from the cathode and anode, respectively; then, the bipolar current gradually reaches a steady state. Typical CGL materials include n- and p-conductivity dopants used in the transport layer.

[0075] OLEDs and other devices can be made using a variety of vapor deposition techniques. For example, physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods use an inert carrier gas to deliver a condensable vapor onto a substrate. The carrier gas picks up the vapor in one or more evaporation units upstream of the substrate. Figure 3 A schematic diagram of a general evaporation cell is illustrated in cross-sectional view in FIG. The cell contains an inlet 301 and an outlet 302 for respectively allowing a carrier gas to enter and leave the cell. A charge of condensing material 303 is held in one or more trays or crucibles 304. The charge of material may be solid or liquid. In operation, a charge of condensing material 303 is placed in a container 304. Figure 3The evaporator unit shown in is uniformly heated to a constant temperature. The walls 306 are typically thermally conductive. Heat is provided, for example, by a resistive heater 305 monitored by a thermocouple. The flow path of the carrier gas through the evaporation unit can be designed to maximize the surface area of ​​the material charge bed. This can be done, for example, by separating the material charge between multiple trays and introducing the carrier through a long injector tube 307 so that it must flow across the entire height of the source unit.

[0076] The molar flux j of the dilution vapor at the interface between the material charge and the gas flow depends on four factors: the diffusivity D of the sublimating vapor, the gas flow velocity u , the characteristic headspace L above the material charge and the equilibrium vapor pressure P of sublimation v * . The relationship is shown in Equation 1:

[0077]

[0078] It also depends on P v , the partial pressure of the sublimated vapor in the gas in the region. u and P v * The behavior of a source at any given location can therefore depend on its upstream components. R is the ideal gas constant and T is the temperature. The mass exchange coefficient h is given by Equation 2, where the Nusselt number Nu is a function of both the flow field and the source container geometry:

[0079]

[0080] Saturation of source discharge Θ = (P v / P v * ) is an important figure of merit. The vapor will diffuse into the gas stream until it is saturated (θ=1) for any large interfacial area. However, source size is often limited by design considerations. It is desirable that the source operates at θ close to unity for a wide range of carrier gas flow rates Q and be stable in time. Process variables such as T, Q, and the molar composition of the carrier gas, as well as the geometry of the source container can be optimized to obtain the desired performance. The time dependence of θ increases because the volume of the material charge decreases as it evaporates. This changes the surface area of ​​the charge and the shape of the headspace above it. If j is evenly distributed throughout the vapor charge, then the time dependence decreases.

[0081] A simple source design is described in Figure 4A The carrier gas enters the cell from the left 401, flows through the material charge 402, and exits through the outlet on the right 403. The contour lines 404 are plotted showing θ. It can be seen that the vapor flux is highest along the leading edge 405 of the material charge.

[0082] As a specific example, the carrier gas may flow through the source at 30 seem. Figure 4B Display the vertical axis in mol / m 2 A plot of j in units of cm versus the linear distance x in centimeters downstream of the leading edge of the material charge. Notably, the flux drops off suddenly downstream of the leading edge. Figure 4B The data presented in were generated by numerical simulations, but this source behavior can also be understood analytically. Equation 3 provides Nu near the leading edge of a mass transfer surface in fully developed laminar flow:

[0083]

[0084] The singularity at x=0 corresponds to a region of high but finite flux, due to the absence of vapor in the carrier gas.The flux slows as a diffusion boundary layer of vapor-laden carrier gas forms over the material charge downstream and further slows evaporation.

[0085] The consequence of uneven j is Figure 5A This is evident in FIG, which shows the same source after 61 hours of operation. The material charge has become completely depleted near the crucible front edge 501, moving the front edge of the sublimation zone backwards and reducing the interfacial area. Figure 5B As plotted in , the maximum value 502 of j moves backward and the surface area of ​​the charge decreases. Evaporation of the downstream portion of the charge becomes faster; however, there is not sufficient area for the exiting carrier gas to approach saturation. Figure 6 Θ is plotted on the vertical axis against time t in seconds on the horizontal axis. It can be seen that Θ ≥ 0.90 at 603 when t < 56 hours but drops suddenly at 604 as the source is further depleted. Therefore, in such devices, the source must be replenished to maintain a time-stable output.

[0086] The temperature gradient along the source flow path can be adjusted by adjusting P v * Improve the uniformity along the solid-gas interface j. T and P v * The relationship between is given by Equation 4: Clausius-Colaberron equation:

[0087]

[0088] Coefficient P v0 * and enthalpy of vaporization H v Both depend on the material being vaporized.

[0089] Lowering the temperature at the leading edge of the material charge by ΔT slows down local evaporation and prevents the material source charge from retreating as previously described. Fig. 7AThe temperature curves of the four sources are plotted as a function of position. The vertical axis 701 is the temperature T in K and the horizontal axis is the horizontal position x in cm. The curves ΔT=-40K (702), ΔT=-20K (703), ΔT=0K (704) and ΔT=20K (705) are shown. Figure 7B Plot j versus x of the source at various temperature gradients. For the ΔT=-40K case 706, the evaporation rate is nearly constant over the length of the source. The solid material charge is uniformly consumed, so its surface area remains constant. The flux is uniform but low. The ΔT=-20K case 707 produces an initial flux greater than the -40K case, the flux decreases downstream, but is therefore lower than the following cases. The isothermal source with ΔT=0K (708) evaporates material rapidly from the leading edge of the charge, more rapidly than the previous two cases. Evaporation from its trailing edge is relatively slow. Heating the inlet relative to the downstream portion, so that ΔT=20K 709 produces extremely rapid evaporation from the leading edge and negligible evaporation downstream.

[0090] Figure 8 Curves showing θ as a function of time t for various temperature gradient situations are shown. The ΔT = -40K situation (801) is nearly time independent. Its lower saturation can be overcome by using a larger source with a larger surface area. The ΔT = -20K situation at 802 is intermediate between the ΔT = -40K and ΔT = 0K situations. The ΔT = 0K situation (803) starts with θ close to unity, but the saturation changes rapidly become unacceptable. Finally, the ΔT = 20K situation at 804 shows a more extreme form of the behavior of the ΔT = 0K behavior. The noteworthy behavior of the ΔT = 20K situation is that the vapor flow leaving it is supersaturated, θ>1. The source characteristics are summarized in Table 1, which provides the initial saturation θ (t = 0), and the fraction η of its material charge that the source can deliver before its output saturation is less than 80% of the initial value.

[0091] Table 1

[0092] ΔT(K) <![CDATA[c(0) / c ＊ ]]> η -40 0.566 0.903 -20 0.805 0.876 0 0.996 0.830 20 1.23 0.801

[0093] Therefore, it may be necessary to apply a thermal gradient to the material source unit. Fig.9A A practical implementation of a source unit utilizing a thermal gradient according to embodiments disclosed herein is shown. A charge of material may be stored in one or more crucibles 901, which may be arranged, for example, in depressions stamped into metal disks 902. Each disk may include one or more exhaust ports 903 in fluid communication with the disk below it. The disks may be separated by spacers 904, which are sealed to form a closed flow path above the disks. In this arrangement, a carrier gas flows through the stack of disks in a zigzag pattern, passing through each crucible.

[0094] Fig. 9B A side view of a stack of four trays connected together by a spacer is shown. In this arrangement, the carrier gas enters through the bottom of the lower tray at 905 and exits through the top of the uppermost spacer 906. The trays are held in place by one or more tabs 907 located at each end of the trays. The tabs may contain contacts for heaters and thermocouples, for example, that are integral to the trays. The temperature of each tray may be independently controlled by means of such heaters and thermocouples or other similar mechanisms. For example, each tray may include one or more temperature monitoring devices, such as thermometers, thermocouples, etc., and one or more temperature regulating devices, such as heaters. The temperature of each crucible may be controlled by setting the crucible temperature using a heater, which may be selected based on data provided by a thermometer or thermocouple. The temperature of each crucible may be controlled via an integrated electronic device, such as an integrated processor. Alternatively or additionally, the data from the temperature monitoring device for each crucible may be provided to an external processor, which may then control the heater for each crucible independently of each other heater.

[0095] Can be operated as Figures 9A-9B , such that the upstream disk is at a lower temperature than the downstream disk, e.g., such that each disk is at a higher temperature than the previous disk. During operation, the carrier gas may be preheated to a temperature slightly lower than the temperature of the first disk 908. The first disk then transfers both heat and organic vapor to the carrier gas as the carrier gas flows through the disk. The next disk 909 may be maintained at a higher temperature than the first disk, and the P of the material in the disk may be increased. v * 910. The carrier gas can therefore leave the last plate in a thermal equilibrium with θ close to unity. The thermal gradient along the flow direction evenly distributes heat and mass flux over the surface area. Although a stacked arrangement is shown in FIGS. 9 and 10, it should be understood that other crucible arrangements can be used. For example, the crucibles can be aligned horizontally in series while still maintaining the thermal gradient arrangement as disclosed. More generally, the crucibles can be arranged so that one is located downstream of the other, i.e., as the carrier gas moves through the crucibles of the source unit as disclosed herein, it moves sequentially from the upstream crucible to the downstream crucible. A crucible that is arranged later in the sequence can therefore be described as "downstream" of a crucible that appears earlier in the sequence, regardless of whether the crucibles are stacked, arranged horizontally in series, or arranged in any other arrangement.

[0096] When compared to conventional vapor sources, thermal gradients can improve the stability of the source in several ways. First, evaporation can occur more uniformly above the material surface. Therefore, the change of the material surface slows down over time, and the saturation of the exhaust gas from the source remains more stable over time. Secondly, the carrier gas can be gradually heated as the carrier gas flows through the source. This diffuses the heat load over the entire source and thus reduces the load on the upstream heater. Finally, the time that the material charge can be stored in the source before degradation is often a function of temperature. Maintaining the portion of the material charge at low temperatures can increase the period of time that the source will produce vapor from the high-quality source material. In addition, it is generally expected that a source of higher quality materials will be produced at a given point in its life cycle to provide a better final result. For example, it can be expected that an organic source that provides consistent high-quality materials will produce an OLED with a lifespan higher than the lifespan of those OLEDs formed with inconsistent or lower quality materials.

[0097] The thermal profile within the source can also be changed over time to reduce the temperature exposure of the organic vapor charge overall. For example, the source can start the deposition process after the initial charge, where the downstream disk is heated to the sublimation temperature and the upstream disk is maintained at a significantly lower temperature. The material evaporates rapidly from the hot downstream disk. Before it is exhausted, the disk immediately upstream is heated to the sublimation temperature. The next set of upstream disks is then raised in temperature when the second set of disks is exhausted. This pattern can continue for any length of disk chain. The exhausted disk can be maintained at the sublimation temperature so that the organic vapor does not recondense on it. Before each aliquot of material evaporates, each aliquot of material can be exposed to the sublimation temperature for only a brief period of time. This reduces thermal degradation of the material within the source and can increase the interval over which the source can operate, while also increasing the life of the OLED device prepared using the source.

[0098] In one embodiment, mass transfer in a stacked disk configuration may be further enhanced by flow paths that reverse the flow of carrier gas passing between disks. Fig. 10AAn example configuration of such a source is shown. In this example, the carrier gas inlet 1001 is located at the lower left and the outlet 1002 is located at the upper left. The material charge is stored in a crucible located at the bottom of each of the four straight segments 1003 of the flow path. In this graph, the crucible itself is not shown in the graph, but is represented as a boundary condition. The straight segments are connected by three U-shaped bends. It should be understood that although four segments connected by three U-shaped bends are shown, any number of segments and connections can be used in this example and other examples disclosed herein. A contour map of θ is overlaid on the schematic flow path. This structure causes the carrier gas flow to reverse when it moves from one straight segment to the next segment. For example, a thin layer of carrier gas flow in contact with the material charge in one disk 1005 is located near the top of the head space 1006 of the next disk. The fresh thin layer is brought into contact with the leading edge of the next disk, thereby removing the diffusion boundary layer at its leading edge 1008. The boundary layer reestablishes itself further downstream, but recirculates away from the material charge through the next U-bend. Laminar flow streamlines are provided by dashed lines to guide the eye. More generally, connections such as Fig. 10A The U-bend connection shown in can be referred to as a "reverse connection" between crucibles. Reverse connections as disclosed herein may include other configurations as an alternative or in addition to the U-bend type configuration shown. For example, any twisting, spiral, or other flow path that reverses the flow of a carrier gas as previously disclosed may be used.

[0099] Fig. 10B exhibit Fig. 10A 1014. The arrangement shown in FIG. 1015 shows the normalized vapor flux as a function of the path length (in centimeters) above the material charge measured from the leading edge of the upstream crucible 1011. The length of each crucible is 5 cm. Each discontinuous length of the line reflects the change in mass flux through the length of the disk. The solid line 1012 shows the data for the flip source. Each flip increases j at the leading edge of the next downstream crucible 1013 by effectively resetting x in the Nusselt number equation to 0. The overall downward trend in j at the leading edge crucible is attributed to the downstream average P v increase.

[0100] A comparative case where the crucibles are arranged so that the flow does not tumble is shown by dotted line 1014. The initial evaporation rate at the leading edge of each subsequent crucible is lower and the evaporation rate drops more rapidly than in the tumbling case because evaporation is hindered by the boundary layer established by the upstream crucible.

[0101] Fig.11A vortex source assembly according to an embodiment disclosed herein is shown. In this embodiment, a carrier gas enters through an injection port 1101, which is arranged around a central distribution ring 1102. The injection port 1101 can be in fluid communication with one or more carrier gas sources. During unit operation, the jet of the carrier gas merges into a vortex above a crucible of a vaporizable material 1103 (such as an organic source material for making an OLED, etc.) placed in a material charge carrier. The injector can offset the radius of the circular crucible to give each jet a relatively significant angular momentum around the center of the crucible. Alternatively or additionally, the injector can be angled downward toward the crucible so that the carrier gas more directly impinges on the material charge. The vortex can obtain vapor from the material charge as previously disclosed, and then rise through a flue 1104 at or near the center of the source. The flue can be placed and oriented so that it is parallel to the axis of the vortex, and the material can be moved in a direction away from the material source along the direction. Due to the pressure difference and gas circulation within the unit, the carrier gas can rise through the flue 1104, or the flue can be in fluid communication with a vacuum source. The bottom of the flue can be equipped with a separator 1105 to increase the path length of the streamlines within the vortex and reduce the head space above the material charge. The vortex drives the recirculation unit around the distribution ring.

[0102] like Fig.11 The effect of the in-plane vortex shown is threefold. First, it maximizes the leading edge length of the evaporation interface by introducing the carrier gas along the circumference of the circular crucible. Fig. 12A Show from Fig.11 Contour plot of organic vapor flux for a crucible with a vortex source as shown. The contour values ​​are normalized to the maximum evaporation rate. Evaporation is fastest on the edge of the crucible as shown at 1201, close to the carrier gas injector. This fully utilizes the sharp front of Nu at the leading edge of the evaporation bed.

[0103] Second, the use of in-plane vortices can increase the path length of a given set of carrier gas streamlines following through the source. Evaporation slows down closer to the center of the crucible, as seen at 1202. Fig. 12B Arrow curve showing flow rate in vortex source. As shown, the carrier gas rotates above the crucible as it moves toward the center. The radial velocity 1203 is determined by the mass flow rate. However, the tangential velocity 1204 can be much higher than the radial velocity. This increases the flow rate for a given mass flow rate through the source, and therefore increases Nu.

[0104] Third, eddies create mixing and recirculation zones. These secondary eddies can Fig. 10A1206. Each injector is offset by a constant tangential distance 1208 from a parallel radius 1207.

[0105] Fig.13 The vortex flow pattern along the radial section of the source unit is shown, which illustrates other features of the arrangement. The direction of the carrier gas flow is indicated by arrows. Due to the wide difference in speed between the through flow and the recirculation flow, the arrows only indicate the direction. The standardized vapor concentration is drawn in the contour lines. A wisp of vapor rises upward at the center of the vortex, thereby producing a high concentration zone 1301. The saturation of the exhaust can be increased or maximized by arranging a flue 1302 through which the carrier gas leaves above this zone 1301. Although the main flow is circular, there is a downward flow from the injection ring 1303 toward the crucible 1304. This flow forks when it strikes the material charge 1305. The separator disc 1306 covered by the displacer fairing 1307 can guide the carrier gas flow. A part of the flow moves under the separator towards the siphon 1308 and leaves. Another part 1309 flows radially outward. The outward flowing gas can be sucked into the recirculation unit 1310 driven by the low pressure area inside the vortex. This recirculation may allow the carrier gas to contact the material charge multiple times, thereby potentially increasing saturation.Axis 1311 indicates vessel dimensions in mm, but it is understood that specific dimensions and proportions are provided only as illustrative examples and that other dimensions and proportions may be used without departing from the embodiments disclosed herein.

[0106] Fig.14 Curves are shown that demonstrate other features and benefits of a vortex source as disclosed herein. The behavior of θ with respect to time of the source is plotted, with the injector offset by a radius of 10 mm to create a vortex, or positioned along the radius so that the flow goes directly from the injector to the siphon. The vortex configuration 1401 and the non-vortex case 1402 are plotted for example carrier gas flows of 500 sccm (dashed line) and 1000 sccm (solid line). It can be seen that the vortex improves the mass transfer coefficient between the material charge and the carrier gas, and also increases its temporal stability.

[0107] The vortex source as disclosed herein can also make the saturation of the effluent less dependent on the volumetric gas flow rate through the source unit. The vortex effect is weaker for low flows because the longer residence time of the carrier gas causes it to become saturated with organic vapor. The vortex becomes stronger for high carrier gas flows, offsetting the reduced residence time of the gas with more mixing to increase mass transfer from the condensing material interface. Recirculation of the carrier gas inside the source helps prevent vaporized material accumulation and recondensation in areas of stagnant flow.

[0108] As can be seen from these examples, a vortex source as disclosed herein can improve the lifetime of an OLED formed using the source. This is because the improved recycling can reduce or eliminate areas of organic material that might otherwise foul and degrade prior to printing. Additionally, the improved mass transfer of the organic vapor source can allow it to produce a given saturation of organic vapor at a lower source temperature. This reduces the overall temperature exposure of the source material and reduces the chance of material degradation.

[0109] The presence of a good flow splitter as disclosed herein can also improve the saturation and temporal stability of the exiting flow. For example, Fig.15 The behavior of saturation θ as a function of time (in hours) for each case is shown, in which the siphon with a 32 mm OD separator disk and a 60 ° fairing is replaced by a simple 3 mm OD tube 1501. It also shows a case where the separator plate is retained at 1502 and the fairing above it is removed. As shown, it has been found that the separator plate redirects the streamlines of the flow that is not in contact with the surrounding material charge to perform another transfer and it reduces the effective head space between the vortex vortex gas and the material charge, thereby increasing the saturation of the carrier gas. The separator plate can also provide extremely good time stability after the initial combustion in the about 20 hr stage. If the plate is removed, the 500 sccm case shows a saturation θ that rapidly decreases over time, while the 1000 sccm case shows a θ that passes through the minimum 1503 at about 30 hr. This more complex behavior is attributed to the eddy flow that erodes the material charge in a manner that increases its surface area. The separator can be optimized so that this effect is counteracted by an increase in headspace as the material erodes and θ remains stable in time. A fairing above the separator can improve saturation and temporal stability by reducing dead volume within the source cell.

[0110] The siphon can be moved downward into the crucible to preserve a constant headspace as the material charge in the crucible is withdrawn. This can maintain θ at or near its initial value throughout the life of the material charge and can reduce or eliminate the aging period before stabilizing it. The time behavior of θ for 500 and 1000 sccm carrier gas flows is plotted for the case where the average headspace under the separator is maintained at 3 mm 1601. The best case for a stable flue is plotted for comparison. In actual implementation, the position of the siphon can be controlled by a mechanical actuator. The flue can be lowered as the deposition tool operates, or the material content in the crucible can be measured in situ and maintained at a constant set point. Alternatively, the flue position can be changed instantly by a control loop designed to maintain a constant partial pressure of vapor in the flue gas. The partial pressure can be measured by techniques such as laser induced fluorescence.

[0111] Multiple eddy current sources as disclosed herein may also be connected in series as desired to further increase saturation. If they are operated in series, the cells within the series may be maintained at different steady-state or time-varying temperatures, similar to the multi-disk sources discussed previously. Such source designs are expected to achieve similar lifetime benefits for OLEDs formed by tools equipped with the sources.

[0112] experiment

[0113] For all simulation data presented in this article, the sources were simulated in COMSOL Multiphysics using the physics packages for laminar flow, fluid heat transfer, and dilute material transport. Unless otherwise noted, all simulations assumed an N2 carrier gas at an absolute pressure of 200 Torr and a temperature of 533 K. Sublimation has a P at this temperature. v * =9 Pa. This is the value used in the denominator of Θ. v =79 kJ / mol.

[0114] The linear bed source used in the variable temperature simulations had a 2 mm headspace, a 10 mm width, and a 25 mm length. The crucible was 4 mm deep. The stacked disk case featured four 5×1 cm crucibles connected by a Z-shaped flow path with a 4 mm headspace. Unless otherwise noted, a 30 sccm carrier gas flow was assumed.

[0115] The vortex source consists of a roughly disc-shaped housing with a diameter of 76 mm and a height of 20 mm. A cylindrical crucible 48 mm wide and 4 mm deep sits below it. The injection ring of the vortex source is placed inside the housing. It has a diameter of 50 mm and has 8 evenly placed nozzles. Unless otherwise specified, each injector is offset by a radius of 10 mm and is angled 40° towards the crucible located at the bottom of the source assembly. The ID of the injector is 2 mm. The injection block is placed 9 mm above the crucible lip. The siphon located at the central disc has an inner diameter of 5 mm and a tip located 2 mm above the crucible lip. The crucible is initially filled to a level of 1 mm below its lip.

[0116] The erosion of the material charge and the motion of the siphon were modeled using the deformed geometry package in COMSOL. The mesh deformation was calculated using the volume change of the material charge, which is consistent with the calculated deposition rate at each step. The molar mass of the material charge was assumed to be 500 g / mol and the specific gravity was 1.1.

[0117] It should be understood that the various embodiments described herein are by way of example only, and are not intended to limit the scope of the present invention. For example, other materials and structures may be used to replace many materials and structures described herein without departing from the spirit of the present invention. The present invention as required may therefore include variations of specific examples and preferred embodiments described herein, as will be apparent to those skilled in the art. It should be understood that the various theories about why the present invention works are not intended to be restrictive.

Claims

1. A source unit for providing a material to be deposited via vapor deposition, the source unit comprising: a first material crucible comprising a recess for holding a first material to be deposited via vapor deposition; a first heater configured to set a temperature gradient through the first material crucible; a second material crucible disposed downstream of the first material crucible, the second material crucible comprising: a recess for holding a second material to be deposited via vapor deposition; and a first exhaust port in fluid communication with the first material crucible; and a second heater configured to set a gradient temperature through the second material crucible independently of the gradient temperature through the first material crucible, The first material crucible and the second material crucible are arranged side by side.

2. The source unit according to claim 1, further comprising: a third material crucible disposed downstream of the second material crucible, the third material crucible comprising: a recess for holding a third material to be deposited via vapor deposition; and a second exhaust port in fluid communication with the second material crucible; and A third heater is configured to set a temperature of the third material crucible independently of the temperatures of the first and second material crucibles. The source unit of claim 1 , further comprising the first material.

4. The source unit of claim 2, further comprising the second material and the third material, and wherein the first, second, and third materials comprise the same material. The source unit of claim 3 , wherein the first material is an organic emissive material.

6. The source unit of claim 1, wherein the first exhaust hole comprises a reverse connection between the first material crucible and the second material crucible.

7. The source unit of claim 2, wherein the second exhaust hole comprises a reverse connection between the second material crucible and the third material crucible.

8. The source unit according to claim 2, wherein the second material crucible and the third material crucible are arranged in parallel.

9. The source unit of claim 1, wherein the source unit is configured to maintain a temperature of the first material crucible at a lower temperature than a temperature of the second material crucible during operation of the source unit in a vapor deposition system.

10. The source unit of claim 2, wherein during operation of the source unit in the vapor deposition system, the source unit is configured to maintain a temperature of the second material crucible lower than a temperature of the third material crucible.

11. The source unit of claim 1, wherein the source unit is configured to change the temperature of the first material crucible and the temperature of the second material crucible over time during operation of the source unit in a vapor deposition system.

12. A method for operating an evaporation source unit, the method comprising: directing an inert carrier gas through a first material crucible including a recess for holding a first material to be deposited via vapor deposition; heating the first material crucible to a first gradient temperature; directing the inert carrier gas from the first material crucible through a second material crucible disposed downstream of the first material crucible, the second material crucible comprising: a recess for holding a second material to be deposited via vapor deposition; and a first exhaust port in fluid communication with the first material crucible; and The second material crucible is heated to a second gradient temperature independent of the first gradient temperature, wherein the first material crucible and the second material crucible are arranged in parallel.

13. The method according to claim 12, further comprising: The carrier gas is directed through a reverse connection after directing the carrier gas through the first material crucible and before directing the carrier gas through the second material crucible.

14. An evaporation source unit, comprising: a plurality of carrier gas injection ports arranged around a central interior region of the cell; and A material charge carrier for holding a vaporizable material source; The plurality of carrier gas injection ports are directed toward the material charge carrier at an angle sufficient to form a vortex of carrier gas above the material charge carrier during operation of the evaporation source unit.

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