Method of depositing organic layers in organic light emitting devices

A method of depositing organic layers on a substrate in organic light emitting devices is disclosed. The method uses a donor support which is coated with a transferable coating of an organic donor material selected as one of a plurality of organic materials useful in an organic light emitting device. The donor coating is positioned in transferable relationship with the substrate in an environment of reduced pressure. The donor support is heated to cause the transferable coating of organic donor material to transfer to a position on or over the substrate and to form a layer of the organic material on the substrate.

FIELD OF THE INVENTION 
The present invention relates to methods of making organic light emitting 
devices. 
BACKGROUND OF THE INVENTION 
For the fabrication of organic, light-emitting devices (also referred to as 
electroluminescent devices and, in abbreviation, as EL devices), it is 
important that the thin film preparation method is scaleable to substrates 
of various sizes and particularly to large area substrates for economic 
reasons. Among various fabrication methods, physical vapor deposition has 
been widely used because it is relatively simple and is capable of 
producing highly efficient devices. 
Turning to FIG. 1, which shows a schematic view of a prior art method of 
making organic layers for organic light emitting devices. A substrate 10 
which is to receive an organic layer, is positioned adjacent to an 
aperture mask 12. The aperture mask 12 provides an aperture shown as a 
dimension A over a portion of the substrate 10. An organic material 3 
which is to provide a layer on or over the substrate, is disposed in a 
source crucible 4 which is heated by suitable arrangements such as shown 
heating coils 5. When heat is applied to the crucible 4, the organic 
material vaporizes in a reduced pressure environment, such as in a reduced 
pressure chamber 1 having a pump port 2. The vapor emanates from the 
crucible 4 as schematically indicated by the dotted vapor arrows 3v and 
condenses as a deposited layer 3d, also depicted in dotted outline, on 
portions of the chamber 1, the underside of the aperture mask 12, on the 
substrate 10 through the aperture A in mask 12, on the underside of a 
shutter blade 7 and associated shutter shaft 8, as well as on the surfaces 
of deposition monitors 9a and 9b. 
In order to fabricate highly efficient organic light mitting devices it is 
preferred to sequentially deposit on the substrate 10 a plurality of 
relatively thin (approximately 100-500 .ANG.) organic layers of different 
organic materials, as will be detailed below. Prior to forming each of 
these layers on the substrate, the shutter shaft 8 is rotated such that 
the shutter blade 7 is positioned to shield the substrate 10 until such 
time as is needed to initiate and stabilize the vaporizing of an organic 
material 3 from the source crucible 4, measured by the deposition monitors 
9a, 9b. During this start-up and stabilizing period, the above-mentioned 
layers 3d of organic material are formed within portions of the chamber 1, 
but not on the substrate. Upon opening the shutter blade 7 to the position 
shown in FIG. 1, an organic layer 3d is formed on the substrate, and the 
layers elsewhere in the chamber keep growing in thickness. Such growth of 
layer thickness within the portions of the chamber and its associated 
parts can lead to cracking, flaking or dusting of these layers during 
cycles of pressure reduction (pump-down) and pressure increase (venting) 
of the chamber and during rotation of the shutter between open and closed 
positions. 
It will be appreciated that the generation of these undesirable 
particulates reduces the yield of devices having consistent quality. 
Frequent cleaning of the chamber and associated parts can overcome the 
yield concern, but at the cost of reduced throughput of fabricated 
devices. 
Another disadvantage of this prior art method of depositing organic layers 
in organic light emitting devices is relatively poor utilization of the 
organic material 3 in the source crucible 4, i.e., as little as 
approximately 10-20% of organic material 3 may be utilized to form a layer 
3d on the substrate 10, with 80-90% of the material forming undesirable 
layers elsewhere in the chamber. Since the fabrication of highly efficient 
organic light emitting devices calls for purified, and therefore 
relatively expensive, organic materials, poor material utilization is 
clearly undesirable. 
The aforementioned significant disadvantages are magnified when 
contemplating the fabrication of organic EL devices over relatively large 
area substrates, for example over substrates as large as 30 cm by 30 cm. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved method of 
making organic light emitting devices which obviates the above 
difficulties, provides uniform organic layers over the emitting area of 
such devices, and provides low cost and high quality light emitting 
devices. 
This object is achieved by a method of making an organic light emitting 
device on a substrate which has a plurality of organic layers, the 
improvement wherein at least one of the layers is formed by the steps 
comprising: 
a) providing a transferable coating of organic material on a donor support; 
b) positioning the donor support in transferable relationship with the 
substrate in an environment of reduced pressure; and 
c) heating the donor support to cause the organic material to transfer to a 
position on or over the substrate, whereby a layer of organic material is 
formed on the substrate. 
Advantages 
Advantages of this technique are: excellent utilization of the transferable 
organic material; excellent uniformity of the layer over a large area; 
precise control of the layer thickness; conformal deposition; high 
deposition rate; reduced time at the transfer temperature of the 
transferable material; compact reduced pressure system for large area 
deposition; lower maintenance deposition chamber; capability of multilayer 
deposition from a single donor support source; scalability to large-area 
deposition; continuous feed of transferable material; and minimal control 
for a deposition process that does not require deposition monitoring or a 
complex shutter arrangement. 
Briefly described, the present invention discloses a simple vapor 
deposition method for the production of thin organic layers on a flat 
substrate with excellent uniformity. A feature of this method is to 
provide a coating of an organic material on a donor support as the 
physical vapor deposition source. By positioning the support and the 
substrate in transferable relationship, the organic material previously 
coated on the support is thermally transferred from the donor support to 
form a uniform layer on or over the substrate. The thickness and 
uniformity of the deposited layer is therefore determined by the donor 
coating on the donor support and the degree of transfer of the donor from 
the support to the substrate. 
In practice, the donor support is first provided with a transferable 
coating of an organic donor material thereon by a suitable process. 
Examples of suitable methods for coating the support include solution 
coating, meniscus coating, dip coating, spraying, screen printing, and 
roll-to-roll-coating in a vacuum chamber. These methods are specifically 
designed to produce a uniform coating of a precise thickness on a donor 
support which may be a sheet, a foil or a flexible web. Using any one of 
these methods, a support coated with a predetermined thickness of the 
desired transferable organic donor material can be readily prepared in 
large quantity. For organic light emitting devices, a preferred method for 
the preparation of a donor coating on a flexible donor web support is the 
roll-to-roll vacuum coating because the coating thickness and uniformly on 
the web can be precisely controlled with an accuracy of better than a few 
percent. 
When desired, an aperture mask is positioned adjacent to the substrate on 
which a layer is to be formed. The aperture mask is oriented with respect 
to features or orientation marks on the substrate. The donor support is 
positioned in a transferable relationship with the substrate. The transfer 
of the organic donor material from the coating on the donor support to the 
substrate is then carried out by a thermal process in which the organic 
material is transferred in an environment of reduced pressure to form a 
layer of organic material on the substrate.

It will be understood that the drawings are not to scale and have been 
shown for clarity of illustration. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now to FIG. 2A, which shows a specific arrangement for practice of 
the method in accordance with the present invention. There are provided a 
donor supply roll 30 and a donor return roll 32 which carry a flexible 
donor support 24 having a donor coating 23 of organic material. The donor 
support 24 is advanced from the supply roll 30 and is driven over a 
spindle 34 and another spindle 36 to the donor return roll 32. In a 
position between the spindles 34 and 36 is where the coating of organic 
donor material 23 is transferred from the support 24 to a light emitting 
device substrate 10. The light emitting device substrate 10 can have 
suitably patterned electrically conductive regions (not shown) and 
previously formed organic layers (not shown) on and over the surface 
facing the donor coating 23. If desired, an aperture mask 12 depicted here 
with an aperture dimension A, is positioned adjacent to the substrate 
surface and provided with features or orientation marks (not shown) for 
alignment registration on the substrate. The aperture mask 12 may have a 
plurality of apertures, each of which serves to delineate an area on the 
substrate where an organic layer is to be formed. When an unused portion 
of the donor coating 23 is positioned approximately between the spindles 
34 and 36, and is spaced from the substrate by a distance D, the donor 
coating is in a transferable relationship with the substrate. Heating 
elements 25 are provided on the backside of the donor support at the donor 
transfer position. 
The substrate, aperture mask, donor coating and donor support, the 
spindles, the heating elements, and a heating station 40 are shown as 
being enclosed within a reduced pressure chamber 21 having a pump port 22. 
Prior to actuating the heating elements 25, the chamber 21 is provided with 
an environment of reduced pressure by partial evacuation via the pump port 
22. Alternatively, the entire arrangement depicted in FIG. 2A can be 
placed in a reduced pressure environment. Upon actuating these heating 
elements, the organic material of the donor coating 23 on the donor 
support 24 is heated to a sufficient temperature to vaporize as donor 
vapor 23v and to transfer to form a uniform deposited layer 23d on or over 
the substrate 10 in areas delineated by the aperture mask 12. The transfer 
is schematically indicated by a plurality of dotted arrows 23v, and the 
layer 23d is also depicted in dotted outline. 
In a preferred arrangement, a heating station 40 is provided to preheat the 
donor support 24 prior to its being moved to its transfer position to 
eliminate volatile contaminants such as water vapor from the donor coating 
23. 
The door support 24 with donor coating 23 thereon enters and leaves the 
reduced pressure chamber 21 through suitably designed ports (not shown) 
which are well known to vacuum technologists. Likewise, the aperture mask 
12 is inserted or exchanged through a port of this type. 
It will be appreciated that, in forming an organic layer having a dimension 
A, the spacing D between the transferable donor coating 23 on the donor 
support 24 and the substrate 10 is significantly smaller than the spacing 
B between the source crucible 14 and the substrate 10 of the prior art 
method (see FIG. 1) of making organic layers for organic light emitting 
devices. In addition to the aforementioned advantages of the present 
invention, the smaller spacing D makes it possible to transfer the 
transferable coating of organic donor material from the donor support and 
to form an organic layer on the substrate in an environment of reduced 
pressure, with the reduced pressure being related to the spacing D through 
the mean free path of the organic vapor molecules in a gaseous 
environment. Stated differently, the pressure in the environment of the 
present invention needs to be reduced just sufficiently from atmospheric 
pressure to ensure that the mean free path of vapor molecules of the 
organic materials transferred from the donor coating 23 is at least equal 
to the spacing dimension D if minimal scattering of vapor molecules is 
desired. By contrast, the pressure in the environment of the prior art 
method has to be reduced to a significantly lower value to ensure a mean 
free path of at least equal to the dimension B. In the practice of the 
present invention, the environment of reduced pressure is preferably at a 
pressure value of less than 0.01 Torr during the heating step so that the 
organic material transferred from the donor support forms a uniform 
organic layer on the substrate at a spacing D ranging from about 2 cm to 
about 0.2 cm. If an increased degree of scattering of organic donor vapor 
molecules by residual gases in the chamber can be tolerated, then the 
pressure during the heating step can be increased to a value of less than 
1 Torr. 
The donor support 24 can be made of any of several materials which meet at 
least the following requirements: The donor support must be sufficiently 
flexible and possess adequate tensile strength to tolerate precoating 
steps and roll-to-roll transport of the support in the practice of the 
invention. The donor support must be capable of maintaining the structural 
integrity during the heat-induced transfer step and during any preheating 
steps contemplated to remove volatile constituents such as water vapor. 
Additionally, the donor support must be capable of receiving on one 
surface a relatively thin coating of organic donor material, and of 
retaining this coating without degradation during anticipated storage 
periods of the coated support. Support materials meeting these 
requirements include, for example, metal foils, certain plastic foils 
which exhibit a glass transition temperature value higher than a support 
temperature value anticipated to cause transfer of the transferable 
organic donor materials of the coating on the support, and 
fiber-reinforced plastic foils. While selection of suitable support 
materials can rely on known engineering approaches, it will be appreciated 
that certain aspects of a selected support material merit further 
consideration when configured as a donor support useful in the practice of 
the invention. For example, the support may require a multi-step cleaning 
and surface preparation process prior to precoating with transferable 
organic material. If the support material is a radiation transmissive 
material, the incorporation into the support or onto a surface thereof 
opposing the surface to receive the donor coating, of a 
radiation-absorptive material may be advantageous to more effectively heat 
the donor support and to provide a correspondingly enhanced transfer of 
transferable organic donor material from the support to the substrate, if 
the heating step contemplates using a flash of radiation from a suitable 
flash lamp. 
Heating the donor support to cause the organic donor material to transfer 
to the substrate can be performed by one of several methods known to those 
skilled in this art. For example, the flash-induced heating method 
mentioned above with reference to a radiation transmissive support can 
also be tailored to be effective on opaque supports such as metal foil 
supports. Particular surface preparation of the support surface receiving 
the radiation flash are known to enhance the radiation absorptive 
properties of a metal foil. A metal foil donor support can, of course, be 
heated by suitably arranged rod-type or coil-type heating elements 25 as 
schematically indicated in FIG. 2A. In contrast to the aforementioned 
heating methods using stationary or fixed heating elements or a stationary 
flash lamp, the transfer of the organic donor material 23 from the donor 
support 24 to the substrate 10 can be caused by translating or scanning a 
heat source in proximity to and along the support surface to be heated, 
for example scanning approximately between the spindles 34 and 36. While a 
scanning heat source may increase the total time required to form a layer 
on the substrate 10, a scanning heat source may advantageously reduce 
excessive heating of the substrate surface and any attendant undesirable 
crystallization or aggregation of the layer 23d being formed on the 
substrate. Using a metal foil support as the donor support affords direct 
heating of the foil by applying a source of electrical potential between 
points or zones extending along the support when the donor support with 
the donor coating is in transferable relationship with the substrate. For 
example, if each of the spindles 34 and 36 are electrically conductive but 
electrically insulated from other members of the arrangement in FIG. 2A, 
an electrical potential can be applied between the spindles so as to cause 
an electrical current to flow in the electrically conductive web portion 
between the spindles and to provide resultant Joule heating of the donor 
web. 
Referring now to FIG. 2B, there in shown, in schematic form, an arrangement 
for depositing organic layers in light emitting organic devices, in which 
an electrically conductive donor support 24 (for example, a metal foil 
support) with organic donor coating 23 is heated directly by Joule heating 
through application of an electrical voltage V between contact clamps 27 
and 28 which contact the donor support 24. An ammeter I is used to monitor 
the electrical current flowing through the support 24, and temperature 
sensors (not shown) can be installed to measure the temperature of the 
donor support 24. All other numerals and designations refer to like parts 
and functions as described with reference to FIG. 2A. 
The aperture mask 12 is conveniently fabricated from a metallic foil or 
sheet by micromachining methods well known in this art. Such 
micromachining methods are capable of rendering apertures which can be as 
small as a few micrometers in dimension and, if the aperture mask 12 is to 
contain a plurality of apertures, the distance between adjacent apertures 
can also be as small as a few micrometers. 
Referring now to FIG. 3, there is depicted a schematic plan view of an 
illustrative example of an aperture mask 50 useful in the practice of the 
invention. The mask has a plurality of apertures 51, shown here as each 
aperture 51 being of equal dimensions a and b. The sum of all apertures 
dimensions and all spacings between apertures is designated as A to 
represent the same dimension A as in FIGS. 1, 2A and 2B. 
Also provided are orientation marks 52, sometimes referred to as alignment 
targets. Orientation marks 52 can be apertures through which a directed 
beam of light can pass, or they can be opaque in appearance. In any event, 
the orientation marks 52 on the aperture mask 50 are used to position the 
aperture mask 50 in an oriented relationship with the substrate 10, which 
has a spatially matching or coincident set of orientation marks (not 
shown). Aperture masks defining particular aperture patterns are 
advantageously used in the practice of the invention when an organic layer 
is to be formed in correspondence with a particular aperture pattern. 
The organic materials used in the method of making organic layers in 
organic light emitting devices in accordance with this invention can take 
any of the forms, such as those disclosed in the following commonly 
assigned: Tang U.S. Pat. No. 4,356,429; VanSlyke et al U.S. Pat. No. 
4,539,507; VanSlyke et al U.S. Pat. No. 4,720,432; Tang et al U.S. Pat. 
No. 4,885,211; Tang et al U.S. Pat. No. 4,769,292; Littman et al U.S. Pat. 
No. 5,059,861; VanSlyke U.S. Pat. No. 5,047,687; VanSlyke et al U.S. Pat. 
No. 5,059,862; VanSlyke et al U.S. Pat. No. 5,061,617; and Tang et al U.S. 
Pat. No. 5,294,870; the disclosures of which are here incorporated by 
reference. 
In fabricating efficient organic light emitting devices it is known that 
depositing a plurality of organic layers on a substrate is advantageous. 
Tang et al U.S. Pat. No. 5,294,870, cited above shows in FIG. 7 a 
plurality of organic layers HI, HT, LU, EI which, together, are referred 
to as an organic electroluminescent (EL) medium being disposed between 
electrodes E1 and E2. These organic layers are vapor-deposited, thin films 
comprising in sequence a hole injecting (HI) layer, a hole transporting 
(HT) layer, a luminescent (LU) layer, and an electron injecting (EI) 
layer. The luminescent layer LU will be referred to here as the light 
emitting layer. 
The method in accordance with the present invention is particularly 
advantageous in forming the above-mentioned sequence of organic layers on 
a substrate. For example, the donor support can be precoated in segments 
extending along the support in the support transport direction, with 
segments arranged in spatial sequence to provide a transferable coating of 
organic donor material of HI, HT, LU, and EI in this spatial sequence. 
Each segment of the donor support is then sequentially positioned in 
transferable relationship with the substrate in an environment of reduced 
pressure, followed by heating the respective segment of the donor support 
to cause the respective segment of transferable coating of organic donor 
material to transfer to a position on or over the substrate and to form a 
layer thereon. 
Alternatively, a plurality of donor supply rolls or sheets are prepared by 
precoating each one with a transferable coating of a particular 
composition of organic donor material, such as one of the aforementioned 
materials HI or HT or LU or EI. Each of these donors is then used in an 
arrangement dedicated for depositing an organic layer of that particular 
composition. 
Numerous organic materials, disclosed in the above-cited references, can be 
useful to form the layers HI, HT, LU, and EI on a substrate in accordance 
with the present invention. Selection of particular organic materials is 
influenced, among other considerations, by their ability to provide 
uniform transferable donor coatings on a donor support, and by their 
ability to maintain transferable properties during a storage interval 
between preparation of a coating on the donor support and its deployment 
in the heat transfer step. 
With reference to the light emitting layer, the light emitting properties 
of an organic light emitting device can be improved if the light emitting 
layer contains at least one highly fluorescent organic material. Following 
the teachings of Tang et al U.S. Pat. No. 4,769,292, cited above, the 
present invention contemplates precoating a donor support with an organic 
transferable donor composition comprising an organic light emitting 
material and one or more highly fluorescent organic materials and 
transferring the materials of this composition to form a light emitting 
layer with improved light emitting properties on a substrate. In the 
practice of the invention the highly fluorescent organic materials are 
selected, in one aspect, to transfer from the donor coating on the donor 
support together with the light emitting material so as to provide a light 
emitting layer on the substrate which has a desired composition of light 
emitting and highly fluorescent organic materials and thus having the 
desired improved light emitting properties. 
EXAMPLES 
Example 1 
This example describes the pre-coating of a metal foil donor sheet with an 
organic hole transporting donor material (NPB), and the transfer of the 
donor coating to form a layer on a silicon substrate. 
The donor sheet was a 0.005 inch tantalum sheet. The donor sheet was then 
coated with approximately 1000 .ANG. of NPB 
(4,4'-bis-N-(1-naphthyl)-N-phenylamino!-bi-phenyl) using standard thermal 
evaporation at 1*10.sup.-5 Torr from a graphite source at a source to 
sheet distance of approximately 11-12 inches. A bare silicon wafer was 
then positioned as a substrate about 1 cm from the NPB coated surface of 
the donor sheet, which was resistively heated with a current of 
approximately 40 amps for 1.5-2 minutes. This produced a temperature of 
207.degree. C. at the donor sheet which was sufficiently high for complete 
transfer of the NPB from the donor sheet to the silicon substrate. The 
donor sheet was then removed and inspected under UV light. No fluorescence 
was observed, indicating complete transfer of the organic material. 
A uniform layer of NPB was formed over the surface of the silicon 
substrate. The thickness of the layer was 540 .ANG., and the layer was 
formed over a substrate area of approximately 10 cm.sup.2 due to the 
non-directional transfer of material from the donor sheet to the substrate 
(no aperture mask was used adjacent to the substrate during the transfer). 
Example 2 
This example describes the pre-coating of a metal foil donor sheet with an 
organic light emitting donor material (AlQ), and the transfer of the donor 
coating to form a layer on a silicon substrate. 
The experiment in Example #1 was repeated except 1000 .ANG. of AlQ 
(Tris(8-quinolinolato-Nl,08)-aluminum) was coated onto the donor sheet. A 
bare silicon wafer was then positioned as a substrate about 1 cm from the 
AlQ coated surface of the donor sheet, which was resistively heated with a 
current of approximately 40 amps for 1.5-2 minutes. This produced a donor 
sheet temperature of 222.degree. C. which was sufficiently high for 
complete transfer of the AlQ from the donor sheet to the substrate. 
A uniform layer of AlQ was formed over the surface of the silicon 
substrate. The thickness of the layer was 570 .ANG., and the layer was 
formed over a substrate area of approximately 10 c.sup.m2 due to the 
non-directional transfer of material from the donor sheet to the 
substrate. 
Example 3 
This examples describes the fabrication of two-layer organic light emitting 
devices by the prior art method of forming organic layers (see FIG. 1). 
An ITO coated glass substrate was rigorously cleaned by scrubbing followed 
by a two minute oxygen plasma treatment at (500 mTorr oxygen and 500 watts 
RF). The glass substrate was then loaded into a vacuum deposition system 
which was evacuated to about 1*10.sup.-5 Torr before deposition of the 
organic layers. 
Organic layer #1 
A 600 .ANG. NPB hole transporting layer was deposited onto the ITO coated 
glass by standard thermal deposition from a graphite source. The graphite 
source temperature was controlled at 285.degree. C. which resulted in a 
deposition rate of 5-7 .ANG./s. The source to substrate distance was about 
25 cm. 
Organic Layer #2 
A 750 .ANG. AlQ light emitting layer was deposited by standard thermal 
deposition from a graphite source. The temperature of the graphite source 
was controlled at 320.degree. C. which resulted in a deposition rate of 
4-5 .ANG./s. The source to substrate distance was about 25 cm. 
Metal Layer 
The vacuum system was then vented and the substrates were aligned to an 
aperture mask used to define the electrode area. The vacuum system was 
pumped down to 1*10-5 and a 2000 .ANG. magnesium: silver cathode was 
deposited over layer 2 through the apertures in the mask using standard 
thermal evaporation from two independently controlled sources. The ratio 
of Mg to Ag is 10:1 by volume. The source to substrate distance was about 
300 cm. 
Example 4a 
This example describes the fabrication of two-layer organic light emitting 
devices by the inventive method of forming organic layers. 
An ITO coated glass substrate was cleaned as detailed in Example 3. 
A donor sheet of the hole transporting donor material (NPB) was prepared as 
described in Example 1. The thickness of NPB deposited onto the donor 
sheet was 1000 .ANG.. The ITO coated substrate was positioned under the 
donor sheet, and the NPB was then transferred to the ITO substrate as 
described in Example 1. The substrate was then moved, and a 1000 .ANG. AlQ 
donor sheet was prepared as described in Example 2 The substrate was 
repositioned under the donor sheet, and the AlQ coating was then 
transferred as described in Example 2, to form a light emitting layer on 
the substrate. A magnesium:silver cathode was deposited over the AlQ layer 
by the method described in Example 3. 
Example 4b 
Example 4a was repeated, except that a coating of 1300 .ANG. thickness of 
NPB was prepared as the hole transporting donor material, and a coating of 
1300 .ANG. thickness of AlQ was prepared as the light emitting donor 
material. 
Example 4c 
Example 4a was repeated, except that a coating of 1600 .ANG. thickness of 
NPB was prepared as the hole transporting donor material, and a coating of 
1600 .ANG. thickness of AlQ was prepared as the light emitting donor 
material. 
Table 1 
Table 1 summarizes, for the two-layer light emitting devices of Examples 3 
and 4a-c, the coating thickness values of the respective donor coatings 
and the layer thickness values of the respective layers formed on the 
substrates. Also provided are measures of operating performance of the 
devices at an operating current density of 20 mA/cm.sup.2 : the operating 
voltage applied to each device to obtain the stated current density, and 
an indicator of the efficiency of light emission expressed in terms of 
light output in Watt (W)/current flowing through the device in Amperes 
(A). 
TABLE 1 
__________________________________________________________________________ 
NPB NPB AlQ 
Thickness .ANG. 
Thickness .ANG. 
Thickness .ANG. 
AlQ Thickness 
Efficiency 
(Donor 
(ITO (Donor 
.ANG.(ITO 
Voltage 
(W/A) 
Example 
Sheet) 
Substrate) 
Sheet) 
Substrate) 
at 20 mA/cm.sup.2 
__________________________________________________________________________ 
3 NA 600 NA 750 8.7 0.027 
4a 1000 550 1000 580 9.1 0.029 
4b 1300 700 1300 750 8.5 0.029 
4c 1600 850 1600 900 8.0 0.023 
__________________________________________________________________________ 
It is apparent from the above data that the operating performance of the 
devices of Examples 4a-c, prepared by the method in accordance with the 
present invention, is comparable to the operating performance of the 
device of Example 3 which was prepared by the prior art method. 
The invention has been described in detail, with particular reference to 
certain preferred embodiments thereof, but it will be understood that 
variations and modifications can be effected within the spirit and scope 
of the invention. 
______________________________________ 
Parts List 
______________________________________ 
1 reduced pressure chamber (prior art) 
2 pump port 
3 organic material 
3v vapor of organic material 
3d deposited layers 
4 source crucible 
5 heating coils 
7 shutter blade 
8 shutter shaft 
9a deposition monitor 
9b deposition monitor 
10 substrate 
12 aperture mask (single aperture A) 
21 reduced pressure chamber 
22 pump port 
23 coating of organic donor material 
23v donor vapor 
23d deposited donor layer 
24 donor support 
25 heating elements 
27 contact clamp 
28 contact clamp 
30 donor supply roll 
32 donor return roll 
34 spindle 
36 spindle 
40 heating station 
50 aperture mask (plurality of apertures) 
51 apertures 
52 orientation marks 
______________________________________