US 2023/0280417 Al

compounds such as radical scavengers, getter materials, or
antioxidants that aim to increase the sensor’s lifetime by
preventing chemical degradation of organic compounds that
compromise the MFS 100 due to environmental influences.

[0017] In one embodiment, the MFS 100 is operated in the
following manner, following FIG. 2. Current [1 is applied at
contacts 6 and 8 to inject electrons and holes which produce
photons in OLED 7 (comprising subparts 7a-7c). The num-
ber of photons produced, and therefore the light generated
by the OLED 7, is modulated by the external magnetic field.
The orientation of the sensor with respect to the direction of
the external magnetic field does not impact the OLED
output. Photons produced by the process described above
are detected at OPD 3 (comprising subparts 3a-3c) follow-
ing the photon path indicated by an arrow and labeled as
“Photon,” and the resulting hole and electron current 12
produced from absorbing the photon in OPD 3 is then
extracted using contacts 2 and 4. The magnitude of the
current output I2 from the OPD 3 is referenced to a cali-
bration for the sensor which indicates the external magnetic
field strength.

[0018] The Hall effect sensor is currently a commonly
used MFS. Unlike the subject invention, the Hall effect
sensor is constructed of rigid material which is not printable.
The solubility of the materials used to make the MFS that is
the subject of this invention allows this sensor to be printed
as opposed to being produced through the standard lithog-
raphy process.

[0019] Printed electronics can be integrated into a wider
variety of substrates, such as plastics and paper, and allow
for broader accessibility of repeatable circuit board manu-
facturing, allowing for smaller scale development for indi-
vidual users and small businesses, similar to the opportuni-
ties presented by 3D printing. Printed electronics are
projected to be used more widely in conjunction with
technology associated with the Internet of Things.

[0020] The subject invention, however, promises to pro-
vide a solution to the current problem of integrating MFS
technology into a larger variety of objects, such as fabrics
and curved surfaces, which will require electronics that are
flexible and capable of conforming to surfaces with various
contours, as well as being printable.

[0021] While one or more embodiments have been shown
and described, modifications and substitutions may be made
thereto without departing from the spirit and scope of the
invention. Accordingly, it is to be understood that the present
invention has been described by way of illustrations and not
limitation, Embodiments herein can be used independently
or can be combined.

[0022] All ranges disclosed herein are inclusive of the
endpoints, and the endpoints are independently combinable
with each other. The ranges are continuous and thus contain
every value and subset thereof in the range. Unless other-
wise stated or contextually inapplicable, all percentages,
when expressing a quantity, are weight percentages. The
suffix (s) as used herein is intended to include both the
singular and the plural of the term that it modifies, thereby
including at least one of that term (e.g., the colorant(s)
includes at least one colorants). Option, optional, or option-
ally means that the subsequently described event or circum-
stance can or cannot occur, and that the description includes
instances where the event occurs and instances where it does

Sep. 7, 2023

not. As used herein, combination is inclusive of blends,
mixtures, alloys, reaction products, collection of elements,
and the like.
[0023] As used herein, a combination thereof refers to a
combination comprising at least one of the named constitu-
ents, components, compounds, or elements, optionally
together with one or more of the same class of constituents,
components, compounds, or elements.

[0024] All references are incorporated herein by reference.
[0025] The use of the terms “a,” “an,” and “the” and
similar referents in the context of describing the invention
(especially in the context of the following claims) are to be
construed to cover both the singular and the plural, unless
otherwise indicated herein or clearly contradicted by con-
text. It can further be noted that the terms first, second,
primary, secondary, and the like herein do not denote any
order, quantity, or importance, but rather are used to distin-
guish one element from another. It will also be understood
that, although the terms first, second, etc. are, in some
instances, used herein to describe various elements, these
elements should not be limited by these terms. For example,
a first current could be termed a second current, and,
similarly, a second current could be termed a first current,
without departing from the scope of the various described
embodiments. The first current and the second current are
both currents, but they are not the same condition unless
explicitly stated as such.

[0026] The modifier about used in connection with a
quantity is inclusive of the stated value and has the meaning
dictated by the context (eg., it includes the degree of error
associated with measurement of the particular quantity). The
conjunction or is used to link objects of a list or alternatives
and is not disjunctive; rather the elements can be used
separately or can be combined together under appropriate
circumstances.

1. A magnetic field sensor, the magnetic field sensor
comprising:

a substrate onto which the magnetic field sensor is

applied;

an organic photodetector; and

an organic light emitting diode;

wherein the organic photodetector further comprises a

hole extraction/electron blocking layer and an electron
extraction/hole blocking layer;

wherein the organic light emitting diode further comprises

a hole injection/electron blocking layer and an electron
injecting/hole blocking layer; and

wherein at least one of the organic photodetector and the

organic light emitting diode is magnetically isotropic.

2. The magnetic field sensor of claim 1, wherein the
substrate is rigid.

3. The magnetic field sensor of claim 1, wherein the
substrate is flexible.

4. The magnetic field sensor of claim 1, wherein the hole
extraction/electron blocking layer, the electron extraction/
hole blocking layer, the hole injection/electron blocking
layer, and the electron injecting/hole blocking layer are all
discrete, separate layers.

5. The magnetic field sensor of claim 1, wherein the hole
injection/electron blocking layer or the electron injecting/
hole blocking layer of the organic light emitting diode is the
same layer as the hole extraction/electron blocking layer of
the organic photodetector.


US 2023/0280417 Al

THIN FILM MAGNETIC FIELD
MAGNITUDE SENSOR

CROSS REFERENCE TO RELATED
APPLICATIONS

[0001] This application claims the benefit of U.S. Provi-
sional Patent Application Ser. No. 63/315,474 (filed Mar. 1,
2022), which is herein incorporated by reference in its
entirety.

[0002] This invention was made with United States Gov-
ernment support from the National Institute of Standards and
Technology (NIST), an agency of the United States Depart-
ment of Commerce. The Government has certain rights in
this invention.

[0003] This patent disclosure may contain material that is
subject to copyright protection. The copyright owner has no
objection to the facsimile reproduction by anyone of the
patent document or the patent disclosure as it appears in the
US. Patent and Trademark Office patent file or records, but
otherwise reserves any and all copyright rights.

Brief Description.

[0004] Disclosed is a novel, all organic magnetic field
sensor comprising an organic light emitting diode (OLED)
and an organic photodetector (OPD). The sensor function is
believed to be driven by the large magneto-electrolumines-
cence (MEL) of an OLED, but the function of the present
invention is not limited to this belief. In certain embodi-
ments, the OPD is based on a solution processed organic
absorber layer. In other embodiments, similar structures may
be fabricated using sequential sublimed or thermally evapo-
rated thin films. In certain embodiments, the OLED and
OPD of the invention are separated from each other by a thin
dielectric spacer layer. In other embodiments, the dielectric
spacer layer is not required.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The following description cannot be considered
limiting in any way. Various objectives, features, and advan-
tages of the disclosed subject matter can be more fully
appreciated with reference to the following detailed descrip-
tion of the disclosed subject matter when considered in
connection with the following drawings, in which like
reference numerals identify like elements.

[0006] FIG. 1 shows a cross-sectional and perspective
view of a magnetic field sensor, according to some embodi-
meats.

[0007] FIG. 2 shows a scheme for operation of a magnetic
field sensor, according to some embodiments.

DETAILED DESCRIPTION

[0008] A detailed description of one or more embodiments
is presented herein by way of exemplification and not
limitation,

[0009] It has been discovered that a novel magnetic field
sensor (MFS) may be created with an organic light emitting
diode (OLED) made from an organic semiconductor mate-
rial and an organic photodetector (OPD) built directly on top
(or below) of the OLED, wherein either the OLED or the
OPD is made from an oriented molecular or polymer organic
semiconductor material with strong magnetic anisotropy,
and which material has a magneto-resistive or magneto-
electroluminescent signal that varies with the directionality

Sep. 7, 2023

and magnitude of a magnetic field. When electricity is
applied to the MFS, the OLED outputs light which is
measured as current at the OPD. The current output of the
OPD may then be measured to determine the magnetic field
strength in reference to a calibration curve. Changes to the
output current is used to detect the external magnetic field
direction and magnitude. It is believed that the MFS uses the
magnetic dependence of optical signals (luminescence) to
measure a magnetic field by means of an OLED and OPD
acting together, although the present invention is not limited
to this proposed mechanism.

[0010] The MFS of this invention features a magnetically
isotropic layer to allow for measuring only the magnitude of
the external magnetic field without regard to magnetic field
direction. This allows the MFS to detect field magnitude
without regard to the orientation of the magnetic field, which
can be useful if the MFS is mounted on a flexible surface
where the orientation of the device may not be controlled
and would cause uncertainty in measurements.

(0011] In an embodiment, with reference to FIG. 1 and
FIG. 2, includes:

[0012] A magnetic field sensor (MES) 100 is fabricated on
top of a rigid or flexible substrate 1 to support the sensor.
The main components of the sensor are the organic photo-
detector (OPD) 3 (comprising of subparts 3a-3c) and
organic light emitting diode (OLED) 7 (comprising subparts
7a-Tc) layer stacks. OPD 3 further comprises a hole extrac-
tion/electron blocking layer 3a and an electron extraction/
hole blocking layer 3c sandwiching the active layer, OPD
absorber 3b, OLED 7 further comprises a hole injection/
electron blocking layer 7¢ and an electron injecting/hole
blocking layer 7a sandwiching the active layer, OLED
emitter 7b, The depicted order of 3a-3c and 7a-7c can be
inverted depending on the architecture of the OLED/OPD
and processing requirements. Individually, the hole or elec-
tron injection and electron blocking layer can be compro-
mised of one or several layers, and this is also the case for
the electron injection and hole blocking layer.

[0013] Layers compromising the OPD stack 3 and OLED
stack 7 can be processed via various methods, including but
not limited to: physical vapor deposition (PVD); chemical
vapor deposition (CVD); and solution deposition techniques
(spin-coating, slot-die-coating, spray-coating, etc). The pro-
cess of injecting charge carriers to the OLED is accom-
plished through a back contact 8 and an optically semitrans-
parent or transparent front contact 6 electrically coupled to
the OLED layer stack 7.

[0014] The process of extracting charge carriers/current
due to light detected in the OPD 3 is accomplished through
a front contact 2 and optically semi-transparent or transpar-
ent back contact 4 electrically coupled to the OPD layer
stack 3

[0015] The OLED and OPD layer stacks are separated by
an optional, optically transparent spacer layer 5 which
modulates the electrical coupling between the OLED stack
7 and OPD stack 3, and which also acts as an optical spacer
layer that allows for optimization of light outcoupling of the
OLED stack 7 into the OPD stack 3 via optical interference.
Optically transparent spacer layer 5 may not be required in
optimized sensor structures.

[0016] The MFS 100 is optionally encapsulated by an
insulating layer 9 that protects the sensor from mechanical
and environmental influences. The encapsulation can be
either rigid or flexible and might incorporate stabilizing


US 2023/0280417 Al

6. The magnetic field sensor of claim 1, wherein the hole
injection/electron blocking layer or the electron injecting/
hole blocking layer of the organic light emitting diode is the
same layer as the electron extraction/hole blocking layer of
the organic photodetector.

7. The magnetic field sensor of claim 1, further compris-
ing:

a back contact and an optically semitransparent or trans-
parent front contact electrically coupled to the organic
light emitting diode; and

a front contact and an optically semi-transparent or trans-
parent back contact electrically coupled to the organic
photodetector.

8. The magnetic field sensor of claim 7, wherein the
organic light emitting diode and the organic photodetector
are separated by an optically transparent spacer layer.

9. The magnetic field sensor of claim 1, further compris-
ing an insulating layer encompassing the organic light
emitting diode and the organic photodetector.

10. The magnetic field sensor of claim 9, wherein the
insulating layer further comprises radical scavengers, getter
materials, or antioxidants.

11. A method for detecting the magnitude of an external
magnetic field, the method comprising:

Sep. 7, 2023

exposing a magnetic field sensor comprising an organic
light emitting diode and an organic photodetector to an
external magnetic field;

applying current through a first set of electrical contacts to

the organic light emitting diode, producing photons;
and
detecting the photons with the organic photodetector;
wherein the organic photodetector on detection of the
photons produces a current which is extracted through
a second set of electrical contacts;

wherein the number of photons produced by the organic
light emitting diode is modulated by a magnitude of the
external magnetic field; and

wherein the magnitude of the current output from the

second set of electrical contacts is reflective of the
magnitude of the external magnetic field.

12. The method of claim 11, wherein the magnetic field
sensor has been calibrated such that, for a known current
input to the first set of electrical contacts, the current output
from the second set of electrical contacts allows a measure-
ment of the magnitude of the external magnetic field.

+ ke ee


as) United States
a2 Patent Application Publication 1) Pub. No.: US 2023/0280417 A1

Gundlach et al.

US 20230280417A1

(43) Pub. Date: Sep. 7, 2023

(54)

(71)

(72)

(21)

(22)

(60)

THIN FILM MAGNETIC FIELD
MAGNITUDE SENSOR

Applicant: Government of the United States of
America, as represented by the
Secretary of Commerce, Gaithersburg,
MD (US)

Inventors: David James Gundlach, Montgomery
Village, MD (US); Emily Geraldine
Bittle, Bethesda, MD (US); Sebastian
Engmann, Gaithersburg, MD (US)

Appl. No.: 18/116,217
Filed: Mar. 1, 2023

Related U.S. Application Data

Provisional application No. 63/315,474, filed on Mar,
1, 2022

Publication Classification
Int. Cl.
GOIR 33/032
US. Cl.
CPC .....

G1)
(62)

(2006.01)

GOIR 33/032 (2013.01)

(7) ABSTRACT

Anovel magnetic field sensor (MFS) may be created with an
organic light emitting diode (OLED) made from an organic
semiconductor material and an organic photodetector (OPD)
built directly on top (or below) of the OLED, wherein one
layer is made from a magnetically isotropic material, and
which material has a magneto-resistive or magneto-elec-
troluminescent signal that varies with the magnitude of a
magnetic field to allow for measuring only the magnitude of
the external magnetic field without regard to magnetic field
direction.



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