US 2023/0280418 Al

photons. Photons are then absorbed in layer 5 which pro-
duces electrons and holes in response. The electrons and
holes modulate the current detected at 12, as collected from
contacts 4a and 4. The final current is amplified by apply-
ing a voltage to contact 2 in the three-terminal example of
the MFS 200. The final signal can be referenced to a
calibration curve to determine the direction and amplitude of
the external magnetic field, shown in two directions a and b.
[0018] In current applications, when direction and mag-
nitude of a magnetic field are to be measured, it is typical to
use an integrated set of three Hall sensors. By using the
optical output or light detection response of an oriented
molecular or polymer film to detect magnetic fields with an
integrated stack of OLED and OPD, this invention allows
for the novel use of a single sensor using optical signals to
measure magnetic field magnitude and orientation.

[0019] Use ofa single MFS for magnetic field magnitude
and orientation measurement cuts down on the power usage
compared to the use of three integrated Hall sensors which
are now the industry standard and in widespread use, for
example, in smart phone technology. In the case of smart
phone applications, the use of a single MFS would translate
to longer battery life.

[0020] Further, 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 lithography process. 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 manufacturing, allowing for smaller scale
development for individual users and small businesses,
similar to the opportunities presented by 3D printing.
Printed electronics are projected to be used more widely in
conjunction with technology associated with the Internet of
Things.

[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
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.

Sep. 7, 2023

[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 (¢.g., 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;

an organic light emitting diode;

wherein the organic photodetector further comprises an
insulating dielectric layer and a metal gate electrode;

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 a magnetic field sensi-
tive semiconductor comprised of materials including
but not limited to: single crystal semiconductors,
aligned polymer films, and aligned small molecule
films.

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, further compris-
ing:

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

5. The magnetic field sensor of claim 1, further compris-
ing a set of contacts electrically coupled to the organic
photodetector.

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

7. The magnetic field sensor of claim 6, wherein the
insulating layer further comprises radical scavengers, getter
materials, or antioxidants.

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


US 2023/0280418 Al

THIN FILM MAGNETIC FIELD VECTOR
SENSOR

CROSS REFERENCE TO RELATED
APPLICATIONS

[0001] This application claims the benefit of U.S. Provi-
sional Patent Application Ser. No. 613/315,475 (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
oriented layer to allow for measuring of the direction of the
external magnetic field in addition to its magnitude. Direc-
tion of field is used to align sensors in applications such as
smart phones to determine the direction with respect to the
Earth’s magnetic field for GPS and other features.

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

[0012] In one embodiment, a magnetic field sensor (MFS)
200 using an OLED 8 (comprising subparts 8a-8¢) built
directly on top of an OPD (comprising parts 2-5), where the
OPD is demonstrated as a three-terminal transistor (two-
terminal OPDs are also possible and contemplated within
the scope of this invention). A substrate 1 supports the
sensor, and may be composed of flexible or rigid materials.
The main components of the sensor are the OLED 8a-8c and
the OPD 2-5. The OLED 8 consists of an emitter layer 8b
surrounded by a hole injection/electron blocking layer 8a
and an electron injecting/hole blocking layer 8c. The OLED
8 and OPD 2-5 are separated by an electrically insulating
layer 6. The OPD is demonstrated here as a transistor made
of a light sensitive semiconductor 5, metal electrodes for
charge injection 4a and extraction 46, a metal gate electrode
2, and an insulating dielectric layer 3.

[0013] In one embodiment, the oriented, magnetic field
sensitive semiconductor must be placed in either layer 8b or
5 and is comprised of materials including but not limited to:
single crystal semiconductors, aligned polymer films, and
aligned small molecule films.

[0014] In one embodiment, the oriented magnetic field
sensitive semiconductor may be made by various processes,
including but not limited to: standard crystallization tech-
niques; blade coating; stretch alignment; and physical vapor
deposition. Layers 7 and 9 are metal electrodes used to
electrically drive the OLED, with layer 7 being fully trans-
parent or semi-transparent to the light generated in the
OLED. Layer 10 is an encapsulation layer to protect the
sensor from environmental influences.

[0015] In one embodiment, the encapsulation layer 10 can
be either rigid or flexible and might incorporate stabilizing
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 200 due to environmental influences.
[0016] In one embodiment, layers compromising the OPD
stack 2-5 and OLED stack 8a-8¢ 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).

[0017] In one embodiment, the MFS 200 is operated in the
following manner, following FIG. 2. Current is applied at [1
to inject holes and electrons into layer 8 which then produces


US 2023/0280418 Al

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 at least one of the organic photodetector and the
organic light emitting diode is a magnetic field sensi-
tive semiconductor comprised of materials including
but not limited to: single crystal semiconductors,
aligned polymer films, and aligned small molecule
films;

wherein the number of photons produced by the organic

light emitting diode is modulated by a magnitude of the
external magnetic field;
wherein the magnitude of the current output from the
second set of electrical contacts is reflective of the
magnitude of the external magnetic field; and

wherein the current output from the second set of elec-
trical contacts is sensitive to the orientation of the
magnetic field sensor within the external magnetic
field.

9. The method of claim 8, wherein the magnetic field
sensor further comprises an insulating dielectric layer and a
metal gate electrode.

10. The method of claim 9, wherein the current output
from the second set of electrical contacts is amplified by the
application of a voltage to the metal gate electrode.

11. The method of claim 8, 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.

12. The method of claim 10, wherein the magnetic field
sensor has been calibrated such that, for a known current

Sep. 7, 2023

input to the first set of electrical contacts and a known
voltage applied to the metal gate electrode, the current
output from the second set of electrical contacts allows a
measurement of the magnitude of the external magnetic
field.
13. A method for detecting a vector of an external
magnetic field, the method comprising:
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 at least one of the organic photodetector and the
organic light emitting diode is a magnetic field sensi-
tive semiconductor comprised of materials including
but not limited to: single crystal semiconductors,
aligned polymer films, and aligned small molecule
films;
wherein the number of photons produced by the organic
light emitting diode is modulated by a magnitude of the
external magnetic field;
wherein the magnitude of the current output from the
second set of electrical contacts is reflective of the
magnitude of the external magnetic field;
wherein the current output from the second set of elec-
trical contacts is sensitive to the orientation of the
magnetic field sensor within the external magnetic
field; and
wherein the direction and magnitude of the external
magnetic field is determined by reference to a calibra-
tion curve for a known current input to the first set of
electrical contacts and a known voltage applied to the
metal gate electrode.

+ ke ee


as) United States
a2 Patent Application Publication i) Pub. No.: US 2023/0280418 A1

Bittle et al.

US 20230280418A1

(54)

(71)

(72)

2)
(22)

(60)

THIN FILM MAGNETIC FIELD VECTOR
SENSOR

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

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

Appl. No.: 18/116,274

Filed: Mar. 1, 2023

Related U.S. Application Data

Provisional application No. 63/315,475, filed on Mar,
1, 2022

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

(51) Int. Ch

GOIR 33/032 (2006.01)

HIOK 39/34 (2006.01)
(52) US. CL

CPC vases GOIR 33/032 (2013.01); HIOK 39/34

(2023.02)

(57) 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 at
least one layer is made from an oriented molecular or
polymer organic semiconductor material with strong mag-
netic anisotropy, and which material has a magneto-resistive
or magneto-electroluminescent signal that varies with the
magnitude and direction of a magnetic field to allow for
measuring the vector of the external magnetic field.



Patent Application Publication Sep. 7, 2023 Sheet 1 of 2 US 2023/0280418 Al



Patent Application Publication Sep. 7, 2023 Sheet 2 of 2 US 2023/0280418 Al

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