Transient organic electronic devices

Abstract

Herein disclosed is a water-degradable conjugated polymer material comprising: a semiconducting polymer; and a crown ether, wherein the crown ether resides in an interstitial region of the semiconducting polymer, wherein the interstitial region is defined by polymer chains of the semiconducting polymer. A method for forming the water-degradable conjugated polymer material, and devices including the water-degradable conjugated polymer material, are also disclosed herein. No suitable figure to be published with abstract

Description

TRANSIENT ORGANIC ELECTRONIC DEVICESCross-Reference to Related Application

[0001] This application claims the benefit of priority of Singapore Patent Application No. 10202401341R, filed 14 May 2024, the content of it being hereby incorporated by reference in its entirety for all purposes.Technical Field

[0002] The present disclosure relates to a water-degradable conjugated polymer material and a method for forming the water-degradable conjugated polymer material. The present disclosure also relates to devices comprising the water-degradable conjugated polymer material.Background

[0003] Electronic devices may be becoming more and more ubiquitous with the advent of the information age. However, the capacity for technology to interact with the environment without leaving a lasting footprint may be growing in demand. Preparing disintegrable transient electronic devices appears to be increasingly urgent to lighten environmental burden.

[0004] Generally, materials with the ability to disintegrate or vanish, leaving minimal or no trace in a controlled condition may be referred to as transient material (may be referred to as having a transient property or transcience property). Correspondingly, a transient device needs to be able to operate under its operational conditions and disintegrate under certain conditions. Transience property can be enabled by degradability, solubility, resorbability, disintegrable ability, and so on. Also, the requirement for invasive and expensive retrieval operations may often be eliminated for many applications by only disintegrating devices rather than completely breaking down polymers into their monomeric constituents. However, it is never easy to realize transient functionality without compromising device performance, and finding a way to simultaneously enable transient functionality and enhanced device performance is more challenging.

[0005] Polymers may offer several strategies to enable the transience property for transient electronic devices. One strategy is to use a synthetic polymeric material as substrate or dielectric layer for electronic devices. The transience property of devices using these materials as a substrate or dielectric may then be achieved via their degradation or dissolution. For instance, some synthetic and naturally generated components can be used to make transient materials due to their inherent enzymatic degradability or hydrolytic degradation ability enabled by enzymatically and chemically degradable moieties such as ester bonds. However, the degradation time of these materials tend to be as long as a few days to several years.

[0006] Meanwhile, such degradable substrate may have to withstand certain harsh chemicals or conditions. For instance, the preparation of high-performance electronic devices may frequently entail photolithography and etching, which involve extremely harsh chemical environments or high temperature. Thus, the preparation involving such degradable substrate to achieve the transience property of such devices tends to require a highly complicated process of preparing the device and then transferring it to the degradable substrate. For instance, the fabrication of a complementary metal-oxide- semiconductor array on degradable substrates using a transfer printing technique has been attempted. A sacrificial layer of poly (methyl methacrylate) and a top layer of diluted polyimide were used in the process, wherein the patterned array may be retrieved by the polydimethylsiloxane stamp for transfer after etching the top layer and dissolving the sacrificial layer. Several studies appear to have reported such transfer strategies.

[0007] Conjugated polymeric semiconductors appear to be greatly used in various devices, including solar cells, light-emitting diodes, and transistors, with applications in biosensors, physiological signal detectors, integrated circuits, etc. A strategy for developing transient devices wherein the most significant part, the semiconductor layer, of the device can be disintegrated, and the remaining parts, such as substrates and electrodes, can be recycled, may also be very effective for alleviating the environmental pressure, save materials and reduce production costs. Thus, an easily disintegrable semiconductor material may be pivotal in the development of transient electronics.

[0008] However, traditional methods that enable the disintegrable capability of traditional semiconducting polymers may compromise other properties of thesemiconducting polymers or the resultant product may have properties compromised. For instance, traditional methods may involve blending disintegrable insulating polymers with semiconducting polymers or inducing disintegrable non-conjugated chemical groups along the backbone of the semiconducting polymer. For instance, thermoplastic polyurethane appears to have been reportedly blended with poly(3- thiophene methyl acetate), but conductivity of the resultant composite was sacrificed due to the highly insulating property of thermoplastic pol urethane. In another instance, poly(e-caprolactone) was co-spun with poly(3-hexylthiophene-2,5-diyl) (P3HT) to prepare degradable fibers, but mobility of the co-spun fibers was reduced by one to two orders of magnitude.

[0009] Alternatively, testing of hydrolysable chemical groups incorporated into a semiconducting polymer backbone was tried, such as reversible imine bonds that were used as conjugated connections between diketopyrrolopyrrole and p- phenylenediamine, and the resultant semiconducting polymer maintained conjugation along the backbone, retaining relatively high hole mobilities. However, this method involved an overly complex polymer synthesis process that was not easily scalable. These past studies indicate that the challenges to develop disintegrable semiconducting materials for transient electronics without compromising the device performance remains.

[0010] There is thus a need to provide for a solution that addresses one or more of the limitations mentioned above.Summary

[0011] In a first aspect, there is provided for a water-degradable conjugated polymer material comprising: a semiconducting polymer; and a crown ether, wherein the crown ether resides in an interstitial region of the semiconducting polymer, wherein the interstitial region is defined by polymer chains of the semiconducting polymer.

[0012] In another aspect, there is provided a method for forming the water-degradable conjugated polymer material described in various embodiments of the first aspect, the method comprising: providing an organic solution comprising the semiconducting polymer; and mixing the organic solution and the crown ether.

[0013] In another aspect, there is provided a device comprising the water-degradable conjugated polymer material described in various embodiments of the first aspect.Brief Description of the Drawings

[0014] The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the present disclosure. In the following description, various embodiments of the present disclosure arc described with reference to the following drawings, in which:

[0015] FIG. 1A shows a schematic diagram of an organic electrochemical transistor (OECT) and molecular structure of P3HT, 15-Crown-5, 1 -ethyl-3-methylimidazolium tetrafluoroborate (EMIM:BF4), and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). D, G, and S denote for the drain, gate, and source electrodes, respectively, x and y in PVDF-HFP may denote integers.

[0016] FIG. IB shows the transfer characteristics of a Cr-P3HT-based OECT at Eds = - 0.5 V. Cr-P3HT denotes the water-degradable conjugated polymer material comprising P3HT and a crown ether, such as 15-Crown-5.

[0017] FIG. 1C is a plot of the peak transconductance of the Cr-P3HT -based OECT as a function of Wd (V*- Vgs) / L.

[0018] FIG. ID is a plot of the transient response of the Cr-P3HT-based OECT determined by fitting an exponential to the change in drain current.

[0019] FIG. IE shows the transfer characteristics of a pristine P3HT-bascd OECT at Vds = -0.5 V.

[0020] FIG. IF is a plot of the peak transconductance of the pristine P3HT-based OECTs as a function of Wd (Vth-Vgs) / E.

[0021] FIG. 1G is a plot of the transient response of the pristine P3HT-based OECT determined by fitting an exponential to the change in drain current.

[0022] FIG. 1H is a plot of an OFET device performance when the weight ratios of P3HT to crown ether is 2:1.

[0023] FIG. 11 is a plot of an OFET device performance when the weight ratios of P3HT to crown ether is 1:1.

[0024] FIG. 1J is a plot of an OFET device performance when the weight ratios of P3HT to crown ether is 1:2.

[0025] FIG. IK is a table showing the OFET device parameters with different weight ratios between P3HT and crown ether.

[0026] FIG. IL shows plots of output characteristics of the Cr-P3HT -based (left plot) and the pristine P3HT-based (right plot) OECTs.

[0027] FIG. IM is a table showing comparison of OECT devices’ performance.

[0028] FIG. 2A is a schematic of an OFET device. D, G, and S denote for the drain, gate, and source electrodes, respectively.

[0029] FIG. 2B shows transfer curves of the 15-Crown-5 P3HT-based OEFTs at VDS = -80 V.

[0030] FIG. 2C shows transfer curves of pristine P3HT-based OFETs at VDS = -80 V.

[0031] FIG. 2D is a plot of G1WAXS analysis along the out-of-plane direction.

[0032] FIG. 2E is a plot of the UV-vis-NIR spectra of the Cr-P3HT and pristine P3HT films.

[0033] FIG. 2F is a plot of the calculated Ao-o / Ao-1 and IE values of the Cr-P3HT and pristine P3HT-based OFETs.

[0034] FIG. 2G is a plot of the UV-vis-NIR spectra with constant gate bias as a function of time for the Cr-P3HT film.

[0035] FIG. 2H is a plot of the UV-vis-NIR spectra with constant gate bias as a function of time for the pristine P3HT films.

[0036] FIG. 21 is a plot of the extracted n-n* transition and polaron peak absorbance as a function of time.

[0037] FIG. 2J shows the switching stability when Vgsvaries between 0 and -0.7 V for 500 cycles of (a) the Cr-P3HT-based and (b) the P3HT -based OECTs.

[0038] FIG. 2K is a table showing device parameters of the Cr-P3HT and P3HT -based OFETs.

[0039] FIG. 2L shows the output characteristics of the Cr-P3HT -based (left plot) and pristine P3HT-based (right plot) OFETs.

[0040] FIG. 2M is an Illustration of the edge-on and face-on orientations of P3HT crystallite (the arrows indicate the directions of faster charge carrier transport) and the cross-section of the schematic of an OFET device.

[0041] FIG. 2N shows the UV-vis-NIR spectra as a function of gate bias of the Cr- P3HT (left plot) and pristine P3HT (right plot) films, the progressive varied gate bias was applied from 0 to -1 V with a step of -0.2 V.

[0042] FIG. 3A shows the AFM topography of a Cr-P3HT film.

[0043] FIG. 3B is a phase image (several crown ether clusters are marked with dotted circles for reference) of the C1-P3HT film.

[0044] FIG. 3C shows the P3HT molecular packing schematic of the Cr-P3HT film.

[0045] FIG.3D shows the AFM topography of a pristine P3HT film.

[0046] FIG. 3E shows the phase image of the pristine P3HT film.

[0047] FIG. 3F shows P3HT molecular packing schematic of the pristine P3HT film.

[0048] FIG. 3G is a plot of the cyclic voltammetry response of the Cr-P3HT and pristine P3HT films.

[0049] FIG. 3H shows the the molecular structure of BBL (left image) and the transfer characteristics of the BBL-based OECT used for inverters (right plot).

[0050] FIG. 4A shows a circuit diagram of the complementary inverter.

[0051] FIG. 4B shows the voltage transfer characteristics of the Cr-P3HT -based inverters with incremental Vinfrom 0.5V to 0.7V.

[0052] FIG. 4C shows the voltage transfer characteristics of P3HT-based inverters with incremental Vinfrom 0.5 V to 0.7 V.

[0053] FIG. 4D is a plot of the gain as a function of Vinof the Cr-P3HT-based inverters

[0054] FIG. 4E is a plot of the gain as a function of Vm of the P3HT-bascd inverters.

[0055] FIG. 4F is a plot of the peak Voui / Vdd ratios as a function of Wi-

[0056] FIG. 4G is a plot of the dynamic performance of the Cr-P3HT -based inverters working at frequency of 0.5 Hz with various Vinpulses.

[0057] FIG. 4H is a plot of the dynamic performance of the P3HT-based inverters working at frequency of 0.5 Hz with various Vinpulses.

[0058] FIG. 41 is a table comparing the performance of traditional complementary inverter with that of the present disclosure (denoted “this work”).

[0059] FIG. 5A is a plot of the UV-vis-NIR spectra of the Cr-P3HT film before dripping water and after removing from water. Inserts are photographs of these films corresponding to the experiment (substrate size: 1x1 cm).

[0060] FIG. 5B is a plot of the UV-vis-NIR spectra of the pristine P3HT film before dripping water and after removing from water. Inserts are photographs of these films corresponding to the experiment (substrate size: 1 x1 cm).

[0061] FIG. 5C shows a schematic of the setup for the transient capability demonstration.

[0062] FIG. 5D shows demonstration of the water-disintegrable ability of OECT active layers by the water dripping experiment, the active layers of these organic transistors consisting of the pristine P3HT are resistant to water while the active layers with the Cr-P3HT readily disintegrate (scale bar: 1 cm).

[0063] FIG. 5E shows demonstration of the water-disintegrable ability of OFET active layers by the water dripping experiment, the active layers of these organic transistors consisting of the pristine P3HT are resistant to water while the active layers with the Cr-P3HT readily disintegrate (scale bar: 1 cm).

[0064] FIG. 5F shows photographs taken from contact angle measurements of the Cr- P3HT (top row) and pristine P3HT (bottom row) films.

[0065] FIG. 6A is a plot of the output characteristics of the Cr-P3HT-based OECTs without parylene-patterning.

[0066] FIG. 6B is a plot of the output characteristics of the pristine P3HT-based OECTs without parylene-patterning.

[0067] FIG. 6C is a plot of the transfer characteristics of the Cr-P3HT-based and pristine P3HT-bascd OECTs without parylene-patterning at Vds = -0.5 V.

[0068] FIG. 7A is a plot of the transfer performance of the Cr-P3HT OECT-based pressure sensor under different pressures.

[0069] FIG. 7B is a plot of the sensitivity to pressure of the the Cr-P3HT OECT-based pressure sensor at different pressure region.

[0070] FIG. 7C is a plot of the tunability of sensitivity by gate voltage of the Cr-P3HT OECT-based pressure sensor.

[0071] FIG. 7D is a plot of the transfer performance of the pristine P3HT OECT-based pressure sensor under different pressure.

[0072] FIG. 7E is a plot of the sensitivity to pressure of the pristine P3HT OECT-based pressure sensor at different pressure region

[0073] FIG. 7F is a plot of the tunability of sensitivity by gate voltage of the pristine P3HT OECT-based pressure sensor.

[0074] FIG. 7G is a plot of the pulse signals recorded by the Cr-P3HT OECT-based pressure sensor.

[0075] FIG. 7H is a plot of the pulse signals recorded by the pristine P3HT OECT- based pressure sensor.Detailed Description

[0076] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the present disclosure may be practised.

[0077] Features that arc described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar' feature in the other embodiments.

[0078] The present disclosure relates to a watcr-dcgradablc conjugated polymer material (also referred to as “transient conjugated polymer” in the present disclosure). The water-degradable conjugated polymer material is advantageous, as it possesses transient property and enhances an electronic device’s electrical performance. The terms “water-degradable” and “water-disintegrable” are interchangeably used in the present disclosure, both meaning that the conjugated polymer material can be degraded using water (e.g., in the presence of liquid water). The water-degradable conjugated polymer material of the present disclosure also has a balanced ionic and electronic transport properties. For example, a device (e.g., an organic electrochemical transistor (OECT)) comprising the water-degradable conjugated polymer material is able toexhibit higher transconductance, lower threshold voltage, and faster transient response, compared to one without. As another example, an OECT-based pressure sensor has greater sensitivity compared to one without.

[0079] The water-degradable conjugated polymer material of the present disclosure includes a semiconducting polymer. Non-limiting examples of the water-degradable conjugated polymer material of the present disclosure having such semiconducting polymer include are thiophene-based. For instance, the semiconducting polymer may include a thiophene and / or a derivative thereof. A non-limiting example is poly(3- hexylthiophene-2,5-diyl) (P3HT). P3HT is advantageous due to its ready availability, tunable microstructure, and ease in solution processing. However, P3HT is a hydrophobic semiconducting polymer due to the presence of alkyl side groups (see FIG. 1A), which means P3HT may not be readily degraded by water. Traditionally explored conjugated polymeric semiconducting materials involving P3HT, even combined with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), may not be readily susceptible to degradation by water.

[0080] The ability of water-soluble polymers to dissolve in water originates from their hydrophilic groups that can form hydrogen bonds with water. A traditional study demonstrated disintegrable semiconducting films by photo-oxidation of polystyrene in the presence of phenyl-C61 -butyric acid methyl ester, which generates photo-oxidized products with hydrophilic chemical groups that can form hydrogen bonds with water, rendering the films water disintegrable. In such instance, the film was modified with a chemical substance that aids in forming enough hydrogen bonds with water to maybe render a film that is water-disintegrable. However, the approach in such traditional study was not explored for preparing transient electronic devices, an entirely distinct paradigm. In this connection, the present disclosure demonstrates water-degradable conjugated polymer material developed through the incorporation of crown ether to introduce a transience property in semiconducting conjugated polymer films, as hydrogen bonds can be formed between water molecules and crown ethers. Particularly, the hydrogen atoms of a water molecule can directly bond to the oxygen atoms of a crown ether, such as 15-Crown-5. A crown ether, such as 15-Crown-5, can take on the role of a hydrogen bond acceptor.

[0081] In addition to the water-disintegrable ability, the present disclosure demonstrates the impact of the crown ether in the water-degradable conjugated polymer material on the ionic-electronic transport property and device performance, which helps in developing high-performance transient electronic devices.

[0082] The water-degradable conjugated polymer material can be used in organic transistors. Organic transistors have several prospective applications such as low-power electronics, digital integrated circuits, neuromorphic applications, physiological signal detection, and sensors. The water-degradable conjugated polymer material as a semiconducting material is demonstrated, and by way of a non-limiting example, the water-degradable conjugated polymer material containing a blend of P3HT and crown ether is one developed example of the present disclosure, and the blend is employed as active layers demonstrated using two different types of organic transistors, namely, an organic electrochemical transistor (OECT) and an organic field effect transistor (OFET). Films and devices with the pristine P3HT, and blends of 15-Crown-5 and P3HT, are prepared and the resultant OECT and OFET device performances are examined in detail. The role of crown ether, such as 15-Crown-5, on the morphology, crystallite orientation, aggregate ordering, and electrochemical doping process of P3HT are thoroughly investigated. To demonstrate the advantages of including a crown ether, such as 15-Crown-5, on the ionic-electronic transport properties of the resultant conjugated polymer material, two complementary inverters using the P3HT-based and Cr-P3HT-based OECTs are fabricated with the same n-type OECT device. The gain values and inverter transient behaviours of the Cr-P3HT-based and P3HT -based inverters are studied. The water-disintegrable ability of the films and devices consisting of 15-Crown-5 and P3HT are demonstrated. The resultant Cr-P3HT semiconductor composite (i.e, the water-degradable conjugated polymer material) is successfully demonstrated to overcome challenges associated with achieving ultrafast water- disintegrable transient property while simultaneously enabling enhanced device performance.

[0083] The advantageous water-disintegrable capability and well balanced hybrid ionic and electronic transport properties are enabled owing to the intrinsic chemical properties, molecular packing and morphology change of the transient conjugated polymer. As a result, higher transconductance, lower threshold voltage, and fastertransient response of a transient conjugated polymer-based OECT are achieved. The faster transient response entails, for example, the operation speed of a device, such as how fast a device (e.g., an OECT) switches on / off in response to a change in applied voltage. Further applications of the transient conjugated polymer-based OECT in inverters and pressure sensors arc demonstrated, exhibiting higher gain values and greater sensitivities. Other advantages of this transient conjugated polymer include reducing electronic wastes and facilitating recycling, low-cost solution processes, and adaptable on flexible substrates.

[0084] In traditional transient organic semiconductor technology, most transient organic semiconductors tend to be prepared by blending semiconductor materials with degradable materials, and such traditional approaches tend to sacrifice the properties and performance of semiconductor materials. Alternatively, some traditional transient organic semiconductors were synthesized using the mechanism of imine chemistry. However, all of these traditional materials tend to require the undesirable addition of acid to achieve the transient functionalities. When compared to traditional transient organic semiconductor technology, the transient conjugated polymer demonstrated in the present disclosure exhibits favourable water-disintegrable functionality with simultaneously device performance enhancement capability. Only water needs to be involved for the disintegration. Also, the transient conjugated polymer can be prepared by the cost-saving solution processes. All the transient conjugated polymer-based devices of the present disclosure demonstrated enhanced performance with low operating voltage.

[0085] The present disclosure also relates to a method for forming the water-degradable conjugated polymer material and devices comprising the water-degradable conjugated polymer material.

[0086] Details of various embodiments of the water-degradable conjugated polymer material, its method of forming, and devices comprising the water-degradable conjugated polymer material as well as uses of the water-degradable conjugated polymer material, and advantages associated with the various embodiments are now described below.

[0087] In the present disclosure, there is provided a water-degradable conjugated polymer material. The water-degradable conjugated polymer material may comprise asemiconducting polymer, and a crown ether, wherein the crown ether may reside in an interstitial region of the semiconducting polymer, wherein the interstitial region is defined by polymer chains of the semiconducting polymer. An example of this configuration is shown in FIG. 3C.

[0088] In various embodiments, the semiconducting polymer may comprise a hydrophobic polymer. In other words, the water-degradable conjugated polymer material is unexpectedly unadvantageous in that it can be degraded by water even with a hydrophoboic semiconducting polymer incorporated.

[0089] In various embodiments, the semiconducting polymer may comprise a polythiophene-based mixed ionic-electronic conductor. In various embodiments, the polythiophene-based mixed ionic-electronic conductor may comprise poly(3- hcxylthiophcnc-2,5-diyl), cthylcnc-glycol substituted thiophcnc-thicnothiophcnc- polymer p(gBTTT), p(glT2-g5T2), and / or p(g2T2-g4T2). In other words, the semiconducting polymer may comprise poly(3-hexylthiophene-2,5-diyl), ethyleneglycol (EG) substituted thiophene-thienothiophene-polymer p(gBTTT), p(g 1 T2-g5T2), and / or p(g2T2-g4T2). “p(glT2-g5T2)” denotes monoethyleneglycolpentaethyleneglycol substituted bithiophene polymer. “p(g2T2-g4T2)” denotes diethyleneglycol-tetraethyleneglycol substituted bithiophene polymer.

[0090] hi various embodiments, the crown ether may comprise 15-Crown-5, 18-crown- 6, dicyclohexano-18-crown-6, or a derivative thereof. In various embodiments and examples, 15-Crown-5 was used for the purpose of demonstration and not to limit the embodiments and examples.

[0091] In various embodiments, the crown ether may be conjugated to the semiconducting polymer in a manner which an oxygen atom of the crown ether remains accessible to a hydrogen of a water molecule for forming a hydrogen bond. Said differently, the term “conjugated” in the context of the pressure disclosure includes within its meaning that one chemical moiety interacts (e.g., is bonded) with another via a hydrogen bond.

[0092] Tn various embodiments, the semiconducting polymer and the crown ether may comprise a weight ratio of 100: 1 to 1:100, 75: 1 to 1:75, 50: 1 to 1:50, 25: 1 to 1:25, 10: 1 to 1 : 10, 5: 1 to 1 :5, 2:1 to 1 :2, etc. (i.e., in the water-degradable conjugated polymer material). For example, the semiconducting polymer and the crown ether may comprisea weight ratio of 1:1. In various embodiments, the weight ratio may have a range of 2: 1 to 1:2.

[0093] Advantages of aforesaid embodiments and features of the water-degradable conjugated polymer material are already demonstrated in one or more examples below, hence not reiterated for brevity.

[0094] The present disclosure also provides for a method for forming the water- degradable conjugated polymer material described in various embodiments of the first aspect. Embodiments and advantages described for the water-degradable conjugated polymer material of the first aspect can be analogously valid for the present method subsequently described herein, and vice versa. As the various embodiments and advantages have already been described above and in examples demonstrated herein, they shall not be iterated for brevity.

[0095] The method may comprise providing an organic solution comprising the semiconducting polymer, and mixing the organic solution and the crown ether.

[0096] Tn various embodiments, the method may be absent of an acid. The absence of acid advantageously improves biocompatibility for bioelectronic applications of the OECT. It also increases fabrication compatibility with wider range of substrates since presence of acids may corrode sensitive substrates such as flexible plastics or biocompatible substrates.

[0097] hi various embodiments, providing the organic solution may comprise dissolving the semiconducting polymer in an organic solvent.

[0098] Tn various embodiments, the organic solvent may comprise chloroform, dichloromethane, chlorobenzene, or dichlorobenzene.

[0099] In various embodiments, mixing the organic solution and the crown ether may comprise mixing the organic solution with an amount of crown ether which is more than the semiconducting polymer in the organic solution.

[0100] In various embodiments, mixing the organic solution and the crown ether is carried out for at least 30 minutes, at least 1 hour, at least 2 hours, etc.

[0101] Advantages of aforesaid embodiments and features of the method are already demonstrated in one or more examples below, hence not reiterated for brevity.

[0102] The present disclosure provides for a device comprising the water-degradable conjugated polymer material described in various embodiments of the first aspect.Embodiments and advantages described for the water-degradable conjugated polymer material of the first aspect and its method of forming can be analogously valid for the present device subsequently described herein, and vice versa. As the various embodiments and advantages have already been described above and in examples demonstrated herein, they shall not be iterated for brevity. rooio3] In various embodiments, the device may be a transistor, an inverter, or a pressure sensor.

[0104] Tn various embodiments, the transistor may comprise an organic electrochemical transistor or an organic field effect transistor.

[0105] In various embodiments, the organic electrochemical transistor may comprise a substrate, a source electrode and a drain electrode spaced apart and configured on the substrate, a channel layer configured between and in contact with the source electrode and the drain electrode, wherein the channel layer comprises the water-degradable conjugated polymer material described in various embodiments of the first aspect, a solid-state electrolyte configured on the channel layer, and a gate electrode configured on the solid-state electrolyte. In various embodiments, the solid-state electrolyte may comprise l-ethyl-3-methylimidazolium tetrafluoroborate and poly (vinylidene fluoride- co-hexafluoropropylene) .

[0106] In various embodiments, the organic field effect transistor may comprise a substrate configured as a bottom gate electrode, a dielectric layer configured on the substrate, an active layer configured on the dielectric layer, wherein the active layer comprises the water-degradable conjugated polymer described in various embodiments of the first aspect, and a source electrode and a drain electrode spaced apart and configured on the active layer.

[0107] In various embodiments, the semiconducting polymer of the water-degradable conjugated polymer material described in various embodiments of the first aspect may comprise a cyclic ring structure defining a planar surface, and wherein the planar surface is configured orthogonal or parallel to a surface of the dielectric layer which faces the active layer.

[0108] Advantages of aforesaid embodiments and features of the devices are already demonstrated in one or more examples below, hence not reiterated for brevity.

[0109] The word “substantially” does not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary, the word “substantially” may be omitted from the definition of the present disclosure.

[0110] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or clement include a reference to one or more of the features or elements.

[0111] In the context of various embodiments, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance. The variance may be ±20%, ±10%, ±5%, ±1%, ±0.5%, ±0.1%, etc.

[0112] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0113] Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements.Examples

[0114] The present disclosure relates to a water-degradable conjugated polymer material (also referred to as a “transient conjugated polymer” in the present disclosure). The present disclosure also relates to the construction of the water-disintegrable transient conjugated polymer (i.e, the water-degradable conjugated polymer material), the use of it in electronic devices, such as organic electrochemical transistors and its application in digital circuits such as inverters, and health monitoring devices such as pressure sensors.

[0115] The high transconductance and low operating voltage characteristics of an electronic device (e.g., OECT) arc conferred by the ionic-electronic coupling over the entire volume of the organic semiconductor-based channel layers. However, traditionally, obtaining the organic semiconductor films with both (i) transient functionality and (ii) balanced ionic and electronic transport properties, has been considerably challenging.

[0116] The present disclosure provides for a water-degradable conjugated polymer material (which is an example of an organic semiconductor) containing a conjugatedpolymer and a crown ethers, having a higher charge carrier transport and easier ion penetration. The water-degradable conjugated polymer material is advantageous for device enhancement when such transient conjugated polymer (i.e., the water- degradable conjugated polymer material) is employed as the channel layer of OECT. As a result, the developed film from such transient conjugated polymer and developed devices show favourable water-disintegrable capability in the presence of water and well balanced mixed ionic and electronic transport properties, the transient conjugated polymer-based OECT exhibits higher transconductance, lower threshold voltage, and faster transient response, the transient conjugated polymer OECT-based inverter shows higher gain value and the transient conjugated polymer OECT-based pressure sensor achieves greater sensitivity.

[0117] The present water-degradable conjugated polymer, method of its forming, and uses, are described in further details, by way of non-limiting examples, as set forth below.

[0118] Example la: Overview

[0119] With the dawn of the information age, electronic waste is becoming more commonplace, burdening the environment as electronics grow increasingly incorporated into daily lives. To lessen the load on the environment and make recycling more accessible, the concept of disintegrable transient electronics is becoming increasingly relevant. Realizing transient functionality without sacrificing device performance is never simple, and it can be even harder to find a strategy to enable transient functionality while also improving device performance. Tn various examples of the present disclosure, the semiconducting polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) has been demonstrated. P3HT is advantageous in the field of organic electronics, because of its easy accessibility, customizable microstructure, and solution processing simplicity. In various examples of the present disclosure, application of crown ether in introducing transience property into the P3HT-based thin films, owing to its capability to form hydrogen bonds with water, are demonstrated.

[0120] Firstly, the semiconducting material obtained by blending P3HT with crown ether (e.g., 15-Crown-5) is employed as active layers in two types of organic transistors, i.e., organic electrochemical transistors (OECTs) and organic field-effect transistors (OFETs). Organic transistors of the present disclosure including the water-degradableconjugated polymer material are found to exhibit better charge carrier transport, enhanced mixed ionic-electronic transport, and improved device performance. Higher normalized transconductance (163.18 ± 16.95 S cm-1), larger / / C* value (415.44 ± 43.58 F cm'1V1s1), lower threshold voltage (-0.45 ± 0.01 V), and faster transient response (0.26 s) were achieved in the Cr-P3HT-bascd OECTs, while highly improved hole mobilities were seen in the Cr-P3HT -based OFETs. The implications of crown ether on the morphology, crystallite orientation, aggregate ordering, and electrochemical doping process of P3HT are discussed in detail in one or more examples below.

[0121] Next, two complementary inverters using the Cr-P3HT -based and P3HT -based OECT s with the same n-type OECT device were prepared to show the advantages of a crown ether (e.g., 15-Crown-5) on the ionic-electronic transport properties of the conjugated polymer, the addition of 15-Crown-5 allows the Cr-P3HT-bascd inverter to obtain very high gain values (82 V / V at 0.7V) and to operate at much faster responses when compared to that of the P3HT -based inverter.

[0122] Also, transient organic transistors are prepared and their ultrafast water- disintegrable abilities are successfully demonstrated. This approach opens up opportunities for high-performance transient organic electronics.

[0123] Example lb: Materials

[0124] Poly(3-hexylthiophene) (P3HT) (regioregular, Mw ~37k) was supplied by Rieke Metals, 15-Crown-5, chloroform, l-ethyl-3-methylimidazolium tetrafluoroborate (EMIM:BF4), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), methanesulfonic acid (MSA), poly(benzimidazobenzophenanthroline) (BBL), poly(sodium-4-styrene sulfonate) (PSSNa), and 3-(trimethoxysilyl)propyl methacrylate (A174) were purchased from Sigma Aldrich, and used as received. Poly(3,4-ethylenedioxy thiophene) :poly styrene sulfonate (PEDOT:PSS) was purchased from Heraeus and parylene dimer (DPX-C) was supplied by Specialty Coating Systems Inc.

[0125] Example 2: Film Preparation

[0126] P3HT was dissolved in chloroform at 50°C (5 mg mL1), and the pristine P3HT films were prepared by the chloroform-dissolved P3HT solution. Crown ether- modified P3HT (Cr-P3HT) films were prepared by mixing the chloroform-dissolved P3HT with crown ether and shaking vigorously. This involves enough amount of crown ethers toform hydrogen bonds with water to enable the water-disintegrable ability, which is due to the need for enough amount of crown ethers to form hydrogen bonds with water.

[0127] Furthermore, as shown in FIG. 1H to F1G.1J and FIG. IK, OFET devices with different weight ratios between P3HT and crown ether were prepared. The weight ratios of P3HT and crown ether arc 2:1, 1: 1 and 1:2 respectively. It was observed that when the P3HT:crown ether ratio changed from 2: 1 to 1:1, the mobility of the material increased, while when the P3HT:crown ether ratio was 1:2, the mobility of the material decreased significantly. In addition, since the higher the crown content, the easier it is for the ion penetration, therefore, to study for a well-balanced mixed ionic and electronic transport capabilities in the channels of OECTs, a recipe that the weight ratio between P3HT and crown ether is 1:1 was selected in this study. All films (if not specified) were prepared by spin-coating at 500 rpm for 3 seconds (i.c., 3 s) followed by 3000 rpm for 30 s in the glove box.

[0128] Solid state electrolyte was prepared using EMIM:BF4 and PVDF-HFP. Acetone-dissolved PVDF-HFP (10 mg mL1) was stirred for 12 hr at room temperature, then EMIM:BF4 with a weight ratio of 1:2 was added into the solution and vibrated vigorously for 30 min. Next, PVDF-HFP film containing EM1M:BF4 was prepared by spin-coating the mixed solution for 60 s at 1500 rpm. Solid state electrolyte was obtained after annealing the PVDF-HFP / EMIM:BF4 film at 70 °C for 24 hr and can be peeled off from the substrate.

[0129] Example 3: Characterizations

[0130] An optical contact angle measurement system (OCA 15EC, DataPhysics) was utilized to measure the water contact angle. The film morphology was recorded by an atomic force microscope (AFM, Cypher ES) in tapping mode. Grazing-incidence wide- angle X-ray scattering (GIWAXS) patterns of the films were carried out using a Xenocs Nanoinxidcr with a Cu-Ka microsourcc (40 pm), 30W and 100K detector in vacuum (0.1 mbar). An incidence angle of 0.2° was used and Foxtrot software was employed to process and analyze the raw scattering data. The cyclic voltammetry experiment was performed by a potentiostat / galvanostat (Autolab, PGSTAT302N, Metrohm). The sample films with various geometries cast onto Au-evaporated and parylene-patterned substrates act as the working electrodes.

[0131] Example 4: UV-vis-NIR Spectroelectrochemistry

[0132] Ultraviolet-visible-near-infrared (UV-vis-NIR) spectra over the wavelength range from 350 to 1000 nm were captured to study the water-disintegrable ability, P3HT aggregate ordering and electrochemical doping process of P3HT using a UV-vis-NIR spectrophotometer (Ocean Optics, DH-2000). For the first two studies, films were spin- coated on glass substrates. The changes in absorption spectra before and after the water dripping experiment were recorded for the water-disintegrable ability study. The A0-2 peak at 522 nm corresponds to the P3HT intrachain TI-TI* transition, A0-1 peak at 558 nm and Ao-opeak at 605 nm indicate the P3HT interchain TT-TT stacking interactions. The Ao 2 peak is commonly used for the normalization of the P3HT UV-Vis absorption spectra. For the latter research with applying gate bias, films were spin-coated on the indium tin oxide (ITO) substrates, care was taken to define an active area of 8 mm x 5 mm and UV-vis-NIR absorption spectra were recorded with applying bias, the solid state electrolyte consisting of EMIM:BF4 and PVDF-HFP was assembled with the film- coated ITO substrate and another ITO glass was used as the gate electrode. A constant gate bias (-1 V) was applied by a Keysight precision source / measure unit (B2900A Series), and all the changes in absorption spectra as a function of time were captured. Furthermore, the gate bias varying from zero to negative between gate electrode and the film-coated ITO substrate was applied by the Keysight precision source / measure unit. Then the UV-vis-NIR spectrophotometer recorded all the changes in absorption spectra as a function of gate bias.

[0133] Example 5; OECT and Inverter Fabrication and Measurement

[0134] Organic electrochemical transistors (OECTs) were fabricated by the patterning method with two parylene layers. Concisely, the Au source and drain electrodes were patterned onto Si / SiO2 substrates with the assistance of photoresist AZ 5214. The bottom parylene layer (thickness: 1.9 pm) was deposited onto these substrates with 3- (trimcthoxysilyl)-propyl methacrylate (as the adhesion promoter). Then, the dilute soap solution (10% Micro-90 in water) treated substrates were coated with the top parylene layer (thickness: 2.5 pm). The substrates covered by two parylene layers were covered by photoresist AZ P4620 and reactive ion etching (RTE) was performed to expose the channels after the AZ P4620 was developed with AZ developer. The parylene-patterned substrates were washed with acetone, cleaned and dried with nitrogen. The chloroformdissolved P3HT and C1-P3HT solutions were spin-coated onto the parylene-patternedsubstrates in the glove box and the top parylene layers were torn off and removed. After that, all these substrates, gate electrodes made with Au and PEDOT:PSS and the solid state electrolytes containing EM1M:BF4 and PVDF-HFP were assembled. BBL was dissolved in the MSA solvent with a concentration of 5 mg mL1. The BBL solution was spin-coatcd onto the parylene-patterned substrate and then immersed into deionized water for 15 min to remove the MSA solvent. The top parylene layer was torn off and removed, after which the BBL-based OECT was annealed on a hotplate at 200°C for 1 hour under a nitrogen atmosphere. After the BBL-based OECT was cooled to room temperature, the solid electrolyte PSSNa was assembled with the BBL-coated substrate. The BBL-based OECT was assembled with the Cr-P3HT and P3HT-based OECTs, respectively, to form two different complementary inverters. The OECT and inverter electrical characteristics were measured using a probe station (Karl Suss PM5) and Keysight precision source / measure unit (B2900A Series) at room temperature.

[0135] Example 6: OFET Fabrication and Measurement

[0136] Organic field effect transistors (OFETs) with the bottom-gate top-contact configuration were prepared on SiO2 / Si substrates by the mask patterning method. On the heavily doped Si wafer (0.001-0.005 fi cm, Addison Engineering, CA), a SiO? layer that was thermally grown with a thickness of 200 nm serves as the dielectric layer. The substrates were successively cleaned with soap solution, deionized water, acetone, and isopropyl alcohol by ultrasonic cleaning for 15 minutes. Then all the substrates were dried thoroughly with nitrogen gas. The P3HT and Cr-P3HT solutions were prepared and spin-coated at 500 rpm for 3s followed by 3000 rpm for 30s in the glove box. With the use of a shadow mask and a thermal evaporator (Kiyon, DDHT-SP027), the source and drain electrodes were deposited onto the films spin-coated substrates. The width and length of the channels were 200 pm, 100 pm with a thickness of 50 ± 2 nm. All characterization of the produced OFET devices were carried out in a glovebox under dark condition using the Keysight precision source / measure device (B2900A Series).

[0137] Example 7: Results and Discussion

[0138] Pristine P3HT films, and films obtained by blending 15-Crown-5 and P3HT (defined as Cr-P3HT in the present disclosure), were fabricated by spin-coating and used to prepare two types of organic transistors, i.e., OECTs and OFETs. Firstly, the effect of a crown ether, e.g., 15-Crown-5, on OECT performance was studied. Theschematic of an OECT and molecular structures of P3HT, 15-Crown-5, l-ethyl-3- methylimidazolium tetrafluoroborate (EMIM:BF4) and poly(vinylidene fluoride-co- hexafluoropropylene) (PVDF-HFP) are demonstrated in FIG. 1A. The solid-state electrolyte (SSE) was prepared using EMIM:BF4 and PVDF-HFP. The Cr-P3HT films were used as the channel layers for OECTs, and the pristine P3HT -based OECTs were also prepared for comparison (see more details in the experimental section and FIG. 1H to FIG. 1J and FIG. IK). The organic electrochemical transistor includes a substrate, a source electrode and a drain electrode spaced apart and configured on the substrate, a channel layer configured between and in contact with the source electrode and the drain electrode, wherein the channel layer contains the water-degradable conjugated polymer material, a solid-state electrolyte configured on the channel layer, and a gate electrode configured on the solid-state electrolyte.

[0139] The basic working principle of an OECT is based on ion injection from the electrolyte into the bulk semiconducting channel layer, changing the redox state of this layer and consequently its conductivity. As a result, the electronic and ionic transport characteristics of the active layer, which significantly depend on the molecular nanostructure of the semiconducting conjugated polymer, determine how well an OECT performs. The transconductance (gm) of an OECT can be used to assess the steady-state device performance, which is expressed as

[0141] where ,u is the OECT mobility, C* is the volumetric capacitance, W, d, and L are the width, thickness, and length of the OECT channel, respectively, and Vth and VC, are the threshold voltage and the gate voltage, respectively.

[0142] The output characteristics of the Cr-P3HT-based and pristine P3HT-based OECTs are plotted in FIG. IL, respectively (IT: 100 pm and L: 10 pm, d\ 54 ± 2 nm). All OECTs operate in accumulation mode, where the BF4 anions from the electrolyte penetrate the active layer upon application of a negative gate bias, doping the P3HT and changing its redox state, resulting in an increase in the drain current. As shown in FIG. IB, the transconductance of the Cr-P3HT-based OECT is found to be 6.90 mS, which is much higher than that obtained for the pristine P3HT-based OECT (3.57 mS, see FIG. IE). Furthermore, when normalizing the transconductance with channel dimensions, a higher normalized of 163.18 ± 16.95 S cm'1is obtained for the Cr-P3HT -based OECTs, while the pristine P3HT-based OECTs show a normalized gmof 101.62 ± 12.87 S cm1, implying better signal amplification ability of the Cr-P3HT- based OECTs. Both OECTs show high current ON / OFF ratios of ~105.

[0143] For OECT, there may be a trade-off between char ge transport and ion injection since higher charge transport property comes from highly ordered conjugated polymer chains, whereas easier ion penetration requires loosely packed polymer chains or more amorphous bulk. Thus, a product of mobility and volumetric capacitance, the fiC* figure of merit, is commonly defined and adopted to reflect the mixed electronic and ionic transport capability of the active layer. TheμC* product is extracted from equation (1) and the calculated / JC'' value for the Cr-P3HT-based OECTs is 415.44 ± 43.58 F cm1V1s ', while the P3HT-based OECTs show aμC* of 270.07 ± 31.09 F cm'1V1s’1, sec FIG. 1C and FIG. IF, and FIG. IM. A higherμC* value of the Cr- P3HT -based OECTs represent their better mixed electronic and ionic transport properties and superiority of preparing OECTs with higher amplification capability.

[0144] Another crucial performance indicator of an OECT is the transient response, which is governed by the ionic-electronic transport efficiency of the active layer. With the application of a square gate bias step, the transient response of an OECT can be determined by fitting an exponential to the change in drain current according to Bernards and Malliaras’ model, see FIG. ID and FIG. 1G for the fitting curves. The transient responses of the Cr-P3HT -based and P3HT-based OECTs with similar thicknesses are extracted to be 0.26 s and 0.53 s, respectively, when the square step of the applied gate voltage is 1 s. Since the OECT works on the principle of the volumetric doping / de-doping process and mixed ionic-electronic transport, the faster transient response of the Cr-P3HT -based OECT indicates its faster change in the active layer redox state and more efficient ionic-electronic transport. Furthermore, as shown in FIG. 2J, the drain current of the Cr-P3HT-bascd OECT maintained > 90% of its initial value after 500 cycles, demonstrating good switching stability, which is similar to that of the P3HT -based OECT.

[0145] Next, the effect of 15-Crown-5 on OFET performance is investigated in detail. The study of OFET mobility also helps us to understand the role of charge carrier migration for OECT performance, since OFET hole mobility is commonly used to evaluate the charge transport efficiency. In an OFET, the source-drain current (IDS) is afunction of the accumulated charge carriers in the active layer and is determined by the applied gate voltage (YGS). Charge carriers migrate from the source to the drain electrode when a small drain voltage (YDS) is applied ( YDS«YGS), forming a linear charge density gradient and current flows, and the current of the active layer is proportional to the applied drain voltage. The channel is pinched off at a point where YDS = YGS-YTH if the drain voltage is further increased and the current flow will be saturated, which is called the saturation regime. Here, the relationship between the hole mobility (fih. OFET) and IDS is expressed as equation (2),

[0148] where IV' and L’ are the width and length of an OFET channel, respectively, YTH is the threshold voltage and Ci is the capacitance of the dielectric layer (17 nF cm’ 2 for S1O2 with a thickness of 200 nm). The hole mobility ph. OFET is calculated by equation (3).

[0149] The schematic of an OFET with bottom gate top contact architecture is shown in FIG. 2A. The organic field effect transistor includes a substrate configured as a bottom gate electrode, a dielectric layer configured on the substrate, an active layer configured on the dielectric layer, wherein the active layer contains the water- degradable conjugated polymer material, and a source electrode and a drain electrode spaced apart and configured on the active layer. The Cr-P3HT film takes the role of the active layer for an OFET, and the pristine P3HT-based OFET was also prepared for comparison. OFET characteristics were measured as shown in FIG. 2B and FIG. 2C and FIG. 2L ( W’: 200 pm and L’: 100 pm, thickness: 50 + 2 nm). The device parameters of the Cr-P3HT and pristine P3HT OFETs arc summarized in FIG. 2K. Evidently, the Cr-P3HT OFET shows much higher hole mobility than the OFET prepared with the pristine P3HT, indicating enhanced charge transport of Cr-P3HT films.

[0150] Regarding the molecular ordering of P3HT, there are two general orientations for P3HT crystallites: i) edge-on, with the alkyl side chain lying perpendicular to the substrate surface, and ii) face-on, with the polymer backbone oriented parallel to the substrate surface. For the polythiophene-based materials, the preferential edge-on orientation can results in higher hole mobility due to the stacked lamellae along thesubstrate, favoring interchain charge transport across the source and drain electrodes, as illustrated in FIG. 2M. Many studies have also reported that edge-on molecular packing may be ideal for efficient lateral charge carrier transport. Grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis was conducted, as shown in FIG. 2D, wherein several diffraction peaks were detected in both films along the out-of-planc direction, corresponding to the P3HT lamellar spacing of the (100), (200), and (300) planes and K-K stacking of (010) plane. Here, stronger lamellar spacing peaks along the out-of-plane direction represent the crystallites of P3HT adopting a more edge-on orientation, in contrast, a more intense TI-TT stacking peak indicates a dominant face-on orientation. Clearly, GIWAXS analysis reveals a significantly higher contribution of edge-on oriented crystallites in the Cr-P3HT films when compared to the pristine P3HT films, resulting in the observed higher mobility of the Cr-P3HT-bascd OFET. rooisn Furthermore, the absorption characteristics of the pristine P3HT and Cr-P3HT films were explored. The ultraviolet-visible-near-infrared (UV-vis-NIR) spectra shown in FIG. 2E reveal the Ao-zpeak at 522 nm (due to the P3HT intrachain 7t-7i* transition), Ao i peak at 558 nm, and Ao o peak at 605 nm (due to P3HT interchain jt-Tt stacking interactions). The Ao-o / Ao-i value and the interchain coupling energy (W) were calculated by equation (4) to estimate the molecular aggregate ordering of P3HT in these films,

[0153] where no-t and no-o are the refractive indices at Ao-i and Ao-o peaks, respectively, and the no-i / no-o ratio for P3HT is 0.97. £pis the vibration energy coupled to the electronic transition of the polymer, and Epfor P3HT = 0.18 eV.

[0154] As plotted in FIG. 2F, the Cr-P3HT film exhibits a clearly higher Ao-o / Ao-i value (0.815) than the pristine P3HT film (0.686), corresponding to the lower interchain coupling energy of the Cr-P3HT film (0.049 eV) in comparison with the pristine P3HT film (0.095 eV). Lower interchain coupling energy comes from higher-ordered P3HT molecular aggregates with longer conjugation lengths. Thus, this result indicates that Cr-P3HT film exhibits a higher degree of P3HT aggregate ordering, which benefits its charge carrier transport properties and result in more favorable hole transport in the Cr- P3HT -based OFET, and more efficient charge transport is also one of the mostsignificant contributors to higher OECT device performance in the Cr-P3HT -based OECTs.

[0155] In addition to having enhanced mobility, better ion penetration and easier change in the redox state are also essential factors in determining the resultant performance of the OECT device. Thus, the real-time UV-vis-NIR absorbances for the pristine P3HT and Cr-P3HT films were collected to demonstrate how the absorption spectrum varies over time with the electrochemical doping process (constant Vgs= -1 V and at a step of 1 .5 s). The intensities of the main P3HT 71-71* transition absorption peaks of both the pristine P3HT and Cr-P3HT films diminish over time, while the polaron peaks centered at -800 nm develop, see FIG. 2G and FIG. 2H. The absorption spectrum variations of 71-71* transition and polaron peaks as a function of time were extracted and normalized as demonstrated in FIG. 21. In comparison to pristine P3HT, the addition of 15-Crown-5 in films causes the 7t-7t* transition of P3HT to decline more and the polaron peak to develop more as time goes by, indicating more efficient doping occurs in the Cr-P3HT film, which is in line with faster ion injection and more efficient change of P3HT redox state than the pristine P3HT film. Thus, the presence of crown ether has a significant impact on how quickly the electrochemical doping occurs. The change in the P3HT redox state with increasing negative gate bias was also studied. UV-vis-NIR measurement with a continuous gate bias ranging from 0 V to - 1 V (at a step of -0.2 V) was also performed, and the absorbance was recorded after the current response had reached the steady state, as shown in FIG. 2N. The P3HT 71-71* transition absorption peak from about 400 to 700 nm decreases with increasing gate bias, and a polaronic peak centered at around 800 nm appears concurrently. These spectrochemical responses along with the increasing gate bias illustrate the doping processes of ions in the Cr- P3HT and pristine P3HT films. A more efficient doping process is observed in the 15Cr-5-P3HT film, since its P3HT TT-TI* transition declines more when the same gate bias was applied, further confirming easier doping of Cr-P3HT film.

[0156] Furthermore, the threshold voltage (Vth) of an OECT is the gate bias required for switching the channel between its doping and de-doping states. A lower V* is preferred in order to reduce power consumption and prevent overoxidation / reduction of the channel semiconductor and electrochemical breakdown of the electrolyte. As shown in FIG. IM, the Cr-P3HT-based OECTs exhibit lower Vth (-0.45 ± 0.01 V) thanthat of the P3HT -based OECTs (-0.50 ± 0.01 V), further confirming that the Cr-P3HT film has more efficient ion injection. Therefore, the Cr-P3HT film has a more beneficial microstructure, which is favorable for charge carrier transport and ion penetration, resulting in a greater / C* value, corresponding to larger normalized guiand faster response of the Cr-P3HT -based OECTs in comparison to the pristine P3HT-bascd OECTs.

[0157] Furthermore, the morphologies of the Cr-P3HT and pristine P3HT films are evaluated by atomic force microscopy (AFM). The topography images of the Cr-P.3HT and pristine P3HT films are shown in FIG. 3A and FIG. 3D, respectively, wherein the Cr-P3HT film shows a significantly increased root mean square roughness (RMS) value of 9.50 nm, while the pristine P3HT film is quite smooth, with a RMS of 1.26 nm. Meanwhile, phase separation observed in the phase image of the Cr-P3HT film, as shown in FIG. 3B, evidenced by the presence of distinctive 15-Crown-5 granular cluster domains and network-like P3HT domains, a morphology noticeably different from the disconnected and small domains in the pristine P3HT film as seen in FIG. 3E.

[0158] In comparison to the smaller and isolated domains of the pristine P3HT film, the Cr-P3HT film has more interconnected network-like P3HT domains. Connectivity among P3HT grain boundaries in the Cr-P3HT film can be improved by this networklike domain morphology, while smaller domains in the pristine P3HT film make charge carrier transport challenging. Thus, higher hole mobility of the Cr-P3HT-based OFET can be expected. For OECT, the 15-Crown-5 granular cluster and amorphous P3HT domain originates from the phase separation provide better transport pathways for the anions from the electrolyte, whereas the highly interconnected network-like P3HT domains support better hole transport. Thus, the smaller and more isolated P3HT domains in the pristine P3HT film are responsible for the relatively poor performance of the pristine P3HT-bascd OECTs, whereas the obvious phase separation in the Cr- P3HT film accounts for the higher transconductance and better mixed ionic-electronic transport property of the Cr-P3HT-based OECTs, as illustrated in FIG. 3C and FIG. 3F.

[0159] Furthermore, cyclic voltammetry response measurements were performed on these films and the responses normalized to the weight of P3HT are shown in FIG. 3G. With the addition of the 15-Crown-5, an increase in the cyclic voltammetry response of the Cr-P3HT film can be observed where both the oxidation and reduction currents arepronounced, indicating that the build-up of electrical double layers is facilitated in the Cr-P3HT film, further confirming that the Cr-P3HT film has more efficient ion injection. Therefore, the Cr-P3HT film has a more beneficial microstructure, which is favorable for charge carrier transport and ion penetration, resulting in a greater pC* value, corresponding to larger normalizedand faster response of the Cr-P3HT -based OECT in comparison to pristine P3HT -based device.

[0160] OECT is also well suited for circuit applications due to its high transconductance, low operating voltage and high ON / OFF ratio. Two complementary inverters were prepared using these p-type Cr-P3HT-based OECT and P3HT -based OECT as the pull-up transistors, respectively to demonstrate the advantages of the Cr- P3HT -based OECT in circuit applications. A n-type poly(bcnzimidazobcnzophcnanthrolincdionc) (BBL)-bascd OECT operates as the pulldown transistor in these inverters. For brevity, the complementary inverters using the Cr-P3HT-based and pristine P3HT-based OECTs as the pull-up transistors are referred to as the Cr-P3HT-based and P3HT -based inverters, respectively, in the present disclosure. The molecular structure of the BBL and the OECT device performance of the n-type BBL-based OECT are provided in FIG. 3H.

[0161] The circuit diagram of the complementary inverter prepared in this study is depicted in FIG. 4A. As shown in FIG. 4B and FIC. 4C, the equivalent gate bias of the p-type OECT (p-OECT) in each inverter decreases as the input voltage ( Vin) gradually increases, causing the decrease of the conductivity of its channel, while the equivalent gate bias of the n-type OECT (n-OECT) and the conductivity of its channel increase accordingly, so the output voltage (Vout) changes from close to the supply voltage (Vaa) to close to the ground (0 V) and vice versa. It is noted that both the Cr-P3HT-based and P3HT -based inverters achieve the full rail-to-rail swings at steady state with sharp transition curves. The gain value ) of these inverters arc shown inFIG. 4D and FIG. 4E. The Cr-P3HT-based inverter exhibits a gain value of up to 82 \r / \rat 0.7 V at the peak of the transition, which is greater than that of many traditional P3HT or BBL-based complementary inverters, as shown in FIG. 41, indicating the excellent amplification capability of the Cr-P3HT-based inverter. However, the P3HT- based inverter has a gain value of only 28 V / V at 0.7 V at the peak of the transition.

[0162] The transient characteristics of these inverters were then investigated using a pulse Vin with a frequency of 0.5 Hz, as shown in FIG. 4F to 4H. It is noteworthy that the Vout of the Cr-P3HT-based inverter can swing in response to the pulse Vinover all the range of Vinpulses that were examined. On the other hand, the Voutof the P3HT- bascd inverter is unable to swing when the pulse Vin varies between 0 and 0.5V / 0.55V. The ratios of peak Voutto Vdd (peak Vout / Vdd) as a function of Vdd are plotted to discuss this phenomenon in detail, as shown in FIG. 4F. It can be clearly seen that the peak Vout / Vdd ratios of the Cr-P3HT-based inverter are all maintained at ~100% over all the range of Vinpulses that were examined, indicating that the Cr-P3HT-based inverter is capable of fully inverting the voltage, implying its excellent inverting capability. While when the applied pulse V;nvaries between 0 and 0.5V / 0.55V, the peak Vout / Vddratios of the P3HT-bascd inverter arc only about 22% and 61%, indicating that the change in the conductivity of the pristine P3HT-based OECT channel in the P3HT-based inverter is too slow to respond to the change of its equivalent gate voltage, implying that the ionic- electronic hybrid transport of the pristine P3HT-based OECT is limited, which is consistent with the conclusion of the study on the OECT transient response. The peak Vout / Vdd ratio of the P3HT -based inverter reaches 96% when the variation range of the pulse Vin is increased to vary between 0 and 0.6V. Furthermore, the pulse Vin variation range of the P3HT-based inverter needs to be increased to vary between 0 and 0.7 V if its peak Vout / Vdd ratio is to reach 100%. Thus, thanks to the enhanced ionic-electronic mixed transport property, the Cr-P3HT-based inverter has much higher gain values and is able to operate at lower supply voltages, which can effectively reduce the power consumption of inverters and circuits.

[0163] For exploring the water-disintegrable capability of the Cr-P3HT films, a water dripping experiment was conducted and UV-vis-NIR spectra were measured to explore whether the addition of the water droplet causes any changes in the absorption of the resultant films. The spectra of the film before dripping were recorded and drops of water were separately dripped onto each film until the water covered the entire film. Then, the film was removed from the water and the spectra of the films were re-measured as can be seen in FIG. 5 A and FIG. 5B. Photographs of the samples before and after performing the water dripping experiment were captured and shown as inserts. As demonstrated from the inserted photographs of the C1-P3HT film, only the substrateremains after the water dripping experiment, while no characteristic spectrum of P3HT is detected, implying that the film with 15-Crown-5 is completely disintegrated with water. Meanwhile, it is observed that the pristine P3HT film remains intact after the dripping experiment, and the spectra of the pristine P3HT film before and after dripping water arc almost identical, confirming that the pristine P3HT film could not be disintegrated with water.

[0164] Moreover, FIG. 5F shows the resultant photographs from water contact angle measurements of the Cr-P3HT and pristine P3HT films. The Cr-P3HT film gets cracked after dripping water drops, which is consistent with the results of experiments showing that water can disintegrate the Cr-P3HT film. However, the pristine P3HT film has a low water wettability (contact angle > 105°) due to its hydrophobic alkyl side chains, implying that the pristine P3HT film is very hydrophobic, which is the reason why water could not break the film integrity in the water dripping experiment. As mentioned earlier, the formation of hydrogen bonds between the oxygen of 15-Crown-5 and hydrogen of water molecules causes the observed water-disintegrable behavior of the Cr-P3HT film. Thus, a transient film that easily disintegrates in the presence of water is obtained.

[0165] To demonstrate the transient functionality of the Cr-P3HT-based organic transistors, a series of OECT and OFET devices using both the Cr-P3HT and pristine P3HT as active layers were prepared. Here, OECTs without parylene-patteming were prepared for better demonstration of the transient ability of the Cr-P3HT film, wherein the source and drain electrodes were evaporated on the top of the Cr-P3HT films. The transfer and output characteristics of these OECTs without parylene-patterning for the transient ability demonstration were measured to prove that these OECTs still function as electrochemical transistors, as shown in FIG. 6A to 6C. Thus, these organic transistors can operate well under working conditions. Sec the schematic of the transient ability demonstration in FIG. 5C, which is also realized by dripping water.

[0166] As shown in FIG. 5D for OECT and FIG. 5E for OFET devices, upon dripping water onto the surface of the Cr-P3HT-based devices, cracks immediately form (therefore, it can be called ultrafast disintegration) on the semiconductor layer of the device, and when the device is submerged with more water droplets, the semiconductor film completely breaks and detaches from the substrate, exposing the bare Si / SiO2substrate and leaving fragments of the broken film in the water. On the other hand, the pristine P3HT devices show hydrophobic behavior upon dripping water onto the surface of them, and after enough water was dripped to submerge the whole device and the device was retrieved from the water, the pristine P3HT -based devices still remain visibly intact, without leaving any visible traces in water.

[0167] Example 8: Summary

[0168] The Cr-P3HT films have been shown to be effective in developing water- disintegrable and high-performance transient organic transistors. The Cr-P3HT -based OECTs with higher normalizedmof 163.18 ± 16.95 S cm-1, larger C* value of 415.44 ± 43.58 F cm-1V"1s’1, lower threshold voltage (-0.45 ± 0.01 V), and faster transient response of 0.26 s are demonstrated, while the C1-P3HT -based OFET appears to have improved hole mobility in comparison to the pristine P3HT-bascd OFET. GIWAXS and UV-vis-NIR measurements reveal that the enhanced hole mobility arises from the edge-on oriented crystallites and better P3HT aggregate ordering enabled by the addition of 15-Crown-5, while AFM studies demonstrate that 15-Crown-5 induces phase separation and network-like P3HT domains of P3HT. The electrochemical doping studies show a more prominent and faster doping process when employing 15- Crown-5 in P3HT. Both effects contribute to more efficient charge transport, ion penetration, and thus better mixed electronic and ionic transport, higher transconductance, lower threshold voltage and faster response in the Cr-P3HT -based OECT, and higher hole mobility in the Cr-P3HT-based OFET. Moreover, two complementary inverters using the Cr-P3HT-based and P3HT-based OECTs with the same n-type BBL-based OECT were designed to demonstrate the benefits of 15-Crown- 5 on the conjugated polymer's ionic-electronic transport properties. As a result, the Cr- P3HT -based inverter can achieve very high gain values (82 N!N at 0.7V) and operate at lower supply voltages when compared to that of the P3HT- based inverter. Furthermore, the water-disintegrable capability of the Cr-P3HT films and the corresponding OECTs and OFETs are demonstrated by water dripping experiments, wherein both films and devices based on the Cr-P3HT undergo ultrafast disintegration in the presence of water. Thus, the incorporation of crown ether into the conjugated polymer is successfully shown to overcome the challenges associated with achieving ultrafast transience functionality with simultaneously improved device performance.

[0169] Example 9: Pressure Sensors

[0170] Solid electrolyte with micro-pyramid structures are combined with previous OECTs to prepare OECT-based pressure sensors. As shown in FIG. 7 A and FIG. 7D, the transfer curves of these OECT-based pressure sensors were captured under different pressure, and the changes in the drain current were recorded to obtain the sensitivities to pressure at different pressure region as can be seen in FIG. 7B and FIG. 7E, the sensitivities of the Cr-P3HT OECT-based pressure sensor in 0-5 and 6-60 kPa are 8657 and 764 kPa1, respectively, while the sensitivities of the P3HT OECT-based pressure sensor in 0-5 and 6-60 kPa are 6754 and 530 kPa"1, respectively. Furthermore, the tune abilities of sensitivity by gate voltage of these OECT-based pressure sensors were studied as shown in FIG. 7C and 7F, the Cr-P3HT OECT-based pressure sensor achieves greater sensitivity when the same gate bias is applied, while when achieving the same sensitivity, the Cr-P3HT OECT-based pressure sensor has lower power consumption. These pressure sensors were used to detect pulse signals in order to demonstrate their potentials in practical applications. Pulse waveforms with distinguishable peaks (percussion wave, tidal wave, and diastolic wave) were recorded by both OECT-based pressure sensors as shown in FIG. 7G and 7H, and the heart rates of the volunteer were calculated to be 69 bpm (beats per minute). Clearer and sharper characteristic peaks are observed in the pulse signals recorded by the Cr-P3HT OECT- based pressure sensor, which is in line with its higher sensitivities.

[0171] Example 10: Further Examples

[0172] The present disclosure describes a transient conjugated polymer (i.e., the water-degradable conjugated polymer material) that can disintegrate in water and exhibit favorable water-disintegrable functionality and better mixed ionic and electronic transport properties. The transient conjugated polymer may be referred to as the “water-degradable conjugated polymer material”. The transient conjugated polymer demonstrates enhanced charge carrier transport and ion penetration capabilities and can be used as a channel layer in an organic electrochemical transistor (OECTs). The transient conjugated polymer can also be implemented in applications such as inverters and pressure sensors. In various examples, the transient conjugated polymer is water disintegrable.

[0173] In various examples, the transient conjugated polymer may include a hydrophobic polymer thin film (i.e., the semiconducting polymer as a layer), and a crown ether. In various examples, the hydrophobic polymer thin film may include a hydrophobic polymer. In various examples, the hydrophobic polymer can be poly(3- hcxylthiophcnc-2,5-diyl) (P3HT). In various examples, the crown ether can be 15- Crown-5, or a derivative thereof. In various examples, the hydrophobic polymer is a semiconducting material. In various examples, organic semiconductor devices comprising the transient conjugated polymer are demonstrated. In various examples, the hydrophobic polymer and the crown ether can be present in a weight ratio ranging from 100: 1 to 1:100, 2: 1 to 1:2, etc. Other weight ratios are already described above.

[0174] Various examples also related to a method for forming the transient conjugated polymer. The method can include providing a hydrophobic polymer, forming a solution I comprising the hydrophobic polymer, forming a solution II comprising the crown ether, and mixing the solution I and the solution II. In various examples, forming the solution I may involve dissolving the hydrophobic semiconducting polymer in an organic solvent. In various examples, mixing the solution I and the solution II can be carried out for at least 30 minutes.

[0175] Various examples relate to an organic electrochemical transistor (OECT) that can comprise a source electrode and a drain electrode, and the transient conjugated polymer described above configured as a channel layer between and / or in contact with both the source electrode and the drain electrode. In various examples, the source electrode and the drain electrode can be in contact with the transient conjugated polymer. In various examples, the organic electrochemical transistor can further comprise an electrolyte arranged in contact with the channel layer. In various examples, the organic electrochemical transistor may further comprise a gate electrode arranged in contact with the electrolyte.

[0176] Various examples also relate to a method for forming the organic electrochemical transistor, the method can comprise forming a source electrode and a drain electrode, forming a transient conjugated polymer described above as a channel layer between and in contact with both the source electrode and the drain electrode. In various examples, the method may further comprise depositing an electrolyte on the channel layer, wherein the electrolyte is in contact with the channel layer. In variousexamples, the method may further comprise forming a gate electrode in contact with the electrolyte.

[0177] Various examples relate to an inverter comprising a p-type OECT and / or a n- type OECT as described above.

[0178] In various examples, the p-typc OECT can comprise a source electrode and a drain electrode, and a p-type semiconducting polymer comprising a transient conjugated polymer described above configured as a channel layer between and in contact with both the source electrode and the drain electrode.

[0179] Various examples relate to an inverter that can comprise a p-type OECT and / or a n-type OECT.

[0180] Various examples relate to a method for forming the p-type OECT that constitute the inverter described above, the method can comprise forming a source electrode and a drain electrode, and forming a polymer comprising the transient conjugated polymer described above configured as a channel layer between and in contact with both the source electrode and the drain electrode.

[0181] In various examples, the method of forming the inverter can comprise forming a p-type OECT described above, and forming a n-type OECT, assembling the p-type OECT and a n-type OECT into an inverter.

[0182] Various examples, also relate to a pressure sensor comprising an OECT described above, the pressure sensor can comprise a source electrode and a drain electrode, a polymer comprising the transient conjugated polymer described above configured as a channel layer between and in contact with both the source electrode and the drain electrode, and a sensing component comprising a solid-state electrolyte layer with protruding structures. In various examples, the sensing component can comprise a solid-state electrolyte layer having protruding structures configured to face the channel layer.

[0183] Various examples relate to a method for forming the pressure sensor, the method comprising forming a source electrode and a drain electrode, forming a polymer comprising the transient conjugated polymer described above configured as a channel layer on and in contact with both the source electrode and the drain electrode, and forming a sensing component comprises a solid-state electrolyte layer having protruding structures configured to face the channel layer. In various examples, formingthe sensing component can comprise forming a solid-state polymer layer having protruding structures from a mould, depositing the transient conjugated polymer as a channel layer, and assembling the solid-state polymer layer with the side where the protruding structure is located facing the channel layer.

[0184] Various embodiments and examples of the present disclosure arc directed to the water-disintegrable transient conjugated polymer exhibiting advantageous water- disintegrable functionality and higher mixed ionic and electronic transport properties. Examples of such transient conjugated polymers demonstrated enhanced charge carrier transport and ion penetration capabilities and can be used as channel layers of OECTs. Other examples of such transient conjugated polymers in different applications such as inverters and pressure sensors were presented above to further evaluate the use of the transient conjugated polymer.

[0185] An increasing number of applications, such as implantable electronics, eco- friendly electronics, and hardware- secure electronics, are pursuing the objective of developing high-performance transient electronic devices. The present disclosure is advantageous to industrial applications, as it offers a competitive advantage in the commercialization of developing water-disintegrable transient conjugated polymer- based high performance electronics to meet the application needs of transient digital circuits and transient health monitoring devices.

[0186] The examples have presented high performance OECTs, inverters and pressure sensors based on the transient conjugated polymer with favourable water- disintegrable functionality and balanced ionic and electronic transport properties. It is notable that the water-disintegrable abilities of the transient conjugated polymer-based films and devices are successfully demonstrated. Higher normalized transconductance, lower threshold voltage and faster transient response are achieved in the transient conjugated polymer-based OECTs, the transient conjugated polymer-based inverter obtains high gain values and can operate at much faster responses, and the greater sensitivities are realized in the transient conjugated polymer OECT-based pressure sensors. This opens up opportunities for high-performance transient organic electronics.

[0187] While the present disclosure has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing fromthe spirit and scope of the present disclosure as defined by the appended claims. The scope of the present disclosure is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

CLAIMS1. A water-degradable conjugated polymer material comprising: a semiconducting polymer; and a crown ether, wherein the crown ether resides in an interstitial region of the semiconducting polymer, wherein the interstitial region is defined by polymer chains of the semiconducting polymer.

2. The water-degradable conjugated polymer material of claim 1, wherein the semiconducting polymer comprises a hydrophobic polymer.

3. The water-degradable conjugated polymer material of claim 1 or 2, wherein the semiconducting polymer comprises a polythiophene-based mixed ionic -electronic conductor.

4. The water-degradable conjugated polymer material of any one of claims 1 to 3, wherein the crown ether comprises 15-Crown-5, 18-crown-6, dicyclohexano-18- crown-6, or a derivative thereof.

5. The water-degradable conjugated polymer material of any one of claims 1 to 4, wherein the crown ether is conjugated to the semiconducting polymer in a manner which an oxygen atom of the crown ether remains accessible to a hydrogen of a water molecule for forming a hydrogen bond.

6. The watcr-dcgradablc conjugated polymer material of any one of claims 1 to 5, wherein the semiconducting polymer and the crown ether comprises a weight ratio of 100:1 to 1: 100.

7. The water-degradable conjugated polymer material of claim 6, wherein the weight ratio has a range of 2: 1 to 1 :2.

8. A method for forming the water-degradable conjugated polymer material of any one of claim 1 to 7, the method comprising: providing an organic solution comprising the semiconducting polymer; and mixing the organic solution and the crown ether.

9. The method of claim 8, wherein the method is absent of an acid.

10. The method of claim 8 or 9, wherein providing the organic solution comprises dissolving the semiconducting polymer in an organic solvent.

11. The method of claim 10, wherein the organic solvent comprises chloroform, dichloromc thane, chlorobenzene, or dichloro benzene.

12. The method of any one of claims 8 to 11, wherein mixing the organic solution and the crown ether comprises mixing the organic solution with an amount of crown ether which is more than the semiconducting polymer in the organic solution.

13. The method of any one of claims 8 to 12, wherein mixing the organic solution and the crown ether is carried out for at least 30 minutes.

14. A device comprising the water-degradable conjugated polymer material of any one of claims 1 to 7.

15. The device of claim 14, wherein the device is a transistor, an inverter, or a pressure sensor.

16. The device of claim 15, wherein the transistor comprises an organic electrochemical transistor or an organic field effect transistor.

17. The device of claim 16, wherein the organic electrochemical transistor comprises: a substrate;a source electrode and a drain electrode spaced apart and configured on the substrate; a channel layer configured between and in contact with the source electrode and the drain electrode, wherein the channel layer comprises the water-degradable conjugated polymer material of any one of claims 1 to 7 ; a solid-state electrolyte configured on the channel layer; and a gate electrode configured on the solid-state electrolyte.

18. The device of claim 17, wherein the solid-state electrolyte comprises l-ethyl-3- methylimidazolium tetrafluoroborate and poly(vinylidene fluoride-co- hexafluoropropylene) .

19. The device of claim 16, wherein the organic field effect transistor comprises: a substrate configured as a bottom gate electrode; a dielectric layer configured on the substrate; an active layer configured on the dielectric layer, wherein the active layer comprises the water-degradable conjugated polymer material of any one of claims 1 to 7; and a source electrode and a drain electrode spaced apart and configured on the active layer.

20. The device of claim 19, wherein the semiconducting polymer of the water- degradable conjugated polymer material of any one of claims 1 to 7 comprises a cyclic ring structure defining a planar surface, and wherein the planar surface is configured orthogonal or parallel to a surface of the dielectric layer which faces the active layer.

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