Photo-electric device

Abstract

This disclosure relates to a photo-electric device. An absorber layer is located within an optical cavity and absorbs photons in the optical cavity. The absorber layer has a first energy level being higher than a second meta-stable energy level. Electrodes discharge electric charge carriers generated in the optical cavity. Charge transport layers are located within the optical cavity and facilitate transport of the electric charge carriers from the absorber layer to the electrodes. The optical cavity is resonant at a resonance frequency that corresponds to the first energy level to facilitate excitation by the photons into the first energy level. The absorber layer provides energy transfer from the first energy level to the second energy level and energy is stored in the second energy level. The charge transport layers transport the electric charge carriers, provided by the absorber layer, to the electrodes.

Description

"Photo-electric device" Cross-Reference to Related Applications

[0001] The present application claims priority from Australian Provisional Patent Application No 2024903360 filed on 17 October 2024, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] This disclosure relates to a photo-electric device that absorbs photons and generates charge carriers, such as, but not limited to, a quantum battery. Background

[0003] Electrical energy storage has become a major focus in recent times and advances have been achieved in conventional battery technologies. In particular, chemical batteries have become more efficient and energy dense at reduced cost. However, the charging time of chemical batteries is still substantial.

[0004] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims.

[0005] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.Summary

[0006] In some examples, there are described photo-electric devices, methods of manufacture, use and method of modelling, as well as specific device applications, such as quantum battery devices, absorber devices, photo-voltaic devices, etc.

[0007] In one example, there is described a photo-electric device comprising an optical cavity, which may be configured to receive photons and reflect photons within the optical cavity. The device may comprise an absorber layer located within the optical cavity and configured to absorb photons in the optical cavity. In some particular examples, the absorber layer may having a first energy level and a second energy level, the first energy level being higher than the second energy level, and the second energy level being meta-stable. The device may comprise Electrodes configured to discharge electric charge carriers generated in the optical cavity. The device may comprise one or more charge transport layers, which may be located within the optical cavity, and may be configured to facilitate transport of the electric charge carriers from the absorber layer to the electrodes. he optical cavity may be configured to be resonant at a resonance frequency, which may corresponds to the first energy level of the absorber layer. The optical cavity may be configured to facilitate excitation by the photons into the first energy level. The absorber layer may be configured to provide energy transfer from the first energy level to the second energy level, and energy may be stored or storable in the second energy level. One or more charge transport layers may be configured to transport the electric charge carriers, e.g., provided by the absorber layer being excited to the second energy level, to the electrodes.

[0008] In some embodiments, the device may be configured to store energy to the first energy level using an optical signal providing the photons. The device may be configured to release the electric charge carriers from the second energy level via the one or more charge transport layers, e.g., and the electrodes.

[0009] In some embodiments, the one or more charge transport layers may comprise at least one charge transport layer on either side of the absorber layer.

[0010] In some embodiments, the one or more charge transport layers may comprise one or more of a hole blocking layer, hole injection layer, and electron injection layer.

[0011] In some embodiments, the one or more charge transport layers may comprise an acceptor layer, and a transition layer, which may be located between the acceptor layer and the absorber layer. In some examples, the transition layer may be provided to increase the surface area of the interface between the acceptor layer and the absorber layer compared to the case in which one face of the acceptor layer is interfaced directly with one face of the absorber layer yielding a rectangular interface.

[0012] In some embodiments, the absorber layer may be made of a first material and the acceptor layer may be made of a second material. The transition layer may be made of a mixture of the first material and the second material.

[0013] In some embodiments, the mixture may be selected or otherwise provided such that, in use, the mixture ratio facilitates being at resonance.

[0014] In some embodiments, the first material may act as an electron donor, which may form complexes with the second material in the transition layer.

[0015] In some embodiments, the one or more charge transport layers may comprise blocking layers that block electrons and / or holes.

[0016] In some embodiments, the charge transport layers may comprise materials that, in combination, form an energy gradient across the optical cavity, e.g., which may facilitate charge separation, supresses re-combination of charge carriers, etc..

[0017] In some embodiments, a first electrode may be comprised with or otherwise formed by, a first reflective layer forming the optical cavity. The first electrode may form an entry layer for photons into the optical cavity. The one or more charge transport layers may comprise an electron injection layer, which may be adjacent to the first electrode; The one or more charge transport layers may comprise a hole blocking layer, which may be adjacent to the electron injection layer. The one or more charge transport layers may comprise an electron acceptor layer, which may be adjacent to the hole blocking layer. The one or more charge transport layers may comprise a transition layer, e.g., between the electron acceptor layer and the absorber layer. The one or more charge transport layers may comprise a hole injection layer, e.g., between the absorber layer and a second reflective layer forming the optical cavity.In some example, such a second reflective layer may be located between the hole injection layer and a second electrode.

[0018] In some embodiments, excitation by photons into the first energy level may comprise excitation by the photons into a third energy level created by an interaction between resonant light in the optical cavity and molecules of the absorber layer, and transfer of energy from the third energy level to the first energy level.

[0019] In some embodiments, the third energy level may relate to a many-body state, which may be created by synchronised molecule excitations under a photon field created by the photons resonant in the cavity.

[0020] In some embodiments, the first energy level and the third energy level may facilitate transitioning of the many-body state into the first energy level by dephasing of the synchronised molecule excitations.

[0021] In some embodiments, the third energy level may provide for superabsorption, e.g., by many-body state transitions in the absorber layer.

[0022] In some embodiments, the third energy level may relate to a polariton state.

[0023] In some embodiments, the second energy level may be an electron configuration in the absorber layer.

[0024] In some embodiments, the energy transfer may comprises an intersystem crossing from the first energy level to the second energy level.

[0025] In some embodiments, the second energy level may be a triplet energy level of electrons in the absorber layer.

[0026] In some embodiments, the absorber layer may comprise chromophores.

[0027] In some embodiments, the absorber layer may comprise copper phthalocyanine.

[0028] In some embodiments, the one or more charge transport layers may comprise a fullerene layer as an acceptor layer.

[0029] In some embodiments, one or more of the following parameters may be selected (e.g., set) to facilitate resonance: the length of the optical cavity, the thickness and optical property of the absorber layer, and the thickness and optical property of the one or more charge transport layers.

[0030] In some embodiments, at least one of the electrodes may be located within the optical cavity.

[0031] In some examples, there is described an energy storage device that stores electrical energy and delivers the electrical energy to an energy consuming device. The energy storage device may comprises any of the features of the above-described photo-electric device.

[0032] In some examples, there is described a method for manufacturing a photo-electric device (e.g., as described above). The method may comprises providing model parameters for the photo-electric device. The model parameters may characterise an absorber layer located within an optical cavity and configured to absorb photons in the optical cavity. The parameters may characterise electrodes configured to discharge electric charge carriers generated in the optical cavity. The parameters may characterise one or more charge transport layers located within the optical cavity and configured to facilitate transport of charge carriers from the absorber layer to the electrodes. The method may comprise evaluating a molecule model based on the model parameters. The method may comprise fabricating the photo- electric device. The method may comprise making measurements on the photo-electric device. The method may comprise extending the molecule model to account for quantum effects in transport of charge carriers. The method may compriseusing the extended molecule model to determine the model parameters that facilitate resonance in the optical cavity.

[0033] In some embodiments, the method may comprise adjusting a concentration of molecules in the absorber layer to selected (e.g. maximise, or otherwise optimise) an amount of charge carriers discharged by the electrodes.

[0034] There is also described a photo-electric device comprising an absorber layer located within an optical cavity and configured to absorb photons in the optical cavity having a thickness of 15 nm. The device may comprise electrodes configured to discharge electric charge carriers generated in the optical cavity. The device may comprise one or more charge transport layers located within the optical cavity configured to facilitate transport of charge carriers from the absorber layer to the electrodes. One, some or all of of the charge transport layers may have a thickness of 1 nm to 40 nm. Brief Description of Drawings

[0035] An example will now be described with reference to the following drawings:

[0036] Figure 1 is a schematic illustration of a photo-electric device.

[0037] Figure 2 illustrates an energy structure of the photo-electric device.

[0038] Figure 3 illustrates an example stack of layers with materials of a photo-electric device.

[0039] Figure 4 illustrates an energy storage device.

[0040] Figure 5 illustrates a method for manufacturing a photo-electric device.

[0041] Figure 6 illustrates the relevant energy levels of a candidate molecular absorber (in this case copper(II) phthalocyanine) that features in the superabsorption layer of our microcavity device. The ground singlet and Davydov split excited singlet states are labelled ^^00and ^^1, ^^11, respectively. A meta-stable triplet state is labelled as ^^1. Mechanistic arrows schematically illustrate superabsorption from the ground singlet to first excited singlet state (device charging), followed by rapid intersystem crossing (conversion of energy to the triplet state) which only very slowly relaxes back to the singlet ground state (i.e. is meta-stabilised).

[0042] Figure 7 illustrates steady-state reflectance measurements made on our photoelectric cavity device (labelled “Cavity”) and a no cavity control (labelled “No cavity”) providing compelling evidence for strong coupling between light and matter excitations in the cavitydevice. The excited singlet resonances are labelled ^^10for the no cavity molecular excitations and the resonances from hybrid light-matter states (polaritons) are labelled LP, MP and UP for lower, middle and upper polariton.

[0043] Figure 8 illustrates superabsorption for a characteristic device. The square data points (including error bars) are experimental data from differential reflectance measurements performed on the device that maps to the summed excited state populations (labelled ^^01,whose individual time-evolution are shown as faint orange lines). Simulation of the experimental data is shown as a solid line partly covered by the squares and labelled “Diff. Refl.” The solid line underneath represents the time-evolution of the device energy density (the energy stored per molecule) and is labelled ^^(^^).

[0044] Figure 9 illustrates a table containing figures of merit for each of the eight devices fabricated (with differing numbers of absorbers N). Each row records the name of a given device, the approximate number of absorbers in the laser cross-section for each device, the maximum charging power density attained for each device, the charging time for each device and the maximum energy density stored in each device, respectively.

[0045] Figure 10 illustrates the theoretical maximum charging power density (top), charging time (middle) and maximum energy density (bottom) for an idealised quantum battery device operating in the regime of fabricated devices. The measured maximum charging power density, charging time and maximum energy density of each device is superimposed on each plot as a coloured circle labelled with the device (as per Figure 9).

[0046] Figure 11 illustrates the long-time differential reflectance of a representative device from those fabricated. The positive (top of scale) and negative (bottom of scale) signals arise from ground state bleach and excited state absorption pathways that both persist for tens of nanoseconds. This indicates that population of excited states in the device persist for at least tens of nanoseconds.

[0047] Figure 12 illustrates a comparison of the external quantum efficiency (EQE) of the cavity (left) and no cavity (right) control devices as a function of wavelength. This measures the efficiency of devices to convert light (the charging source) to an electric current that canpower an external electronic device. Each cavity device shows a threefold enhanced photon to electric current conversion compared to the no cavity controls.

[0048] Figure 13 illustrates the experimentally measured current (descending curves labelled Current) and discharging power (parabolic curves labelled Power) as a function of applied voltage for each cavity (solid lines) and no cavity (dashed lines) device that was fabricated. The maximum discharging power of the cavity devices exceeds the no cavity controls.

[0049] Figure 14 illustrates the ratio of the maximum discharging power for each cavity device over its no cavity counterpart as a function of the number of absorbers N. A clear linear trend is observed in the discharging power of this ratio, indicating the discharging power of the cavity devices is superextensive. Description of Embodiments

[0050] This disclosure relates to a photo-electric device that absorbs energy from incoming light, stores energy, and delivers the stored energy in the form of electrical current. In one example, the device exploits strong light-matter interactions between the molecules in an absorber layer and an photon field. This interaction creates a polaritonic state, which is an ensemble state of many molecules of the absorber layer entangled with the state of the photon field. More particularly, the absorber layer is located in a cavity that confines a photon field in space therefore inducing a discretisation of the energy levels of the photon field. The absorber layer is composed with at least one species of molecule with an excited state that is approximately resonant with a level of the confined photon field. As a result of the photon field interacting with the molecules, the molecules become synchronised, i.e. form a polaritonic state, which means they can be excited simultaneously when the cavity is populated with photons (e.g. by exciting the confined photon field with a laser light source). This leads to superabsorption of energy, which results in significantly increased energy absorption efficiency. Once the molecules are collectively excited, the molecular ensemble rapidly decoheres into a collective dark state whereby energy is stored in ‘out-of-phase’ singlet excitations of each molecule (quenching a superradiant self-discharging of the energy). These singlet excitations now behave independently and can transition to meta-stable triplet states localised on each molecular centre. It is this triplet state that stores the energy until it is extracted using the electrodes of the device.

[0051] Figure 1 illustrates a photo-electric device 100. This device can be used in some applications as a battery, which is also referred to as a quantum battery because quantum effects may take place to improve the performance of the photo-electric device 100. These quantum effects include the ensemble of excited molecules forming a polariton state, that is, the molecular states become highly entangled with the confined photon field of the device in a quantum sense, and thus individual molecules become correlated with one another. The device may be configured to function in some applications as a more general absorber or in a photo-voltaic application.

[0052] Device 100 comprises an optical cavity formed by a first mirror 101 and a second mirror 102. The cavity is configured to receive photons and reflect photons within the optical cavity. For example, the first mirror is configured to permit transmission of photons into the device 100 (left to right) but reflect photons that would otherwise exit the device (right to left), such as a semi-transparent mirror. The second mirror 102 reflects the photons to prevent them from exiting the device at the back side. As a result, photons become ‘trapped’ as they are reflected multiple times within the cavity.

[0053] The device further comprises an absorber layer 103 located within the optical cavity. The absorber layer 103 is configured to absorb photons in the optical cavity. More particularly, the absorber layer 103 has a first energy level 105 and a second energy level 106, where the first energy level 105 is higher than the second energy level 106. The second energy level 106 is meta-stable. In this context, meta-stable means that an excitation of the molecule into the second energy level 106 persists without external influence for an extended period of time. This is in contrast to the first energy level 105 that can be unstable since an excitation quickly transitions into the second energy level 106 or to the ground energy level 107.

[0054] Figure 1 also shows a ground energy level 107. In some examples, the first energy level 105 is a singlet state and the second energy level 106 is a triplet state. Via rapid intersystem crossing (a phonon-mediated relaxation mechanism), the molecule transitions from the first energy level 105 into the second energy level 106 because the second energy level 106 is lower than the first energy level. In this case, the second energy level 106 has a spin state that differs from the ground energy level 107 and is thus blocked from relaxation bythe Pauli exclusion principle. Thus, energy is stored in the second energy level 106 for an extended period of time.

[0055] The device 100 further comprises electrodes configured to discharge electric charge carriers generated in the optical cavity. Figure 1 shows one electrode at 104 while the second electrode is formed by the first mirror 101, noting that both electrodes can be formed by the respective mirrors or both electrodes are separate and not formed by the mirrors. The device further comprises one or more charge transport layers located within the optical cavity. Figure 1 shows a first charge transport layer 109 and a second charge transport layer 108. The charge transport layers 109, 108 may include layers for electron / hole injection / blocking and are configured to facilitate transport of charge carriers from the absorber layer 103 to the electrodes formed by electrode 104 and a first mirror 101 (also referred to as first reflective layer).

[0056] It is an advantage that the excitation into the first energy level is orders of magnitude faster than for charging a chemical battery. Therefore, noting that charging power is inversely proportional to charging time, substantially higher charging powers can be achieved with the proposed device as a result of significantly reduced charging times.

[0057] The device 100 of Figure 1 may further comprise a light source, such as a laser. In some examples, the light source is narrow-band so that the light energy is concentrated near, or substantially overlaps with the wavelength at which the cavity of device 100 is resonant. In other examples, the light source is wide spectrum and the device absorbs part of the energy in that spectrum where the cavity is resonant.

[0058] The performance of device 100, such as the absorption efficiency of light, can be improved by creating a polariton state in the absorber layer 103. To that end, the optical cavity is configured to be resonant at a resonance frequency that corresponds to the first energy level 105 of the absorber layer. This facilitates excitation by the photons into the first energy level. The absorber layer is configured to provide energy transfer from the first energy level 105 to the second energy level 106. As a result, the energy is stored in the second energy level 106. The one or more charge transport layers 108 / 109 are configured to transport the charge carriers to the electrodes. The charge carriers are provided by the absorber layer 103 due to the absorber layer being excited to the second state. More particularly, theabsorber layer stores energy in a molecular state (the second energy level 106) also referred to as an exciton where electrons and holes form bound pairs that do not readily recombine. The excitons dissociate into free electrons and holes, which are then extracted in the form of electrical energy extracted from the second energy level 106.

[0059] Device 100 can be used as a battery in the sense that device 100 is configured to be charged by the energy represented by the first energy level 105 using an optical signal, such as from a laser, providing the photons. The energy is then stored in the second energy level 106. Device 100 is configured to release the charge carriers dissociated from excitons in the second energy level 106 via the one or more charge transport layers and the electrodes.

[0060] The following examples provide more details on the charge transport layers 108 / 109 to facilitate the transport of charge carriers (e.g., electrons and holes) to the electrodes. It is noted that a range of different architectures can be used to achieve this goal. In some examples, charge transport layers comprise at least one charge transport layer on either side of the absorber layer as shown by the first charge transport layer 109 and the second charge transport layer 108 in Figure 1.

[0061] Each charge transport layer may perform a particular function in the transport of charges and may relate to only holes, only electrons or both. Some charge transport layers may be configured for hole injection, electron injection, hole blocking or electron blocking. In that sense, device 100 comprises charge transport layers that include a hole blocking layer, hole injection layer, and electron injection layer. It is noted that not all layers are shown in Figure 1 since the device 100 may comprise a smaller or larger number of layers than those shown in Figure 1.

[0062] It is noted that electron-hole pairs are generated in the absorber layer as a result of the absorber layer being in the state corresponding to the second energy level 106. The purpose of the charge transport layers is to transport holes to one electrode and electrons to another electrode. To that end, the hole injection layer is located at the same side of the absorber layer 103 as the electron blocking layer. Vice versa, the electron injection layer is located at the same side of the absorber layer 103 as the hole blocking layer. As a result, electrons are injected into the electron injection layer and on that side, the holes a blocked. Onthe other side, holes are injected into the hole injection layer and electrons are blocked. This set-up facilitates the separation and transport of electrons and holes to opposite electrodes.

[0063] Further, the charge transport layers may comprise an electron acceptor layer. In that case, the absorber layer may function as an electron donor layer. When a photon hits the absorber layer, it creates a pair of opposite charges: a negatively charged electron and a positively charged hole. However, unlike in silicon, these charges are not free to move independently in some example materials, such as organic semiconductors. Instead, they are bound together by Coulomb attraction, forming a quasi-particle referred to as an exciton. The exciton can move within the material from one molecule to another. In order to cross the interface between two different materials, the exciton is separated into free charges that can be collected by the electrodes, which is referred to as dissociation.

[0064] This is achieved by creating an interface between the absorber layer 103 and the acceptor layer that have different energy levels, such as copper phthalocyanine (CuPc) and buckminsterfullerene (C60). The absorber layer may be of a donor material, which means it has a higher energy level for the valence band (or highest occupied molecular orbit – HOMO) and a lower energy level for the conduction band (or lowest unoccupied molecular orbit – LUMO) than the material of the acceptor layer, such as C60. When an exciton reaches the interface between absorber layer (donor) and the acceptor layer, it can undergo dissociation. This creates a charge transfer state, where the electron and the hole are separated by the interface but still coupled by Coulomb attraction. The probability of dissociation or recombination depends on several factors, such as the energy difference between the materials, the electric field across the interface, the morphology of the interface, and the presence of defects or impurities.

[0065] In order to improve the morphology of the interface, there may be a transition layer located between the acceptor layer and the absorber layer. This effectively increases the surface area between the acceptor layer and the absorber layer and thus the rate of dissociation. The transition layer may be made of a mixture of the donor material and the acceptor material, such as a mixture of CuPc and C60. It is possible to adjust the mixing ratio between the two materials in the mixture to facilitate the resonance in the cavity. In other words, the mixing ratio may affect the optical property of the transition layer and therefore thecavity. Therefore, the mixing ratio can be used as a tuning parameter to achieve resonance. In some examples, the absorber material acts as an electron donor to from complexes with the acceptor material in the transition layer. This mechanism provides for an advantageous morphology of the transition layer.

[0066] It is noted that, during manufacture of the disclosed device, the transition layer may not be manufactured as a separate layer explicitly. Instead, the transition layer may be created by adjusting the manufacturing parameters such that the transition layer is created as an implicit result of creating the absorber layer and the acceptor layer. For example, the absorber layer is created and then the acceptor layer is created on top of the absorber layer and at the interface, the absorber material mixes with the acceptor material to create the transition layer. As a result, the mixing ratio may not be constant across the transition layer but may gradually change from full absorber material to full acceptor material.

[0067] A subsequent step after dissociation in the operation of the device 100 is to extract the free charges from the interface and transport them to the electrodes. This can be achieved by creating a gradient of energy levels across the device, such that the electrons in the acceptor are driven to the cathode and the holes in absorber (donor) are driven to the anode. The charge transport in the device is facilitated by the charges moving from one molecule to another by overcoming the energy barriers and the Coulomb interactions.

[0068] As set out above, in order to facilitate charge transport, the charge transport layers may be made of materials that, in combination, form an energy gradient across the cavity that facilitate charge separation and supresses re-combination of charge carriers. That is, the lowest unoccupied molecular orbit (LUMO) is lower for materials closer to the cathode and the highest occupied molecular orbit (HOMO) is higher for materials closer to the anode.

[0069] Vice versa, in order to improve the charge transport, the one or more charge transport layers may comprise blocking layers that block electrons or blocking layers that block holes or both. More particularly, hole blocking layers have a lower LUMO than the previous layer in direction of the cathode and electron blocking layers have a higher HOMO in the direction of the anode. In some examples there are separate layers for blocking holes and for blocking electrons. In other examples, some layers are multi-purpose in that they inject holes and at the same time block electrons, or inject electrons and at the same time block holes. In those cases,a separate blocking layer may not be used. This also applies to the reflective layers (or mirrors) which may take the function of electrodes or charge transport layers.

[0070] Figure 2 illustrates an example band structure comprising an absorber layer 201 and a transition layer 203 that generates excitons and provides for energy storage in a meta-stable state, such as a triplet state. The excitons dissociate, facilitated by the acceptor layer 202 and the transition layer 203 into electrons and holes. Electrons are transmitted to the acceptor layer 202 since the acceptor layer has a lower LUMO (top edge of the bar). Holes remain in the absorber layer 201 and are blocked by the hole blocking layer 204 due to the lower HOMO and are therefore prevented from recombination with electrons in the cathode 205. In this example, electrons are blocked by the gap between the LUMO of the hole injection layer 206 and work function of the bottom silver mirror 207 and therefore prevented from recombination with holes in the anode. It is noted here again that the layers in Figure 2 are chosen with the suitable energy levels to facilitate charge transport while at the same time, for having material properties that provide for resonance in the cavity.

[0071] Figure 3 illustrates an example device in the form of a stack 300 of layers. In this example, a cathode 301 (“first electrode”) is formed by a first reflective layer (“top mirror”) forming the cavity and forming an entry layer of the photons (such as from a laser) into the cavity. The one or more charge transport layers comprise an electron injection layer 302 adjacent to the cathode 301. The HOMO and LUMO levels of the electron injection layer 302 facilitate electron injection by creating an energy structure that lowers the barrier for electron transfer from the cathode to the next layer. Electron injection layer 302 may have a wide bandgap with its LUMO level positioned sufficient (e.g., high enough) to effectively reduce the work function of the cathode 301. This reduction in work function aligns the cathode's Fermi level more closely with the LUMO level of the adjacent layer, thereby minimizing the energy barrier for electron injection. The presence of electron injection layer 302 at the interface also helps to passivate surface states on the cathode 301, which can otherwise trap electrons and impede efficient injection. Consequently, the modified energy levels and passivation effects of electron injection layer 302 promote a more efficient and easier electron injection process into the organic semiconductor layer. At the same time, the electron injection layer 302 has optical properties that facilitate resonance of the cavity as describedherein. As an example, the electron injection layer 302 may be made of Lithium Fluoride (LiF) or any other material that shows some or all of the above properties.

[0072] Stack 300 further comprises a hole blocking layer 303 adjacent to the electron injection layer 302. The HOMO and LUMO levels of hole blocking layer 303 facilitate hole blocking by creating an energy barrier that prevents holes from crossing into adjacent layers while allowing electrons to pass through efficiently. Hole blocking layer 303 has a high LUMO level, which aligns well with the LUMO levels of other layers, enabling efficient electron transport. However, its HOMO level is significantly lower than those of other hole- transporting materials, creating a substantial energy barrier that is difficult for holes to overcome. This large energy gap between the HOMO levels of hole blocking layer 303 and adjacent hole-transporting materials effectively blocks the movement of holes. This selective transport property is useful for maintaining charge balance and improving the overall efficiency of stack 300 by ensuring that only electrons are transported through hole blocking layer 303, thereby enhancing device performance. At the same time, the hole blocking layer 303 has optical properties that facilitate resonance of the cavity as described herein. The hole blocking layer 303 may be made of Bathophenanthroline (BPhen) or any other material that shows some or all of the properties provided above.

[0073] Stack 300 further comprises an electron acceptor layer 304 adjacent to the hole blocking layer. Electron acceptor layer 304 possesses a relatively low-lying LUMO level, which makes it energetically favourable for accepting electrons from donor materials with higher HOMO levels. The low LUMO level creates a strong driving force for electron transfer from the donor material to electron acceptor layer 304, resulting in efficient electron acceptance. Additionally, the high electron affinity of electron acceptor layer 304, associated with its low LUMO level, enhances its ability to stabilize the negative charge after electron uptake. The energy gap between the HOMO and LUMO levels of electron acceptor layer 304 is sufficiently large to prevent undesired back electron transfer, thus maintaining its role as an effective electron acceptor. At the same time, the electron acceptor layer 304 has optical properties that facilitate resonance of the cavity as described herein. Electron acceptor layer 304 may be made of Buckminster fullerene (C60) or any other material that shows some or all of the properties provided above.

[0074] Stack 300 further comprises a transition layer 305 between the electron acceptor layer and the absorber layer. The physical properties of transition layer 305 between electron acceptor layer 304 and an absorber layer 306 enhance the performance of the device through several mechanisms. First, the transition layer 305 facilitates efficient charge separation at the donor-acceptor interface due to the complementary electronic properties of the materials. This mixed layer creates an energy level gradient, promoting efficient exciton dissociation and minimizing recombination losses. Additionally, the interpenetrating network of molecules in the transition layer 305 increases the interfacial area, further improving the probability of exciton dissociation. The transition layer 305 also acts as an efficient charge transport pathway, with the acceptor material providing a high electron mobility pathway and absorber material offering good hole mobility, thereby reducing charge carrier recombination. Moreover, the transition layer 305 can optimize the morphology of the active layer, improving the overall device stability and efficiency. By enhancing charge separation, transport, and reducing recombination, the transition layer 305 significantly improves the performance of the device. At the same time, the transition layer 305 has optical properties that facilitate resonance of the cavity as described herein. Transition layer 305 may be made of a mixture of the electron acceptor material and the absorber material or any other material that shows some or all of the properties provided above.

[0075] Stack 300 further comprises absorber layer 306 (also referred to as electron donor layer). The energy structure of absorber layer 306 has been described above with reference to Figure 1. The energy levels of the absorber layer 306 may have a favourable alignment with other materials used in stack 300. Absorber layer 306 has a relatively high HOMO level, which aligns well with the work function of anode materials, facilitating efficient hole injection and transport. Additionally, its LUMO level is appropriately positioned to allow effective electron blocking while enabling the transfer of holes to adjacent layers. This energy level configuration supports efficient exciton dissociation when paired with electron acceptors like C60, as the energy difference between the HOMO of absorber layer 306 and the LUMO of electron acceptor layer 304 creates a driving force for charge separation. The alignment of energy levels of absorber layer 306 with those of other materials in the device ensures minimal energy losses during charge transfer processes, enhancing the overall power conversion efficiency of the photovoltaic cell. At the same time, the absorber layer 306 has optical properties that facilitate resonance of the cavity as described herein. In one example,the absorber layer 306 is made of chromophores, such as copper phthalocyanine (CuPc) or any other material that shows some or all of the properties provided above.

[0076] Stack 300 further comprises a hole injection layer between the absorber layer and a second reflective layer 308 forming the cavity. The second reflective layer 308 being located between the hole injection layer 307 and anode 309. The HOMO level of the hole injection layer 307 may be well-aligned with the work function of the anode material, such as indium tin oxide (ITO) or other high work function materials, which reduces the energy barrier for hole injection from the anode 309 into the hole injection layer 307. Additionally, a low LUMO level means that the hole injection layer 307 can easily accept electrons, stabilizing the positive charge (holes) created during the injection process, which is useful for efficient hole injection and transport. Hole injection layer 307 may have a wide bandgap, i.e., a significant energy difference between its HOMO and LUMO levels, preventing unwanted electron injection from the anode 309 and ensuring holes are the primary carriers injected. Its high ionization potential requires more energy to remove an electron, making it easier to inject holes, as the HOMO level is closer to the anode's Fermi level. Furthermore, a high electron affinity of hole injection layer 307 may ensure that once holes are injected, they are efficiently transported through the material, contributing to the overall efficiency of the device. Thus, the HOMO and LUMO levels of hole injection layer 307 facilitate hole injection by aligning well with the anode's work function, stabilizing injected charges, and promoting efficient hole transport. At the same time, the hole injection layer 307 has optical properties that facilitate resonance of the cavity as described herein. The hole injection layer 307 may be made of 1,4,5,8,9,11-Hexaazatriphenylenehexacarbonitrile (HAT-CN) or any other material that shows some or all of the properties provided above.

[0077] It is noted that stack 300 may also comprise a separate electron blocking layer, which is not shown in Figure 3 as hole injection layer 307 may also block electrons to some degree. However, a separate electron blocking layer may also improve performance. In that sense, it may be possible to remove some layers from Figure 3, such as the hole blocking layer 303 or the electron injection layer 302 or other layers, which may degrade performance but still provide a functioning device.

[0078] As described above, a polariton state may be available and this state may be referred to as a third energy level. This means the excitation of molecules in the absorber layer 306 by the photons into the first energy level involves excitation by the photons into the third energy level created by the interaction between resonant light in the optical cavity and molecules of the absorber layer. This is followed by a transfer of energy from the third energy level to the first energy level of each molecular absorber. More particularly, the third energy level relates to a many-body state created by synchronised molecule excitations under a photon field created by the photons resonant in the cavity. The first energy level and the third energy level facilitate transitioning of the many-body state into the first energy level by dephasing of the synchronised molecule excitations. As a result, the third energy level provides for superabsorption by many-body state transitions in the absorber layer, which significantly improves photon to electron conversion efficiency.

[0079] It is noted here that the molecular excitations are synchronised as a consequence of the many-body polariton state formed from strong light-matter coupling between the molecular ensemble in the absorption layer and the confined photon field. In this state, oscillations ensue between in-phase, synchronous molecular excitations in the absorber layer (with the associated depletion of photons in the confined photon field) and a complete depletion of molecular excitations (with the associated creation of photons in the confined photon field). In some cases, it is exactly half of one oscillation that leads to the synchronised excitation of the molecular ensemble from populating the confined cavity photon field with an external light source. Since the frequency of these oscillations is directly proportional to the light-matter coupling constant multiplied by√^^ (where ^^ is the number of molecules in the absorber layer), the population of excited states in the device (charging) can occur on a timescale inversely proportional to the number of molecules ^^.

[0080] From the first energy level (e.g., the singlet state), a transition (e.g., intersystem crossing) results in an excitation into a second energy level, which is an electron configuration (e.g., exciton) of the molecules in the absorber layer. That is, the energy transfer comprises an intersystem crossing from the first energy level to the second energy level and the second energy level is a triplet energy level of electrons in the absorber layer.

[0081] In order to provide the functionalities described above, there are parameters that can be selected to facilitate, improve or optimise the resonance in the cavity. These parameters may include one or more of: • the length of the optical cavity, • the thickness and optical property of the absorber layer, • the thickness and optical property of the one or more charge transport layers, and • the material of the individual layers.

[0082] It is noted that, regarding the thickness of the absorber layer, superextensive scaling of the charging time may not hold for all N. In further examples, the gap between the first energy level and the unexcited energy level, such as the gap between singlet states S0 and S1 is (approximately) equal to the cavity resonance frequency. This frequency may take values corresponding to the range of wavelengths for visible light (200 nm – 900 nm). That is, the band gap can be chosen subject to the desired frequency band in the light to be absorbed. For example, if a particular laser is to be used for generating the light signal, the band gap may match the laser frequency and then the cavity resonance may also match that frequency. It is noted that the terms relating to frequencies and band gaps, such as “matching”, “corresponding”, does not mean that those are exactly identical but that the frequency of the light is sufficiently close to the band gap to create excitons and sufficiently close to the resonance frequency so that the light induces resonance in the cavity.

[0083] The T1 energy level is lower in energy than S1 but otherwise may take any value. Intersystem crossing may occur on a timescale of about 10 fs to 1000 fs. Light-matter coupling strength for organic molecules is typically between 1 neV and 1 ^^eV and the number of absorbers for superabsorption ranges depending on what this light matter coupling is, and may be between 106and 1014molecules.

[0084] In some examples, the absorber is patterned into different separated cells so that each cell contains an optimal number of molecules, such as between 106and 1014molecules. This may further increase the maximum energy that can be absorbed in a single charging cycle.

[0085] In a further example, it is noted that at least one of the electrodes may be located within the optical cavity. Further, there may be a third electrode in addition to those shown in Figure 3 and that third electrode may be located within the optical cavity.

[0086] Figure 4 illustrates an energy storage device 400 to store electrical energy and deliver the electrical energy to an energy consuming device (not shown). This may also be referred to as a quantum battery because it utilises the quantum effect of strongly correlated molecular excitations. Energy storage device 400 comprises the photo-electric device disclosed herein, such as in Figures 1, 2, or 3. In particular, energy storage device 400 may comprise a first mirror 101, a second mirror 102, an absorber layer 103, an electrode 104 (mirror 101 acting as the other electrode) and one or more charge transport layers 109, 108. Energy storage device 400 may comprise a first connector 401 and a second connector 402 to galvanically connect the energy consuming device.

[0087] Figure 5 illustrates a method 500 for manufacturing a photo-electric device. As set out above, there are a number of parameters that can be adjusted or tuned to improve the operation of the device. One difficulty is that most models are inaccurate when it comes to incorporating quantum phenomena that lead to macroscopic phenomena. In other words, there are accurate models that describe molecules individually and there are accurate models that describe ensemble states, such as polariton states. However, these molecular models do not adequately describe the transport of excitons, disassociation and charge transport through those molecules modelled by the molecule model and the resonance in the cavity. Method 500 provides a solution for tuning or optimising device parameters that affect both the molecule model as well as the underlying transport characteristics.

[0088] Method 500 comprises the step of providing 501 model parameters for the photo- electric device. These model parameters characterise the absorber layer located within the optical cavity. As described above, the absorber layer is configured to absorb photons in the optical cavity. There are also parameters for the electrodes configured to discharge electric charge carriers generated in the optical cavity, and for the charge transport layers located within the optical cavity. As also described above, those charge transport layers are configured to facilitate transport of charge carriers from the absorber layer to the electrodes.

[0089] Method 500 comprises evaluating 502 a molecule model based on the model parameters, which means calculating resulting characteristics of the device based on the molecule model. In some examples, the resulting characteristics would be inaccurate because the molecule model does not fully describe the device. Therefore, method 500 comprises fabricating 503 the photo-electric device as disclosed herein and making measurements 504 on the photo-electric device, such as electrical measurements on voltages and currents and / or optical measurements that indicate the behaviour of the device, such as transitions into different energy levels as described below. Fabrication may involve spin coating, chemical vapour deposition, electron beam epitaxy and other fabrication techniques.

[0090] Method 500 then comprises extending the molecule model to account for quantum effects in transport of charge carriers. In this sense, extending means adjusting the model so that it more accurately reflects the actual observations in the form of the measurements from step 504. Method 500 then uses 506 the extended molecule model to determine the model parameters that facilitate resonance in the optical cavity.

[0091] In one example, the method 500 further comprises adjusting a concentration of molecules in the absorber layer to maximise an amount of charge carriers discharged by the electrodes as described above.

[0092] As shown in Figure 3, the disclosed photo-electric device may have layers of specific thickness (exemplified in Figure 3). For example, the absorber layer 306, located within the optical cavity and configured to absorb photons in the optical cavity, may have a thickness of about 15 nm. Stack 300 further comprises electrodes with a thickness that is less relevant to the overall performance although the cathode 301 on the side of the stack where the photons arrive, which also serves as a mirror, and may be sufficiently thin to transmit most of the photons, such as about 25 nm. The one or more charge transport layers comprise layers of a thickness between about 1 nm and about 40 nm. In particular, the electron injection layer 302 may be significantly thinner than the other layers in the cavity and may have a thickness of about 1 nm, the hole blocking layer 303 a thickness of about 15 nm, the electron acceptor layer 304 a thickness of about 20 nm, the transition layer may be substantially thicker than the electron acceptor layer and the absorber layer and may have a thickness of about 40 nm, the absorber layer a thickness of about 15 nm, the hole injection layer a thickness of about 15 nm.The second reflective layer 308 (bottom mirror) may be thicker, such as about 75 nm because it does not need to transmit photons. The anode 309 may have a thickness of about 110 nm. It is noted that these thickness values are only one example and other values are equally possible.

[0093] More particularly, the thickness values of the layers can be adjusted depending on the other material properties of the selected materials and concentrations of materials and the mixing ratio in the transition layer 305. That is, for a different material for one of the layers, the thickness of that material or the thickness of all layers can be adjusted to account for the different optical properties of the new material so that resonance is still achieved at the desired frequency. The disclosed method of extending the molecular model allows for a multi-parameter optimisation to find a solution of the parameter space that accounts for optical properties by changing the thickness of the materials to achieve resonance at a desired frequency.

[0094] For example, the multi-parameter optimisation may be performed by an optimisation algorithm that solves an optimisation problem, such as a linear integer problem, mixed linear integer problem or non-linear problem. The problem may have one or more constraints and the one or more constraints may comprise a constraint that the optical cavity has a resonance at the first energy level (e.g., the singlet state S1) of the absorber material. This constraint may be formulated based on the optical length of each layer. In one example, the constraint formalises that the sum of the optical length values of the layers is equal to an integer multiple of the wavelength of the incoming light. The optical length of each layer can be calculated using the thickness and the refractive index of the material. When optimising only continuous variables, such as the thickness values of the layers and concentration parameters, the problem becomes more efficient to solve with gradient descent methods, for example. However, when material selection is also considered, the problem may be formulated as a mixed integer problem or a discrete optimisation problem.

[0095] Computationally, optical simulations using transfer matrix methods or finite- difference time-domain (FDTD) simulations can model light absorption and distribution within the layers. These simulations help identify the optimal thickness by predicting how light interacts with the material stack, considering interference effects and absorption profiles.Additionally, device simulations using tools like drift-diffusion models can predict the electrical performance of the photo absorber, accounting for charge carrier generation, transport, and recombination dynamics.

[0096] In this context, it is noted that for other light absorbing materials, it is desirable to make those layers relatively thick so that the maximum amount of light is absorbed. In this case, however, the resonance and photon field leads to the creation of a polariton and therefore, light absorption is more efficient. As a result, and as described above, the thickness of the absorber layer 306 may be dominated by the maximum number of molecules that provide superabsorption. This is an advantage because it may provide more freedom in choosing the thickness values of the remaining layers to achieve resonance since the absorber layer 306 can be thinner than for classical absorption without the creation of polaritons. Experiments

[0097] As set out above, this disclosure provides a microcavity-based quantum battery with superextensive charging rates, stabilisation of stored energy, and electrical energy extraction. The following sections provide further details and experimental results of example implementations. The device operates in the strong light-matter coupling regime resulting in charging power that superextensively scales with the number of molecules. Upon charging, the underlying molecular excitations are rapidly shuttled to meta-stable triplet states, leading to energy retention times six orders of magnitude longer than the device takes to charge. A three-fold photon-to-charge conversion enhancement is demonstrated for the cavity device, out-performing non-cavity controls in external quantum efficiency measurements. The combination of superextensive charging rates, triplet state meta-stabilisation, and energy extraction in a single device is a demonstration of the full cycle of a quantum battery. By coupling collective phenomena to the generation of charge current, the device provides for femtosecond light-to-charge conversion.

[0098] The device design utilises rapid intersystem crossing in copper phthalocyanine (CuPc) chromophores to engineer superabsorbing microcavity quantum batteries that store energy as long-lived triplet excitations for tens of nanoseconds; six orders of magnitude longer than the device takes to charge. Using ultrafast transient reflectance measurements, we demonstrate battery charging times of tens of femtoseconds that scale inversely withchromophore number, the hallmark of superabsorption. Moreover, the device incorporates a donor-acceptor combination of CuPc and fullerene (C60) to ensure efficient energy extraction from our devices as electrical work. Device engineering

[0099] The disclosed device may be fabricated based on Fabry-Perot microcavities whose optical length is tuned to the absorption frequency of an ensemble of CuPc chromophores. To facilitate energy extraction from each device via a charge current (vide infra), the device incorporates a charge donor-acceptor combination of CuPc and fullerene (C60) as well as a suitable choice of optically inert electron-hole blocking and transport materials that are integrated into the cavity. A cross-sectional schematic of the device is shown in Figure 3 which also indicates the direction of laser irradiation. Each device is fabricated with six spatially separated structures (labelled P1, P2, P3, P4, P5 and P6) of approximately 10 mm2surface area. All structures observe the same layer composition as shown in Figure 3 except for P1 and P6. P1 does not include the 75 nm Ag bottom mirror and P6 does not include the 25 nm Ag top mirror, thus these structures act as no-cavity optical and electrical controls, respectively.

[0100] The CuPc chromophores can effectively be described as non-interacting four level systems with energy spacings as shown in Figure 6. The first excited singlet S1 is separated from the ground state S0 by ~ 2 eV with a lower-lying triplet state T1 at approximately ~ 1.2 eV. The excited singlet features a characteristic Davydov splitting common to most porphyrin optical absorbers. This feature is prominent in the reflection measurements of the no cavity devices (see Figure 7) and manifests as two weakly split signals with approximately equal oscillator strengths labelled ^^10and ^^11. For P2-5, these absorption bands are strongly hybridised with the fundamental mode of the confined photon field leading to the formation of upper (UP), middle (MP) and lower (LP) polariton states (Figure 7).

[0101] By systematically varying the concentration of CuPc chromophores in the mixed CuPc:C60layer while keeping the cavity length fixed, we were able to tune the Rabi splitting between UP and LP of each device as a function of N. Changing CuPc concentration was shown to moderately influence the fundamental cavity frequency of each quantum battery, leading to asymmetries in the UP and LP reflectance bands.

[0102] To faithfully represent the MP feature in the theoretical reflectance spectra of D1-8, it was useful to include a coupling of the photon field to both Davydov resonances. Accordingly, the disclosed model gives rise spontaneously to a MP wavefunction with hybridised photon-matter components without ad hoc recourse to dark states. Superextensive battery charging and energy stabilisation

[0103] To reveal the energetic dynamics of the devices, we utilise ultrafast differential reflectance (pump-probe) spectroscopy --- a technique for probing electronic and / or vibrational evolution in chromophores and inorganic semiconductors. In our experiments, an ultra-short resonant pump pulse excites polaritonic states of the device, then the time- evolution of the excited ensemble is monitored by a time delayed probe pulse.

[0104] The femtosecond charging dynamics of a representative device D5 is shown in Figure 8, where we employ two-colour pump-probe to measure the summed excited state populations via the differential reflectance (orange data points). The pump was resonant with the LP, while the probe was resonant with the UP. Using this scheme, we probe the depletion of a common ground state between the LP and UP and are free of pump scatter which typically obscures pump-probe measurements. We observe a sharp increase in the differential reflectance signal, which is matched by our theoretical prediction (solid line following experimental data points indicated by squares). The time-evolution of the individual average state populations are shown as curves labelled by ^^10,and ^^1. The simulated energy density is labelled ^^(^^). After approximately 75fs the energy density diverges from the experimental differential reflectance measurement signifying an average population of the lower energy triplet state via an efficient intersystem crossing mechanism.

[0105] The differential reflectance experiments provide a time-resolved measure of thecombined singlet and triplet excited state populations of CuPc,We capture these dynamics within a cumulant expansion approach and superimpose the simulated Δ^^ / ^^ with the experimental data points in Figure 8. On charging the device, the pump laser populates the microcavity with photons that hybridise with the excited singlet states of the CuPc molecules and induce collective Rabi oscillations between photonic and singlet molecular excitations. Insofar as mechanisms of decoherence operate on longertimescales than those of the light-matter interaction, the charging time τ (defined by ^^(^^) =^^^^^^^^2 s proportional to the rate of the first Rabi flop between the photonic and excitonic components of the LP wavefunction.

[0106] During the coherent evolution of the LP wavefunction, two-level dephasing transitions the system into a collective dark state and quenches superradiant discharge of the battery. By virtue of fast dephasing times γ−1^^ ∼ 50 fs, this mechanism is active in CuPc for^^ > 1010 allowing for 10 times faster charging than other devices of before transitioning intothe deep coupling-dominated charging regime. At approximately 200 fs intersystem crossing (ISC) becomes the dominant singlet relaxation mechanism forming meta-stable CuPc triplet excitations with lifetimes on the order of 10-50 ns. This transition manifests in the energy density (line labelled E(t) in Figure 8) as a biexponential decay.

[0107] Figure 9 summarises the main figures of merit for each of the eight devices studied. As well as the approximate number of CuPc absorbers in the laser cross-section ^^, we report the maximum charging power density ^^max, the charging time ^^ and the maximum energy density ^^maxfrom the theoretical model. In Figure 10, we plot these figures of merit as a function of chromophore number for an idealised quantum battery device including the figures of merit reported in Figure 9 for reference. Notably, the maximum charging power density increases as a function of absorber number ^^, the quintessential feature of superabsorption. The origin of this superextensive charging power stems from the subextensive charging times ^^ that decrease as the capacity of the devices increases. Note that the devices reported in this document do not fall in line with the exact theoretically predicted values owing to variations in device fabrication parameters not accounted for in the theoretical curves.

[0108] Following the charging study, we measured the long-time decay dynamics of the devices using a spectrally broad supercontinuum probe with spectral width spanning 500- 1000 nm. Figure 11 displays a representative differential reflectance spectrum as a function of probe wavelength and probe time delay for device D5. The positive (top of scale) and negative (bottom of scale) signals in this spectrum are assigned to ground state bleach and excited state absorption mechanisms, respectively, which are both dependent upon population of the meta-stable triplet state. Since both of these signals persist for at least 20 ns, thissignifies a non-zero average triplet state population (i.e. energy retention of the device) of tens of nanoseconds. This is six orders of magnitude longer than the devices take to charge. Cavity-enhanced photon to charge conversion

[0109] Controlled extraction of stored energy is a feature of the disclosed quantum battery device. To power, for example, a small electronic device, it is desirable for the extracted energy to be available as electrical work. In Figure 12 we report external quantum efficiency (EQE) measurements for the cavity (left) and no-cavity control (right) of each device D1-8. The polariton branches are clearly visible in the EQE measurements of the cavity and show a threefold overall photon to charge conversion enhancement over the no cavity controls.

[0110] To evaluate the photocurrent generation aspect of the disclosed devices, we measured the current versus applied voltage curves of the cavity (solid lines) and no cavity (dashed lines) for each device under constant irradiation. From these measurements we were able to extract the discharging power as a function of voltage for the cavity and no cavity devices. These data are plotted for each device in Figure 13. Each cavity device displayed a maximal discharging power that was enhanced over its no cavity counterpart.

[0111] In Figure 14, we plot the ratio of the maximal discharging power for the cavity and no cavity analogues of each device and observe a linear scaling with absorber number in each device. Thus, we demonstrate a superextensive enhancement in the discharging of our cavity devices as well as in charging. Summary

[0112] This disclosure provides a finely tuned and physically fabricated device with systematic ultrafast spectroscopic analysis, that experimentally demonstrates a full operational cycle in one device, from superextensive charging to enhanced electrical energy extraction. The larger scale quantum battery performance of this device is not limited by intermolecular emission quenching. By engineering microcavities with strong light-matter coupling this disclosure overcomes fast decoherence mechanisms. The collective effects benefit from strong decoherence mechanisms such as intermolecular dephasing such that superabsorption can occur, but superradiant self-discharing is strongly quenched, stabilising the stored energy.

[0113] At longer timescales, inter-system crossing shuttles the stabilised energy into long lived triplet states which persist for tens of nanoseconds, before disassociating into free carriers and ultimately contributing to a photocurrent.

[0114] In some examples of the disclosed device, intersystem crossing, triplet lifetime and triplet exciton mobility are balanced to lengthen energy storage times without compromising efficient charging and energy extraction. Ultrafast spectroscopy

[0115] Both two-colour pump-probe and pump-supercontinuum-probe measurements were performed on the quantum battery devices in reflection geometry, at room temperature in air. The two-colour femtosecond laser pulses were generated by two non-collinear optical parametric amplifiers (NOPAs) (Light Conversion, Orpheus-N-2H and Orpheus-N-3H) which were pumped by 40% of the intensity of a Yb:KGW laser amplifier (Light Conversion Pharos, 1030nm 180fs pulses). The remaining 60% amplifier output was focused onto a 2 mm sapphire crystal to generate a broadband supercontinuum which spanned 500-1000 nm. The amplifier pulses were selected at a repetition rate of 33.3 kHz for all measurements.

[0116] Cross-correlation measurements showed that the compressed pulses out of the NOPAs had a pulse width of < 35 fs across all measurements. The pump and probe beams were focused onto the quantum battery devices with an almost collinear geometry, with the approximate full width at half-maximum spot diameter at the sample position of ~40 ^m. The quantum battery devices were rotated 25° to the incoming pump and probe pulses so the reflected probe beam could be spatially isolated and re-collimated. The probe was then directed into a spectrometer with a high-speed charge coupled device (CCD) (Entwicklungsbuero Stresing, FLC3030) triggered by the laser amplifier.

[0117] To measure the Δ^^ / ^^ signal, the pump was modulated by a mechanical chopper operating at 16.67 kHz (SciTec Instruments, 310CD) providing shot-to-shot probe-only and pump-probe pulses. To scan the Δ^^ / ^^ signal as a function of time, the probe beam was sent through optical retroreflector delay lines, which extended to 8 ns for the supercontinuum pulses (Newport, DL325), or to 0.8 ns for the NOPA pulses (Newport, ESP300).

[0118] To compare the ultrafast dynamics across different devices it was important to keep a constant ratio of incident photons to absorber molecules in the laser volume. To achieve this, the fluence and wavelength of the pump-probe pulses were varied to account for the steady- state reflection spectra of each device. The fluence of the pump as a function of signal amplitude followed a linear dependence for all fluences used in the experiments ensuring higher order effects induced by the pump are not present in the measurements. Theoretical model

[0119] The reflectance spectra were modelled using a coupled oscillator Hamiltonianannihilates (creates) excitations of the confined photon field with frequency Δ^^and X_^^^^ = |^^┤^^├ ^^┤| are Hilbert operators that work on the low-lying electronic levels ofthe CuPc absorber. The indices α, β ∈ {0,1,2} enumerate the ground ^^0, first-excited ^^10and second-excitedlevels, respectively, with energies 0, Δ1and Δ2as in Figure 6. Since we do not probe the steady-state reflectance of our devices in the near infra-red, the triplet state dynamics do not contribute to the simulated reflectance, thus we do not consider their population in our coupled oscillator model. The collective light-matter coupling constant ^^^^^^quantifies the interaction of the CuPc ensemble electric dipole with the quantised cavityradiation field and is related to the bare coupling (per molecule) ^^ via ^^^^^^ = √^^^^. Thesteady-state reflectance of the cavity was simulated within a Fermi golden rule approach 2 / 2σinvolving the coupled oscillator eigenstates |^^^^^ with corresponding energies ^μthat depend upon the microscopic parameters of Hamiltonian (1). The intensity ^^0and combined homogeneous and inhomogeneous broadening σ are fitting parameters and ν is the frequency of incident photons external to the quantum battery.

[0120] The pertinent dynamics of the ultrafast charging experiments are captured by the Tavis-Cummings Hamiltonianwritten in the rotating frame of the laser. We assume a Gaussian temporal profile η(^^) =exp [−((^^ − ^^2 0) / 2σ) ] / σ√2π for the pulse envelope and FWHH 35 fs. The dissipativeinteractions between the cavity quantum battery and its environment are accounted for with the Lindblad master equationwhere ℒ[^^] =ρ} are Lindblad jump operators. In Eq. (4) we account for therate of photon loss from the cavity κ, the rate of non-radiative relaxation from the singlet ^^−and triplet ^^^−^states, intersystem crossing γISCand singlet dephasing ^^^^.

[0121] The ultrafast transient reflectance experiments provide a measure of the summedexcited state CuPc populations Δ^^ / ^^ ∝ ^^^^^^^^ + ^^^11^ + ^^^22^. The populations ^^^αα^ for amolecule in the ensemble are obtained by numerically solving a hierarchical set of coupled equations of motion for the molecular and cavity degrees of freedom which, in general, do not close. We enforce the closure of these equations by approximating the time-evolution of three ^^ ^ ^^ ^ ^ ^^ ^ ^ ^^ ^ ^ ^^ ^^ ^ body correlators as ^^^^^^ = ^^^^ ^^ + ^^^^ ^^ + ^^ ^^^^ − 2 ^^ ^^ ^^ , thus capturingthe pertinent dynamics with corrections scaling as ^^1 / ^^. By solving for the populations( )^^^ ^, we obtain the time-evolution of the quantum battery energy density ^^(^^) =ααℏ(Δ ^^^ ^ + Δ ^^^ ^ + Δ ^^^ ^), the charging time τ (defined by ^^(τ) =^^^^^^^^1 11 2 22 ^^ ^^^^2 nd the ^^^^^^^^maximum charging power ^^ = ill be appreciated by persons skilled in the art that^^^^^^^^ numerous variations and / or modifications may be made to the above-described embodiments,without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

[0122] It will be appreciated by persons skilled in the art that numerous variations and / or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A photo-electric device comprising: an optical cavity configured to receive photons and reflect photons within the optical cavity; an absorber layer located within the optical cavity and configured to absorb photons in the optical cavity, the absorber layer having a first energy level and a second energy level, the first energy level being higher than the second energy level, and the second energy level being meta-stable; electrodes configured to discharge electric charge carriers generated in the optical cavity; and one or more charge transport layers located within the optical cavity and configured to facilitate transport of the electric charge carriers from the absorber layer to the electrodes; wherein the optical cavity is configured to be resonant at a resonance frequency that corresponds to the first energy level of the absorber layer to facilitate excitation by the photons into the first energy level, wherein the absorber layer is configured to provide energy transfer from the first energy level to the second energy level and energy is stored in the second energy level, and the one or more charge transport layers are configured to transport the electric charge carriers, provided by the absorber layer being excited to the second energy level, to the electrodes.

2. The device of claim 1, wherein the device is configured to store energy to the first energy level using an optical signal providing the photons, and release the electric charge carriers from the second energy level via the one or more charge transport layers and the electrodes.

3. The device of claim 1 or 2, wherein the one or more charge transport layers comprise at least one charge transport layer on either side of the absorber layer.

4. The device of any one of the preceding claims, wherein the one or more charge transport layers comprise a hole blocking layer, hole injection layer, and electron injection layer.

5. The device of any one of the preceding claims, wherein the one or more charge transport layers comprise an acceptor layer, and a transition layer is located between the acceptor layer and the absorber layer to increase a surface area between the acceptor layer and the absorber layer.

6. The device of claim 5, wherein the absorber layer is made of a first material and the acceptor layer is made of a second material and the transition layer is made of a mixture of the first material and the second material.

7. The device of claim 6, wherein the mixture is according to a mixture ratio that facilitates being at resonance.

8. The device of any one of claims 6 or 7, wherein the first material acts as an electron donor to from complexes with the second material in the transition layer.

9. The device of any one of the preceding claims, wherein the one or more charge transport layers comprise blocking layers that block electrons and / or holes.

10. The device of any one of the preceding claims, wherein the charge transport layers are made of materials that, in combination, form an energy gradient across the optical cavity that facilitate charge separation and supresses re-combination of charge carriers.

11. The device of any one of the preceding claims, wherein a first electrode is formed by a first reflective layer forming the optical cavity and forming an entry layer of the photons into the optical cavity, and the one or more charge transport layers comprise: an electron injection layer adjacent to the first electrode; a hole blocking layer adjacent to the electron injection layer; an electron acceptor layer adjacent to the hole blocking layer; a transition layer between the electron acceptor layer and the absorber layer; and a hole injection layer between the absorber layer and a second reflective layer forming the optical cavity, the second reflective layer being located between the hole injection layer and a second electrode.

12. The device of any one of the preceding claims, wherein the excitation by the photons into the first energy level comprises: excitation by the photons into a third energy level created by an interaction between resonant light in the optical cavity and molecules of the absorber layer, and transfer of energy from the third energy level to the first energy level.

13. The device of claim 12, wherein the third energy level relates to a many-body state created by synchronised molecule excitations under a photon field created by the photons resonant in the cavity.

14. The device of claim 13, wherein the first energy level and the third energy level facilitate transitioning of the many-body state into the first energy level by dephasing of the synchronised molecule excitations.

15. The device of claim 12, 13 or 14, wherein the third energy level provides for superabsorption by many-body state transitions in the absorber layer.

16. The device of any one of claims 12 to 15, wherein the third energy level relates to a polariton state.

17. The device of any one of the preceding claims, wherein the second energy level is an electron configuration in the absorber layer.

18. The device of any one of the preceding claims, wherein the energy transfer comprises an intersystem crossing from the first energy level to the second energy level.

19. The device of any one of the preceding claims, wherein the second energy level is a triplet energy level of electrons in the absorber layer.

20. The device of any one of the preceding claims, wherein the absorber layer comprises chromophores.

21. The device of any one of the preceding claims, wherein the absorber layer comprises copper phthalocyanine.

22. The device of any one of the preceding claims, wherein the one or more charge transport layers comprise a fullerene layer as an acceptor layer.

23. The device of any one of the preceding claims, wherein the following parameters are set to facilitate being at resonance: the length of the optical cavity, the thickness and optical property of the absorber layer, and the thickness and optical property of the one or more charge transport layers.

24. The device of any one of the preceding claims, wherein at least one of the electrodes is located within the optical cavity.

25. An energy storage device to store electrical energy and deliver the electrical energy to an energy consuming device, the energy storage device comprising the photo-electric device of any one of claims 1 to 24.

26. A method for manufacturing a photo-electric device, the method comprising: providing model parameters for the photo-electric device, the model parameters characterising an absorber layer located within an optical cavity and configured to absorb photons in the optical cavity, electrodes configured to discharge electric charge carriers generated in the optical cavity, and one or more charge transport layers located within the optical cavity and configured to facilitate transport of charge carriers from the absorber layer to the electrodes; evaluating a molecule model based on the model parameters; fabricating the photo-electric device; making measurements on the photo-electric device; extending the molecule model to account for quantum effects in transport of charge carriers; and using the extended molecule model to determine the model parameters that facilitate resonance in the optical cavity.

27. The method of claim 26, wherein the method comprises adjusting a concentration of molecules in the absorber layer to maximise an amount of charge carriers discharged by the electrodes.

28. A photo-electric device comprising: an absorber layer located within an optical cavity and configured to absorb photons in the optical cavity having a thickness of 15 nm; electrodes configured to discharge electric charge carriers generated in the optical cavity; and one or more charge transport layers located within the optical cavity and configured to facilitate transport of charge carriers from the absorber layer to the electrodes, each of the charge transport layers having a thickness of 1 nm to 40 nm.

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