Photovoltaic-powered electronic shelf labels

Abstract

Electronic sign label devices including a housing having a translucent backside element and a frontside window element, a display arrangement within the housing, and a photovoltaic element housed within the housing between the translucent backside element and the display arrangement. The display arrangement includes a circuit board and a display element configured to display information viewable through a translucent portion of the frontside window element. The photovoltaic element is configured to generate electrical power for powering the ESL device based on light received from an external environment.

Description

PHOTOVOLTAIC-POWERED ELECTRONIC SHELF LABELSINCORPORATION BY REFERENCE

[0001] A PCT Request Form is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed PCT Request Form is incorporated by reference herein in their entireties and for all purposes.FIELD

[0002] Certain aspects generally pertain to electronic signs that integrate at least one energy harvesting element such as a photovoltaic cell.BACKGROUND

[0003] Electronic devices can consume a significant amount of power. Many electronic devices, especially those that are portable, rely on battery power. Traditional batteries are disposable devices that contain harmful chemicals. Rechargeable batteries might be considered an environmentally friendlier alternative in certain respects, and some electronic devices have an integrated rechargeable battery that is not user replaceable. The rechargeable battery may be charged through a wired interface or may be charged wirelessly. A photovoltaic cell is an example of an energy harvesting element that can be used as a fully integrated charging solution that does not rely on an external charging device.SUMMARY

[0004] Certain embodiments pertain to electronic sign label (ESL) devices. In some cases, an ESL device includes a housing having a translucent backside element and a frontside window element, a display arrangement within the housing, and a photovoltaic element housed within the housing between the translucent backside element and the display arrangement. The display arrangement includes a circuit board (e.g., a printed circuit board (PCB)) and a display element configured to display information viewable through a translucent portion of the frontside window element. The photovoltaic element is configured to generate electrical power for powering the ESL device based on light received from an external environment.

[0005] Certain embodiments pertain to digital signage devices. In some cases, an digital signage device includes a first housing comprising a first translucent element and a second translucent element, a plurality of photovoltaic cells housed within the first housing between the first translucent element and the second translucent element, a second housing comprising a frontside window element, and a display arrangement housed within the second housing. Thephotovoltaic cells are configured to generate electrical power for powering the digital signage device based on light received from an exterior environment. The display arrangement comprising a circuit board and an electronic display configured to display information viewable through a translucent portion of the frontside window element.

[0006] Some techniques disclosed herein may be practiced with a processor-implemented method, a system comprising one or more processors and one or more processor-readable media, and / or one or more non-transitory processor-readable media.

[0007] These and other features are described in more detail below with reference to the associated drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Illustrative embodiments are described in detail below with reference to the following figures.

[0009] Figure 1 depicts an exploded view of an example of components of an electronic shelf label device 100, according to certain embodiments.

[0010] Figure 2A depicts front and side views of electronic shelf label device of Figure 1.

[0011] Figure 2B depicts a back view of electronic shelf label device of Figure 1.

[0012] Figure 3A depicts a perspective view of an example of components of an electronic shelf label device, according to certain embodiments.

[0013] Figure 3B depicts another perspective view of the example of the electronic shelf label device in Figure 3A, according to certain embodiments.

[0014] Figure 3C depicts a front view of the example of the electronic shelf label device in Figure 3A, according to certain embodiments.

[0015] Figure 4A depicts a back view of components of electronic shelf label device of Figures 3A-3C.

[0016] Figure 4B depicts a cross-sectional view of components of electronic shelf label device of Figures 3A-3C.

[0017] Figure 5 depicts an exploded view of another example of components of an electronic shelf label device, according to certain embodiments.

[0018] Figure 6A depicts a perspective view of an example of an electronic shelf label device, according to certain embodiments.

[0019] Figure 6B depicts another perspective view of the example of the electronic shelf label device in Figure 6A, according to certain embodiments.

[0020] Figure 6C depicts a front view of components of the electronic shelf label device ofFigures 6A- 6C.

[0021] Figure 7 depicts a back view of components of the electronic shelf label device ofFigures 6A - 6C.

[0022] Figure 7B depicts a cross-sectional view of components of the electronic shelf label device of Figures 6 A and 6B.

[0023] Figure 8A depicts an isometric view of an example of a digital signage device with integrated photovoltaic cells in a housing at a first angle, according to certain embodiments.

[0024] Figure 8B depicts an isometric view of an example of the digital signage device in Figure 8A with the housing at a second angle.

[0025] Figure 8C depicts an isometric view of an example of the digital signage device in Figure 8A with the housing at a third angle.

[0026] Figure 8D depicts an isometric view of an example of the digital signage device in Figure 8A with the housing at a fourth angle.

[0027] Figure 9 is a schematic diagram illustrating the general architecture of a dye-sensitized photovoltaic cell, according to embodiments.

[0028] Figure 10 depicts a cross section of an example of a bifacial photovoltaic cell, according to embodiments.

[0029] Figure 11 depicts a cross section of an alternate embodiment of a bifacial photovoltaic cell, according to embodiments.

[0030] Figure 12 is a simplified block diagram of an energy harvesting system, according to embodiments.

[0031] The figures and components therein may not be drawn to scale. Various components of the figures described herein may not be drawn to scale.DETAILED DESCRIPTION

[0032] Provided herein are electronic signs such as electronic shelf labels (ESLs) and digital signage that are powered by integrated energy harvesting elements. An energy harvesting element may be, for example, a photovoltaic cell configured to generate electricity from light via the photoelectric effect. These electronic signs may be powered by integrated energy harvesting elements without requiring battery power or other energy source. Electronic signs powered by integrated energy harvesting elements such as photovoltaic cells may allow for continuous and indefinitely long operation without battery recharging, replacement, and waste.

[0033] An electronic shelf label is a device having an electronic display that can display product and / or price information (sometimes collectively referred to herein as “display information”). Some examples of display information include images of a product or products, product identification codes (e.g., quick response (QR) codes, barcodes, etc.), product descriptors, sale announcements and other messages. Typically, the electronic shelf label is placed on or near a shelf, bin, or other structure upon which, or within which, a product may be located.

[0034] Certain embodiments pertain to electronic shelf labels (ESLs) powered by integrated photovoltaic (PV) cells. These photovoltaic-powered electronic shelf labels include an electronic display (e.g., an electronic screen) and a frontside window element through which information on the electronic display can be viewed. The photovoltaic-powered electronic shelf labels also include a photovoltaic cell for harvesting ambient light to power the ESL and a translucent backside element that allows transmission of light from an exterior environment to the photovoltaic cell. The photovoltaic cell is located between the translucent backside case and the electronic display. In some cases, the photovoltaic cell is sloped at an angle with respect to the frontside window element to enhance light collection.

[0035] Generally speaking, ESLs may be manufactured in various sizes, which are often characterized by the size of the electronic display as measured along its diagonal. Example display sizes along the diagonal include 1.54 inches, 2.13 inches, 2.66 inches, 2.9 inches, 3.7 inches, 4.2 inches, and 7.5 inches. A battery-operated 2.9-inch screen averaging four updates per day may have, for example, a lifespan of about two years and requires a case with mechanical fasteners for battery replacement.

[0036] Some examples of photovoltaic cells described in Section II can provide a total amount of power for powering operations of an ESL and also fit within a typical ESL packaging. For example, a 3.25 cm2bifacial photovoltaic cell under nominal retail lighting of about 600 lux canprovide battery-free operation at four updates per day for ESLs described herein having display sizes ranging from 1.54 inches to 7.5 inches. In some cases, nominal retail lighting may be in a range between 500 lux and 600 lux. Typical retail grocery lighting per ANSI IES RP 2-20 is 600 lx at floor, and 1500 lx at displays. Illuminating Engineering Society (IES), OSHA and the state of California require a minimum floor level illumination of 500 lx for grocery retail locations. These and other trade organizations advise higher illumination ranges for eye level shelf positions and featured items (up to 1.5 klx).

[0037] Certain photovoltaic-powered ESLs described herein include a PV cell disposed behind the electronic display. While this allows the ESL to have the same area and total thickness as battery-operated ESLs, the sign (front) portion of the display and the PV cell compete for light exposure, creating a challenge for light collection. According to various embodiments, the ESLs may include one or more features that may enhance light collection: the use of a clear back housing, a back-facing PV cell, a bifacial PV cell, a PV cell disposed at a non- vertical angle with the housing, a white or mirrored plate disposed between the circuit board and the PV cell, a display arrangement including a PCB-mounted display having a backside mirror finish material to reflect light back to the PV cell, and a window.

[0038] Digital signage is a device having an electronic display for displaying digital content such videos, images, and / or text. In some cases, digital signage can deliver dynamic content. Certain embodiments described herein pertain to digital signage powered by integrated photovoltaic (PV) cells. The photovoltaic powered digital signage includes an electronic display and a frontside window element through which display information on the electronic display can be viewed. The photovoltaic-powered digital signage also includes a plurality of photovoltaic cells for harvesting ambient light to power the ESL and a translucent backside element that allows transmission of light from an exterior environment to the photovoltaic cell. In these embodiments, the PV cell(s) are located adjacent the electronic display.

[0039] Using photovoltaic cells can afford the ability to use less carbon footprint intensive alternatives to batteries. The resulting “battery-free” electronic signs may be indefinitely powered without battery recharging or replacement. In certain implementations, electronic signs described herein may include other energy storage elements such as capacitors to store energy generated by the energy harvesting elements or as an alternative or supplemental energy source.I. Electronic Shelf Labels and digital signage

[0040] Certain electronic signs (e.g., ESLs) described herein include a housing with a translucent backside element (sometimes referred to herein as a “case” or “back case”) and afrontside window element. The translucent backside element allows for transmission of light from an external environment to an integrated photovoltaic element located within the housing. The translucent backside element may have any texture or coloration suitable for appearance if it is optically transparent and allows for transmission of light. An example of a material that can be used is a plastic material such as a polycarbonate. The translucent backside element may be a molded piece of plastic in some cases. In one aspect, the translucent backside element and frontside window element are sealed together (e.g., via an adhesive bond at mating surfaces) to seal the housing.

[0041] The frontside window element includes a translucent portion (sometimes referred to herein as a “window”) through which at least a portion of the electronic display within the housing can be viewed by an observer from a vantage point outside the frontside of the electronic sign. The frontside window element may also include an opaque portion along at least a portion of the perimeter edge that can obscure from view components within the housing such as wiring. The opaque portion may have any suitable width. For example, the opaque portion (border) may be a band between 5mm and 10mm wide.

[0042] The translucent portion (window) may have any suitable size and shape. In some cases, the translucent portion may be generally rectangular in shape with dimensions of a length, Iwindow, and a width, wwindow, as shown, for example, in Figure 2A. For example, a 2.9 ESL may have a window with width and length dimensions of 30mm and 68 mm.

[0043] In certain implementations, the frontside window element is a translucent cover (e.g., clear plastic covering) with back painting of an opaque material. Typically a clear optical cover of an opaque material (e.g., ABS, polycarbonate, or PMMA, and Nylon) can provide protection from bumps and scratches. The back painting provides a visual barrier from viewing, e.g., device internals. The back painting can be a mask, a smaller window in an opaque housing, an inserted piece of opaque material, etc. In other implementations, the frontside window element may include a simple cutout. For example, the frontside window element may include an opaque sheet of material with a cutout forming the translucent portion and with a strip of remaining opaque material at the edge perimeter forming the opaque portion.

[0044] The translucent backside element has a translucent wall at the backside that can pass light from the external environment. The photovoltaic element may be placed in contact with, or adjacent to, the translucent wall to allow transmission of light received from the external environment a light facing surface of the photovoltaic element at or near the backside of the electronic sign.

[0045] In various examples, the translucent backside element includes one or more positioning elements (e.g., translucent sloped wall) for receiving the photovoltaic cell and maintaining the photovoltaic cell (e.g., bifacial photovoltaic cell) at a distance away (gap) from the electronic display arrangement within the housing and / or at an angle relative to an outer surface of the frontside window element and to the circuit board. In some cases, the photovoltaic element may be attached to a positioning element using, for example, an adhesive material bond.

[0046] In examples that include an integrated bifacial photovoltaic cell, light may be harvested from both the anode side surface (e.g., first light facing surface 138 in Figure 1 and first light facing surface 638 in Figure 5) and cathode side surface (e.g., second light facing surface 139 in Figure 1 and second light facing surface 639 in Figure 5). The gap between the photovoltaic element and the electronic display arrangement allows light from the exterior environment to pass through the translucent portion of the housing to the frontside facing surface of the photovoltaic element and / or to one or more reflective surfaces (e.g., backside facing surface having reflective material 149 in Figure 1 or reflective material 549 in Figure 5) which can reflect the light to the frontside facing surface of the photovoltaic element. Figure 4B and Figure 7B illustrate example light paths of the light passing through the translucent backside elements to the frontside facing surface of a bifacial photovoltaic element. In some embodiments that include an integrated bifacial photovoltaic cell, the anode side of the integrated bifacial photovoltaic cell may face the backside of the housing. This back-facing bifacial photovoltaic cell can harvest light at its anode side more efficiently than at the opposing cathode side and can advantageously harvest higher photon propagation received at the backside of the housing.

[0047] Photovoltaic cells are typically most efficient at harvesting light that impinges their photo voltaically active areas at a direction normal to these areas. In some embodiments, electronic signs such as the ESL 600 shown in Figure 7B have a translucent backside element with a sloped translucent wall that is disposed an angle relative to an outer surface of the frontside window element and to the circuit board. The photovoltaic element may be placed in contact with or otherwise disposed on the sloped wall to position photovoltaic element at the angle (e.g., angle (e) 608 in Figure 7B) relative to an outer surface (e.g., outer surface 625 in Figure 7B) relative of the frontside window element and to the circuit board. In this position, the PV cell is non-parallel to that of the circuit board and the frontside window element. This angled (non-parallel) position may allow for increased light collection (e.g., greater angle of acceptance) from light passing through the upward portion of the translucent backside element of the housing of the electronic sign as compared to a photovoltaic element that is in a parallel position (e.g., photovoltaic element 330 in Figure 4B). This angled (non-parallel) position also allows for lightto pass to the frontside facing surface of the photovoltaic element at a less oblique angle (closer to normal) than with a photovoltaic element that is parallel to the outer surface of the frontside window element such as with the electronic shelf label device 300 shown in Figure 4B.

[0048] With increasing angles of the photovoltaic element, the potential for light collection by the photovoltaic element increases. The angle may vary for different total thicknesses of electronic shelf label devices. For example, electronic shelf label device 600 shown in Figure 7B has a total thickness, ttotai, that is no more than 12.50 mm and the photovoltaic element 630 is at an angle, e, of about 15 degrees from vertical defined at outer surface 625 of frontside window element 620. In one implementation, the angle may be in a range between 5 degrees and 45 degrees. Some examples of angles include 5 degrees, 10 degrees, 15, degrees, 20 degrees, 25 degrees, 30 degrees, 40 degrees, and 45 degrees. In various implementations, the angle may be in a ranges between 1 - 40 degrees, between 1 - 35 degrees, between 1 - 30 degrees, between 1 - 25 degrees, between 1 - 20 degrees, between 1 - 15 degrees, between 1 - 10 degrees, and between 1 - 5 degrees from vertical defined at outer surface of frontside window element. These example ranges are inclusive of endpoints.

[0049] In some cases, an ESL may be configured for attachment to a structure (e.g., a shelf, a bin, a box, a table, a rack, a wall, a hook (e.g., J-hook), a hanger, etc.) upon which, or within which, a product may be located or to a nearby structure. For example, the ESL may be attached to a front edge of a store shelf or bin. In one implementation, the ESL may include a structural component integral to its housing such as a lip element that may fit over mating edge to secure the ESL to a structure. In another implementation, the ESL may include a separate component such as a clip, a hook, other mechanical fastener, or an adhesive mount that can be used to attach the ESL to a structure.

[0050] In various embodiments, an electronic sign such as an ESL includes a display arrangement with a circuit board (e.g., printed circuit board (PCB)) having circuitry installed on or placed on a substrate. The circuitry includes control circuitry configured to control operations of the electronic sign. For example, the circuitry may include a logic circuit for controlling the display of the information on the electronic display and for updating the display information. As another example, the circuitry may include an RF antenna to receive signals for programming the display. As another example, the circuitry may include energy management and storage elements to manage any uneven power that may be gathered from the exterior environment, then change that to a regulated source suitable for consumption by the device. In some cases, the electronic display element (e.g., one or more layers of electronic ink) may be disposed directly on a surface of a printed circuit board (also referred to herein as a “PCB-mounted display”). In other cases,the electronic display element may be disposed on another substrate and the electronic display element is in electronic communication with the circuitry on the circuit board.

[0051] In certain embodiments, the circuit board includes a reflective finish on its outer surface facing the backside of the electronic sign (backside facing surface) that can reflect light from the external environment through a gap between the display arrangement and the photovoltaic element to the backside facing surface of the photovoltaic element. The reflective finish may include a reflective material (e.g., reflective material 149 in Figure 1 reflective material 549 in Figure 5) coated to at least a portion of the backside facing surface of the circuit board. Some examples of reflective materials that can be used include metalized plastics such as PMMA, ABS, or Polycarbonate. In some cases, the circuit board may have reflective finish in its natural state without a coating of a reflective material.

[0052] In certain embodiments, the electronic sign may include a separate white, mirrored, or otherwise reflective plate between the circuit board and the photovoltaic element that can reflect light from the external environment through the translucent backside element to the backside facing surface of the photovoltaic element. The separate plate may be a plate of reflective material or may be a thin substrate with one or more reflective materials coated thereon. Some examples of reflective materials that can be used include metalized plastic such as PMMA, polycarbonate, or ABS. The plate may have any suitable thickness. For example, the thickness of the plate may be in a range of range between 0.5 mm and 2.00 mm.

[0053] In various embodiments, the electronic signs may receive communication signals from an external device with updated display information and other control instructions for updating the display information to an updated display state. These communication signals are sometimes referred to herein as “update signals” or “updates.” The updates may be received on any appropriate basis such as, for example, one time per day, two times per day, three times per day, four times per day, etc. In one example, an ESL receives at least four updates each day with updated display information. The external device may be a base station, a mobile device (e.g. a mobile device with a radio frequency (RF) transmitter), etc. For example, the external device may be operated by a retailer in order to create and transmit updated display information with new price and product information for updating the display state of an ESL. In some cases, the display information may be stored in memory such as a buffer prior to updating the display state.

[0054] In some embodiments, electronic signs may include a receiving element (e.g., electrically conductive antenna element 148 in Figure 1 and electrically conductive antenna element 548 in Figure 5) that can wirelessly receive the update signals from the external device.In some cases, the receiving element is an electrically conductive antenna element such a radiofrequency antenna that can receive the updated signals via electromagnetic induction. For example, the RF antenna may be a short-range radio antenna capable of receiving data from a distance of less than about 12 inches, less than about 10 feet, or less than about 100 feet. Other examples of receiver elements include an infrared (IR) sensor, an audio sensor, and other devices that can wirelessly receive the update signals. The receiving element may be disposed on any suitable component of the electronic sign such as on the display arrangement, on the translucent backside element, etc. Typically, the receiving element is located to minimize interference. In one example, the receiver element may be located on an outer surface of the frontside window element. In other embodiments, the electronic sign may, in addition or alternatively, include a communication port (e.g., USB port, ethernet port, etc.) for electrically connecting to the external device to receive the update signals via a wired format.

[0055] The display arrangement includes a display element (sometimes also referred to herein as an electronic display or electronic screen) that uses digital display technology such as electronic ink, light-emitting diode (LED), liquid crystal display (LCD), etc. Although the display element is shown in various illustrated examples as being flat, according to other implementations, the display element may be curved.

[0056] In some embodiments, the display element includes one or more layers of electronic ink coated on a substrate such as the substrate of a printed circuit board (PCB). Electronic ink can provide a high degree of reflectance and contrast because it is pigment-based as are common printing inks. Light scattered from electronic ink comes from a thin layer near the top of the viewing surface. Thus, electronic ink resembles a common printed image and is viewable from a wide range of viewing angles and under various lighting conditions in the same manner as a printed page. Electronic ink can also be coated (printed) onto the surface of a circuit board using appropriate binders such as polyvinyl chlorides (PVCs), urethanes and silicone binders.

[0057] The display element may be rectangular in shape and have various suitable sizes. Some examples of rectangular display element sizes along the diagonal include 1.54 inches, 2.13 inches, 2.66 inches, 2.9 inches, 3.7 inches, 4.2 inches, and 7.5 inches. In some cases, the diagonal of a rectangular display element may be in a range of 1.54 inches and 7.5 inches. A rectangular display element has a width and a length.

[0058] An electronic display element that includes electronic ink can be created so that the display state (optical state) of the electronic ink is stable for some length of time. An electronic ink display requires substantially no power to maintain the display state. Electrical power is consumed when the display is updated. Another advantage of an electronic ink display is that relatively poor electrical conductors, for example, materials with resistivities on the order of 10 -10 ohms square, can be used as electrodes to apply the electric field to the display to generate the displayed image.

[0059] In various embodiments, the electronic display element can form a full color display (e.g., 24-bit color) or a multi-color display (e.g., a red, black, and white display, a black and white display, etc.). For example, an electronic display may be formed of an electronic ink that includes an electrophoretic display medium disposed on a substrate. In one example, the electrophoretic display medium is an optoelectronically active material having an electrophoretic contrast media phase and a coating / binding phase.

[0060] Photovoltaic elements integrated into electronic signs can function as energy harvesting elements to power operations of the electronic signs such as updating the display information. The photovoltaic elements may include a single photovoltaic cell (e.g., bifacial photovoltaic cell132 in Figure 1) or include multiple photovoltaic cells, e.g., two or more photovoltaic cells arranged in a one-dimensional or two-dimensional array (e.g., array 831 of photovoltaic cells 832, 833, and 834). In some embodiments, the photovoltaic cell is a thin-film solar cell. Thin- film solar cells are typically formed through depositing one or more layers (thin films) of photovoltaic material onto a substrate, using semiconductor device manufacturing methods. Thin-film solar cells include dye- sensitized solar cells (DSSCs), also referred to as dye- sensitized photovoltaic cells. DSSCs may be a lower-cost alternative to traditional photovoltaic cells, which are non-dye sensitized and usually formed on a rigid, glass or metal substrate. In comparison, DSSCs can be manufactured with less expense (e.g., with a lesser quantity of platinum or other noble metals) and on a greater variety of substrates such as plastic or other flexible materials. In some cases, bifacial photovoltaic cells may be implemented. A bifacial photovoltaic cell generally refers to a photovoltaic cell that can harvest photons from both sides. For example, a bifacial photovoltaic cell may allow for harvesting of photons from both the anode-side and the cathode-side of the cell. In another example, a bifacial photovoltaic cell may be two monofacial photovoltaic cells (i.e., photovoltaic cells that harvest from one face) placed back-to-back to allow for harvesting of photons received from an outer side of each of the back- to-back cells. Some examples of appropriate photovoltaic cells that can be implemented into electronic signs are described in Section II. The photovoltaic cell of various implementations can capture photons and generate energy from ambient light of various sources such as, for example, LED light, compact fluorescent light, incandescent light, sunlight from interior side of a window, etc.

[0061] A photovoltaic cell has a photovoltaically active area (e.g., photo voltaically active area133 in Figure 2B). The photovoltaic cell and its photovoltaically active area may each be anyappropriate shape. In some embodiments, the photovoltaically active area may be a rectangle. In other embodiments, other shapes of active area may be used. The size of the photovoltaically active area is typically at least a minimum area that would be sufficient to power the electronic sign under normal operating conditions (e.g., 1 update per day, two updates per day, three updates per day, four updates per day, and five updates per day). An example of a minimum active area for a back-facing bifacial photovoltaic cell that is sufficient to power an ESL with a display diagonal of 2.9 inches operating at four updates per day under nominal lighting is 3.25 cm2. An example of a minimum active area for a monofacial photovoltaic cell that is sufficient to power an ESL with an electronic display having a diagonal of 2.9 inches that is operating at four updates per day under nominal lighting is 3.9 cm2.

[0062] In the examples shown in FIGS. 1-4B, the photovoltaically active area 133 may have a width of 17.50 mmm and a length of 64.50 mm such that the size of the photovoltaically active area 133 is about 11.30 cm2. In the examples shown in FIGS. 5 -7B, the photovoltaically active area may have a width of 13.00 mm and a length of 79.00 mm such that the size of the photovoltaically active area is about 10.30 cm2. In some cases, the photovoltaically active area is in a range between 10 cm2and 14 cm2. Nominal lighting in a retail establishment may be in range between 500 lux and 600 lux. The bifacial photovoltaic cell generally has a photovoltaically active area disposed between two substrates (e.g., glass sheets).

[0063] Figure 1 depicts an exploded view of an example of an electronic shelf label device 100, according to certain embodiments. Figure 2A depicts front and side views of electronic shelf label device 100 of Figure 1. Figure 2B depicts a back view of electronic shelf label device 100 of Figure 1.

[0064] Electronic shelf label device 100 has a frontside 102 and a backside 103, and includes a housing 101 having a translucent backside element 110 (sometimes referred to herein as a “clear back case”) and a frontside window element 120. The translucent backside element 110 may be formed of molded plastic. Electronic shelf label device 100 also includes a photovoltaic element 130 including an integrated back-facing bifacial photovoltaic cell 132 and display arrangement 140 (sometimes referred to herein as a “display module”) including an electronic display element 142, both housed within housing 101. The back-facing bifacial photovoltaic cell 132 includes a first light facing surface 138 and a second light facing surface 139. Both first and second light facing surfaces 138, 139 can harvest light. The integrated back-facing bifacial photovoltaic cell 132 is “back-facing” in that it is positioned to have its anode-side (at first light facing surface 138) facing the backside 103 of the electronic shelf label device 100. Electronic shelf labeldevice 100 also includes one or more electrical connectors between photovoltaic element 130 and display arrangement 140.

[0065] The translucent backside element 110 is used to allow light transmission from an exterior environment 109 to back-facing bifacial photovoltaic cell 132 within the housing 101. For example, light may pass from the exterior environment 109 through a translucent wall 113 of the translucent backside element 110 at the backside 103 to the first light facing surface 138 (anode-side) of back-facing bifacial photovoltaic cell 132. Translucent backside element 110 also includes a positioning arrangement 112 that can position photovoltaic element 130 at a distance away from display arrangement 140 forming a gap (e.g., gap 318 in Figure 4B) therebetween through which light from the exterior environment 109 may pass to the second light facing surface 139 (cathode-side) of the back-facing bifacial photovoltaic cell 132. The positioning arrangement 112 includes a translucent wall 113, a first flange 114 extending from one edge of translucent wall 113, and second flange 115 extending from an opposing edge of translucent wall 113. The photovoltaic element 130 is located within an enclosure formed by the translucent wall 113 and the first and second flanges 114, 115 to position the first light facing surface 138 of photovoltaic element 130 to be parallel to an outer surface 125 of the frontside window element 120.

[0066] The outer surface 125 of the frontside window element 120 is generally rectangular with dimensions of length, lfront, and width, Wf1Ont. The translucent backside element 110 also includes a lip 119 that can fit over a mating edge of a structure such as a shelf edge to be able to attach the electronic shelf label device 100 to the structure. The electronic shelf label device 100 has a total thickness, ttotai, between outer surface 125 of frontside window element 120 and an outer backside surface of translucent backside element 110.

[0067] Frontside window element 120 includes a translucent portion 122 (sometimes referred to herein as a “window”) that is rectangular in shape with dimensions of width, w window, and a length, Iwindow. In other implementations, other shapes may be used. Frontside window element 120 also includes an opaque portion 124 at an outer surface 125 along the perimeter edge. In other implementations, the opaque portion may be located along only a portion of the perimeter edge or may be omitted.

[0068] In various embodiments, the translucent portion may be formed using various techniques. For example, in one implementation, frontside window element may include an opaque plate with a cutout forming the translucent portion. In another implementation, frontside window element may include a transparent plate with an opaque material (e.g., Polycarbonate, ABS, or PMMA) coated thereon at the perimeter forming the opaque portion.

[0069] In various examples such as the examples illustrated in Figures 1-7B, the translucent backside element and frontside window element of the electronic shelf label device form the housing of the electronic shelf label device. In these implementations, the translucent backside element and the frontside window element may be sealed together to seal the housing (e.g., with adhesive bond) without using mechanical fasteners. Because the integrated photovoltaic cell within the housing may be able to operate indefinitely without replacement or recharging, the electronic shelf label device may be manufactured to seal the housing without the need of mechanical fasteners or others means of opening and closing the housing.

[0070] Returning to Figures 1, 2A and 2B, the display arrangement 140 includes a printed circuit board (PCB) 141 and an electronic display element 142 having one or more layers of electronic ink coated on a frontside facing surface (e.g., frontside facing surface 347 in Figure 4B) of the PCB 141, for example, using appropriate binders such as polyvinyl chlorides (PVCs), urethanes, and silicone binders. In the illustrated example, electronic display element 142 is a rectangular display element with a size along its diagonal of 2.9 inches. In other implementations, other display sizes can be used. In one implementation, electronic display element 142 may be able to form a full color display (e.g., 24-bit color). In another implementation, electronic display element 142 may be able to form a multi-color display such as a red, black, and white display, a black and white display, etc. Printed circuit board (PCB) 141 includes circuitry including control circuitry for controlling functions of electronic shelf label device 100 including updating display states on electronic display element 142. Printed circuit board (PCB) 141 also includes a backside facing surface having reflective material 149 with a mirror or other reflective finish to reflect light received from the exterior environment 109 through the gap between the display arrangement 140 and the photovoltaic element 130 to the second light facing surface 139 of back-facing bifacial photovoltaic cell 132.

[0071] The electronic shelf label devices in Figures 1-7B also include electrically conductive antenna elements or other receiver elements for receiving update signals from external devices. For example, display arrangement 140 in Figure 1 includes an electrically conductive antenna element 148 disposed on PCB 141 and display arrangement 540 in Figure 5 includes an electrically conductive antenna element 548 disposed on PCB 541. In other implementations, the electrically conductive antenna element may be in other locations, for example, to minimize interference. According to one aspect, an electrically conductive antenna element may be a radio frequency antenna that can receive the updated signals via electromagnetic induction. For example, the RF antenna may be a short-range radio antenna capable of receiving data from a distance of less than about 12 inches, less than about 10 feet, or less than about 100 feet. Otherexamples of receiver elements include an infrared (IR) sensor, an audio sensor, and other devices that can wirelessly receive the update signals. In other embodiments, an electronic shelf label device of certain examples may, in addition or alternatively, include a communication port (e.g., USB port, ethemet port, etc.) for electrically connecting to the external device to receive the update signals via a wired format.

[0072] Returning to FIGS. 1 and 2A, at least a portion of the electronic display element 142 can be viewed through translucent portion 122 of the frontside window element 120. In the example shown in Figures 1-2B, the electronic display element 142 occupies 74% of the front plane. In the example shown in Figure 5, the electronic display element 542 occupies 65% of the front plane (outer surface of the frontside window element). According to various embodiments, the electronic display may occupy any appropriate area, but is generally more than 50%, more than 60%, or more than 70% of the front plane of the electronic shelf label devices. Figure 2A illustrates an example of display information 143 (e.g., price and product information) that may be displayed on electronic display element 142.

[0073] The back-facing bifacial photovoltaic cell 132 typically has a photovoltaically active area 133 disposed between two substrates (e.g., glass sheets). Photovoltaically active area 133 has a length, lactive, of 64.5 mm and a width, wactive, of 17.5 mm. The size of the photovoltaically active area 133 is about 1 1 .3 cm2based on the dimensions of 64.5 mm x 17.5 mm. In other implementations, other dimensions may be used. In the illustrated example shown in Figures 1- 2B, the photovoltaic element 130 can receive light at first light facing surface 138 and / or second light facing surface 139 from exterior environment 309 through translucent backside element 110 and generate electric power from light collected. Electric power generated by photovoltaic element 130 can be used to power operations of electronic shelf label device 100 such as updating display states to update display information 143.

[0074] In the illustrated example of Figures 1-2B, a plane formed by the xi axis and yi axis at the first light facing surface 138 of the photovoltaic element 130 is parallel to a plane formed by the X2 axis and y2 axis at the outer surface 225 of the translucent backside element 110. The gap between the translucent backside element 110 and the display arrangement 140 allows light received through the translucent backside element 110 at the gap to pass directly to the second light facing surface 139 of the photovoltaic element 130 or to reflective material 149 or other reflective surfaces to be reflected to the second light facing surface 139.

[0075] In the illustrated examples describe with reference to Figures 1-7B, the photovoltaic element includes a single bifacial photovoltaic cell. Some examples of appropriate bifacial photovoltaic cells are described in Section II. In other implementations, the photovoltaicelement of these examples may be a single monofacial photovoltaic cell, for example, facing the backside of the electronic shelf label device. In yet other implementations, the photovoltaic element may include multiple photovoltaic cells, monofacial and / or bifacial. Any photovoltaic cell or cells capable of providing the power requirements of the electronic shelf label device may be used.

[0076] In alternate embodiments, the electronic shelf label device 100 in Figures 1-2B, the electronic shelf label device 300 in Figures 3A-4B, the electronic shelf label device 500 in Figure 5, and / or the electronic shelf label device 600 in Figures 6A-7B may also include a white or mirrored plate disposed between the PCB and the photovoltaic element that can reflect light from the external environment through the translucent backside element to the second light facing surface the photovoltaic element. This may be done in addition or instead of applying a reflective material or other coloring to the backside facing surface of the PCB. This separate plate may be a plate of reflective material or may be a substrate (e.g. Polycarbonate, ABS, or PMMA) with a reflective coating (e.g., coating of aluminum or silver).

[0077] Figures 3A and 3B depict perspective views of an example of an electronic shelf label device 300, according to certain embodiments. Figure 3C depicts a front view of components of electronic shelf label device 300 of Figures 3A and 3B. Figure 4A depicts a 4B depicts a cross- sectional view of components of electronic shelf label device 300 of Figures 3A and 3B. Some of the elements shown in Figures 3A-4B are similar or analogous to elements shown in Figures 1-2B. For the sake of brevity, the prior discussion of such similar or analogous elements with regard to Figures 1-2B may be assumed to be equally applicable, unless indicated otherwise in the following discussion, to the similar or analogous counterparts of those elements in Figures 3A-4B that share the same last two digits in their respective callouts as in Figures 1-2B.

[0078] Electronic shelf label device 300 has a frontside 302 and a backside 303, and includes a housing 301 having a translucent backside element 310 and a frontside window element 320. Electronic shelf label device 300 also includes a photovoltaic element 330 including an integrated back-facing bifacial photovoltaic cell 332 and display arrangement 340 including an electronic display element 342. The photovoltaic element 330 and display arrangement 340 are both housed within housing 301. The back-facing bifacial photovoltaic cell 332 includes first and second light facing surfaces 338, 339, which can both harvest light. The anode-side at first light facing surface 338 faces the backside 303 of the electronic shelf label device 300. Translucent backside element 310 is used to allow light transmission from an exterior environment 309 to back-facing bifacial photovoltaic cell 332 within the housing 301.

[0079] Figure 4B illustrates example light paths of light passing through the translucent backside element 310 to the photovoltaic element 330. As shown, an example light path (denoted by dash dotted line) is from the backside 303 of the ESL device 300 through the translucent wall 313 of the translucent backside element 310 to the first light facing surface 338 of the photovoltaic element 330. Another example light path (denoted by long dashed line) is through a top portion of the translucent backside element 310 through the gap 318 directly to the second light facing surface 339 of the photovoltaic element 330. Another example light path (denoted by a short dashed line) is through the top portion of the translucent backside element 310 through the gap 318 to a reflective surface (e.g., reflective material), which reflects the light to the second light facing surface 339 of the photovoltaic element 330.

[0080] Translucent backside element 310 includes a positioning arrangement 312 that can position photovoltaic element 330 at a distance away from display arrangement 340 forming a gap 318 therebetween through which light from the exterior environment 309 may pass, either directly to or by reflection from one or more reflective surfaces to, the second light facing surface 339 of the back-facing bifacial photovoltaic cell 332. The positioning arrangement 312 includes a translucent wall 313, a first flange 314 extending from one edge of translucent wall 313, and second flange 315 extending from an opposing edge of translucent wall 313. The photovoltaic element 330 is located within an enclosure formed by the translucent wall 313 and the first and second flanges 314, 315 to position the first light facing surface 338 of photovoltaic element 330 to be parallel to an outer surface 325 of the frontside window element 320. The outer surface 325 is generally rectangular with dimensions of length, Ifront, and width, Wfront- The translucent backside element 110 also includes a lip 319 that can fit over a mating edge of a structure.

[0081] The electronic shelf label 300 has a total thickness, ttotai, between the outer surface 325 of the frontside window element 320 and the outer backside surface of the translucent backside element 310 and a first thickness, ti, between the outer surface 325 of the frontside window element 320 and the backside surface of a fourth flange 317 of translucent backside element 310. In one aspect, the total thickness, ttotai, is no more than 11.50 mm and / or the first thickness, ti , is no more than 5 mm.

[0082] Frontside window element 320 includes a translucent portion 322 that is rectangular in shape. In other implementations, other shapes may be used. Frontside window element 320 also includes an opaque portion 324 at an outer surface 325 along the perimeter edge. In other implementations, the opaque portion may be located along only a portion of the perimeter edge or may be omitted. In one aspect, the width of the opaque portion 324 may be in a range between5 mm and 10 mm. The translucent backside element 310 and frontside window element 320 of the electronic shelf label device 300 form the housing 301 and may be sealed together to seal the housing (e.g., with adhesive bond) without using mechanical fasteners.

[0083] Display arrangement 340 includes a printed circuit board (PCB) 341 and an electronic display element 342 having one or more layers of electronic ink coated on a frontside facing surface 347 of the PCB 341. The display arrangement 340 also includes an electrically conductive antenna element 348. In the illustrated example, electronic display element 342 is a rectangular display element with a size along its diagonal of 2.9 inches. In other implementations, other display sizes can be used. Electronic display element 342 may be any suitable display such as, for example, a full color display, a multi-color display, etc. Printed circuit board (PCB) 341 includes circuitry including control circuitry for controlling functions of electronic shelf label device 300 including updating display states on electronic display element 342. Printed circuit board (PCB) 341 also includes a backside facing surface having reflective material 349 with a mirror or other reflective finish to reflect light received from the exterior environment 309 through the gap between the display arrangement 340 and the photovoltaic element 330 to the second light facing surface 339 of back- facing bifacial photovoltaic cell 332. At least a portion of the electronic display element 342 can be viewed through translucent portion 322 of the frontside window element 320. Electronic shelf label device 300 also includes a ribbon cable 351 that can provide electrical communication between the display arrangement 340 and the photovoltaic element 330.

[0084] As shown in Figure 4B, back-facing bifacial photovoltaic cell 332 has a photovoltaically active area 333 disposed between two substrates (e.g., glass sheets). As shown in Figure 4A, photovoltaically active area 333 is generally rectangular in shape having a length, lactive, and a width, wactive. In one case, lactive, is 64.5 mm and the width, wactive, is 5 mm. The size of the photovoltaically active area 333 is about 11.3 cm2based on the example dimensions of 64.5 mm x 17.5 mm. In other implementations, other dimensions may be used.

[0085] In the illustrated example, the integrated bifacial photovoltaic element 330 can receive light at first light facing surface 338 and / or second light facing surface 339 from exterior environment 309 through translucent backside element 310 and generate electric power from light collected. Electric power generated by photovoltaic element 330 can be used to power operations of electronic shelf label device 300 such as updating display states to update display information. Figure 2A illustrates examples of display information that may be displayed on electronic display element 342. The example display information includes price information 343, product information 344, a QR code 345, and a barcode 346.

[0086] The gap 318 between the translucent backside element 310 and the display arrangement 340 allows light received through the translucent backside element 310 at the gap to pass directly to the second light facing surface 339 of the photovoltaic element 330 or to pass to reflective surfaces such as reflective material 349, which reflect the light to the second light facing surface 339. In the illustrated example, the first light facing surface 338 of the photovoltaic element 330 is at a plane parallel to a plane formed at the outer surface 325 of the translucent backside element 310.

[0087] Figure 5 depicts an exploded view of another example of an electronic shelf label device 500, according to certain embodiments. Electronic shelf label device 500 has a frontside 502 and a backside 503, and includes a housing 501 having a translucent backside element 510 and a frontside window element 520. The electronic shelf label device 500 also includes a photovoltaic element 530 with an integrated back-facing bifacial photovoltaic cell 532 and a display arrangement 540 with an electronic display element 542. Both the photovoltaic element 530 and display arrangement 540 are housed within housing 501.

[0088] Like the examples in Figures 1-4B, the electronic shelf label device 500 includes a translucent backside element 510, an integrated back-facing bifacial photovoltaic cell 532, a display arrangement 540 with a PCB 541 having a reflective material 549 with a mirror or otherwise reflective finish to reflect light to the integrated back-facing bifacial photovoltaic cell 532, and a frontside window element 520 with a translucent portion 522. However, in this example, the integrated back-facing bifacial photovoltaic cell 532 is sloped or disposed an angle, e, 508 relative to the PCB 541 and the frontside window element 520. That is, the plane of the integrated back-facing bifacial photovoltaic cell 532 is non-parallel to that of the PCB 541 and the frontside window element 520. This allows for increased light collection from the bottom and / or top of the electronic shelf label device 500. The translucent backside element 510 (sometimes referred to as “back case”) similarly has an angled wall 513 against which the integrated back-facing bifacial photovoltaic cell 532 is disposed. The angle may vary with larger angles increasing light collection and thickness of the electronic shelf label device 500.Examples of ranges of angles include 1 - 45 degrees, 1 - 40 degrees , 1 - 35 degrees, 1 - 30 degrees, 1 - 25 degrees, 1 - 20 degrees , 1 - 15 degrees, 1 - 10 degrees , and 1 -5 degrees from vertical (ranges inclusive of endpoints).

[0089] In the example shown in Figure 5, the photovoltaic element 530 is at an angle, e, 508 from vertical defined at an outer surface of frontside window element 520. The back-facing bifacial photovoltaic cell 532 includes first and second light facing surfaces 538, 539 that can each harvest light. The translucent backside element 510 includes a sloped translucent wall 513that is sloped at the angle, e, relative to an outer surface of the frontside window element 520. The translucent backside element 510 also includes a first flange 514, a second flange 515 extending from one edge of translucent wall 513, and a third flange 516 extending from an opposing edge of the translucent wall 513, and a fourth flange (e.g., fourth flange 617 in Figure 7B).

[0090] The translucent backside element 510 is used to allow light transmission from an exterior environment 509 to back-facing bifacial photovoltaic cell 532 within the housing 501. For example, light may pass from the exterior environment 509 through a translucent wall 513 of the translucent backside element 510 at the backside 503 of the electronic shelf label device 500 to the first light facing surface 538 (anode-side) of back-facing bifacial photovoltaic cell 532.

[0091] Translucent backside element 510 also includes a positioning arrangement 512 that can position photovoltaic element 530 at angle, e, 508 from vertical. The positioning arrangement 512 includes the sloped translucent wall 513 that is sloped at the angle, e, 508 relative to an outer surface of the frontside window element 520. The photovoltaic element 530 may be placed in contact with or otherwise disposed on the sloped translucent wall 513 to position photovoltaic element 530 at the angle e, 508, relative to an outer surface (e.g., outer surface 625 in Figure 7B). In some cases, the photovoltaic element 530 may be coupled to the inner surface, for example, via adhesive bonding. This angled (non-parallel) position may allow for an increased angle of acceptance of light from above the translucent backside element 510 through a gap between the photovoltaic element 530 and the display arrangement 540 which may increase light collection at the second light facing surface 539 (cathode-side) of the back-facing bifacial photovoltaic cell 532. This angled position of the photovoltaic element 530 may also allow for light to pass to the second light facing surface 139 of the photovoltaic element 530 at a less oblique angle (closer to normal) than with a photovoltaic element that is parallel to the outer surface of the frontside window element. In one aspect, angle, e, is 15 degrees. In some cases, angle, e, is in a range between 0 degrees and 90 degrees.

[0092] Frontside window element 520 includes a translucent portion 522 that is generally rectangular in shape. In other implementations, other shapes may be used. Frontside window element 320 also includes an opaque portion 524 at an outer surface along the perimeter edge. In other implementations, the opaque portion may be located along only a portion of the perimeter edge or may be omitted. In one aspect, the width of the opaque portion 524 may be in a range between 5 mm and 20 mm thick. The translucent backside element 510 and frontside window element 520 of the electronic shelf label device 500 form the housing 501 and may be sealed together to seal the housing (e.g., with adhesive bond) without using mechanical fasteners.

[0093] Display arrangement 540 includes a printed circuit board (PCB) 541 and an electronic display element 542 having one or more layers of electronic ink coated on a frontside facing surface of the PCB 541. The display arrangement 540 also includes an electrically conductive antenna element 548. In the illustrated example, electronic display element 542 is a generally rectangular display element. In one aspect, the electronic display element 542 has a size along its diagonal of 2.9 inches. In other aspects, other display sizes can be used. Electronic display element 542 may be any suitable display such as, for example, a full color display, a multi-color display, etc. Printed circuit board (PCB) 541 includes circuitry including control circuitry for controlling functions of electronic shelf label device 500. Printed circuit board (PCB) 541 also includes a backside facing surface having reflective material 549 with a mirror or other reflective finish to reflect light received from the exterior environment 509 through the gap between the display arrangement 540 and the photovoltaic element 530 to second light facing surface 539 of back-facing bifacial photovoltaic cell 532. Electronic shelf label device 500 also includes one or more electrical connectors between PV element 530 and display arrangement 540.

[0094] At least a portion of the electronic display element 542 can be viewed through translucent portion 522 of the frontside window element 520. In the example shown in Figure 5, the electronic display element 542 occupies 65% of the front plane.

[0095] The bifacial photovoltaic cell 532 typically has a photovoltaically active area disposed between two substrates (e.g., glass sheets). According to one aspect, the photovoltaically active area in the example in Figure 5 may a photovoltaically active area with has a length, lactive, of 79.00 mm and a width, wactive, of 13.00 mm. The size of the photovoltaically active area is about 10.30 cm2based on these dimensions. In other implementations, other dimensions may be used.

[0096] The integrated back-facing bifacial photovoltaic element 532 can receive light at first light facing surface 538 and / or second light facing surface 539 from exterior environment 509 through translucent backside element 510 and generate electric power from light collected. Electric power generated by photovoltaic element 530 can be used to power operations of electronic shelf label device 500 such as updating display states to update display information. In Figure 5, a plane formed by the xi axis and yi axis at the first light facing surface 538 of the photovoltaic element 530 is at an angle, e, 508 to a plane formed by the XT axis and y axis at the outer surface of the frontside window element 520.

[0097] Figures 6A and 6B depict perspective views of an example of an electronic shelf label device 600, according to certain embodiments. Figure 6C depicts a front view of components of electronic shelf label device 600 of Figures 6A and 6B. Figure 7A depicts a back view of components of electronic shelf label device 600 of Figures 6A and 6B. Figure 7B depicts across-sectional view of components of electronic shelf label device 600 of Figures 6A and 6B. Some of the elements shown in Figures 6A-7B are similar or analogous to elements shown in Figures 5. For the sake of brevity, the prior discussion of such similar or analogous elements with regard to Figure 5 may be assumed to be equally applicable, unless indicated otherwise in the following discussion, to the similar or analogous counterparts of those elements in Figures 6A-7B that share the same last two digits in their respective callouts as in Figure 5.

[0098] Electronic shelf label device 600 has a frontside 602 and a backside 603, and includes a housing 601 having a translucent backside element 610 and a frontside window element 620. Electronic shelf label device 600 also includes a photovoltaic element 630 having an integrated back-facing bifacial photovoltaic cell 632 and a display arrangement 640 including an electronic display element 642. The photovoltaic element 630 and display arrangement 640 are both housed within housing 601. The back-facing bifacial photovoltaic cell 632 includes first and second light facing surfaces 638, 639, which can both harvest light. The anode-side at first light facing surface 638 faces the backside 603 of the electronic shelf label device 600. Electronic shelf label device 600 also includes a ribbon cable 651 that can provide electrical communication between the display arrangement 640 and the photovoltaic element 630.

[0099] Figure 7B illustrates example light paths of light passing through the translucent backside element 610 to the photovoltaic element 630. As shown, an example light path (denoted by dash dotted line) is from the backside 603 of the electronic shelf label device 600 through the translucent wall 613 of the translucent backside element 610 to the first light facing surface 638 of the photovoltaic element 630. Another example light path (denoted by long dashed line) is through a top portion of the translucent backside element 610 through the gap 618 directly to the second light facing surface 639 of the photovoltaic element 630. Another example light path (denoted by a short dashed line) is through the top portion of the translucent backside element 610 through the gap 618 to a reflective surface (e.g., reflective material), which reflects the light to the second light facing surface 639 of the photovoltaic element 630.

[0100] In the example shown in Figures 6A-7B, the photovoltaic element 630 is at an angle, e, 608 from vertical defined at an outer surface of frontside window element 620. The translucent backside element 610 includes a sloped translucent wall 613 that is sloped at the angle, e, 608 relative to an outer surface of the frontside window element 620. The translucent backside element 610 also includes a first flange 614, a second flange 615 extending from one edge of translucent wall 613, a third flange 616 extending from an opposing edge of the translucent wall 613, and a fourth flange 617.

[0101] The electronic shelf label 600 has a total thickness, ttotai, between the outer surface 625 of the frontside window element 620 and the outer backside surface of the translucent backside element 610 and a first thickness, ti , between the outer surface 625 of the frontside window element 620 and the backside surface of the fourth flange of translucent backside element 610. In one implementation, the total thickness, ttotai, of the electronic shelf label device 600 is no more than 12.50 mm and the first thickness, ti, is no more than 6 mm. The electronic shelf label device 600 shown in Figure 7B has a total thickness, ttotai, of no more than 11.50 mm between the outer surface 625 of the frontside window element 620 and the outer backside surface of the translucent backside element 610. The electronic shelf label device 600 also has a first thickness, ti , of no more than 5 mm between the outer surface 625 of the frontside window element 620 and the backside surface of the fourth flange. As compared to the example in Figures 3A-4B where the integrated back-facing bifacial photovoltaic cells are parallel to the frontside window elements, the total thickness, ttotai, of the ESL 600 and the first thickness, ti , are both 1 mm greater.

[0102] Display arrangement 640 includes a printed circuit board (PCB) 641 and an electronic display element 642 having one or more layers of electronic ink coated on a frontside facing surface 647 of the PCB 641. The display arrangement 640 also includes an electrically conductive antenna element 648. In the illustrated example, electronic display element 642 is a rectangular display element with a size along its diagonal of 2.9 inches. In other implementations, other display sizes can be used. Electronic display element 642 may be any suitable display such as, for example, a full color display, a multi-color display, etc. Printed circuit board (PCB) 641 includes circuitry including control circuitry for controlling functions of electronic shelf label device 600 including updating display states on electronic display element 642. Printed circuit board (PCB) 641 also includes a backside facing surface having reflective material 649 with a mirror or other reflective finish to reflect light received from the exterior environment 609 through the gap 618 between the display arrangement 640 and the photovoltaic element 630 to the second light facing surface 639 of back- facing bifacial photovoltaic cell 632. At least a portion of the electronic display element 642 can be viewed through translucent portion 622 of the frontside window element 620. In this illustrated example, the electronic display element 642 occupies 65% of the front plane. In other implementations, other display sizes may be used.

[0103] Similar to the example in Figure 5, electronic shelf label device 600 has an integrated back-facing bifacial photovoltaic cell 632 that is sloped or disposed at an angle, e, 608 relative to the PCB 641 and the frontside window element 620. In this example, the plane of the integratedback-facing bifacial photovoltaic cell 632 is non-parallel to that of the PCB 641 and the frontside window element 620, which allows for increased light collection from the bottom and / or top of the electronic shelf label device 600. The translucent backside element 610 similarly has an angled wall 613 against which the integrated back-facing bifacial photovoltaic cell 632 is disposed. The angle, e, 608 may vary with larger angles increasing light collection and thickness of the electronic shelf label device 600. Examples of ranges of angles, e, 608 include 1 - 45 degrees, 1 - 40 degrees, 1 - 35 degrees, 1 - 30 degrees, 1 - 25 degrees, 1 - 20 degrees, 1 - 15 degrees, 1 - 10 degrees, and 1 -5 degrees from vertical (ranges inclusive of endpoints).

[0104] The translucent backside element 610 is used to allow light transmission from an exterior environment 609 to back-facing bifacial photovoltaic cell 632 within the housing 601. For example, light may pass from the exterior environment 609 through a translucent wall 613 of the translucent backside element 610 at the backside 603 of the electronic shelf label device 600 to the first light facing surface 638 (anode-side) of back-facing bifacial photovoltaic cell 632.

[0105] As discussed above, translucent backside element 610 includes a sloped translucent wall 613 that is at the angle, e, 608 relative to an outer surface 625 of the frontside window element 620. The photovoltaic element 630 may be placed in contact with or otherwise disposed on the sloped translucent wall 613 to position photovoltaic element 630 at the angle e, 608, relative to an outer surface 625. Tn some cases, the photovoltaic element 630 may be coupled to the sloped translucent wall 613, for example, via adhesive bonding. In one aspect, angle, e, is 15 degrees. In some cases, angle, e, is in a range between 0 degrees and 90 degrees, sloped wall 613 may also position photovoltaic element 630 at a distance away from display arrangement 640 forming a gap 618 therebetween through which light passing through the translucent backside element 610 from the exterior environment 609 may pass.

[0106] Frontside window element 620 includes a translucent portion 622 that is generally rectangular in shape. In other implementations, other shapes may be used. Frontside window element 620 also includes an opaque portion 624 at an outer surface along the perimeter edge. In other implementations, the opaque portion may be located along only a portion of the perimeter edge or may be omitted. In one aspect, the width of the opaque portion 624 may be in a range between 5mm to 20 mm. The translucent backside element 610 and frontside window element 620 of the electronic shelf label device 600 form the housing 601 and may be sealed together to seal the housing (e.g., with adhesive bond) without using mechanical fasteners. The outer surface 625 of frontside window element 620 is generally rectangular with dimensions of length, lfrOnt, and width, WfrOnt. The translucent backside element 610 also includes a lip 619 that can fit over a mating edge of a structure.

[0107] The bifacial photovoltaic cell 632 typically has a photovoltaically active area disposed between two substrates. According to one aspect, the photovoltaically active area may a photovoltaically active area with has a length, ctive, of 79.00 mm and a width, Wactive, of 13.00 mm. The size of the photovoltaically active area is about 10.30 cm2based on these dimensions. In other implementations, other dimensions may be used.

[0108] The integrated bifacial photovoltaic cell 632 can receive light at first light facing surface 638 and / or second light facing surface 639 from exterior environment 609 through translucent backside element 610 and generate electric power from light collected. Electric power generated by photovoltaic element 630 can be used to power operations of electronic shelf label device 600 such as updating display states to update display information. Figures 6A and 6B illustrates example display information that may be displayed on electronic display element 642. The example display information includes price information 643, product information 644, a QR code 645, and a barcode 646.

[0109] Figures 8A-8D depict isometric views of an example of a digital signage device 800 with integrated photovoltaic cells, according to certain embodiments. Digital signage device 800 has a frontside 802 and a backside 803, and includes a first housing 801 and a second housing 805. Second housing 805 includes a first translucent element 821 and a second translucent element 822. First translucent element 821 and / or second translucent element 822 may be made of molded plastic. First translucent element 821 and second translucent element 822 form the second housing 805 and may be sealed together to seal the first housing (e.g., with adhesive bond) without using mechanical fasteners. Digital signage device 800 also includes a plurality of photovoltaic cells 830 having a first integrated photovoltaic cell 832, a second integrated photovoltaic cell 833, and a third integrated photovoltaic cell 834. The photovoltaic cells 832, 833, and 834 are housed within second housing 805. Figures 8A-8D depict the second housing at four different angles. In other implementations, the second housing may be at a fixed angle. In yet another implementation, the second housing may be integral to the first housing.

[0110] In one implementation, the photovoltaic cells 832, 833, and 834 are bifacial photovoltaic cells. In some cases, the integrated back-facing bifacial photovoltaic cell 132 may be placed with its anode-side facing the frontside 802 relative to the first position in Figure 8A. In other implementations, the photovoltaic cells may be monofacial photovoltaic cells or a combination of monofacial and bifacial photovoltaic cells. Some examples of appropriate photovoltaic cells are described in Section II. Any number and type of photovoltaic cell or cells capable of providing the power requirements of the digital signage 800 may be used.

[0111] The first translucent element 821 and a second translucent element 822 are used to allow light transmission from an exterior environment 509 to both light facing surfaces of photovoltaic cells photovoltaic cells 832, 833, and 834 within the second housing 805. For example, light may pass from the exterior environment 809 through first translucent element 821 and / or second translucent element 822 to the light facing surface(s) of photovoltaic cells 832, 833, and 834.

[0112] Frontside window element 820 includes a translucent portion 826 that is rectangular in shape. In other implementations, other shapes may be used. Frontside window element 820 also includes an opaque portion 824 at an outer surface 825 along the perimeter edge. In other implementations, the opaque portion may be located along only a portion of the perimeter edge or may be omitted. In one aspect, the width of the opaque portion 824 may be in a range 5 mm and 20 mm. The frontside window element 820 and opaque element 860 form the first housing 801 and may be sealed together to seal the first housing (e.g., with adhesive bond) without using mechanical fasteners.

[0113] Digital signage 800 also includes an electronic display element 842 including a printed circuit board (PCB) 841 and an electronic display element 842 having one or more layers of electronic ink coated on a frontside facing surface of the PCB 841, for example, using appropriate binders such as polyvinyl chlorides (PVCs), urethanes, and silicone binders. In the illustrated example, electronic display element 842 is a rectangular display element. In other implementations, other display sizes can be used. In one implementation, electronic display element 842 may be able to form a full color display (e.g., 24-bit color). In another implementation, electronic display element 842 may be able to form a multi-color display such as a red, black, and white display, a black and white display, etc. Printed circuit board (PCB) 841 includes circuitry including control circuitry for controlling functions of a digital signage 800 including updating display states on electronic display element 842.

[0114] The digital signage 800 also includes a hinge 806 between the first housing 801 and a second housing 805. Electrical connectors such as wiring may pass through the hinge 806 to electrically connect components of the electronic display element 842 with the plurality of photovoltaic cells 830.IL Examples of Photovoltaic Cells

[0115] Any appropriate photovoltaic cell may be implemented in the ESLs and electronic signage discussed herein. Some examples of appropriate photovoltaic cells are discussed in this section. Typically, an ESL includes a single, monolithic photovoltaic cell. In other embodiments,multiple monolithic photovoltaic cells may be included such as an array of photovoltaic cells. Electronic signage usually includes a plurality of monolithic photovoltaic cells such as a linear array of photovoltaic cells (e.g., linear array 831 in FIGS. 8A-8D). A photovoltaic cell generally includes a cathode, one or more light absorbing layers, an electrolyte, and an anode.

[0116] The photovoltaic cell of various implementations may be a bifacial photovoltaic cell that can harvest light from two opposing light facing surfaces. Some examples of bifacial photovoltaic cells are provided below. In other implementations, the photovoltaic cell may be a monofacial photovoltaic cell that can harvest light from one light facing surface. In these implementations, the monofacial photovoltaic cell may be positioned within a housing to maximize light received at the harvesting light facing surface. For example, the monofacial photovoltaic cell may be positioned such that the harvesting light facing surface faces the translucent backwall of the translucent backside element to receive light from the backside of the housing.- Dye-sensitized photovoltaic cells

[0117] A photovoltaic element including a dye sensitive photovoltaic cell such as those described in U.S. Patent Publication 2020 / 395492, which is incorporated by reference herein for the purpose of describing cell architecture and dyes, may be used in some embodiments. Dye sensitive photovoltaic cells manufactured by Ambient Photonics, Inc. may be used. Further description of dyes that may be used may be found in PCT Publication 2020 / 014194, also incorporated by reference herein for the purpose of describe photovoltaic cells and components thereof.

[0118] In some embodiments, a photovoltaic cell is a dye-sensitized photovoltaic cell (DSPC). DSPCs use a dye to absorb light and initiate a rapid electron transfer to a nanostructured oxide such as TiC) . The mesoscopic structure of the TiO allows building of thick, nanoporous films with active-layer thicknesses of several microns. The dye is then adsorbed on the large surface area of the mesoporous TiCF. Charge balance and transport is achieved by a layer having a redox couple, such as iodide / triiodide, Co(II) / Co(III) complexes, and Cu(I) / Cu(II) complexes. In some cases, a dye-sensitized photovoltaic cell includes a cathode, an electrolyte, a porous dye- sensitized titanium dioxide film, and an anode.

[0119] In some cases, dye-sensitized photovoltaic cells may include a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film. The nonporous “hole-blocking” layer may comprise an organotitanium compound, such as a titanium alkoxide. The organotitanium compound may be polymeric, such as a polymeric titanium alkoxide. Anexemplary polymeric titanium alkoxide is poly(n-butyl titanate). The nonporous or compact hole-blocking layer may also comprise titanium in the form of an oxide, such as compact anatase or rutile film. The thickness of the hole blocking layer may be from about 20 nm to about 100 nm. The nonporous hole blocking layer reduces / inhibits back electron transfer between redox species in the electrolyte and the electrode. The nonporous blocking layer may be applied to the anode using art-known techniques, such as gravure, silkscreen, slot, spin or blade coating.

[0120] Figure 9 is a schematic diagram illustrating the general architecture of a dye-sensitized photovoltaic cell 900, according to embodiments. Dye-sensitized photovoltaic cell 900 includes three layers disposed between an anode-side assembly 920 and a cathode-side assembly 910 with a sealant 940 surrounding the three layers. Cathode-side assembly 910 includes a transparent substrate 912 coated with a first flexible / rigid conductor layer 914 (e.g., a transparent conducting oxide (TCO) layer), and a catalyst layer 915. Anode-side assembly 920 includes a transparent substrate 922 (e.g., glass sheet) coated with a second flexible / rigid conductor layer 924 (e.g., a transparent conducting oxide (TCO) layer). The three layers disposed between the anode-side assembly 920 and cathode-side assembly 910 include an electrolyte layer 934, a porous dye- sensitized titanium dioxide film 936 and a non-porous hole blocking layer 938. The electrolyte layer 934 may be, for example, a copper redux electrolyte.

[0121] The redox couple may include organocopper (T) and organocopper (IT) salts in some cases. Suitable organocopper salts include copper complexes comprising bi- and polydentate organic ligands with counterions. Suitable bidentate organic ligands include, but are not limited to, 6,6'-dialkyl-2,2'-bipyridine; 4,4',6,6'-tetralkyl-2,2'-bipyridine; 2,9-dialkyl-l,10-phenathroline; 1,10-phenathroine; and 2,2'-bipyridine. Suitable counterions include, but are not limited to, bis(trifluorosulfon)imide, hexafluorophosphate, and tetrafluoroborate. The ratio of organocopper(I) to organocopper(II) salts may be from about 4:1 to about 12:1. Alternatively, the ratio of organocopper(i) to organocopper(II) salts may be from about 6:1 to about 10:1. In some implementations, the redox couple may include copper complexes with more than one ligand. For example, the redox couple may include a copper (I) complex with 6,6'-dialkyl-2,2'- bipyridine and a copper (II) complex with a bidentate organic ligand selected from the group consisting of 6,6'-dialkyl-2,2'-bipyridine; 4,4',6,6'-tetralkyl-2,2'-bipyridine; 2,9-dialkyl-l,10- phenathroline; 1,10-phenathroine; and 2,2'-bipyridine. Alternatively, the redox couple may include a copper (I) complex with 2,9-dialkyl-l,10-phenathroline and a copper (II) complex with a bidentate organic ligand selected from the group consisting of 6,6'-dialkyl-2,2'-bipyridine; 4,4',6,6’-tetralkyl-2,2'-bipyridine; 2,9-dialkyl-l,10-phenathroline; 1,10-phenathroine; and 2,2'- bipyridine.

[0122] In some embodiments, the electrolyte of a dye-sensitized photovoltaic cell may include two or more solvents. Suitable solvents include, but are not limited to, sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids and binary / tertiary / quatemary mixtures of these solvents. In an exemplary embodiment, the electrolyte includes at least 50% sulfolane or dialkyl sulfone. Alternatively, the electrolyte may include up to about 50% of 3 -alkoxypropionitrile, cyclic and acyclic lactones, cyclic and acyclic carbonates, low viscosity ionic liquids, or binary / tertiary / quatemary mixtures thereof. The electrolyte may also include up to about 0.6M N-methylbenzimidazole and up to about 0.2 M lithium bis(trifluorosulfon)imide as additives.

[0123] A dye- sensitized photovoltaic cell may include a cathode catalyst disposed on the cathode. A suitable cathode catalyst may include a mixture of 2D conductor and electronic conducting polymer. A “2D conductor” is a molecular semiconductor with thickness in atomic scale. Exemplary 2D conductors include graphenes, transition metal dichalcogenides (ex., molybdenum disulfide or diselenide), or hexagonal boron nitride. For use in embodiments with cathode catalysts, the graphene may include a molecular layer or nano / micro crystal. The graphene may be derived from reduced graphene oxide. Suitable conducting polymers include but are not limited to polythiophene, polypyrrole, polyaniline, and derivatives thereof. An exemplary polythiophene is poly (3, 4-ethyelenedioxy thiophene) (PEDOT).

[0124] In certain embodiments, a dye-sensitized photovoltaic cell includes a cathode, an electrolyte, a porous dye- sensitized titanium dioxide film layer, an anode, and a nonporous holeblocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer. In one such embodiment, the electrolyte includes a redox couple having organocopper (I) and organocopper (II) salts, and the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12: 1. In another such embodiment, the electrolyte includes two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary / tertiary / quatemary mixtures of these solvents.

[0125] In another embodiment, a dye-sensitized photovoltaic cell includes a cathode, and a cathode catalyst disposed on the cathode. In this example, the cathode catalyst includes a 2D conductor and an electronic conducting polymer, an electrolyte, a porous dye- sensitized titanium dioxide film layer, an anode and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer.

[0126] In another embodiment, a dye-sensitized photovoltaic cell includes a cathode, an electrolyte, a porous dye-sensitized titanium dioxide film layer, and an anode. The electrolyteincludes a redox couple having organocopper (I) and organocopper (II) salts, and the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12: 1, In this example, the electrolyte includes two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary / tertiary / quatemary mixtures of these solvents.

[0127] In certain embodiments, a dye-sensitized photovoltaic cell includes a cathode and a cathode catalyst disposed on the cathode. In one such embodiment, the cathode catalyst includes a 2D conductor and an electronic conducting polymer, an electrolyte, a porous dye-sensitized titanium dioxide film layer, and an anode. The electrolyte includes a redox couple comprising organocopper (I) and organocopper (II) salts, and wherein the ratio of organocopper (I) to organocopper (II) salts is from about 4: 1 to about 12:1. In another such embodiment, the cathode catalyst includes a 2D conductor and an electronic conducting polymer, an electrolyte, a porous dye-sensitized titanium dioxide film layer, and an anode. In this example, the electrolyte includes two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary / tertiary / quatemary mixtures of these solvents. In yet another such embodiment, the cathode catalyst includes a 2D conductor and an electronic conducting polymer, an electrolyte, a porous dye-sensitized titanium dioxide film layer, an anode, and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer. In this example, the electrolyte includes a redox couple comprising organocopper (I) and organocopper (II) salts, and the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12:1. In yet another such embodiment, the cathode catalyst includes a 2D conductor and an electronic conducting polymer, an electrolyte, a porous dye- sensitized titanium dioxide film layer, an anode, and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer. In this example, the electrolyte includes two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary / tertiary / quatemary mixtures of these solvents. In yet another such embodiment, the cathode catalyst includes a 2D conductor and an electronic conducting polymer, an electrolyte, a porous dye-sensitized titanium dioxide film layer, and an anode. TIN this example, he electrolyte includes a redox couple comprising organocopper (I) and organocopper (II) salts, and the ratio of organocopper (I) to organocopper (II) salts is from about 4: 1 to about 12:1 and the electrolyte includes two or more solventsselected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary / tertiary / quatemary mixtures of these solvents. In yet another such embodiment, the cathode catalyst includes a 2D conductor and an electronic conducting polymer, an electrolyte, a porous dye-sensitized titanium dioxide film layer, an anode, and a nonporous hole-blocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer. In this example, the electrolyte includes a redox couple comprising organocopper (I) and organocopper (II) salts, and the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12:1 and the electrolyte includes two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary / tertiary / quatemary mixtures of these solvents.

[0128] In one embodiment, a dye-sensitized photovoltaic cell includes a cathode, an electrolyte, a porous dye- sensitized titanium dioxide film layer, an anode, and a nonporous holeblocking layer interposed between the anode and the dye-sensitized titanium dioxide film layer. The electrolyte includes a redox couple comprising organocopper (I) and organocopper (II) salts, and wherein the ratio of organocopper (I) to organocopper (II) salts is from about 4:1 to about 12:1. The electrolyte includes two or more solvents selected from the group consisting of sulfolane, dialkylsulfone, an alkoxypropionitrile, cyclic carbonates, acyclic carbonates, cyclic lactones, acyclic lactones, low viscosity ionic liquids, and binary / tertiary / quaternary mixtures of these solvents.

[0129] In some embodiments, the dye-sensitized photovoltaic cells are copper redox based dye- sensitized PV cells having an electrolyte with a copper redox pair. In some such embodiments, the dyes include those described in U.S. Patent 11,286,244 titled “Solar Cell Dyes for Copper Redox Based Dye-sensitized Solar Cells and Combinations Thereof,” incorporated by reference herein for the purpose of describing dyes, and methods of fabrication and examples of materials for a dye-sensitized photovoltaic cell.

[0130] A method of producing a photovoltaic cell may include the step of polymerizing PEDOT on the cathode from monomeric EDOT. The PEDOT may be polymerized on the cathode by chemical polymerization or electrochemical polymerization. The PEDOT may be polymerized on the cathode using ferric tosylate or ferric chloride as a catalyst. The ratio of EDOT to ferric chloride may be from about 1:3 to about 1:4. In one embodiment, EDOT is mixed with graphene before chemical polymerization. The EDOT / graphene / ferric catalysis maybe deposited from n-butanol on the cathode using spin, gravure, blade or slot coating techniques and allowed to polymerize on the substrate.

[0131] A method of forming composite catalytic layers on the cathode of a dye-sensitized photovoltaic cell may include the step of forming a composite graphene material with one or more conducting polymers. Suitable conducting polymers include, but are not limited to, poly thiophenes, polypyrroles, and polyanilines. The ratio of graphene to conducting polymer may be from about 0.5: 10 to about 2: 10. A suitable polythiophene for use in this method is PEDOT. In one alternative embodiment of the method, the polymer and graphenes are polymerized prior to deposition on the cathode. The composite may be formed by the steps of depositing graphene on an electrode to form a graphene layer; and electrodepositing the polymer on the graphene layer.- Bifacial photovoltaic cells

[0132] In some embodiments, the electronic signs includes one or more bifacial photovoltaic cells. For example, the ESLs shown in Figures 1-7B include bifacial photovoltaic cells. A bifacial photovoltaic cell allows for harvesting of photons from either side of the cell. For example, a bifacial photovoltaic cell may allow for harvesting of photons from both the anodeside and the cathode-side of the cell such as with the bifacial photovoltaic cells 1000 and 1100 described in Figures 10 and 11. In another example, a bifacial photovoltaic cell may be two monofacial photovoltaic cells such as the photovoltaic cell 900 shown in Figure 9 placed back to back to allow for harvesting of photons from one side of each of the back to back cells. A single bifacial cell (such as shown in Figures 10 and 11) may be advantageously used to minimize thickness.

[0133] In some cases, bifacial photovoltaic cells may be dye-sensitized photovoltaic cells. For example, the bifacial photovoltaic cells may be dye-sensitized photovoltaic cells that include a layer with a mixture of two sets of particles: small dye-sensitized particles and large particles. The small dye- sensitized particles are smaller than the wavelength and so are transparent to it. The dye absorbs lights and initiates a rapid electron transfer. The large particles are larger than the wavelength of light. Because the large particles are in a matrix of small dye-sensitized particles, they act as micro-reflectors, allowing light to scatter and eventually be harvested. While not necessary for operation, the large particles may be dye-sensitized, allowing for ease of fabrication. The presence of the light-absorbing layer that includes a mixture of small and large particles as described above allows light from both sides of the cell to be absorbed. A lightabsorbing layer including both small, dye-sensitized particles and large particles may be incorporated into any dye-sensitized photovoltaic cell.

[0134] Figure 10 depicts a cross section of an example of a bifacial photovoltaic cell 1000. Bifacial photovoltaic cell 1000 includes three layers disposed between an anode-side assembly 1030 (anode) and a cathode-side assembly 1010 (cathode). A sealant 1028 surrounds the three layers. Cathode-side assembly 1010 includes a transparent substrate 1012 coated with a transparent conducting oxide (TCO) 1014, and a catalyst layer 1016. Anode-side assembly 1030 includes a transparent substrate 1032 coated with a TCO 1034. Disposed between the cathodeside assembly 1010 and anode-side assembly 1030 are an electrolyte layer 1022, a first lightabsorbing layer 1024, and a second light-absorbing layer 1026. The first light-absorbing layer 1024 contains a mixture of small dye-sensitized particles and large particles as described above. The second light-absorbing layer 1026 contains small dye-sensitized particles without large particles. Most photons incoming through the anode are absorbed in the second light-absorbing layer 1026, with photons that pass through the second light-absorbing layer reflected by and / or absorbed in the first light-absorbing layer 1024. The first light-absorbing layer 1024 allows light from the cathode to be harvested.

[0135] In the example of Figure 10, the second light-absorbing layer 1026 is disposed between the anode-side assembly 1030 and the first light-absorbing layer 1024, such that the first lightabsorbing layer 1024 is closer to the cathode-side assembly 1010. In alternate embodiments, the first light-absorbing layer 1024 may be disposed between the anode-side assembly 1030 and the second light-absorbing layer 1026, such that the first light-absorbing layer 1024 is closer to the cathode-side assembly 1010.

[0136] Figure 11 depicts a cross section of another example of a bifacial photovoltaic cell 1100, according to embodiments. In the example shown in Figure 11, the layers disposed between the cathode-side assembly 1110 and the anode-side assembly 1130 include an electrolyte layer 1122 and a first light-absorbing layer 1124. The first light-absorbing layer 1124 contains a mixture of small dye-sensitized particles and large particles as described above. Because the large particles are in a matrix of small dye-sensitized particles, they act as microreflectors, allowing light to scatter and eventually be harvested by the smaller particles. A sealant 1128 surrounds the electrolyte layer 1122 and first light-absorbing layer 1124. Cathode-side assembly 1110 includes a transparent substrate 1112 coated with a transparent conducting oxide (TCO) 1114, and a catalyst layer 1116. Anode-side assembly 1130 includes a transparent substrate 1132 coated with a TCO 1134.

[0137] Various modifications may be made to the example bifacial photovoltaic cells shown in Figures 10 and 11, including modifications to the anode and / or cathode assemblies. For example, a non-porous hole-blocking layer as described in U.S. Patent Publication2020 / 0395492, titled “Dye-sensitized photovoltaic cells,” may be used. This publication is incorporated by reference herein for the purpose of describing a dye-sensitized photovoltaic cell architecture, related methods of fabrication, and examples of materials for a dye-sensitized photovoltaic cell.

[0138] The bifacial PV cells may be characterized by a comparison of photovoltaic performance from cathode-side illumination and anode-side illumination. According to various embodiments, one or more of the following characteristics may be exhibited. The power density (mW / cm2) resulting from cathode-side illumination may be at least 30%, 40%, 50%, 60%, or 70% of the power density resulting from anode-side illumination. Short circuit current density (Jsc, mA / cm2) resulting from cathode-side illumination may be at least 30%, 40%, 50%, 60%, or 70% of the short circuit current density resulting from anode-side illumination.

[0139] In the embodiments described herein, the anode-side may face the back of the ESL or other electronic sign to receive backside illumination.

[0140] The first light-absorbing layers 1024 and 1124 in bifacial photovoltaic cells 1000 and 1100 shown in Figures 10 and 11 may also be referred to as a light-scattering layer, a light- absorbing-and-scattering layer, or a mixed particle layer. As indicated above, these first lightabsorbing layers 1024 and 1124 include a mixture of small and large particles. According to various embodiments, a distribution of small particles in a light-absorbing layer may be characterized by having an average size between 10 nm and 50 nm. A distribution of a large particles in a light- absorbing layer may be characterized by having an average size between 100 nm and 500 nm. The particles are generally nominally spherical, with size referring to diameter. Particles of other shapes may be used. In such cases, size refers to the largest linear dimension.

[0141] In a mixed particle layer, the large particles may be thought of as distributed in a matrix of small particles. The large particles are generally distributed throughout the layer, though the distribution is not necessarily precisely controlled, with some randomness. As described further below in the examples, the mixed particle layer may be prepared using an aqueous dispersion of particles and a polymer binder. According to various embodiments, fewer than half of the total number of particles are large particles. In some embodiments, between about 5% and 40% or 5% and 20% of the total number of particles are large particles, with all or substantially all (e.g., greater than 90% or 99%) of the remainder being small particles.

[0142] The large particles may be semiconducting or dielectric particles. In some embodiments, they are metal oxides with example materials including TiCE, ZnCE, SiCh, SnCE, TaiCk, and polymeric nanomaterials. The small particles are dye-sensitized metal oxide particles.Examples include titanium dioxide (T1O2), zinc dioxide (ZnCh), tin dioxide (SnC ), and tantalum pentoxide (Ta2Os). Examples of dyes and fabrication techniques are given below.

[0143] As discussed above, in some embodiments, the mixed particle layer is one layer of a bilayer. An example is shown in Figure 10 in which there are two light-absorbing layers, one with and one without large particles, the layers may be of approximately the same thickness, e.g., 2 to 12 nm or 4 to 10 nm thick each. In alternate embodiments, one layer may be thicker than the other.III. Energy Harvesting System

[0144] Figure 12 is a simplified block diagram of an energy harvesting system 1200, according to embodiments that may be used in certain implementations. The energy harvesting system 1200 can be implemented as a single electronic device or as separate components that are electrically coupled to each other. For example, the components depicted in Figure 12 may be mounted on a circuit board housed within the electronic device housing. However, the components can be combined or separated such that the features described with respect to these components are distributed differently than shown in Figure 12.

[0145] Energy harvesting system 1200 includes a photovoltaic element 1210, a power management integrated circuit (PMIC) 1220, one or more energy storage elements 1230, and a load system 1240. Photovoltaic element 1210 operates as an energy harvesting element and may include, e.g., a single photovoltaic cell or multiple PV cells, e.g., two or more photovoltaic cells arranged in a one-dimensional or two-dimensional array. Photovoltaic element 1210 can be implemented using any of a variety of photovoltaic cell technologies such as those described above. The photovoltaic element 1210 may be used as a supplemental power source or as a primary power source for the electronic device. For the ESLs and other electronic signs described herein, it is typically the primary power source. PMIC 1220 may route harvested energy from the photovoltaic element 1210 to the one or more energy storage elements 1230 and deliver the stored energy to load system 1240. The one or more energy storage elements 1230 are configured to store energy transferred from the photovoltaic cell 1210. The one or more energy storage elements 1230 may include, for example, a primary storage element and a secondary storage element. Load system 1240 includes components that can operate to provide functionality to the electronic device. Load system 1240 can include one or more processing units such as a processor or a microcontroller. Each processing unit is operable to execute program instructions in the form of software or firmware. The load system 1240 may also include any number of components to provide the functionality such as input / output ( I / O ) devices, sensors, wireless communication devices, etc. The one or more storage elements 1230are configured to store energy in the form of electrical charge. One example of an energy storage element is a supercapacitor.

[0146] It will be apparent that certain changes and modifications may be practiced within the scope of the disclosure. For example, in certain embodiments, the user interface may include any appropriate number of buttons or other user interface features. In certain embodiments, the user interface may be configured for force sensing and / or gesture detection. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein.

[0147] Modifications, additions, or omissions may be made to any of the above-described implementations without departing from the scope of the disclosure. Any of the implementations described above may include more, fewer, or other features without departing from the scope of the disclosure. Also, one or more features from any implementation may be combined with one or more features of any other implementation without departing from the scope of the disclosure. The components of any implementation may be integrated or separated according to particular needs without departing from the scope of the disclosure.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. An electronic sign label (ESL) device comprising: a housing comprising a translucent backside element and a frontside window element; a display arrangement housed within the housing, the display arrangement comprising a circuit board and a display element configured to display information viewable through a translucent portion of the frontside window element; and a photovoltaic element housed within the housing between the translucent backside element and the display arrangement, wherein the photovoltaic element is configured to generate electrical power for powering the ESL device based on light received from an external environment.

2. The ESL device of claim 1, wherein the translucent backside element is configured to pass light from the external environment to a first light facing surface and a second light facing surface of the photovoltaic element.

3. The ESL device of claim 1, wherein the translucent backside element is configured to provide gap between the photovoltaic element and the display arrangement, the gap configured to pass light from the external environment to (i) a second light facing surface of the photovoltaic element or (ii) one or more reflective surfaces within the housing, the one or more reflective surfaces configured to reflect light to the second light facing surface of the photovoltaic element.

4. The ESL device of claim 3, wherein the translucent backside element comprises one or more translucent flanges configured to pass light from the external environment to the gap between the photovoltaic element and the display arrangement.

5. The ESL device of claim I, wherein the translucent backside element comprises a translucent wall configured to pass light from the external environment to a first light facing surface of the photovoltaic element.

6. The ESL device of claim 5, wherein the translucent wall is sloped at an angle with respect to an outer surface of the frontside window element.

7. The ESL device of claim 1, wherein the translucent backside element comprises a translucent wall configured to position the photovoltaic element at an angle with respect to an outer surface of the frontside window element.

8. The ESL device of claim 1, wherein the photovoltaic element comprises at least one photovoltaic cell.

9. The ESL device of claim 8, wherein the at least one photovoltaic cell comprises a dye-sensitized photovoltaic cell.

10. The ESL device of claim 8, wherein the at least one photovoltaic cell comprises a bifacial photovoltaic cell.

11. The ESL device of claim 10, wherein the bifacial photovoltaic cell comprises: a cathode; an electrolyte; a first light-absorbing layer; a second light-absorbing layer; and an anode.

12. The ESL device of claim 11, wherein: the first light-absorbing layer comprises a mixture of dye-sensitized particles having an average size between 10 nm and 50 nm and particles having an average size between 100 nm and 500 nm; and the second light-absorbing layer comprises dye- sensitized particles having an average size between 10 nm and 50 nm.

13. The ESL device of claim 10, wherein the bifacial photovoltaic cell is capable of generating electrical power from photons from anode-side illumination and from cathode-side illumination.

14. The ESL device of claim 1, wherein a plane at a surface of the photovoltaic element is non-parallel to a plane at a surface of the frontside window element.

15. The ESL device of claim 1, wherein a plane at a surface of the photovoltaic element is parallel to a plane at a surface of the frontside window element.

16. The ESL device of claim 1, wherein the housing is sealed closed.

17. The ESL device of claim 1, wherein the translucent backside element is sealed to the frontside window element.

18. The ESL device of claim 1, wherein the circuit board has a surface facing the photovoltaic element, and wherein the surface has a white or mirror finish.

19. The ESL device of claim 1, wherein the circuit board comprises a reflective coating disposed on a surface facing the photovoltaic element.

20. The ESL device of claim 1, further comprising a plate disposed between the photovoltaic element and the circuit board, wherein the plate is configured to reflect light toward the photovoltaic element.

21. The ESL device of claim 1, wherein the translucent backside element has a pocket configured to receive the photovoltaic element.

22. The ESL device of claim 1, further comprising a conductive antenna element configured to receive one or more updates from an external device.

23. A digital signage device comprising: a first housing comprising a first translucent element and a second translucent element; a plurality of photovoltaic cells housed within the first housing between the first translucent element and the second translucent element, wherein the photovoltaic cells are configured to generate electrical power for powering the digital signage device based on light received from an exterior environment; a second housing comprising a frontside window element; and a display arrangement housed within the second housing, the display arrangement comprising a circuit board and an electronic display configured to display information viewable through a translucent portion of the frontside window element.

24. The digital signage device of claim 23, further comprising a hinge coupled between to the first housing and the second housing.

25. The digital signage device of claim 23, wherein the plurality of photovoltaic cells comprises a linear array of photovoltaic cells.

26. The digital signage device of claim 23, wherein the plurality of photovoltaic cells comprises at least one dye-sensitized photovoltaic cell.

27. The digital signage device of claim 23, wherein the plurality of photovoltaic cells comprises at least one bifacial photovoltaic cell.

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