FIELD OF THE INVENTION

The present invention relates to printed solar cells, and more specifically to a printed solar cell comprising a cell body and edge portions.

BACKGROUND

Solar cells convert light into electricity using semiconducting materials that exhibit a photovoltaic effect. A printed solar cell, also known as a wet processed solar cell, is a type of solar cell that uses organic or hybrid organic electronics. Organic electronics is a branch of electronics that deals with conductive organic polymers or small organic molecules for light absorption and charge transport to produce electricity from light by the photovoltaic effect. A printed solar cell commonly comprises a semiconductor printed on a substrate. This cell body is the area that harvests light, and is protected by encapsulating barrier foils. Such a solar cell may be a perovskite solar cell which includes a perovskite-structured compound as the light-harvesting substrate.

Printed solar cells are becoming ever more efficient, and thus their applications increase rapidly. Printed solar cells are light energy harvesting modules that may not only harvest sunlight, but may also beneficially harvest artificial light indoors. Printed solar cells may thus power low-power applications such as small electric appliances that previously required batteries. Printed solar cells may also be applied in addition to batteries.

It is desirable to design small electric appliances as small and efficient as possible, with regard to both volume and outer surface area. As such, it is desirable with a printed solar cell that is as compact as possible, without compromising on efficiency and longevity. The longevity of a printed solar cell directly affects the environmental footprint of both the solar cell itself, but also the electric appliance the printed solar cell is configured to power. It is also an important aspect to keep the manufacturing cost of such printed solar cells as low as possible, while maintaining adequate longevity of the solar cell.

Printed solar cells manufactured using low-cost adhesives are commonly provided with a wide border or edge portions of barrier foil around the cell body. The edge portions provide adhesion between the barrier foils, and provide a buffer against water and oxygen ingress through the sides. Printed solar cells are commonly sensitive to moisture and oxygen ingress, and wide edge portions thus provide a more robust printed solar cell. Wide edges also improve the production tolerances, and the risk of manufacturing defects is reduced, thus increasing production yield. Printed solar cells comprising narrow barrier foil edge portions around the cell body are commonly more exposed to malfunction, exhibit less resilience and also increase the risk of lower yield in production.

However, it is challenging to fit printed solar cells comprising wide edge portions into limited spaces, and appliances comprising such solar cells may appear more bulky and visible than what is often desired.

Printed solar cells may preferably be mounted on top of a printed circuit board or similar device. Conducting the power generated by a traditional printed solar cell to the printed circuit board may require an additional manufacturing step, and as such be a time consuming and cumbersome process. The process of connecting the printed solar cell to a printed circuit board may advantageously be simplified in order to streamline the production of electric appliances comprising printed solar cells.

There is therefore a need for an improved printed solar cell to reduce or eliminate the above mentioned disadvantages of known techniques.

SUMMARY OF THE INVENTION

It is an object of the present invention to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages in the prior art and solve at least the above mentioned problem.

According to a first aspect, there is provided a printed solar cell, comprising a cell body, the cell body comprising; at least one foil of transparent, flexible substrate, a printed semiconductor provided on the at least one foil of flexible substrate, barrier foils for encapsulating the at least one foil of flexible substrate and the printed semiconductor; the printed solar cell further comprising at least one edge portion arranged around the cell body, the at least one edge portion comprising barrier foil; where at least one edge portion protrudes at an angle relative to the cell body and comprises a printed contact bridge for conducting electric current from the printed semiconductor.

According to an embodiment, the cell body comprises a first foil of a transparent flexible substrate with a printed semiconductor laminated onto a second foil of a transparent flexible substrate with a printed semiconductor.

According to an embodiment, two edge portions protrude at an angle relative to the cell body, each edge portion comprising a printed contact bridge for conducting electric current from the printed semiconductor.

According to an embodiment, contact points are provided at the two edge portions comprising a printed contact bridge.

According to an embodiment, the printed contact bridge is encapsulated by the barrier foils and the contact points pierce the barrier foils.

According to an embodiment, the contact points are conducting arm elements angled relative to a plane of a corresponding edge portion and protrudes on an underside of the cell body.

According to an embodiment the printed solar cell comprises a cut out where two adjacent edge portions meet, for providing a smaller footprint and accommodating the angled edge portions.

According to an embodiment, the at least one edge portion protrudes at an angle approximately 90° relative to the cell body.

According to a second aspect, there is provided a method of forming at least one angled edge portion of a printed solar cell comprising a cell body comprising a semiconductor printed on a flexible substrate encapsulated by barrier foils, the method comprising the steps of: heating at least an edge portion of the printed solar cell; bending the at least one edge portion relative to the cell body. According to an embodiment, the method further comprising a step of removing material from where two adjacent edge portions meet prior to the step of heating at least an edge portion, in order to accommodate bending of the edge portions.

According to an embodiment, the step of heating further comprises heating the at least edge portion up to approximately 80° Celsius.

According to an embodiment, the step of bending comprises bending the at least one edge portion until it is bent approximately 90° relative to the cell body.

A further scope of applicability of the present invention will become apparent from the detailed description given below. However, it should be understood that the detailed description and specific examples, while indicating preferred variants of the present inventive concept, are given by way of illustration only, since various changes and modifications within the scope of the inventive concept will become apparent to those skilled in the art from this detailed description.

Hence, it is to be understood that this inventive concept is not limited to the particular component parts of the device described as such device may vary. It is also to be understood that the terminology used herein is for purpose of describing particular variants only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claim, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the words "comprising", “including”, “containing” and similar wordings does not exclude other elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects of the present inventive concept, including its particular features and advantages, will be readily understood from the following detailed description and the accompanying drawings. The figures are provided to illustrate the general structures of the present inventive concept. Like reference numerals refer to like elements throughout.

Fig. 1 shows a perspective view of a small electric appliance comprising a printed solar cell.

Fig. 2 shows a perspective view of a printed solar cell according to a first embodiment, mounted onto a printed circuit board.

Fig. 3 shows a perspective view of an underside of a printed solar cell according to the first embodiment, mounted onto of a printed circuit board.

Fig. 4 shows a perspective view of an underside of a printed solar cell according to a second embodiment.

Fig. 5 shows a top view of a third embodiment of a printed solar cell, prior to the edge portions being angled.

Fig. 6 shows a schematic partial cross section A-A through the cell body of the printed solar cell of figure 5.

Fig. 7 shows a top view of another embodiment of a printed solar cell, prior to the edge portions being angled.

Fig. 8 shows a perspective view of the embodiment of a printed solar cell of figure 7, when being angled.

Fig. 9 shows a perspective view of another embodiment of a printed solar cell.

DETAILED DESCRIPTION

The present inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred variants of the inventive concept are shown. This inventive concept may, however, be implemented in many different forms and should not be construed as limited to the variants set forth herein; rather, these variants are provided for thoroughness and completeness, and fully convey the scope of the present inventive concept to the skilled person.

Figure 1 shows a perspective view of a small electric appliance 1 . The electric appliance 1 is powered by indoor lightning and comprises a printed solar cell 2 that is incorporated into the design. The electric appliance 1 may be an indoor appliance for controlling or measuring temperature, adjusting lightning, or any device that runs on electric power and that may be powered by a printed solar cell 2. The electric appliance 1 comprises a frame 3 around the visible area of the solar cell 2. The printed solar cell 2 comprises edge portions (not visible in figure 1) which the frame 3 covers in order to e.g. make the electric appliance 1 appear more aesthetically pleasing. The width of the edge portions of the printed solar cell 2 determine the minimum width of the frame 3. In the illustrated embodiment, the frame 3 appears as a protrusion, however, the frame 3 may also be a seamlessly integrated part of the housing of the electric appliance 1 .

In order to maximize the freedom of the design of such an electric appliance 1 , and allow for a design that is as compact and has a small footprint as possible, it is advantageous to keep the frame 3 as thin as possible. It is in most cases desirable to keep the design of such small electric appliances 1 as compact and neutral as the design of the internal components allow. Reducing the width of, or completely removing, the edge portions from the plane of the printed cell body (described with reference to figure 2) may thus drastically affect the design of the electric appliance 1 . Such a reduced footprint of the printed solar cell 2printed may also render new ranges of use possible for the printed solar cell 2. The reduction or elimination of the edge portions 5 must be accomplished without compromising on the robustness or longevity of the printed solar cell 2.

Figure 2 shows a perspective view of the printed solar cell 2 according to a first embodiment, mounted onto a printed circuit board 12. This is further described with reference to figure 3. Alternatively, instead of a printed circuit board, a reflector could also be mounted on the underside of the printed solar cell 2, in order to increase the efficiency of the printed solar cell 2. The printed solar cell 2 comprises a cell body 4. The cell body in the illustrated embodiment is generally square, but may also have a generally rectangular outline. The cell body 4 may as such also be round, elliptical, or have any shape. The cell body 4 is in a relaxed state a generally planar surface, but the cell body 4 may be slightly bent into a curved shape in order to adapt to an e.g. curved outer surface of a small electric appliance. The cell body 4 of the first embodiment comprises four edge portions 5, one edge portion 5 arranged along each edge of the square cell body 4. A printed solar cell 2 may comprise any number of edge portions, depending on the shape of the cell body 2.

The cell body 4 comprises a semiconductor 6 printed on a transparent, flexible substrate 7. Barrier foils 8 encapsulate the printed semiconductor s and flexible substrate 7. The barrier foils 8 may comprise two foils, a top and a bottom foil, of a transparent material. The barrier foils 8 may alternatively comprise a top foil of a transparent material, and a bottom foil of an opaque material. The bottom foil may also be made of aluminum or a similar material. The physical structure of the cell body 4 is described further with reference to figure 6.

The edge portions 5 of the printed solar cell 2 are the portions of the printed solar cell 2 that extends beyond the cell body 4, in particular beyond the cell body 4 that comprises the printed semiconductor 6. The edge portions 5 generally comprise excess material of the barrier foils 8. The barrier foils 8 are adhered together outside the outer periphery of the cell body 4, and an edge portion 5 is the lip that provides adhesion between the barrier foils 8 and seals them together.

In the illustrated embodiment, two edge portions 5 are angled relative to the cell body 4, and protrude in a downwards direction from the cell body 4. The angled edge portions 5 are arranged at opposing edges of the printed solar cell 2. The printed solar cell 2 comprises a printed contact bridge 9, for conducting electric current from the printed semiconductor 6. The contact bridge 9 may be printed on the same flexible substrate 7 as the printed semiconductor 6, and the printed contact bridge 9 may also be encapsulated by the barrier foils 8. The printed contact bridge 9 may comprise carbon, silver or other conductive materials, as is known in the art. The angled edge portions 5 may comprise a contact bridge 9.

In other embodiments, only one edge portion 5 may be angled, or all four edge portions 5 may be angled. If the printed solar cell 2 comprises a plurality of edge portions, several of these may be angled. The design of the small electric appliance the printed solar cell 2 is fitted into may influence how many of the edge portions 5 need to be angled relative to the cell body 4. The design of the small electric appliance may also influence the angle of the protruding edge portion 5. The footprint of the printed solar cell 2, as seen from above, is reduced as the angle of the at least one edge portion 5 is increased, up to 90°. Beyond a 90° angle, the footprint of the printed solar cell 2 is basically maintained, but the edge portion 5 folds inwards towards a back of the printed solar cell 2.

The printed solar cell 2 comprises contact points 10. The contact points 10 are provided to conduct electricity from the printed contact bridge 9 to the outside of the printed solar cell 2. The contact points 10 penetrate the barrier foils 8 such as to expose or come into contact with the printed contact bridge 9 on the inside of the barrier foils 8. printed There are as such two contact points 10 provided on one printed solar cell 2, each contact point 10 contacting an area of the contact bridge 9. If the printed contact bridge 9 is provided on two opposite and angled edge portions 5, the contact points 10 are provided on corresponding edge portions 5.

The contact points 10 of the first embodiment are conducting arm elements that penetrate the barrier foils 8 and are fixed to the printed solar cell 2. The conducting arm elements are made from a conductive material, and is further connected to the device the printed solar cell 2 powers. The conductive material may be silver. The conducting arm elements may be affixed to the printed solar cell 2 prior to or after the edge portions 5 are angled.

In the first embodiment of the printed solar cell 2, the two angled edge portions 5 are angled 90° relative to the cell body 4. As such, the footprint, from a top view, of the printed solar cell 2 is minimized. However, the edge portions 5 may alternatively be angled more or even less, depending on the design of the small electric appliance. The edge portions 5 may even protrude in a non-linear manner relative to the cell body 4. As such, the edge portions 5 may comprise curved and/or plane portions. As the two edge portions 5 protrude 90° relative to the cell body 4, a radius 11 may be formed between the cell body 4 and the edge portions 5.

In the case of a slightly curved printed solar cell 2, as described introductory, an edge portion 5 protruding at an angle relative to the cell body 4 implies that a tangent to the surface of the printed solar cell changes at least between the cell body 4 and the edge portion 5. More specifically, the tangent changes at least through the radius of the edge 11 of the printed solar cell 2.

The edge portions 5 may be angled and protrude in a direction different from that of the planar cell body 4 by bending. Bending the edge portions 5 may be achieved by heating an edge portion 5. In order to reach the glass transition phase of the barrier foil material, the edge portions 5 may advantageously be heated to 80° Celsius. More preferably, the edge portions 5 may be heated up to 100° Celsius. More specifically, the area between the edge portion 5 and the cell body 4, where the radius 11 is formed, may at least be heated prior to bending an associated edge portion 5. The whole printed solar cell 2 may as such be heat treated, but extended heating of the cell body 4 may affect the performance of the printed solar cell 2. The edge portions 5 may be bent by rolling over a die, bending against heated tools, or similar. Normally, in order to maintain the integrity of the barrier foils 8, the minimum bending radius is 1 mm for the radius 11 .

Figure 3 shows a perspective view of an underside of the printed solar cell 2 according to the first embodiment. The underside is the face of the printed solar cell 2 not intended to capture light. A printed circuit board 12, or a similar printed card powered by the printed solar call 2, may be provided on the underside of the cell body. As the edge portions 5 protrudes and are angled 90° relative to the cell body, the edge portions 5 may neatly envelope the printed circuit board 12. The contact points 10 in the form of conducting arms may be bent outwards from the edge portions 5, such that they protrude parallel to the cell body on the underside of the printed circuit board 12, and thus greatly simplifies connection to the printed circuit board 12. Figure 4 shows a perspective view of an underside of a printed solar cell 2 according to a second embodiment. In the second embodiment, the edge portions 5 protrudes at an angle 180° relative to the cell body 4. The edge portions 5 are thus bent on the underside of the cell body 4 and protrudes parallel with the cell body 4. The 180° angle of the edge portions 5 allow the edge portions 5 to further envelope a printed circuit board arranged on the underside of the cell body 4. The bending radius 11 between the cell body 4 and the edge portions 5 may be larger than the bending radius of an edge portion angled at a smaller angle.

Figure 5 shows a top view of a third embodiment of a printed solar cell 2 prior to the edge portions 5 being angled relative to the cell body 4. As manufactured, the printed solar cell 2 is generally planar, and the edge portions 5 are arranged around the cell body 4 in the viewing plane of figure 5. In this third embodiment, the contact points 10’ are simply openings or holes through the printed solar cell 2 where the contact bridge 9 is printed. The openings or holes may be provided by laser or micro machining. These contact points 10’ may be further connected to a printed circuit board or similar as known in the art. If edge portions 5 comprising contact points 10’ protrude at a 180° angle (i.e. on the underside of the cell body 4), the contact points 10’ may be easily connected to a printed circuit board positioned on the underside of the cell body 4.

The printed solar cell 2 may comprise cutouts 12 at the comers. The cutouts 12 are removed material from the corners, such that an outwards pointing corner may be turned into an inwards pointing corner with two adjacent, smaller outwards pointing corners. The comers may be rounded, in order to avoid sharp edges and cracking at the comers. Cutouts 12 at the comers prevent the issue of double curvature if two adjacent edge portions 5 are angled, and in general reduces material usage and minimizes the footprint of the printed solar cell 2. The removal of material for the cut-outs 12 may be done prior to e.g. bending the edge portions 5.

The dotted lines B indicate where the left and right edge portion of figure 5 may be angled. A dotted line B runs through a busbar 13 of the printed contact bridge 9. The busbar 13 extends from the cell body 4 to contact bridge 9, and bending of an edge portion 5 comprising a printed contact bridge 9 may preferably be directed across the busbar 13, in order to minimize the amount of the contact bridge 9 through the bending radius (along the dotted lines B).

Figure 6 shows a schematic cross section A-A through part of the cell body 4 of the printed solar cell 2 of figure 5. The printed semiconductor 6 is printed on a transparent, flexible substrate 7. Both the printed contact bridge (not shown in figure 6, see figure 5) and the printed semiconductor 6 may be printed ultra-thin, and the adhesive used between the two barrier foils 8 may also be applied ultra-thin in order to facilitate the bending of the edge portions. The transparent, flexible substrate 7 may be a plastic material such as PET. The printed semiconductor 6 and flexible substrate 7 is encapsulated by barrier foils 8. At least one of the barrier foils may be made from a plastic material such as PET.

The printed solar cell 2 may preferably be formed by lamination, and the cell body 4 may advantageously be provided by laminating corresponding top and bottom layers. A bottom layer may comprise a printed semiconductor 6 printed onto a flexible substrate 7, and a top layer may comprise a printed semiconductor 6 printed onto a flexible substrate 7. The two layers may be merged by laminating the printed semiconductors 6 facing each other. The top and bottom layers are then encapsulated by adding top and bottom barrier foils 8. As previously described, the barrier foils 8 extend further out than the printed semiconductor 6, such that the top and bottom barrier foils 8 are fixed together around the cell body 4 and form the edge portions 5.

Figure 7 shows a top view of a further embodiment of a printed solar cell 2 prior to the edge portions 5 being angled relative to the cell body 4. In this embodiment the contact bridges 9 continues in the same direction as the elongation of the printed semiconductors 6. The printed contact bridges 9 thereby protrude outside the cell body 4 as continuations of the contact areas that are provided along the outer edge of the outermost printed semiconductors at each side. As in the previous embodiments, the contact bridges 9 are encapsulated by top and bottom barrier foils 8, except for contact points 10”. A part of the barrier foils 8 between the two protruding contact bridges 9 may be omitted, as illustrated in the figure, or the barrier foils 8 may alternatively cover the entire area between the contact bridges, which may influence e.g. the action of bending the edge portions 5.

Figure 8 illustrates the embodiment of Figure 7 when the edge portions 5 have been angled relative to the cell body 4. In this embodiment, the edge portions 5 protrudes at an angle 180° relative to the cell body 4. The edge portions 5 with the contact bridges are thus bent on the underside of the cell body 4 and protrudes parallel with the cell body 4. The contact bridges 9 and the contact points 10” thereby become positioned below the cell body 4, reducing the footprint of the printed solar cell 2, as seen from above. Contacting of the solar cell may therefore also be performed below the cell body 4 and will thereby not affect the footprint either.

Figure 9 illustrates another embodiment, with only one printed semiconductor 6 area. Typically, the printed semiconductor 6 has a high aspect rectangular shape, i.e. is extended more in one direction than in a perpendicular direction, which makes it very well adapted to the contact bridge 9 design parallel to the main extension of the printed semiconductor 6. However, any shape of the printed semiconductor 6 area will be possible to use.

Additionally, variations to the disclosed variants can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.