Gang Shi, Carbondale, IL, USA

Hang Cek Liong, Singapore, SG

Jeevan Sivaraman, Singapore, SG

Weng Kee Loh, Singapore, SG

Bo Zhang, Singapore, SG

SPECIFICATION BACKGROUND OF THE INVENTION

[0001] The present invention is in the technical field of photovoltaics (PV). More particularly, the present invention is in the technical field of PV modules.

[0002] Some known PV modules are constructed by shingling PV cells to form a PV string. The PV cells are full size or segmented PV cells. A full PV cell is cut, by a laser or mechanical means, and then separated to form segmented PV cells. For the remaining of this document the term "PV cell(s)" refers to either full size or segmented PV cell(s). "Shingling" refers to connecting multiple PV cells in series by partially overlapping them, with the front cell electrode of one PV cell couples with the rear cell electrode of an adjacent PV cell. Sometimes electrically conductive adhesive (ECA) or solder is applied at the overlapped interface to improve mechanical strength and electrical connection.

[0003] In conventional PV modules the electrical connections between the PV cells within a PV string is via metal ribbons. In PV modules that are constructed with shingled PV cell there is no metal ribbons between the PV cells within a PV string. Electrical access to the segmented PV cells within a PV string is therefore very limited.

SUMMARY OF THE INVENTION

[0004] The present invention is a PV cell design that enables and enhances electrical access to PV cells in a PV module constructed by shingled PV cells.

[0005] The present invention introduces additional electrical contacts on PV cells. The size and position of these metal contacts are designed to provide reliable electrical connection and minimize the negative impact on PV cell efficiency. [0006] The present invention provides means for PV cells of a PV string constructed by shingled PV cells to be connected to other PV cells in different PV strings, and to external circuitries. Which makes it possible to protect a PV module by means of by-pass diodes in the event of shading or compromised PV cells during operation. It also makes it possible to design PV modules without by-pass diodes by providing multiple inter-string connections in a PV module consist of PV strings constructed by shingled PV cells.

[0007] The present invention enhances reliability and aesthetic appearance of PV modules by avoiding directly coupling metal ribbons to the front surface of the PV cells within PV strings constructed by shingled PV cells.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Fig. 1 is a top plan view of an example PV cell of present invention.

[0009] Fig. 2 is a bottom plan view of an example PV cell of the invention.

[0010] Fig. 3 is a cross-section view of two shingled PV cells of the invention from the side.

[0011] Fig. 4 is a top plan view of an example PV string constructed with PV cells of the invention.

[0012] Fig. 5 is a bottom plan view of an example PV string constructed with PV cells of the invention.

[0013] Fig. 6 is a schematic diagram from the top of an example PV module (with by-pass diodes) constructed with PV cells of the invention.

[0014] Fig. 7 is a schematic diagram from the bottom of an example PV module (with by-pass diodes) constructed with PV cells of the invention.

[0015] Fig. 8 is a schematic diagram from the top of an example PV module (with inter- string metal ribbons) constructed with PV cells of the invention.

[0016] Fig. 9 is a schematic diagram from the bottom of an example PV module (with inter- string metal ribbons) constructed with PV cells of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017] Certain terminology may be used in the following description for the purpose of reference only, and thus are not intended to be limiting. For example, terms such as "front" and "rear" refer to internally consistent directions in the drawings to which reference is made. Terms such as "top", "bottom", and "side" may describe the orientation and/or location of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import.

[0018] Referring now to the invention in more detail, in Fig. 1 there is shown a top plan view of an example PV cell 200. The PV cell 200 includes a front cell electrode 116, along with fingers 114 disposed on the top surface of a silicon substrate 110. There is an anti-reflection layer 112 disposed on the top surface of a silicon substrate 110.

[0019] Fig. 2 shows the bottom plan view of the same example PV cell 200 of the invention as shown in Fig. 1. It is shown a rear cell electrode 118, along with additional electrical contacts 120 disposed on the surface of a silicon substrate 110. There is a metal conductive layer 113 disposed on the top surface of a silicon substrate 110.

[0020] The present invention introduces additional electrical contacts 120 in Fig. 2. The additional electrical contact 120 is electrically coupled to the rear cell electrode 118. The size, shape, and position of the additional electrical contact 120 can vary and consideration is taken to ensure adequate contact area for reliable bounding but no excessive loss of cell efficiency due to reduced back side field (BSF). In the example PV cell 200 in Fig. 2 the additional electrical contact 120 is located along the narrow region along one of the edges, where the PV cell 200 will be overlapping with another PV cell 200 when forming a PV string. Such arrangement of the additional electrical contact 120 minimizes the impact on the efficiency of PV modules that are constructed with shingled PV cell of the invention.

[0021] The additional electrical contact 120 in Fig. 2 is fabricated by similar process during the PV cell fabrication as the rear cell electrode 118.

[0022] Fig. 3 shows the cross-section view of two shingled PV cells of the invention from the side. These two PV cells 200 and 201 are jointed together in series by coupling the rear cell electrode 118 of PV cell 200 to the front cell electrode 116 of PV cell 201. Electrically conductive adhesive (EC A) or solder 117 is sometime applied between the rear cell electrode 118 of PV cell 200 and the front cell electrode 116 of PV cell 201 to mechanically and/or electrically connect the PV cells to each other. The additional electrical contact 120 of PV cells 200 and 201 are exposed and accessible. [0023] Fig. 4 shows the top plan view of an example PV string 300 constructed with PV cells

200, 201, 202, and 203 of the invention. These PV cells are jointed together in series by coupling the rear cell electrode 118 of one PV cell to the front cell electrode 116 of the adjacent PV cell. Electrically conductive adhesive (EC A) or solder 117 is sometime applied between the rear cell electrode 118 and the front cell electrode 116 to mechanically and/or electrically connect the PV cells to each other. Once the PV string 300 is completed with desired number of PV cells (in the case shown in Fig. 4 there are four PV cells 200, 201, 202, 203), only one PV cell 203 has its front cell electrode 116 exposed.

[0024] Fig. 5 shows the bottom plan view of the same example PV string 300 as shown in Fig. 4 constructed with PV cells 200, 201, 202, and 203 of present invention. These PV cells are jointed together in series by coupling the rear cell electrode 118 of one PV cell to the front cell electrode 116 of the adjacent PV cell. Electrically conductive adhesive (ECA) or solder 117 is sometime applied between the rear cell electrode 118 and the front cell electrode 116 to mechanically and/or electrically connect the PV cells to each other. Once the PV string 300 is completed with desired number of PV cells (in the case shown in Fig. 4 there are four PV cells 200, 201, 202, 203), only one PV cell 200 has its rear cell electrode 118 exposed, and all PV cell 200, 201, 202, and 203 have their additional electrical contacts 120 exposed.

[0025] Fig. 6 is a schematic diagram from the top of an example PV module. Fig. 6 only shows the key components that are directly related to the invention. Other necessary components for a PV module such as glass, EVA, backsheet, frame, and junction box are left out. The PV module 500 is consisted of PV strings 400, module metal ribbons 510, by-pass diodes 520, and module electrodes 530 and 540.

[0026] In more details Fig. 6 shows that each PV string 400 is constructed with multiple PV cells

201, 202, 203...217. As described in Fig. 4 and Fig. 5. PV cells 201, 202, 203...217 are connected in series. Note in this arrangement PV cells 201, 202, 203...216 are active PV cells and contribute generating PV electricity when the PV module 500 is in normal operating condition, while PV cell 217 functions solely as electrical contact between PV cell 216 and module metal ribbon 510.

[0027] In Fig. 6 multiple PV strings 400 are connected in parallel by module metal ribbons 510. At one end of the strings, module metal ribbons 510 are connect to the rear cell electrode 118 of PV cell 201 by using ECA or soldered 117. At the other end of the PV string 400, module metal ribbons 510 are connected to the additional electrical contacts 120 of PV cell 217 by using ECA or soldered 117.

[0028] As the positive electrode and negative electrode are on opposite surfaces of a PV cell, it is a common practice to solder metal ribbon to the front and the rear side of PV cells to extract electricity. However, this method causes severe reliability issue as the soldering process leaves micro-cracks on PV cell and later causes PV cell breakage and loss of power in the field.

Soldering metal ribbons to, particularly the front side of, the PV cells of shingled PV module causes even higher rate of PV cell breakage as the soldering happens very close to the PV cell edge. In addition, the metal ribbons attached to the front side of the PV modules are clearly visible, causing the PV modules to have unpleasing appearance.

[0029] The inclusion of the PV cell 217 in Fig. 6 solves the abovementioned problems. The PV cell 217 has its rear cell electrode 118 electrically coupled to PV cell 216, and its additional electrical contact 120 electrically coupled to module metal ribbon 510. Although PV cell 217 doesn't contribute to direct electricity generation it allows electricity being conducted from the PV cell 216 to module metal ribbon 510 in Fig. 6. In addition, the module metal ribbon 510 is hidden behind the PV cell 217, making PV module 500 aesthetically pleasing. Attaching module metal ribbon 510 to the additional electrical contact 120 in the rear side of PV cell 217 by using ECA or soldered 117 has proven to be much more reliable than attaching metal ribbon 510 to the front cell electrode 116 of Fig. 1 by using ECA or soldered 117.

[0030] In PV module design, by-pass diodes are commonly used to protect a PV module in the event of shading or compromised PV cell(s). It is convenient to connect by-pass diodes in parallel with portion of the PV string in conventional PV module as there are metal ribbon between the PV cells in conventional PV modules. However, it is not straightforward to include by-pass diodes in PV modules that are constructed with shingled PV cells, as the PV cells are connected directly by shingling neighboring cells together.

[0031] Current invention introduces additional electrical contacts 120 at the rear side of the PV cells in Fig. 2. The additional electrical contacts 120 are along the edges of the PV cell. In a completed PV string 400 in Fig. 6, the additional electrical contacts 120 are directly behind the area overlapped and shaded by the neighboring PV cells. Therefore, the detrimental effect of the additional electrical contacts 120 on the backside field (BSF) of the PV cells, or on the PV module efficiency is minimized. [0032] The additional electrical contacts 120 make it convenient to incorporate by-pass diodes in PV module design. Fig. 6 shows module metal ribbon 510 are connected to the additional electrical contacts 120 of the PV cell 205 and 211 in the middle of PV string 400 by using ECA or soldered 117. Depend on the PV cell reverse break-down characteristics, module metal ribbon 510 can be configured in such way that the by-pass diodes are connected in parallel with desired number of PV cells.

[0033] In Fig. 6 multiple by-pass diodes 520 are connected in series by module metal ribbons 510. Each by-pass diode 520 are connected in parallel with a portion of the PV strings 400 by module metal ribbon 510.

[0034] Fig. 6 also shows module electrode of positive polarity 530 and module electrode of negative polarity 540 are connected to module metal ribbons 510.

[0035] Fig. 7 is a schematic diagram from the bottom of an example PV module 500 as shown in Fig. 6. Fig. 7 only shows the key components that are directly related to the invention. Other necessary components for a PV module such as glass, EVA, backsheet, frame, and junction box are left out. The PV module 500 is consisted of PV strings 400, module metal ribbons 510, bypass diodes 520, and module electrodes 530 and 540.

[0036] In more details Fig. 7 shows that each PV string 400 is constructed with multiple PV cells 201, 202, 203...217. As described in Fig. 4 and Fig. 5. PV cells 201, 202, 203...217 are connected in series. Note in this arrangement PV cells 201, 202, 203...216 are active PV cells and contribute generating PV electricity when the PV module 500 is in normal operating condition, while PV cell 217 functions solely as electrical contact between PV cell 216 and module metal ribbon 510.

[0037] In Fig. 7 multiple PV strings 400 are connected in parallel by module metal ribbons 510. At one end of the strings, module metal ribbons 510 are connect to the rear cell electrode 118 of PV cell 201 by using ECA or soldered 117. At the other end of the PV string 400, module metal ribbons 510 are connected to the additional electrical contacts 120 of PV cell 217 by using ECA or soldered 117.

[0038] Fig. 7 shows module metal ribbon 510 are connected to the additional electrical contacts 120 of the PV cell 205 and 211 in the middle of PV string 400 by using ECA or soldered 117. [0039] In Fig. 7 multiple by-pass diodes 520 are connected in series by module metal ribbons 510. Each by-pass diode 520 are connected in parallel with a portion of the PV strings 400 by module metal ribbon 510.

[0040] Fig. 7 also shows module electrode of positive polarity 530 and module electrode of negative polarity 540 are connected to module metal ribbons 510.

[0041] In contrast to conventional PV modules, in which all PV cells are connect in series, the PV strings in shingled PV modules can be configured in a mix of serial and parallel connection to provide desired voltage and current output characteristics. Parallel connected PV strings provide additional operational tolerance for shading and/or component damage. In some module designs by-pass diodes is not necessary. Fig. 8 and Fig. 9 show an example of such designs.

[0042] Fig. 8 is a schematic diagram from the front of an example PV module 600. Fig. 8 only shows the key components that are directly related to the current invention. Other necessary components for a PV module such as glass, EVA, backsheet, frame, and junction box are left out. The PV module 600 is consisted of PV strings 400, module metal ribbons 510, inter-string metal ribbon 625, and module electrodes 530 and 540.

[0043] With additional metal contact 120 on every PV cell in Fig. 8, inter-string connections can be made between corresponding locations of neighboring PV strings. In the event of shading, cell breakage, and other damage that cause imbalance of current in one PV string, the inter-string connections allow electrical current to be redistributed to the neighboring PV strings and beyond for better PV module performance.

[0044] In more details Fig. 8 shows that each PV string 400 is constructed with multiple PV cells 201. As described in Fig. 4 and Fig. 5. PV cells 201, 202, 203...217 are connected in series. Note in this arrangement PV cells 201, 202, 203...216 are active PV cells and contribute generating PV electricity when the shingled PV module 600 is in normal operating condition, while PV cell 217 functions solely as electrical contact between PV cell 216 and module metal ribbon 510.

[0045] In Fig. 8 multiple PV strings 400 are connected in parallel by module metal ribbons 510. At one end of the strings, module metal ribbons 510 are connect to the rear cell electrode 118 of PV cell 201 by using ECA or soldered 117. At the other end of the PV string 400, module metal ribbons 510 are connected to the additional electrical contacts 120 of PV cell 217 by using ECA or soldered 117. [0046] Fig. 8 shows multiple inter-string metal ribbon 625 connecting correspondent additional electrical contacts 120 of neighboring PV strings 400 by using ECA or soldered 117. In some cases, inter-connecting a fraction of all the corresponding additional electrical contacts 120 is adequate to provide protection.

[0047] Fig. 8 also shows module electrode of positive polarity 530 and module electrode of negative polarity 540 are connected to module metal ribbons 510.

[0048] Fig. 9 is a schematic diagram front the bottom of the same example PV module 600 as shown in Fig. 8. Fig. 9 only shows the key components that are directly related to the current invention. Other necessary components for a PV module such as glass, EVA, backsheet, frame, and junction box are left out. The PV module 600 is consisted of PV strings 400, module metal ribbons 510, inter-string metal ribbon 625, and module electrodes 530 and 540.

[0049] In more details Fig. 9 shows that each PV string 400 is constructed with multiple PV cells 201. As described in Fig. 4 and Fig. 5. PV cells 201, 202, 203...217 are connected in series. Note in this arrangement PV cells 201, 202, 203...216 are active PV cells and contribute generating PV electricity when the shingled PV module 600 is in normal operating condition, while PV cell 217 functions solely as electrical contact between PV cell 216 and module metal ribbon 510.

[0050] In Fig. 9 multiple PV strings 400 are connected in parallel by module metal ribbons 510. At one end of the strings, module metal ribbons 510 are connect to the rear cell electrode 118 of PV cell 201 by using ECA or soldered 117. At the other end of the PV string 400, module metal ribbons 510 are connected to the additional electrical contacts 120 of PV cell 217 by using ECA or soldered 117.

[0051] Fig. 9 shows multiple inter-string metal ribbon 625 connecting correspondent additional electrical contacts 120 of neighboring PV strings 400 by using ECA or soldered 117. In some cases, inter-connecting a fraction of all the corresponding additional electrical contacts 120 is adequate to provide protection.

[0052] Fig. 9 also shows module electrode of positive polarity 530 and module electrode of negative polarity 540 are connected to module metal ribbons 510.

[0053] While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention.