Patent Publication Number: US-2022238739-A1

Title: Stable perovskite module interconnects

Description:
RELATED APPLICATIONS 
     This application is a divisional of co-pending U.S. patent application Ser. No. 16/255,396 filed on Jan. 23, 2019 which claims the priority of U.S. Provisional Application No. 62/757,619 filed Nov. 8, 2018, both of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Field 
     Embodiments described herein relate to solar cells, and more particularly to interconnect structures for perovskite solar cell modules. 
     Background Information 
     Photovoltaic cells, also referred to solar cells, are devices that convert radiant photo energy into electrical energy. Multiple solar cells may be integrated into a group to constitute a solar panel, or module, in which the solar cells are usually connected in series creating an additive voltage. 
     Monocrystalline solar cells are dominant in the current solar cell industry, offering some of the highest efficiencies and lifetimes. However, the cost associated monocrystalline solar cells is a driving factor in the development of alternative solar cell technologies. One class of development is thin-film solar cells. Thin-film solar cells are attractive due to the potential to implement economical in-line processes of deposition and patterning sequences. As thin-film solar cells continue to improve in efficiency they may be candidates to displace currently adopted monocrystalline solar cells at a reduced cost, or create new solar cell markets. Furthermore, some thin-film solar cells can be flexible with potential applications on curved surfaces, mobile devices, or other components. Two such emerging thin-film technologies include cadmium telluride (CdTe) and copper indium gallium selenide (CIGS). More recently perovskite solar cells have gained attention with a rapid surge in reported cell efficiency. 
     SUMMARY 
     Thin-film solar cell modules and serial cell-to-cell interconnect structures and methods of fabrication are described. In particular embodiments describe structures and fabrication sequences that may protect the integrity of the subcell absorber material, such as a metal-halide perovskite, from decomposition and allow the integration of adjacent metal layers. 
     In an embodiment a solar cell module includes a bottom electrode layer with a plurality of first patterned line openings, a subcell layer over the bottom electrode layer, the subcell layer including a plurality of second patterned line openings, a conformal transport layer over subcell layer and laterally surrounding an outside perimeter the subcell layer, and a patterned top electrode layer over the conformal transport layer. The conformal transport layer may encapsulate the subcell layer to prevent perovskite-metal contact and perovskite decomposition. In an embodiment, a non-metallic intermediate layer, which may be an insulator layer, is located between the conformal transport layer and the subcell layer, with the non-metallic intermediate layer laterally surrounding the outside perimeter of the subcell layer. In such a configuration the conformal transport layer may also surround an outside perimeter of the non-metallic intermediate layer. 
     In an embodiment, a solar cell interconnect includes a bottom electrode layer on a substrate, a first patterned line opening P 1  in the bottom electrode layer, a subcell layer over the bottom electrode layer and within the first patterned line opening P 1 , a second patterned line opening P 2  in the subcell layer, a non-metallic intermediate layer along sidewalls of the second patterned line opening P 2 , a conformal transport layer over the subcell layer, on the non-metallic intermediate layer within the second patterned line opening P 2  and over the bottom electrode layer within the second patterned line opening P 1 , and a top electrode layer over the conformal transport layer and on the conformal transport layer within the second patterned line opening P 2 . A third patterned line opening P 3  may additionally be formed through at least the top electrode layer. 
     In an embodiment, a solar cell interconnect includes a bottom electrode layer, a first patterned line opening P 1  in the bottom electrode layer, a subcell layer over the bottom electrode layer, a second patterned line opening P 2  in the subcell layer, a conductive plug within P 2 , a conformal transport layer over the subcell layer and the conductive plug, a top electrode layer over the conformal transport layer, and a third patterned line opening P 3  in the top electrode layer. The conductive plug may substantially fill P 2  in an embodiment. In another embodiment, a non-metallic intermediate layer may be formed along a single sidewall of P 2 . More specifically, the non-metallic intermediate layer may be formed along a single sidewall of P 1  that is shared with P 1 . 
     In an embodiment, a solar cell interconnect includes a bottom electrode layer, a first patterned line opening P 1  in the bottom electrode layer, a subcell layer over the bottom electrode layer, a conformal transport layer over the subcell layer, a top electrode layer over the conformal transport layer, and a second patterned line opening P 2  through the top electrode layer, the conformal transport layer and the subcell layer. A conductive plug is located within the second patterned line opening. In another embodiment, a non-metallic intermediate layer may be formed along one or more sidewalls of P 2 . 
     The top electrode layer in accordance with embodiments may include a metal layer. The conformal transport layer may provide a physical barrier between the subcell layer and top electrode layer. Additionally, various configurations are possible for forming a third patterned line opening P 3  in the top electrode layer to avoid metal contact with the subcell layer. In some embodiments the top electrode layer may be patterned with a shadow mask. In some embodiments the top electrode layer and underlying layers may be patterned by scribing through the top electrode layer and into underlying layers. The P 3  scribe may be filled with a non-electrically conductive. The P 3  scribe may possibly extend into the non-metallic intermediate layer. In some embodiments P 1  and P 2  do not overlap. In other embodiments, P 2  overlaps P 1 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic top view illustration of a solar cell module in accordance with embodiments. 
         FIGS. 2A-2D  are schematic top view illustrations of a method of fabricating a solar cell module in accordance with embodiments. 
         FIG. 3A  is an illustrative diagram of solar cell stack-up in accordance with embodiments. 
         FIG. 3B  is an illustrative diagram of tandem solar cell stack-up in accordance with embodiments. 
         FIG. 4A  is an illustrative diagram of solar cell stack-up in accordance with embodiments. 
         FIG. 4B  is an illustrative diagram of tandem solar cell stack-up in accordance with embodiments. 
         FIG. 5A  is a schematic cross-sectional side view illustration of an interconnect with printed non-metallic intermediate layer within a subcell patterned line opening and masked top electrode layer in accordance with an embodiment. 
         FIG. 5B  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including the interconnect of  FIG. 3A  in accordance with an embodiment. 
         FIG. 6A  is a schematic cross-sectional side view illustration of a variation of the interconnect of  FIG. 5A  with scribed cells in accordance with an embodiment. 
         FIGS. 6B-6C  are schematic cross-sectional side view illustrations of variations of the interconnect of  FIG. 5A  with a printed non-metallic intermediate layer within an offset subcell patterned line opening in accordance with an embodiment. 
         FIG. 7  is flow chart illustrating a method of forming the interconnect of  FIG. 5A  in accordance with an embodiment. 
         FIGS. 8A-8I  are schematic cross-sectional side view illustrations of a method of forming the interconnect of  FIG. 5A  in accordance with an embodiment. 
         FIG. 9A  is a schematic cross-sectional side view illustration of an interconnect with a transport layer within a subcell patterned line opening in accordance with an embodiment. 
         FIG. 9B  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including the interconnect of  FIG. 9A  in accordance with an embodiment. 
         FIG. 10  is flow chart illustrating a method of forming the interconnect of  FIG. 9A  in accordance with an embodiment. 
         FIGS. 11A-11D  are schematic cross-sectional side view illustrations of a method of forming the interconnect of  FIG. 9A  in accordance with an embodiment. 
         FIG. 12A  is a schematic cross-sectional side view illustration of an interconnect with overlapping bottom electrode and subcell patterned line openings in accordance with an embodiment. 
         FIG. 12B  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including the interconnect of  FIG. 12A  in accordance with an embodiment. 
         FIG. 13  a schematic cross-sectional side view illustration of a variation of the interconnect of  FIG. 12A  with a scribed cell in accordance with an embodiment. 
         FIG. 14  is flow chart illustrating a method of forming the interconnect of  FIG. 12A  in accordance with an embodiment. 
         FIGS. 15A-15H  are schematic cross-sectional side view illustrations of a method of forming the interconnect of  FIG. 12A  in accordance with an embodiment. 
         FIG. 16A  is a schematic cross-sectional side view illustration of an interconnect with a conductive plug in a subcell patterned line opening in accordance with an embodiment. 
         FIG. 16B  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including the interconnect of  FIG. 16A  in accordance with an embodiment. 
         FIG. 17  is a schematic cross-sectional side view illustration of a variation of the interconnect of  FIG. 16A  with scribed cells in accordance with an embodiment. 
         FIG. 18  is flow chart illustrating a method of forming the interconnect of  FIG. 16A  in accordance with an embodiment. 
         FIGS. 19A-19D  are schematic cross-sectional side view illustrations of a method of forming the interconnect of  FIG. 16A  in accordance with an embodiment. 
         FIGS. 20A-20B  are schematic cross-sectional side view illustrations of an interconnect with a printed non-metallic intermediate layer and conductive plug within a subcell patterned line opening in accordance with an embodiment. 
         FIG. 20C  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including an interconnect of  FIG. 20A-20B  in accordance with an embodiment. 
         FIG. 21  is a schematic cross-sectional side view illustration of a variation of the interconnect of  FIG. 20A  with scribed cells in accordance with an embodiment. 
         FIG. 22  is flow chart illustrating a method of forming the interconnect of  FIG. 20A  in accordance with an embodiment. 
         FIGS. 23A-23F  are schematic cross-sectional side view illustrations of a method of forming the interconnect of  FIG. 20A  in accordance with an embodiment. 
         FIGS. 24A-24B  are schematic cross-sectional side view illustrations of an interconnect with a printed non-metallic intermediate layer and conductive plug within a subcell patterned line opening in accordance with an embodiment. 
         FIG. 24C  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including an interconnect of  FIG. 24A-24B  in accordance with an embodiment. 
         FIG. 25  is flow chart illustrating a method of forming the interconnects of  FIGS. 24A-24B  in accordance with embodiments. 
         FIGS. 26A-26C  are schematic cross-sectional side view illustrations of a method of forming the interconnects of  FIGS. 26A-26B  in accordance with embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments describe interconnect structure for thin film solar cell modules, and in particular metal-halide perovskite-based solar cells. In various aspects, embodiments describe interconnect structures and thin-film fabrication methods that allow for economical in-line processing sequences, and the use of a metal rear electrode, which can provide rear reflection for light harvesting, low cost, and high conductivity. It has been observed that the performance and stability of metal-halide perovskite-based solar cells are highly susceptible to metal induced degradation caused by halide-metal interactions. Specifically, metal electrodes may react with halides in the perovskite and act as a sink for halides and corrosion of the metal electrode, degrading conductivity. In accordance with various embodiments, solar cell module interconnect structures are described in which a conformal transport layer may also function as a barrier layer to prevent perovskite-metal contact and the damage of the subcell structure. Furthermore, the interconnect structures in accordance with embodiments may act to prevent the ingress of moisture and oxygen and egress of volatile organic components, which may significantly increase the stability of metal-halide perovskite-based solar cells. 
     In various embodiments, description is made with reference to figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions and processes, etc., in order to provide a thorough understanding of the embodiments. In other instances, well-known processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the embodiments. Reference throughout this specification to “one embodiment” means that a particular feature, structure, configuration, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The terms “over”, “to”, “between”, and “on” as used herein may refer to a relative position of one layer with respect to other layers. One layer “over”, or “on” another layer or in “contact” with another layer may be directly in contact with the other layer or may have one or more intervening layers. One layer “between” layers may be directly in contact with the layers or may have one or more intervening layers. 
     Referring now to  FIG. 1  a schematic top view illustration is provided of a solar cell module in accordance with embodiments. As shown, the module  100  includes a plurality of cells  120  (also referred to as solar cells) coupled in series with interconnects  130 , with the front of one cell connected to the rear of the next cell so that their voltages (V 1  . . . V n ) add. The plurality of cells  120  may be arranged into one or more subsets  110  (e.g. strings) coupled in parallel, which may have the effect of decreasing total module voltage. 
     A thin-film solar cell  120  commonly includes a subcell between two electrodes, at least one of which being transparent. As described in more detail with regard to  FIGS. 3A-3B  and  FIGS. 4A-4B , the subcell may commonly include an absorber layer and one or more transport layers (e.g. hole transport, electron transport). The subcells in accordance with embodiments can include a single junction, or a multiple junction structure with multiple absorber layers. In order to minimize loss due limited conductivity of the transparent electrode, the module is divided into the plurality of smaller cells  120  which are electrically connected in series. The serial interconnect methodologies in accordance with embodiments may generally include a plurality of patterned line openings (P 1 , P 2 , P 3 , etc.) to form interconnects  130 , such as a first patterned line opening P 1  through a bottom electrode, a second patterned line opening P 2  through the subcell which includes the absorber and transport layer(s), and a third patterned line opening P 3  through a top/rear electrode to electrically isolate adjacent cells  120 . 
     Referring now to  FIGS. 2A-2D , schematic top view illustrations are provided of a method of fabricating a solar cell module  100  in accordance with embodiments. As shown in  FIG. 2A , the sequence may begin with the formation of one or more bottom electrode layers  210  on a substrate. In the particular embodiment illustrated two bottom electrode layers  210  are illustrated for the fabrication of two subsets  110  that may be coupled in parallel as described with regard to  FIG. 1 . Each bottom electrode layer  210  includes an outside perimeter  214  and may be patterned to form first patterned line openings P 1 . A subcell layer  220  may then be formed over the patterned bottom electrode layer  210 , followed by patterning of second patterned line openings P 2  as illustrated in  FIG. 2B . As shown, the subcell layer  220  may optionally be wider than the bottom electrode layer  210  such that it surrounds the bottom electrode layer. In some embodiments, the outside perimeter  224  of the subcell layer  220  may be aligned with the outside perimeter  214  of the bottom electrode layer  210 , or laterally surround the outside perimeter  224  of the subcell layer. Alternatively, the subcell layer  220  may have the same width of the bottom electrode layer  210 , which may provide encapsulation function for the subcell layer  220 . Referring now to  FIG. 2C  a conformal transport layer is formed over the subcell layers  220 . This may be a single transport layer or multiple layers corresponding to the subcell layers. In accordance with embodiments, a continuous conformal transport layer  240  is formed over the subcell layer  220  and second patterned line openings P 2  that separate the individual cells  120 . The conformal transport layer  240  may function to transport charge through its thickness, and not be laterally conductive so as to not short adjacent cells  120 . In an embodiment, the conformal transport layer  240  is characterized by a resistivity greater than 0.1 ohm·cm. 
     It has been observed that perovskite materials are prone to decomposition at elevated temperatures, and in particular the A-site cation of ABX 3  metal-halide perovskites. Additionally, perovskite materials are highly susceptible to metal induced degradation caused by halide-metal interactions. In accordance with embodiments, a conformal transport layer  240  may be used to protect against either of decomposition and metal induced degradation due to diffusion from a metal electrode. In accordance with embodiments, the conformal transport layer  240  may encapsulate a subcell layer  220  that includes a perovskite material absorber layer. In an embodiment, the conformal transport layer  240  laterally surrounds the outside perimeter  224  of the subcell layer  220 , or at least the perovskite material absorber layer of the subcell layer  220 . The conformal transport layer  240  may also be formed within the patterned line openings P 2  in the subcell layer  220 . Following the formation of the conformal transport layer  240 , a patterned top electrode layer  250  is formed over the conformal transport layer  240  as illustrated in  FIG. 2D , with the third patterned line openings P 3  though the top electrode layer  250  separating top electrodes of adjacent cells  120 . 
     In an embodiment, a solar cell module  100  includes a bottom electrode layer  210  including a plurality of first patterned line openings P 1 , a subcell layer  220  over the bottom electrode layer  210 , the subcell layer  220  including a plurality of second patterned line openings P 2 , a conformal transport layer  240  over subcell layer  220  and laterally surrounding an outside perimeter  224  the subcell layer  220 , and a patterned top electrode layer  250  over the conformal transport layer  240 . In an embodiment, the patterned top electrode layer  250  includes a metal layer, and the bottom electrode layer  210  a transparent material. Exemplary transparent bottom electrode materials include poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), transparent conductive oxides (TCOs) such as indium tin oxide (ITO), fluorine doped tin oxide (FTO), indium zinc oxide (IZO), aluminum doped zinc oxide (AZO), cadmium stannate, etc. In an embodiment, a non-metallic intermediate layer is located between the conformal transport layer  240  and the subcell layer  220 , the non-metallic intermediate layer laterally surrounding the outside perimeter  224  of the subcell layer  220 . In an embodiment, the conformal transport layer  240  is additionally located within the plurality of second patterned line openings P 2 . Exemplary conformal transport layer materials include oxides (e.g. metal oxides), nitrides (e.g. metal nitrides), polymers, and small molecules. Exemplary metal oxides may be titanium oxide, zinc oxide, tin oxide, nickel oxide, vanadium oxide, tungsten oxide, indium oxide, any of which may be doped. For example, some TCOs may be ITO, AZO, IZO cadmium stannate. Exemplary metal nitrides include at least titanium nitride and tungsten nitride. Some exemplary polymers include poly(triaryl amine) (PTAA) and polyaniline. Some exemplary small molecules include 2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-MeOTAD), and fullerenes. In an embodiment, the conformal transport layer is less than 1,000 nm thick, such as less than 150 nm thick, or more specifically less than 50 nm thick such as 10-40 nm thick. In a specific implementation, the conformal transport layer  240  is formed of aluminum doped zinc oxide (AZO). The aluminum doping concentration need not create a high conductivity, and instead may be sufficient to only pass charge through its thickness, as opposed to laterally. In this aspect, the conformal transport layer in accordance with embodiments can function more as a barrier as opposed to conductor. For example, aluminum dopant concentration with an AZO conformal transport layer  240  may be less than the aluminum dopant concentration with an AZO bottom electrode layer  210 . Morphology can also be different compared to an AZO electrode layer. In embodiment, a conformal transport layer  240  in accordance with embodiments containing AZO may be amorphous, while an AZO electrode layer may be crystalline in order to provide long range mobility and less defects. The conformal transport layer  240  in accordance with embodiments may function to pass charge between the electrodes, yet have a sufficient resistivity to not short across a patterned electrode layer. Furthermore, the conformal transport layer  240  may encapsulate the subcell layer (e.g. metal-halide perovskite) to prevent perovskite-metal contact and perovskite decomposition. 
     Various exemplary solar cell  120  stack-ups are illustrated in  FIGS. 3A-4B .  FIG. 3A  is an illustrative diagram of single junction solar cell stack-up in accordance with an embodiment. As illustrated, the solar cell  120  may include a bottom electrode layer  210 , a top electrode layer  250 , and a subcell layer  220  between the bottom and top electrode layers. Additionally, a conformal transport layer  240  may be formed on the subcell layer  220 . The subcell layer  200  includes an absorber layer  320  and one or more transport layers. In the embodiment illustrated, the subcell layer  200  includes an electron transport layer (ETL)  310  over the bottom electrode, an absorber layer  320  over the ETL  310 , and an optional first hole transport layer (HTL)  330  over the absorber layer  320 . The conformal transport layer  240  may also function as an HTL in this configuration, and physically separate the top electrode layer  250  from the subcell layer  220 , and specifically from the absorber layer  320 . In a specific embodiment, bottom electrode layer  210  is formed of a transparent material such as ITO, ETL  310  is formed of a n-type metal oxide such as titanium oxide, and the absorber layer  320  is a perovskite-based material. In an embodiment, optional HTL  330  is formed of PTAA or spiro-MeOTAD, while the conformal transport layer  240  is formed of a metal oxide such as vanadium oxide or tungsten oxide. In an embodiment, the top electrode layer  250  includes one or more metal layers, such as Ag, Cu, Al, Au, etc. 
       FIG. 3B  is an illustrative diagram of tandem solar cell stack-up in accordance with embodiments. The tandem structure may include multiple absorber layers, which may be the same or different materials. In the specific embodiment described the tandem structure is a perovskite-perovskite tandem structure, though embodiments are not so limited. Electrode layer  210 , ETL  310 , and absorber layer  320 , and HTL  330  may be similar as described with regard to  FIG. 3A . Similarly, ETL  350  may be similar to ETL  310 , absorber layer  360  similar to absorber layers  320 , and HTL  370  similar to HTL  330 . Notably, while absorber layers  320 ,  360  may be formed of similar perovskite-based materials, they may be tuned for different bandgaps. A recombination layer  350  may be located between the stacked subcells, between ETL  350  and HTL  330 . Recombination layer  350  may be a transparent conducting layer such as a TCO, or ITO specifically. Conformal transport layer  240  and top electrode layer  250  may additionally be formed similarly as with regard to  FIG. 3A . 
     Referring now to  FIGS. 4A-4B ,  FIG. 4A  is an illustrative diagram of solar cell stack-up in accordance with an embodiment, and  FIG. 4B  is an illustrative diagram of tandem solar cell stack-up in accordance with an embodiment.  FIGS. 4A-4B  are similar to the structures of  FIGS. 3A-3B , with the order of electron and hole transport layers being flipped. This change in order of layer formation may additionally change materials selection of layers. In an embodiment, HTL  320  is formed of a metal oxide such as nickel oxide. ETL  310  may be a single layer or multiple layers. In an embodiment of  FIG. 4A , ETL  310  is formed of a fullerene, with the conformal transport layer  240  including a transparent metal oxide such a tin oxide or AZO. In an embodiment of  FIG. 4B , ETL  310  may include multiple layers, for example a transparent metal oxide such as tin oxide or AZO formed over a fullerene layer. Other layers illustrated may be similar as described with regard to  FIGS. 3A-3B . 
     Referring now to  FIG. 5A  a schematic cross-sectional side view illustration is provided of an interconnect with printed non-metallic intermediate layer in accordance with an embodiment. Specifically,  FIG. 5A  illustrates the interconnect between serial cells  120 , and additive voltages V 1 , V 2  as shown in  FIG. 1 . The solar cell interconnect may include a bottom electrode layer  210  on a substrate  202 , a first patterned line opening P 1  in the bottom electrode layer  210 , a subcell layer  220  over the bottom electrode layer  210  and within the first patterned line opening P 1 , a second patterned line opening P 2  in the subcell layer  220 , a non-metallic intermediate layer  230  along sidewalls of the second patterned line opening P 2 , a conformal transport layer  240  over the subcell layer  220 , on the non-metallic intermediate layer  230  within the second patterned line opening P 2  and over the bottom electrode layer  210  within the second patterned line opening P 1 , and a top electrode layer  250  over the conformal transport layer  240  and on the conformal transport layer  240  within the second patterned line opening P 2 . The conformal transport layer  240  illustrated in  FIG. 5A  may be a continuous layer over and between multiple adjacent cells  110 , illustrated by the additive voltages V 1  and V 2 . The conformal transport layer  240  may also be continuous past outside perimeter  224  the subcell layer  220  as shown in  FIG. 5B . In the embodiment illustrated, an opening may be formed in the non-metallic intermediate layer that exposes a top surface  211  the bottom electrode layer  210 . For example, the non-metallic intermediate layer  230  may be formed of a non-electrically conductive material and the conformal transport layer  240  is in direct contact with the bottom electrode layer  210  in the second patterned line opening P 2 . 
     In an embodiment, the top electrode layer  250  includes a metal layer, while the bottom electrode layer  210  is formed of a transparent material. In a particular embodiment, the subcell layer  220  includes a perovskite absorber layer. The subcell layer  220  may be a single cell layer, or include multiple subcells. For example, the subcell layer  220  can include a tandem structure including multiple subcells. The conformal transport layer  240  may function to encapsulate and protect the subcell layer  220 , for example from decomposition and metal diffusion. Exemplary materials include oxides (e.g. metal oxides), nitrides (e.g. metal nitrides), polymers, and small molecules. Exemplary metal oxides may be titanium oxide, zinc oxide, tin oxide, nickel oxide, vanadium oxide, tungsten oxide, indium oxide, any of which may be doped. For example, some TCOs may be ITO, AZO, IZO cadmium stannate. Exemplary metal nitrides include at least titanium nitride and tungsten nitride. Some exemplary polymers include poly(triaryl amine) (PTAA) and polyaniline. Some exemplary small molecules include 2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-MeOTAD), and fullerenes. Suitable deposition techniques to form a conformal layer may include chemical vapor deposition (CVD), atomic layer deposition (ALD), solution coating and evaporation. In an embodiment, the conformal transport layer is less than 1,000 nm thick, such as less than 150 nm thick, or more specifically less than 50 nm thick such as 10-40 nm thick. The conformal transport layer may be doped. For example, the conformal transport layer may be AZO. The conformal transport layer may be sufficiently thin to transport charge through its thickness and not be laterally conductive. The conformal transport layer  240  may be characterized by a resistivity greater than 0.1 ohm·cm. The conformal transport layer may prevent metal diffusion, and function as an electron transport layer or hole transport layer for the solar cell  120 . 
     Still referring to  FIG. 5A , the solar cell interconnect may include a third patterned line opening P 3  in the top electrode layer  250 . In the particular embodiment illustrated the third patterned line opening P 3  does not completely extend through a thickness of the conformal transport layer  240  so that the conformal transport layer can protect the underlying subcell layer  220 . 
       FIG. 5B  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including the interconnect of  FIG. 5A  in accordance with an embodiment. In the embodiment illustrated, the solar cell module may include a bottom electrode layer  210  including a plurality of first patterned line openings, a subcell layer  220  over the bottom electrode layer  210 , the subcell layer including a plurality of second patterned line openings, a conformal transport layer  240  over subcell layer and laterally surrounding an outside perimeter  224  the subcell layer  220 , and a patterned top electrode layer  250  over the conformal transport layer  240 . In the embodiment illustrated, a non-metallic intermediate layer  230  is located between the conformal transport layer  240  and the subcell layer  220 , and the non-metallic intermediate layer  230  laterally surrounds the outside perimeter  224  of the subcell layer  220 . Additionally, the conformal transport layer  240  may also surround an outside perimeter  234  of the non-metallic intermediate layer  230 . 
     Several variations of the embodiments illustrated in  FIGS. 5A-5B  are contemplated. For example, referring to  FIG. 6A , the third patterned line opening P 3  may partially or completely extend through any of the top electrode layer  250 , the conformal transport layer  240 , and the subcell layer  220 . As shown, a non-electrically conductive material  260  can fill the third patterning line opening P 3 . For example, the non-electrically conductive material  260  may be a polymer, metal oxide, or nitride material and may function to prevent metal degradation from where the conformal transport layer  240  is interrupted by the third patterned line opening P 3 . In an embodiment the non-electrically conductive material  260  and the non-metallic intermediate layer  230  are formed of the same material. 
     Another alternative is illustrated in  FIG. 6B , where rather than forming a separate non-electrically conductive material in the third patterned line opening P 3 , the non-metallic intermediate layer  230  thickness may be offset within the second patterned line opening P 2 . In this case, the third patterned line opening P 3  extends through a thickness of the non-metallic intermediate layer  230  rather than the subcell layer  220  in order to provide further protection of the subcell layer  220  to third patterned line opening P 3 . In such an embodiment, it may not be necessary to provide a further insulating material within the third patterned line opening P 3 . In the embodiments illustrated in  FIGS. 6A-6B , the third patterned line opening P 3  may extend through the previously continuous conformal transport layer  240 .  FIGS. 6A-6B  illustrate alternatively in which the break is prepared by a non-electrically conductive material  260  or pre-existing non-metallic intermediate layer  230 . Alternatively, or additionally, a continuous protective layer may be formed over the entire device stack.  FIG. 6C  provides an additional alternative to that illustrated in  FIG. 6B , in which the non-metallic intermediate layer  230  is underneath the third patterned line opening P 3  as a precaution, even though the third patterned line opening P 3  does not extend into the non-metallic intermediate layer  230 . 
     Referring now to  FIGS. 7-8I ,  FIG. 7  is flow chart illustrating a method of forming the interconnect of  FIG. 5A  in accordance with an embodiment.  FIGS. 8A-8I  are schematic cross-sectional side view illustrations of a method of forming the interconnect of  FIG. 5A  in accordance with an embodiment. In the following description, the processing sequence of  FIG. 7  is made with regard to the cross-sectional side view illustrations of  FIGS. 8A-8I . In interests of conciseness, and to not overly obscure embodiments the processing sequence variations to for the embodiments illustrated in  FIGS. 6A-6C  are not separately illustrated, and instead are described together along with  FIGS. 7-8I . Additionally, it is understood that certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations described herein. 
     As shown in  FIG. 8A  the processing sequence may begin with a substrate  202 . Substrate  202  may be a single or multiple layer substrate, including one or more layers of glass, plastic, or conductive metal foil. The bottom electrode layer  210  may then be formed on substrate  202  as illustrated in  FIG. 8B . Bottom electrode layer  210  may be formed of materials such as cadmium stannate, TCOs, including ITO, FTO, IZO, etc. Referring now to  FIG. 8C , at operation  710  a first patterned line opening P 1  is then formed in the bottom electrode layer  210 . Various patterning techniques such as mechanical or laser scribing, chemical etching, or deposition with a shadow mask can be used to form P 1 . In an embodiment, mechanical or laser scribing is utilized in a roll-to-roll manufacturing process. 
     The subcell layer  220  is then formed over the patterned bottom electrode layer  210  at operation  720 , as shown in  FIG. 8D . The subcell layer  220  generally includes a subcell including an absorber layer and one or more transport layers. In an embodiment, the subcell layer includes an absorber layer between a hole transport layer and an electron transport layer. The subcell layer  220  may include a single subcell, or multiple subcells such as with a tandem structure. In accordance with embodiments, the subcell layer  220  includes one or more absorber layers including a perovskite material. In an embodiment, the subcell layer  220  includes a tandem structure including a perovskite material in one or both of the subcells. For example, a tandem perovskite cell structure may include two subcells with perovskite absorber layers with different bandgaps. Perovskite materials may be characterized by the formula ABX 3 , with A representing a large atomic or molecular cation (e.g. Cs, methylammonium, formamidinium, etc.), with B representing a positively charged cation (e.g. metal, lead, plumbate, Sn), and X representing a negatively charged anion (e.g. halide, I, Br, Cl). 
     The subcell layer  220  is then patterned to form a second patterned line opening P 2  at operation  730 , as illustrated in  FIG. 8E . Various patterning techniques such as mechanical or laser scribing, chemical etching, or deposition with a shadow mask can be used to form P 2 . In an embodiment, mechanical or laser scribing is utilized due to chemical stability of the perovskite absorber layer(s). Referring now to  FIGS. 8F-G , at operation  740  a non-metallic intermediate layer  230  is formed along sidewalls  222  of P 2 . In the specific embodiment illustrated, the non-metallic intermediate layer  230  is first applied to fill P 2  using a printing technique such as ink jet, extrusion, spraying, etc. The non-metallic intermediate layer  230  is formed of a non-metallic material that does not react with the absorber layer(s). In an embodiment, the non-metallic intermediate layer includes an insulator material. In an embodiment, the non-metallic intermediate layer includes a polymer such as, but are not limited to, poly(methyl methacrylate) (PMMA) and poly(vinyl alcohol) (PVA). As shown in  FIG. 8G , the non-metallic intermediate layer  230  is patterned to form an opening  231  that may expose the bottom electrode layer  210 . For example, this patterning may utilize a mechanical or laser scribing. 
     In the particular embodiment illustrated in  FIG. 8G , opening  231  substantially aligns with the middle of P 2  such that lateral thicknesses of the non-metallic intermediate layer  230  on opposite sidewalls  222  are substantially the same. However, embodiments are not so limited. For example, in a processing sequence to create the interconnect structure of  FIG. 6B  or  FIG. 6C , the opening  231  and P 2  may be offset, with different lateral thicknesses of the non-metallic intermediate layer  230  on opposite sidewalls  222 . 
     Referring now to  FIG. 8H , at operation  750  a conformal transport layer  240  is formed over the subcell layer  220 , on the non-metallic intermediate layer within P 2 , and over the bottom electrode layer within P 2 . The conformal transport layer  240  may be continuous. The conformal transport layer  240  may function to encapsulate and protect the subcell layer  220 , for example from decomposition and metal diffusion. Exemplary materials include oxides (e.g. metal oxides), nitrides (e.g. metal nitrides), polymers, and small molecules. Exemplary metal oxides may be titanium oxide, zinc oxide, tin oxide, nickel oxide, vanadium oxide, tungsten oxide, indium oxide, any of which may be doped. For example, some TCOs may be ITO, AZO, IZO cadmium stannate. Exemplary metal nitrides include at least titanium nitride and tungsten nitride. Some exemplary polymers include poly(triaryl amine) (PTAA) and polyaniline. Some exemplary small molecules include 2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-MeOTAD), and fullerenes. Suitable deposition techniques to form a conformal layer may include chemical vapor deposition (CVD), atomic layer deposition (ALD), solution coating and evaporation. In an embodiment, the conformal transport layer is less than 1,000 nm thick, such as less than 150 nm thick, or more specifically less than 50 nm thick such as 10-40 nm thick. The conformal transport layer may be doped. For example, the transport layer may be AZO. The conformal transport layer may be sufficiently thin to transport charge through its thickness, and not be laterally conductive. The conformal transport layer  240  may be characterized by a resistivity greater than 0.1 ohm·cm. In an embodiment, the conformal transport layer also functions as an electron transport layer for the solar cell  120 . Alternatively, the conformal transport layer may function as a hole transport layer for the solar cell  120 . 
     In an embodiment, an AZO containing conformal transport layer  240  is formed using ALD or low temperature CVD to form an amorphous layer. The low temperature deposition process may not provide necessary conditions for crystal growth. This may be in contrast to a high temperature process (e.g. high temperature sputter and anneal) used for the formation of a crystalline AZO layer for use as an electrode layer. 
     The top electrode layer  250  may then be formed over the conformal transport layer and on the conformal transport layer within P 2  at operation  760  as illustrated in  FIG. 8I . In a particular embodiment, the top electrode layer  250  is deposited through a shadow mask to form the third patterned line opening P 3  during deposition. This may protect underlying layers from solution processing operation. Suitable deposition technique may include evaporation, sputter, printing, and spraying. In an embodiment, the top electrode layer  250  includes one or more metal layers, such as Ag, Cu, Al, Au, etc. 
     In an embodiment scribing is utilized to form P 3  in the top electrode layer  250 . In the embodiments illustrated in  FIGS. 6B-6C , the non-metallic intermediate layer  230  is located underneath P 3 , or P 3  extends into or completely through the non-metallic intermediate layer  230 . Either configuration may provide protection for the absorber layer(s). In the embodiment illustrated in  FIG. 6A , scribing can be used to form P 3  partially or completely through any of the top electrode layer  250 , conformal transport layer  240 , and subcell layer  220 . In such an embodiment, P 3  is partially or fully filled with an insulating material  260  to provide protection for the absorber layer(s). 
     In the foregoing description, specific processing techniques and materials selections have been provided. It is to be appreciated that that the specific processing techniques and materials selections may also be applied to the following embodiments described with regard to  FIGS. 9A-26C . Accordingly, in interest of conciseness, detailed discussion of specific processing techniques and materials selections may not be repeated. 
       FIG. 9A  is a schematic cross-sectional side view illustration of an interconnect with a conformal transport layer within a subcell patterned line opening in accordance with an embodiment. As shown, the solar cell interconnect may include a bottom electrode layer  210  on a substrate  202 , a first patterned line opening P 1  in the bottom electrode layer  210 , a subcell layer  220  over the bottom electrode layer  210  and within the first patterned line opening P 1 , a second patterned line opening P 2  in the subcell layer  220 , a non-metallic intermediate layer  235  along sidewalls of the second patterned line opening P 2 , a conformal transport layer  240  over the subcell layer  220 , on the non-metallic intermediate layer  235  within the second patterned line opening P 2  and over the bottom electrode layer  210  within the second patterned line opening P 1 , and a top electrode layer  250  over the conformal transport layer  240  and on the conformal transport layer  240  within the second patterned line opening P 2 . The conformal transport layer  240  may be continuous. In the embodiment illustrated, the non-metallic intermediate layer  235  is a thin insulator layer or nucleation layer that is globally formed. In an embodiment, non-metallic intermediate layer  235  is less than 10 nm thick, such as 1-5 nm thick. As shown, the non-metallic intermediate layer  235  may physically separate the conformal transport layer  240  from bottom electrode layer  210 . In accordance with embodiment, the non-metallic intermediate layer  235  is formed of a material selected from the group consisting of an insulator, semiconductor, and carbon. The non-metallic intermediate layer  235  may be sufficiently thin to allow the transport of charge. Additionally, conformality of the non-metallic intermediate layer may facilitate uniform and dense growth of a subsequent conformal transport layer  240 . In an embodiment, the non-metallic intermediate layer  235  includes OH groups to help nucleate the growth of a metal oxide containing conformal transport layer  240 . Ethoxylated polyethyleneimine (PEIE) and polyvinyl alcohol (PVA) have such OH groups. The non-metallic intermediate layer  235  may also be formed of materials such as polyvinyl phenol and polystyrene. In an alternative embodiment, the non-metallic intermediate layer  235  may be patterned to expose the bottom electrode layer  210  similarly as non-metallic intermediate layer  230  previously described. 
       FIG. 9B  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including the interconnect of  FIG. 9A  in accordance with an embodiment. In the embodiment illustrated, the solar cell module may include a bottom electrode layer  210  including a plurality of first patterned line openings, a subcell layer  220  over the bottom electrode layer  210 , the subcell layer including a plurality of second patterned line openings, a conformal transport layer  240  over subcell layer and laterally surrounding an outside perimeter  224  the subcell layer  220 , and a patterned top electrode layer  250  over the conformal transport layer  240 . In the embodiment illustrated, a non-metallic intermediate layer  235  is located between the conformal transport layer  240  and the subcell layer  220 , and the non-metallic intermediate layer  235  laterally surrounds the outside perimeter  224  of the subcell layer  220 . Additionally, the conformal transport layer  240  may also surround an outside perimeter  238  of the non-metallic intermediate layer  235 . 
     Referring now to  FIGS. 10-11D ,  FIG. 10  is flow chart illustrating a method of forming the interconnect of  FIG. 9A  in accordance with an embodiment.  FIGS. 11A-11D  are schematic cross-sectional side view illustrations of a method of forming the interconnect of  FIG. 9A  in accordance with an embodiment. In the following description, the processing sequence of  FIG. 10  is made with regard to the cross-sectional side view illustrations of  FIGS. 11A-11D . Additionally, it is understood that certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations described herein. 
     The processing sequence may begin similarly as with that of  FIG. 7 . At operation  1010  a first patterned line opening P 1  is formed in the bottom electrode layer  210 . At operation  1020  the subcell layer  220  is formed over the patterned bottom electrode layer  210 . Referring to  FIG. 11A  the subcell layer  220  is then patterned to form a second patterned line opening P 2  at operation  730 . Referring to  FIG. 11B , at operation  1040  a non-metallic intermediate layer  235  is formed along sidewalls  222  of P 2  and over the top surface of the bottom electrode layer  210 . The non-metallic intermediate layer  235  may be formed directly on the top surface  211  of the bottom electrode layer  210 . Alternatively, the non-metallic intermediate layer  235  may be patterned similarly as non-metallic intermediate layer  230  to expose the bottom electrode layer  210 . In accordance with embodiments, non-metallic intermediate layer  235  may be a nucleation layer or insulator layer less than 10 nm thick. At such a thickness, the thin non-metallic intermediate layer may be thin enough to allow the passage of charge through either conduction or tunneling. Thus, the non-metallic intermediate layer  235  may be a conformal layer, with thickness less than 10 nm along sidewalls  222  of P 2 , and on the top surface  211  of the bottom electrode layer  210 . The non-metallic intermediate layer may be deposited using a suitable printing technique such as spraying, evaporation and vapor transport deposition. If the non-metallic intermediate layer  235  is formed of an insulator or organic material, it may aid in the nucleation or adhesion of the subsequently formed conformal transport layer. The non-metallic intermediate layer  235  may be formed of a non-metallic material that does not react with the absorber layer(s), such as an insulator, semiconductor, and carbon. In the embodiment illustration, the non-metallic intermediate layer  235  is a conformal layer in order to cover the entire surface and aid in nucleation. 
     Referring now to  FIG. 11C , at operation  1050  a conformal transport layer  240  is formed over the subcell layer  220 , on the non-metallic intermediate layer within P 2 . The conformal transport layer  240  may function to encapsulate and protect the subcell layer  220 , for example from decomposition and metal diffusion. Suitable deposition techniques to form a conformal layer may include chemical vapor deposition (CVD), atomic layer deposition (ALD), solution coating and evaporation. In an embodiment, the conformal transport layer is less than 1,000 nm thick, such as less than 150 nm thick, or more specifically less than 50 nm thick such as 10-40 nm thick. The conformal transport layer may be doped. For example, the transport layer may be AZO. The conformal transport layer may be sufficiently thin to transport charge through its thickness, and not be laterally conductive. The conformal transport layer  240  may be characterized by a resistivity greater than 0.1 ohm·cm. In an embodiment, the conformal transport layer also functions as an electron transport layer or hole transport layer for a solar cell  120 . 
     The top electrode layer  250  may then be formed over the conformal transport layer and on the conformal transport layer within P 2  at operation  1060  as illustrated in  FIG. 11D . In a particular embodiment, the top electrode layer  250  is deposited through a shadow mask to form the third patterned line opening P 3  during deposition. This may protect underlying layers from solution processing operation. Suitable deposition technique may include evaporation, sputter, printing, and spraying. In an embodiment, the top electrode layer  250  includes one or more metal layers, such as Ag, Cu, Al, Au, etc. While not separately illustrated, in an alternative embodiment scribing could be performed to create P 3  similarly as described and illustrated with regard to  FIG. 6A , followed by at least partially filling with a non-electrically conductive material  260 . 
       FIG. 12A  is a schematic cross-sectional side view illustration of an interconnect with overlapping bottom electrode and subcell patterned line openings in accordance with an embodiment. As shown, a solar cell interconnect may include a bottom electrode layer  210  on a substrate  202 , a first patterned line opening P 1  in the bottom electrode layer  210 , a subcell layer  220  over the bottom electrode layer  210  and within the first patterned line opening P 1 , a second patterned line opening P 2  in the subcell layer  220 , a non-metallic intermediate layer  235  along sidewalls of the second patterned line opening P 2 , a conformal transport layer  240  over the subcell layer  220 , on the non-metallic intermediate layer  235  within the second patterned line opening P 2  and over the bottom electrode layer  210  within the second patterned line opening P 1 , and a top electrode layer  250  over the conformal transport layer  240  and on the conformal transport layer  240  within the second patterned line opening P 2 . The conformal transport layer  240  may be continuous. In the embodiment illustrated, P 2  overlaps P 1 . Also shown, are the non-metallic intermediate layer  230  formed along one sidewall  222  of P 2  and on the substrate  202  inside of P 1 , and the non-metallic intermediate layer  230  formed along the opposite sidewall  222  of P 2  and on the bottom electrode layer  210 . An opening in the non-metallic intermediate layer  230  exposes a top surface the bottom electrode layer. The conformal transport layer  240  of the embodiment illustrated in  FIG. 12A  may be in direct contact with the bottom electrode layer  210 . 
       FIG. 12B  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including the interconnect of  FIG. 12A  in accordance with an embodiment. Similar to the embodiment illustrated in  FIG. 5B , the solar cell module may include a bottom electrode layer  210  including a plurality of first patterned line openings, a subcell layer  220  over the bottom electrode layer  210 , the subcell layer including a plurality of second patterned line openings, a conformal transport layer  240  over subcell layer and laterally surrounding an outside perimeter  224  the subcell layer  220 , and a patterned top electrode layer  250  over the conformal transport layer  240 . In the embodiment illustrated, a non-metallic intermediate layer  230  is located between the conformal transport layer  240  and the subcell layer  220 , and the non-metallic intermediate layer  230  laterally surrounds the outside perimeter  224  of the subcell layer  220 . Additionally, the conformal transport layer  240  may also surround an outside perimeter  234  of the non-metallic intermediate layer  230 . 
     Several variations of the embodiments illustrated in  FIGS. 12A-12B  are contemplated. For example, referring to  FIG. 13 , the third patterned line opening P 3  may partially or completely extend through any of the top electrode layer  250 , the conformal transport layer  240 , and the subcell layer  220 . As shown, a non-electrically conductive material  260  can fill the third patterning line opening P 3 . For example, the non-electrically conductive material  260  may be a polymer, metal oxide, or nitride material and may function to prevent metal degradation from where the conformal transport layer  240  is interrupted by the third patterned line opening P 3 . In an embodiment the non-electrically conductive material  260  and the non-metallic intermediate layer  230  are formed of the same material. 
     Referring now to  FIGS. 14-15H ,  FIG. 14  is flow chart illustrating a method of forming the interconnect of  FIG. 12A  in accordance with an embodiment.  FIGS. 15A-15H  are schematic cross-sectional side view illustrations of a method of forming the interconnect of  FIG. 12A  in accordance with an embodiment. In the following description, the processing sequence of  FIG. 14  is made with regard to the cross-sectional side view illustrations of  FIGS. 15A-15H . Additionally, it is understood that certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations described herein. 
     Referring to  FIG. 15A  a bottom electrode layer  210  may first be formed on a substrate  202 , followed by the formation of subcell layer  220  as illustrated in  FIG. 15B . At operation  1410 , a first patterned line opening P 1  is formed through the subcell layer  220 , and bottom electrode layer  210 . At operation  1420  a second patterned line opening P 2  is formed in the subcell layer  220 , where P 2  overlaps P 1 . P 2  may be wider than P 1 . Additionally, P 2  and P 1  may share a same sidewall  222  in the subcell layer  220 . 
     Referring now to  FIGS. 15E-15F , at operation  1430  a non-metallic intermediate layer  230  is formed along sidewalls  222  of P 2 . In the specific embodiment illustrated, the non-metallic intermediate layer  230  is first applied to fill P 2  using a printing technique such as ink jet, extrusion, spraying, etc. The non-metallic intermediate layer  230  is formed of a non-metallic material that does not react with the absorber layer(s), such as a polymer, carbon or carbon/polymer blend. In an embodiment, the non-metallic intermediate layer is an insulating material. As shown in  FIG. 15F , the non-metallic intermediate layer  230  is patterned to form an opening  231  that may expose the bottom electrode layer  210  and optionally substrate  202 . For example, this patterning may utilize laser scribing. In the particular embodiment illustrated in  FIG. 15F , opening  231  substantially aligns with the middle of P 2  such that lateral thicknesses of the non-metallic intermediate layer  230  on opposite sidewalls  222  are substantially the same. However, embodiments are not so limited. 
     Referring now to  FIG. 15G , at operation  1440  a conformal transport layer  240  is formed over the subcell layer  220 , and on the non-metallic intermediate layer  230  within P 2 . In an embodiment, the conformal transport layer  240  is formed on the top surface of the bottom electrode  210 . The conformal transport layer  240  may also be formed within P 1 . The conformal transport layer  240  may function to encapsulate and protect the subcell layer  220 , for example from decomposition and metal diffusion. Suitable deposition techniques to form a conformal layer may include chemical vapor deposition (CVD), atomic layer deposition (ALD), solution coating and evaporation. In an embodiment, the conformal transport layer is less than 1,000 nm thick, such as less than 150 nm thick, or more specifically less than 50 nm thick such as 10-40 nm thick. The conformal transport layer may be doped. For example, the transport layer may be AZO. The conformal transport layer may be sufficiently thin to transport charge through its thickness, and not be laterally conductive. The conformal transport layer  240  may be characterized by a resistivity greater than 0.1 ohm·cm. In an embodiment, the conformal transport layer also functions as an electron transport layer or hole transport layer for a solar cell  120 . 
     The top electrode layer  250  may then be formed over the conformal transport layer and on the conformal transport layer within P 2  at operation  1450  as illustrated in  FIG. 15H . In a particular embodiment, the top electrode layer  250  is deposited through a shadow mask to form the third patterned line opening P 3  during deposition. This may protect underlying layers from solution processing operation. Suitable deposition technique may include evaporation, sputter, printing, and spraying. In an embodiment, the top electrode layer  250  includes one or more metal layers, such as Ag, Cu, Al, Au, etc. In the alternative embodiment illustrated in  FIG. 13 , scribing could be performed to create P 3  similarly as described and illustrated with regard to  FIG. 6A , followed by at least partially filling with a non-electrically conductive material  260 . 
       FIG. 16A  is a schematic cross-sectional side view illustration of an interconnect with a conductive plug in a subcell patterned line opening in accordance with an embodiment. As shown, the solar cell interconnect may include a bottom electrode layer  210 , a first patterned line opening P 1  in the bottom electrode layer  210 , a subcell layer  220  over the bottom electrode layer, a second patterned line opening P 2  in the subcell layer  220 , a conductive plug  270  within P 2 , a conformal transport layer  240  over the subcell layer  220  and the conductive plug  270 , a top electrode layer  250  over the conformal transport layer  240 , and a third patterned line opening P 3  in the top electrode layer  250 . The conformal transport layer  240  may be continuous. In the embodiment illustrated, P 3  does not completely extend through a thickness of the conformal transport layer  240 . 
       FIG. 16B  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including the interconnect of  FIG. 16A  in accordance with an embodiment. Similar to the embodiment illustrated in  FIG. 5B , the solar cell module may include a bottom electrode layer  210  including a plurality of first patterned line openings, a subcell layer  220  over the bottom electrode layer  210 , the subcell layer including a plurality of second patterned line openings, a conformal transport layer  240  over subcell layer and laterally surrounding an outside perimeter  224  the subcell layer  220 , and a patterned top electrode layer  250  over the conformal transport layer  240 . 
     Several variations of the embodiments illustrated in  FIGS. 16A-16B  are contemplated. For example, referring to  FIG. 17 , the third patterned line opening P 3  may partially or completely extend through any of the top electrode layer  250 , the conformal transport layer  240 , and the subcell layer  220 . As shown, a non-electrically conductive material  260  can fill the third patterning line opening P 3 . For example, the non-electrically conductive material  260  may be a polymer, metal oxide, or nitride material and may function to prevent metal degradation from where the conformal transport layer  240  is interrupted by the third patterned line opening P 3 . 
     Referring now to  FIGS. 18-19D ,  FIG. 18  is flow chart illustrating a method of forming the interconnect of  FIG. 16A  in accordance with an embodiment.  FIGS. 19A-19D  are schematic cross-sectional side view illustrations of a method of forming the interconnect of  FIG. 16A  in accordance with an embodiment. In the following description, the processing sequence of  FIG. 18  is made with regard to the cross-sectional side view illustrations of  FIGS. 19A-19D . Additionally, it is understood that certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations described herein. 
     The processing sequence may begin similarly as with that of  FIG. 7 . At operation  1810  a first patterned line opening P 1  is formed in the bottom electrode layer  210 . At operation  1820  the subcell layer  220  is formed over the patterned bottom electrode layer  210 . Referring to  FIG. 19A  the subcell layer  220  is then patterned to form a second patterned line opening P 2  at operation  1830 . Referring to  FIG. 19B , at operation  1040  an (electrically) conductive plug  270  is formed within P 2  and on the bottom electrode layer  210 . The conductive plug  270  may be formed of materials that do not react with the absorber layer(s), such as carbon or a carbon/polymer blend, printed ITO nanoparticles or other TCO nanoparticles. The conductive plug  270  may be formed using a suitable printing technique such as ink jet, extrusion, spraying, etc. so that further patterning is not necessary. A conductivity of the conductive plug  270  in accordance with embodiments may only be greater than about 0.001 S/cm due to the short distance of the interconnection based on the thin film thickness in the 0.1-5 μm range. Such a low conductivity can be achieved by a range of materials that do not react with the perovskite such as carbon (bulk conductivity around 1-100 S/cm) and ITO nanoparticles. In an embodiment, the conductive plug  270  includes particles dispersed in a matrix (e.g. polymer matrix). The carbon and/or TCO particles can be mixed into a polymer blend in order to make it easier to suspend the carbon or TCO nanoparticles in a solvent and deposit the interconnects through a printing technique like ink jet or spraying. Due to the low conductivity required, a very high conductive particle to polymer ratio is not required. Such a polymer could be a binder like poly(vinylidene fluoride) (PVDF), polyvinyl fluoride, polyvinylchloride, polystyrene, PMMA, PVA, polyvinyl phenol, polyethylene glycol, etc. The carbon may be graphite or carbon black in an embodiment, but could include graphene or carbon nanotubes or amorphous carbon. The TCO particles may be ITO or IZO nanoparticles with diameters between 10-200 nm in an embodiment, but could be AZO, Sb:SnO 2 , zinc tin oxide, cadmium stannate and could be microparticles with diameters between 0.2-2 μm. 
     Referring now to  FIG. 19C , at operation  1850  a conformal transport layer  240  is formed over the subcell layer  220  and over the electrically conductive plug  270  within P 2 . The conformal transport layer  240  may function to encapsulate and protect the subcell layer  220 , for example from decomposition and metal diffusion. Suitable deposition techniques to form a conformal layer may include chemical vapor deposition (CVD), atomic layer deposition (ALD), solution coating and evaporation. In an embodiment, the conformal transport layer is less than 150 nm thick, or more specifically less than 50 nm thick such as 10-20 nm thick. The conformal transport layer may be doped. For example, the transport layer may be AZO. The conformal transport layer may be sufficiently thin to transport charge through its thickness, and not be laterally conductive. The conformal transport layer  240  may be characterized by a resistivity greater than 0.1 ohm·cm. In an embodiment, the conformal transport layer also functions as an electron transport layer to the subcell layer  220 . 
     The top electrode layer  250  may then be formed over the conformal transport layer  240  at operation  1860  as illustrated in  FIG. 19D . In a particular embodiment, the top electrode layer  250  is deposited through a shadow mask to form the third patterned line opening P 3  during deposition. This may protect underlying layers from solution processing operation. Suitable deposition technique may include evaporation, sputter, printing, and spraying. In an embodiment, the top electrode layer  250  includes one or more metal layers, such as Ag, Cu, Al, Au, etc. In an alternative embodiment illustrated in  FIG. 17 , scribing could be performed to create P 3  similarly as described and illustrated with regard to  FIG. 6A , followed by at least partially filling with a non-electrically conductive material  260 . 
       FIG. 20A  is a schematic cross-sectional side view illustration of an interconnect with a conductive plug in a subcell patterned line opening in accordance with an embodiment. As shown, the solar cell interconnect may include a bottom electrode layer  210 , a first patterned line opening P 1  in the bottom electrode layer  210 , a subcell layer  220  over the bottom electrode layer, a second patterned line opening P 2  in the subcell layer  220 , a conductive plug  270  within P 2 , a conformal transport layer  240  over the subcell layer  220  and the conductive plug  270 , a top electrode layer  250  over the conformal transport layer  240 , and a third patterned line opening P 3  in the top electrode layer  250 . The conformal transport layer  240  may be continuous. P 3  may not completely extend through a thickness of the conformal transport layer  240 . In the particular embodiment illustrated P 2  overlaps P 1 . Additionally, a non-metallic intermediate layer  230  may be formed along a single sidewall  222  of P 2 . Non-metallic intermediate layer  230  may be formed of the same materials as the non-metallic intermediate layer  230  previously described. More specifically, the non-metallic intermediate layer  230  may be formed along a single sidewall  222  of P 1  that is shared with P 1 . The non-metallic intermediate layer  230  may be formed within P 1 . Additionally, P 3  may optionally overlap P 2 . 
     In the particular embodiment illustrated in  FIG. 20A , a lateral edge  232  of the non-metallic intermediate layer  230  is over the bottom electrode layer  210 . The lateral edge  232  may be located elsewhere in accordance with embodiments. For example, the variation illustrated in  FIG. 20B  shows lateral edge  232  located within P 1 . 
       FIG. 20C  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including an interconnect of  FIG. 20A-20B  in accordance with an embodiment. Similar to the embodiment illustrated in  FIG. 5B , the solar cell module may include a bottom electrode layer  210  including a plurality of first patterned line openings, a subcell layer  220  over the bottom electrode layer  210 , the subcell layer including a plurality of second patterned line openings, a conformal transport layer  240  over subcell layer and laterally surrounding an outside perimeter  224  the subcell layer  220 , and a patterned top electrode layer  250  over the conformal transport layer  240 . In the embodiment illustrated, a non-metallic intermediate layer  230  is located between the conformal transport layer  240  and the subcell layer  220 , and the non-metallic intermediate layer  230  laterally surrounds the outside perimeter  224  of the subcell layer  220 . Additionally, the conformal transport layer  240  may also surround an outside perimeter  284  of the non-metallic intermediate layer  230 . 
     Several variations of the embodiments illustrated in  FIGS. 20A-20C  are contemplated. For example, referring to  FIG. 21 , the third patterned line opening P 3  may partially or completely extend through any of the top electrode layer  250 , the conformal transport layer  240 , and the subcell layer  220 . As shown, a non-electrically conductive material  260  can fill the third patterning line opening P 3 . For example, the non-electrically conductive material  260  may be a polymer, metal oxide, or nitride material and may function to prevent metal degradation from where the conformal transport layer  240  is interrupted by the third patterned line opening P 3 . In an embodiment the non-electrically conductive material  260  and the non-metallic intermediate layer  230  are formed of the same material. 
     Referring now to  FIGS. 22-23F ,  FIG. 22  is flow chart illustrating a method of forming the interconnect of  FIG. 19A  in accordance with an embodiment.  FIGS. 23A-23F  are schematic cross-sectional side view illustrations of a method of forming the interconnect of  FIG. 20A  in accordance with an embodiment. In the following description, the processing sequence of  FIG. 22  is made with regard to the cross-sectional side view illustrations of  FIGS. 23A-23F . Additionally, it is understood that certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations described herein. 
     The processing sequence may begin similarly as with that of  FIG. 7 . At operation  2210  a first patterned line opening P 1  is formed in the bottom electrode layer  210 . At operation  2220  the subcell layer  220  is formed over the patterned bottom electrode layer  210  as shown in  FIG. 23A . Referring to  FIG. 23B  the subcell layer  220  is then patterned to form a second patterned line opening P 2  at operation  2230 . Referring to  FIG. 23C , at operation  2240  a non-metallic intermediate layer  230  is formed along a sidewall  222  of P 2 . Non-metallic intermediate layer  230  may be formed along a single sidewall  222  in accordance with an embodiment, and as described with regard to  FIG. 20A . In an embodiment, non-metallic intermediate layer  230  is a polymer material such as, but not limited to, poly(methyl methacrylate) (PMMA), poly(vinyl alcohol) (PVA), and polystyrene. Non-metallic intermediate layer  230  may be formed using a suitable printing technique such as ink jet, extrusion, spraying, etc. In an embodiment, opening  281  exists between a sidewall  232  of the non-metallic intermediate layer  230  and a sidewall  222  of P 2 . Opening  281  may expose the bottom electrode  210 . 
     Referring now to  FIG. 23D , at operation  2250  a conductive plug  270  is formed within P 2 , or more specifically within opening  281  within P 2 . Conductive plug  20  may fill opening  281  between the non-metallic intermediate layer  230  and the sidewall  222  P 2  that is laterally opposite the sidewall  222  which is covered by non-metallic intermediate layer  230 . In an embodiment, conductive plug  270  is in contact with the bottom electrode layer  210 . Conductive plug  270  may optionally be formed over the non-metallic intermediate layer  230 . The conductive plug  270  may be formed of materials that do not react with the absorber layer(s), such as carbon or a carbon/polymer blend, ITO nanoparticles, and TCO nanoparticles. The conductive plug  270  may be formed using a suitable printing technique such as ink jet, extrusion, spraying, etc. so that further patterning is not necessary. 
     Referring now to  FIG. 23E , at operation  2260  a conformal transport layer  240  is formed over the subcell layer  220  and over the electrically conductive plug  270  within P 2 . The conformal transport layer  240  may function to encapsulate and protect the subcell layer  220 , for example from decomposition and metal diffusion. Suitable deposition techniques to form a conformal layer may include chemical vapor deposition (CVD), atomic layer deposition (ALD), solution coating and evaporation. In an embodiment, the conformal transport layer is less than 1,000 nm thick, such as less than 150 nm thick, or more specifically less than 50 nm thick such as 10-40 nm thick. The conformal transport layer may be doped. For example, the transport layer may be AZO. The conformal transport layer may be sufficiently thin to transport charge through its thickness, and not be laterally conductive. The conformal transport layer  240  may be characterized by a resistivity greater than 0.1 ohm·cm. In an embodiment, the conformal transport layer also functions as an electron transport layer or hole transport layer for a solar cell  120 . 
     The top electrode layer  250  may then be formed over the conformal transport layer  240  at operation  2270  as illustrated in  FIG. 23F . In a particular embodiment, the top electrode layer  250  is deposited through a shadow mask to form the third patterned line opening P 3  during deposition. This may protect underlying layers from solution processing operation. Suitable deposition technique may include evaporation, sputter, printing, and spraying. In an embodiment, the top electrode layer  250  includes one or more metal layers, such as Ag, Cu, Al, Au, etc. In an alternative embodiment illustrated in  FIG. 21 , scribing could be performed to create P 3  similarly as described and illustrated with regard to  FIG. 6A , followed by at least partially filling with a non-electrically conductive material  260 . 
       FIGS. 24A-24B  are schematic cross-sectional side view illustrations of an interconnect with a printed non-metallic intermediate layer and conductive plug within a subcell patterned line opening in accordance with an embodiment.  FIG. 24C  is a schematic cross-sectional side view illustration of edge encapsulation of a solar cell module including an interconnect of  FIG. 24A-24B  in accordance with an embodiment. As shown, the solar cell interconnect may include a bottom electrode layer  210 , a first patterned line opening P 1  in the bottom electrode layer, a subcell layer  220  over the bottom electrode layer  210 , a conformal transport layer  240  over the subcell layer  220 , a top electrode layer  250  over the conformal transport layer  240 , and a second patterned line opening P 2  through the top electrode layer  250 , the conformal transport layer  240  and the subcell layer  220 . A conductive plug  270  is formed within the second patterned line opening P 2  to make electrical connection between the top electrode layer  250  of one cell and the bottom electrode layer  210  of an adjacent cell. The second patterned line opening P 2  may overlap the first patented line opening P 1 . For example, P 2  may completely overlap P 1  and be wider than P 1 . 
     The conformal transport layer  240  may be a continuous layer prior to patterning of P 2 . Referring to  FIG. 24C , the conformal transport layer  240  may laterally surround the outside perimeter  224  of the subcell layer  220 , and optionally outside perimeter  214  of the bottom electrode layer  210 . The solar cell interconnect may further include a non-metallic intermediate layer  230  along one or more sidewalls of the second patterned line opening P 2 . For example, this may be sidewalls  222  of the subcell layer  220 , as well as sidewalls of the conformal transport layer  240  and top electrode layer  250 . In the embodiment illustrated in  FIG. 24A  a third patterned line opening P 3  is formed in the conductive plug  270  within the second line opening P 2 . The third patterned line opening P 3  may expose the bottom electrode layer  210 . In the embodiment illustrated in  FIG. 24B  the non-metallic intermediate layer  230  is formed on both laterally opposite sidewalls of the second patterned line opening P 2 , and a third patterned line opening P 3  is formed in the non-metallic intermediate layer  230 . The third patterned line opening P 3  extends into the second patterned line opening P 2 , and the conductive plug  20  fills the third patterned line opening P 3  in the non-metallic intermediate layer. In accordance with embodiments, the top electrode layer  250  of  FIGS. 24A-24C  can include metal layer, and the bottom electrode layer  210  can include a transparent material. 
     Referring now to  FIGS. 25-26C ,  FIG. 25  is flow chart illustrating a method of forming the interconnects of  FIGS. 24A-24B  in accordance with embodiments.  FIGS. 26A-26C  are schematic cross-sectional side view illustrations of a method of forming the interconnects of  FIG. 24A-24B  in accordance with embodiments. In the following description, the processing sequence of  FIG. 25  is made with regard to the cross-sectional side view illustrations of  FIGS. 26A-26C . Additionally, it is understood that certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations described herein. 
     The processing sequence may begin similarly as with that of  FIG. 7 . At operation  2510  a first patterned line opening P 1  is formed in the bottom electrode layer  210 . At operation  2520  the subcell layer  220  is formed over the patterned bottom electrode layer  210 . At operation  2530  a conformal transport layer  240  is formed over the subcell layer, and at operation  2540  a top electrode layer  250  is formed over the conformal transport layer  240  as illustrated in  FIG. 26A . The conformal transport layer  240  may function to encapsulate and protect the subcell layer  220 , for example from decomposition and metal diffusion. Suitable deposition techniques to form a conformal layer may include chemical vapor deposition (CVD), atomic layer deposition (ALD), solution coating and evaporation. In an embodiment, the conformal transport layer is less than 1,000 nm thick, such as less than 150 nm thick, or more specifically less than 50 nm thick such as 10-40 nm thick. The conformal transport layer may be doped. For example, the transport layer may be AZO. The conformal transport layer may be sufficiently thin to transport charge through its thickness, and not be laterally conductive. The conformal transport layer  240  may be characterized by a resistivity greater than 0.1 ohm·cm. In an embodiment, the conformal transport layer also functions as an electron transport layer or hole transport layer for a solar cell  120 . The top electrode layer  250  may be formed using suitable deposition technique such as evaporation, sputter, printing, and spraying. In an embodiment, the top electrode layer  250  includes one or more metal layers, such as Ag, Cu, Al, Au, etc. 
     Referring now to  FIG. 26B  at operation  2550  a second patterned line opening P 2  is then formed through the top electrode layer  250 , the conformal transport layer  240 , and the subcell layer  220 . As shown, the P 2  may overlap P 1 , and may be wider than P 1 . Formation of P 2  may also remove any subcell layer  220  material from within P 1 . 
     A non-metallic intermediate layer  230  may then be formed along one, or both, sidewalls of P 2  as shown in  FIG. 26C . Non-metallic intermediate layer  230  may be formed of the same materials as the non-metallic intermediate layer  230  previously described. Non-metallic intermediate layer  230  may be formed using a suitable printing technique such as ink jet, extrusion, spraying, etc. In an embodiment such as  FIG. 24B , a third patterned line opening P 3  may be formed in the non-metallic intermediate layer  230 . This may be accomplished through the deposition technique. Alternatively this may be accomplished through patterning, such as scribing. This may increase deposition tolerances for the non-metallic intermediate layer  230 . In an embodiment such as  FIG. 24A , the non-metallic intermediate layer  230  may be formed along a single sidewall of P 2 . In both configurations the non-metallic intermediate layer  230  can insulate the top electrode layer  250  from the bottom electrode layer  210  after formation of the plug  270 . 
     Referring to  FIG. 26C , at operation  2570  an (electrically) conductive plug  270  is formed within P 2  and on the bottom electrode layer  210 . In the embodiment of  FIG. 24A , it is not necessary to further pattern the conductive plug  270 . In the embodiment of  FIG. 24B , a third patterned line opening P 3  may be formed in the conductive plug  270  to prevent shorting across the top electrode layer  250 . 
     The conductive plug  270  may be formed of materials that do not react with the absorber layer(s), such as carbon or a carbon/polymer blend, printed ITO nanoparticles or other TCO nanoparticles. The conductive plug  270  may be formed using a suitable printing technique such as ink jet, extrusion, spraying, etc. so that further patterning is not necessary. A conductivity of the conductive plug  270  in accordance with embodiments may only be greater than about 0.001 S/cm due to the short distance of the interconnection based on the thin film thickness in the 0.1-5 range. Such a low conductivity can be achieved by a range of materials that do not react with the perovskite such as carbon (bulk conductivity around 1-100 S/cm) and ITO nanoparticles. In an embodiment, the conductive plug  270  includes particles dispersed in a matrix (e.g. polymer matrix). The carbon and/or TCO particles can be mixed into a polymer blend in order to make it easier to suspend the carbon or TCO nanoparticles in a solvent and deposit the interconnects through a printing technique like ink jet or spraying. Due to the low conductivity required, a very high conductive particle to polymer ratio is not required. Such a polymer could be a binder like poly(vinylidene fluoride) (PVDF), polyvinyl fluoride, polyvinylchloride, polystyrene, PMMA, PVA, polyvinyl phenol, polyethylene glycol, etc. The carbon may be graphite or carbon black in an embodiment, but could include graphene or carbon nanotubes or amorphous carbon. The TCO particles may be ITO or IZO nanoparticles with diameters between 10-200 nm in an embodiment, but could be AZO, Sb:SnO 2 , zinc tin oxide, cadmium stannate and could be microparticles with diameters between 0.2-2 μm. 
     In utilizing the various aspects of the embodiments, it would become apparent to one skilled in the art that combinations or variations of the above embodiments are possible for forming a solar cell module and stable interconnect. Although the embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the appended claims are not necessarily limited to the specific features or acts described. The specific features and acts disclosed are instead to be understood as embodiments of the claims useful for illustration.