Moisture resistant photovoltaic devices with exposed conductive grid

Abstract

The present invention provides strategies for improving the adhesion among two or more of transparent conducting oxides, electrically conductive grid materials, and dielectric barrier layers. As a consequence, these strategies are particularly useful in the fabrication of heterojunction photovoltaic devices such as chalcogenide-based solar cells. When the barrier is formed and then the grid is applied to vias in the barrier, the structure has improved moisture barrier resistance as compared to where the barrier is formed over or around the grid. Adhesion is improved to such a degree that grid materials and dielectric barrier materials can cooperate to provide a hermetic seal over devices to protect against damage induced by environmental conditions, including damage due to water intrusion. This allows the collection grids to be at least partially exposed above the dielectric barrier, making it easy to make electronic connection to the devices.

1 . A heterojunction photovoltaic device, comprising:
 a) a substrate having a light incident surface and a backside surface and comprising at least one photovoltaic absorber, wherein the substrate includes at least one transparent conducting oxide layer interposed between the absorber and the light incident surface, and wherein the at least one photovoltaic absorber comprises a chalcogenide-containing photovoltaic absorber having a thickness of 5 micrometers or less;   b) a dielectric barrier layer positioned over the transparent conducting oxide layer;   c) at least one via present in the dielectric barrier layer that terminates at a location in the device such that the via provides open communication to the transparent conducting oxide layer through the dielectric barrier layer without penetrating all the way through the transparent conducting oxide layer; and   d) an electrical contact that is electrically connected to the transparent conducting oxide layer, said electrical contact comprising a base formed in the via and a cap projecting above the dielectric barrier layer, wherein the cap of the electrical contact is wider than the base of the electrical contact in at least one dimension.   
     
     
         2 . The photovoltaic device according to  claim 1 , further comprising a conductive film comprising nickel interposed between the electrical contact and at least one of the via and the transparent conducting oxide layer. 
     
     
         3 . The photovoltaic device according to  claim 1 , further comprising an adhesion promoting, conductive film interposed between the electrical contact and at least one of the via and the transparent conducting oxide. 
     
     
         4 . The photovoltaic device according to  claim 1 , further comprising at least one additional barrier layer. 
     
     
         5 . (canceled) 
     
     
         6 . (canceled) 
     
     
         7 . The device of  claim 1 , wherein a buffer layer is incorporated into the device between the absorber and the transparent conducting oxide layer. 
     
     
         8 .- 20 . (canceled)