NOVELTY - Thin film device (I), comprises: a substrate (201); and a layer of silicon or silicon-containing material positioned on a first side of the substrate, where the layer comprises an n-doped region and a p-doped region, and the regions are formed on the backside surface of the layer to create an electrical structure characterized by a P-type anode and an N-type cathode forming junction(s) positioned along the backside surface of the layer.    USE - (I) is useful as thin film device (claimed), preferably thin-film solar cells, which are integrated with windows of commercial buildings (also known as building-integrated photovoltaics).    ADVANTAGE - (I): has contacts on the backside, only; includes a simplified contacting scheme, as a single contacting layer (a metal layer) can be used to connect both the n-doped and p-doped regions; achieves ease of electrically coupling the individual areas within a solar panel, without the difficulty of fabricating contacts to the front-side of the solar cells; and are low cost without the efficiency losses as found in conventional systems and techniques, as the regions can be doped without the need for higher furnace temperatures e.g. via laser irradiation and/or are characterized by smaller volumes that do not require higher furnace temperatures to passivate all of the traps throughout a e.g. 150-200 micron silicon wafer, all furnace steps associated with solar cell device fabrication is performed at less than 600 degrees C, or at less than 500 degrees C, utilizes thin silicon layers (e.g. 0.5-30 mu m) on base substrates without any furnace process above 500-600 degrees C, and allows realization of very low material costs as well as use of low temperature substrates (glass and plastic). (I) has uniform grains, high carrier lifetime(s), and/or improved diffusion length(s) and mobilities.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a method of fabricating a device, comprising: providing a substrate (201); providing a layer of silicon or silicon-containing material positioned on a first side of the substrate; doping first regions of the layer with N-type dopant; doping second regions of the layer with P-type dopant, where the n-doped region and the p-doped region are formed on the backside surface of the layer to create an electrical structure characterized by a P-type anode and an N-type cathode forming junctions positioned along the backside surface of the layer;    (2) a thin film device produced by the process of: placing an amorphous/poly material layer on a first side of a base substrate; heating the amorphous/poly material to transform a portion the amorphous/poly material into crystalline form; and placing an n-doped region and a p-doped region on the backside surface of the layer to create an electrical structure characterized by a P-type anode and an N-type cathode forming junctions positioned along the backside surface of the layer;    (3) a thin film device produced by the process of: coating a substrate with a silicon containing material; heating the silicon containing material to at least partially crystallize the material; doping a selected region of the silicon containing material with an N-type dopant; and doping a selected region of the silicon containing material with a P-type dopant;    (4) a thin film device produced by the process of: coating a substrate with a silicon containing material; heating the silicon containing material to at least partially crystallize the material; placing contacts (205) on a selected region of the silicon containing material; and heating the contacts to incorporate dopants into the silicon containing material;    (5) a thin film device produced by the process of: coating a substrate with an antireflective coating; coating the substrate and the antireflective coating with a silicon containing material; heating the silicon containing material to at least partially crystallize the material; coating the substrate, the antireflective coating, and the silicon containing material with an insulating material; forming openings in the insulating material; placing contact material comprising dopants on a selected region; and heating the contact material to incorporate dopants into the silicon containing material; and    (6) a thin film device produced by the process of: coating a substrate with a silicon containing material; coating the substrate and the antireflective coating with a silicon containing material; heating the silicon containing material to at least partially crystallize the material; doping a selected region of the silicon containing material with an N-type dopant and doping a selected region of the silicon containing material with a P-type dopant; coating the substrate with an insulating material; forming openings in the insulating material; and placing contacts above the doped regions.    DESCRIPTION OF DRAWING(S) - The figure illustrates a thin-film solar cell structure/device.    Substrate (201)    Amorphous/poly layer (202)    Contacts (205)