NOVELTY - Formation of a contact to connect to a buried heavily doped layer (1104, 1108) of a thin-film semiconductor structure on a supporting material, comprises forming a patterned etch mask on the semiconductor structure; and etching through the etch mask to form an opening (1302) in the semiconductor structure to expose the buried heavily doped layer, the opening in the semiconductor structure being formed to include an undercut region extending under an edge of the corresponding opening in the etch mask around the entire periphery of the opening in the semiconductor structure.    USE - The method is for formation of a contact to connect to a buried heavily doped layer of a thin-film semiconductor structure (e.g. solar cells (1100) comprising a large-area diode structure) on a supporting material (i.e. glass, glass ceramic, metal, ceramic, or plastic material (polymer)), which acts as the substrate or the superstrate of the solar cell, to provide a bifacial solar cell, useful for a photovoltaic module (claimed). The bifacial solar cell may be converted into a monofacial cell. The thin-film semiconductor structure is e.g. thin-film transistors, liquid crystal cells, micro electrical mechanical systems, and micro machining.    ADVANTAGE - The metal does not bridge the semiconductor junction. The method achieves electrical isolation from the overlying semiconductor material of opposite polarity; and achieves higher efficiencies than currently achievable in commercial solar cell production, including zero front surface metal shading loss, lightly diffused surfaces to reduce surface recombination and avoid any regions of low collection probability for generated carriers, low metal/silicon interface area to minimize the contribution to the device dark saturation current, achievement of minority carrier diffusion lengths in the bulk much greater than the wafer thickness, and low resistive losses. Defects and damage to the silicon do not result and thus the p-n junction retains a very high shunt resistance and produces a floating junction of superior quality compared to those produced using laser scribing. By using inkjet printing based processes to facilitate all of the cell finishing processes, these can be performed without the use of sophisticated equipment that requires technical expertise for its operation and maintenance. Thus, it becomes feasible in regions such as developing countries to do the remaining processing that requires relatively low cost and unsophisticated equipment that is typical of equipment already found in such developing countries. This is not possible with commercial cell technologies, currently in use around the world, which require high temperature diffusions and oxidations and high temperature metal sintering, such as for the conventional screen printed solar cell.    DETAILED DESCRIPTION - Formation of a contact to connect to a buried heavily doped layer of a thin-film semiconductor structure on a supporting material, comprises forming a patterned etch mask on the semiconductor structure; etching through the etch mask to form an opening in the semiconductor structure to expose the buried heavily doped layer, the opening in the semiconductor structure being formed to include an undercut region extending under an edge of the corresponding opening in the etch mask around the entire periphery of the opening in the semiconductor structure; and using a directional deposition method to deposit a conductive layer, which contacts the buried heavily doped layer exposed in the opening in the semiconductor structure without contact to exposed semiconductor sidewalls of the semiconductor structure above the buried heavily doped layer due to a shadowing effect of the etch mask over the undercut region of the opening in the semiconductor structure. Patterning of the etch mask comprises a material deposition and/or material removal method from shadow mask evaporation, screen printing, inkier printing, laser ablation, sputter ablation, photolithography, wet chemical etching, or dry chemical etching. The openings in the semiconductor structure are framed by etching of the semiconductor structure. Etching of the semiconductor structure is plasma etching, reactive ion etching, wet chemical etching, or dry chemical etching. The patterned etch mask comprises a photoresist layer (1112) that, after the deposition of the conductive layer, is chemically dissolved, lifting off the portions of the conductive layer covering the photoresist layer. The etch mask comprises a layer of metal, a layer of transparent conductive oxide, and a double layer consisting of a conductive layer below a photoresist layer. An INDEPENDENT CLAIM is included for a photovoltaic module.    DESCRIPTION OF DRAWING(S) - The figure is a schematic cross-sectional view of the semiconductor diode structure after different processing steps in the making of electrical contact to thin-film solar cells.    Solar cells (1100)    Buried heavily doped layer (1104, 1108)    Photoresist layer (1112)    Opening (1302)