NOVELTY - A photovoltaic cell is made by forming a first layer on a front surface of a semiconductor wafer doped with first dopant; forming grooves in the front surface; adding second dopant to the grooves; depositing dopant material on a wafer back surface; treating the wafer having the dopant material to form a back surface field; applying a mask to a back surface portion; and adding a conductive material to the grooves to form an electrical contact.    USE - For manufacturing a photovoltaic cell for modules (both claimed).    ADVANTAGE - The inventive process can obtain the benefits of screen printing an aluminum-containing paste to the back surface of the wafer followed by firing, yet avoid the use of hydrochloric acid or other aggressive etchant and the formation of the slurry of spent hydrochloric acid and aluminum. It can be used for making highly efficient photovoltaic cells using the multi-crystalline silicon wafers, rather than monocrystalline silicon wafers. It is a safe, environmentally compatible, large-scale manufacturing process. The manufactured photovoltaic cell is highly efficient in converting light energy, and particularly solar energy, to electrical energy that uses a mask on the back surface of the cell during a plating step in the formation of the electrical contacts for the photovoltaic cell.    DETAILED DESCRIPTION - Manufacture of a photovoltaic cell (1) using a semiconductor wafer that is doped with a first dopant and that has a front surface (20) and a back surface, includes forming a first layer on the front surface of the wafer, where the first layer comprises a second dopant of a conductivity type opposite the first dopant; forming grooves in the front surface; adding the second dopant to the grooves; depositing a dopant material on the back surface of the wafer; treating the wafer having the dopant material deposited on the back surface of the wafer to form a back surface field; applying a mask to a portion of the back surface of the wafer after the treating step; and adding a conductive material to the grooves to form an electrical contact. INDEPENDENT CLAIMS are also included for:    (1) a photovoltaic cell, comprising a doped silicon wafer (10) having the front and back surfaces; a p-n junction (25) proximate to the front surface; grooves in the front surface having a conducting metal; a back surface field (45); a layer (50) comprising metal over the back surface field; and a mask (60) over the portion of the back layer comprising the metal;    (2) a wafer for the manufacture of a photovoltaic cell, comprising a semiconductor material; front and back surfaces; a layer on the back surface comprising a metal; and a mask over a portion of the layer comprising the metal; and    (3) modules comprising photovoltaic cells as above.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic cross-section view of a part of a photovoltaic cell.    Photovoltaic cell (1)    Doped silicon wafer (10)    Front surface of the wafer (20)    P-n junction (25)    Back surface field (45)    Layer comprising metal (50)    Mask (60)