Patent ID: 8366954

Claim:
A method of treating a thin film amorphous or mono- or multi-crystalline silicon wafer substrate for use in a photovoltaic cell, the wafer substrate having at least one of a pn- or np junction and a partial phosphosilicate or borosilicate glass layer on a top surface of the wafer substrate, to increase at least one of (a) the sheet resistance and (b) the power density of the photovoltaic cell, the method comprising contacting the wafer substrate with an acidic treatment solution for a time and at a temperature sufficient to increase at least one of (a) the sheet resistance of the wafer and (b) the power density of the photovoltaic cell made from said wafer, the acidic treatment solution comprising: a buffered oxide etch (BOE) solution of: from about 0.1 to about 20% by weight of at least one tetraalkylammonium hydroxide, from about 0.1 to about 5% by weight acetic acid, from about 0.1 to about 5% by weight of at least one non-ionic surfactant, about 0.1 to about 5% by weight of at least one metal chelating agent, from about 0.1 to about 20% by weight of a metal free source of ammonium ions, from about 0.01 to about 20% by weight of a metal free source of fluoride ions, balance water to 100%, mixed with a solution of oxidizer and optionally water in a ratio of oxidizer solution /water/BOE solution of 0.01-10/0-100/1.