Barrier type photovoltaic cells with enhanced open-circuit voltage, and process of manufacture

Claim 2

A photovoltaic cell comprising a layer of crystalline cadmium telluride, an exterior surface portion of said layer having TeO 2 in the crystalline lattice to a depth effective to produce an open-circuit voltage that is enhanced over the open-circuit voltage that is produced without said TeO 2 , a layer of metal in contact with at least part of said exterior surface portion, said layer being capable of forming a barrier with said cadmium telluride altered surface; and an electrode in ohmic contact with said cadmium telluride.

Claim 3

The cell as defined in claim 1, and further including an antireflection layer in contact with at least part of said metal layer, said antireflection layer having a thickness that enhances the transmission of light through the cell.

Claim 4

The cell as defined in claim 1, and further including a current-conducting grid applied over, and in ohmic contact with, said metal layer.

Claim 5

A process for the formation of a photovoltaic cell, the process comprising the steps of (a) forming a layer of crystalline cadmium telluride, (b) heating at least one surface of the layer in air for more than about 2 minutes and less than or equal to about 20 minutes at a temperature between about 250° C and about 350° C, or for a time less than or equal to about 2 minutes but at a temperature in centigrade degrees no lower than about 490/a, where a is the time of heating in minutes; and (c) applying a metal layer in contact with at least part of said one surface, said metal being capable of forming a barrier with cadmium telluride, whereby a cell is produced having an open-circuit voltage which is at least about 50 millivolts greater than a similar cell processed without step (b) above.

Claim 6

A process for the formation of a photovoltaic cell, the process comprising the steps of (a) forming a layer of crystalline cadmium telluride, (b) heating at least one surface of the layer in air for more than about 2 minutes and less than or equal to about 20 minutes at a temperature between about 250° C and about 350° C, or for a time less than or equal to about 2 minutes but at a temperature in centigrade degrees no lower than about 490/a, where a is the time of heating in minutes; and (c) applying a metal layer in contact with at least part of said one surface, said metal being capable of forming a barrier with cadmium telluride, whereby a cell is produced having an open-circuit voltage which is at least about 50 millivolts greater than a similar cell processed without step (b) above.

Claim 7

A photovoltaic cell comprising a layer of crystalline cadmium telluride, a surface of said layer being altered to contain tellurium oxide by heating in an oxygen containing atmosphere for between about one minute and about 20 minutes at a temperature between about 250° and about 500° C, the oxygen being present in an amount that is effective to enhance the open-circuit voltage by at least 50 millivolts; in contact with at least part of said altered surface, a layer of metal capable of forming a barrier with said cadmium telluride altered surface; and an electrode in ohmic contact with said cadmium telluride.

Claim 8

A photovoltaic cell comprising a layer of crystalline cadmium telluride, a surface of said layer being altered to contain tellurium oxide by heating in an oxygen containing atmosphere for between about one minute and about 20 minutes at a temperature between about 250° and about 500° C, the oxygen being present in an amount that is effective to enhance the open-circuit voltage by at least 50 millivolts; in contact with at least part of said altered surface, a layer of metal capable of forming a barrier with said cadmium telluride altered surface; and an electrode in ohmic contact with said cadmium telluride.

Claim 9

A photovoltaic cell exhibiting an enhanced open circuit voltage, comprising a layer of crystalline cadmium telluride, a surface of said layer being in an altered state achieved by heating in air for more than about 2 minutes and less than or equal to about 20 minutes at a temperature between about 250° C and about 350° C, or for a time less than or equal to about 2 minutes but at a temperature in centigrade degrees no lower than about 490/a, where a is the time of heating in minutes; in contact with at least part of said altered surface, a layer of metal capable of forming a barrier with said cadmium telluride altered surface; and an electrode in ohmic contact with said cadmium telluride.

Claim 10

A photovoltaic cell exhibiting an enhanced open circuit voltage, comprising a layer of crystalline cadmium telluride, a surface of said layer being in an altered state achieved by heating in air for more than about 2 minutes and less than or equal to about 20 minutes at a temperature between about 250° C and about 350° C, or for a time less than or equal to about 2 minutes but at a temperature in centigrade degrees no lower than about 490/a, where a is the time of heating in minutes; in contact with at least part of said altered surface, a layer of metal capable of forming a barrier with said cadmium telluride altered surface; and an electrode in ohmic contact with said cadmium telluride.

Claim 11

A process of measuring light, comprising the steps of (a) exposing to light, a photovoltaic cell comprising a layer of crystalline cadmium telluride, an exterior surface portion of said layer having TeO 2 in the crystalline lattice to a depth effective to produce an open-circuit voltage that is enhanced over the open-circuit voltage that is produced without said TeO 2 , a layer of metal in contact with at least part of said exterior surface portion, said layer being capable of forming a barrier with said cadmium telluride altered surface; and an electrode in ohmic contact with said cadmium telluride, and (b) measuring either the open-circuit voltage or short-circuit current generated by the cell.

Claim 12

A process of measuring light, comprising the steps of (a) exposing to light, a photovoltaic cell comprising a layer of crystalline cadmium telluride, an exterior surface portion of said layer having TeO 2 in the crystalline lattice to a depth effective to produce an open-circuit voltage that is enhanced over the open-circuit voltage that is produced without said TeO 2 , a layer of metal in contact with at least part of said exterior surface portion, said layer being capable of forming a barrier with said cadmium telluride altered surface; and an electrode in ohmic contact with said cadmium telluride, and (b) measuring either the open-circuit voltage or short-circuit current generated by the cell.