METHOD AND APPARATUS FORMING COPPER (Cu) OR ANTIMONY (Sb) DOPED ZINC TELLURIDE AND CADMIUM ZINC TELLURIDE LAYERS IN A PHOTOVOLTAIC DEVICE
A method and apparatus for an amount of Cu or Sb dopant incorporated into a zinc-based layer as the layer is being formed. The layer is formed over a coated substrate using an electrochemical deposition (ECD) process. In the ECD process, the bias voltage and plating solution composition may be systematically changed during the electrochemical deposition process to change the amount of Cu or Sb dopant incorporated into the plated layer.
1 . An electrochemical deposition system comprising:
a first plating solution comprising a dopant, a complexing agent and a zinc-based semiconductor solute; and
a first electrochemical deposition unit for forming at least a first portion of a doped zinc-based semiconductor layer on a partially completed photovoltaic device placed in the first plating solution, wherein the first electrochemical deposition unit is configured to incorporate the dopant from the first plating solution into the doped zinc-based semiconductor layer during a deposition process.
2 . The system of claim 1 , wherein the dopant in the first plating solution is a Cu dopant or an Sb dopant.
3 . The system of claim 1 , wherein the complexing agent in the first plating solution is at least one of citrate, phenathroline, thoicyanate, halides, pyridines or their derivatives.
4 . The system of claim 3 , wherein the first electrochemical deposition unit comprises:
a first plating bath for containing the first plating solution, wherein the first plating solution is contacted with the partially completed photovoltaic device;
a first heater below the first plating bath for heating the first plating solution to a predetermined temperature; and
a power source electrically connected to the partially completed photovoltaic device for generating a bias voltage across the partially completed photovoltaic device when it is in contact with the first plating solution.
5 . The system of claim 4 , wherein the semiconductor solute comprises solutes of zinc (Zn) and telluride (Te).
6 . The system of claim 4 , wherein the dopant concentration in the first plating solution is in the range of about 0.01 mM to about 10 M.
7 . The system of claim 4 , wherein the first heater is configured to heat the first plating solution to a temperature in the range of about 10° C. to about 100° C.
8 . The system of claim 4 , wherein the power source is configured to generate a bias voltage across the partially completed photovoltaic device and the first plating solution in the range of about −0.3 V to about −3 V.
9 . The system of claim 4 , wherein the doped zinc-based semiconductor layer is a doped zinc telluride layer or a doped cadmium zinc telluride layer.
10 . The system of claim 4 , wherein the first electrochemical deposition unit further comprises a first power control unit coupled to the power source for adjusting the bias voltage across the partially completed photovoltaic device and the first plating solution.
11 . The system of claim 10 , wherein the first electrochemical deposition unit is configured to change the amount of dopant incorporated into at least the first portion of the doped zinc-based semiconductor layer as it is formed on the partially completed photovoltaic device by changing the bias voltage.
12 . The system of claim 11 , wherein the first power control unit is configured to change the bias voltage from a first set bias voltage to a second set bias voltage during a predetermined period of time for forming at least the first portion of the doped zinc-based semiconductor layer on the partially completed photovoltaic device.
13 . The system of claim 12 , wherein the first power control unit is configured to change the bias voltage in a step-wise or in a gradual fashion.
14 . The system of claim 4 , further comprising:
a second plating solution comprising a dopant, a complexing agent and a zinc-based semiconductor solute, wherein the second plating solution has a different composition than the first plating solution; and
a second electrochemical deposition unit for forming a second portion of the doped zinc-based semiconductor layer on the partially completed photovoltaic device placed in the second plating solution, wherein the second electrochemical deposition unit is configured to incorporate the dopant from the second plating solution into the doped zinc-based semiconductor layer during the deposition process.
15 . The system of claim 14 , wherein the second electrochemical deposition unit comprises:
a second plating bath for containing the second plating solution, wherein the second plating solution is contacted with the partially completed photovoltaic device;
a second heater below the second plating bath for heating the second plating solution to a predetermined temperature.
16 . The system of claim 15 , wherein the power source is electrically connected to the partially completed photovoltaic device for generating a bias voltage across the partially completed photovoltaic device when it is in contact with the second plating solution.
17 . The system of claim 16 , wherein the dopant concentration in the first plating solution is different than the dopant concentration in the second plating solution.
18 . The system of claim 17 , wherein the first and second plating solutions further comprise solutes of zinc (Zn) and telluride (Te).
19 . The system of claim 17 , wherein the first and second heaters are configured to heat the first and second plating solutions to a temperature in the range of about 10° C. to about 100° C.
20 . The system of claim 17 , wherein the power unit is configured to generate a bias voltage across the partially completed photovoltaic device and the first and second plating solutions in a range of about −0.3 V to about −3 V.