Method for producing a compound semiconductor, and thin-film solar cell

1. Method for producing a pentanary compound semiconductor Cu(In,Ga)(S,Se) 2 , comprising the following steps:

producing at least one precursor layer stack, consisting of a first precursor layer, a second precursor layer, and a third precursor layer, wherein, in a first stage, the first precursor layer is produced by depositing the metals copper, indium, and gallium onto a body, and, in a second stage, the second precursor layer is produced by depositing at least one chalcogen, selected from sulfur and selenium, onto the first precursor layer, and, in a third stage, the third precursor layer is produced by depositing the metals copper, indium, and gallium onto the second precursor layer;

heat treating the at least one precursor layer stack in a process chamber such that the metals of the first precursor layer, the at least one chalcogen of the second precursor layer, and the metals of the third precursor layer are reactively converted to form the compound semiconductor, wherein at least one process gas is supplied to the process chamber at least intermittently during the heat treatment of the at least one precursor layer stack, wherein at least sulfur and/or at least one sulfur-containing compound is contained in the process gas, wherein

the second precursor layer is produced by depositing selenium onto the first precursor layer,

wherein a defined sulfur depth profile is formed in the pentanary compound semiconductor by the at least one process gas,

wherein the sulfur depth profile from one surface of the compound semiconductor to an interface with the body is configured such that

the sulfur content has a minimum value at the surface, increases toward the interface and has a maximum value at the interface; or

the sulfur content has a first maximum value at the surface, decreases down to a minimum value toward the interface, and then increases again, and has a second maximum value at the interface; or

the sulfur content has a first minimum value at the surface, increases toward the interface up to a maximum value, and then decreases again, and has a second minimum value at the interface,

wherein the gallium depth profile from one surface of the compound semiconductor to an interface with the body is configured such that the gallium content has a first maximum value at the surface, decreases toward the interface down to a minimum value, and then increases again, and has a second maximum value at the interface.

2. Method according to claim 1 , wherein

the first precursor layer and/or the third precursor layer are deposited by sputtering of one or a plurality of individual layers from a copper-gallium alloy target and an indium target or from a copper-indium alloy target and a copper-gallium alloy target or from a copper-gallium-indium alloy target, and/or

the second precursor layer made of individual layers of the chalcogen selenium is deposited.

3. Method according to claim 1 , wherein a fourth precursor layer is deposited onto the third precursor layer, and the fourth precursor layer contains at least one chalcogen, selected from sulfur and selenium, and the fourth precursor layer is thinner than the third precursor layer.

4. Method according to claim 1 , wherein the precursor layer stack is deposited several times in succession.

5. Method according to claim 1 , wherein the gallium depth profile is configured such that the absolute change in the gallium content is at least 20% at least over a portion of the depth profile.

6. Method according to claim 1 , wherein the sulfur depth profile is configured such that an absolute change of the sulfur content is at least 20% at least over a portion of the depth profile.

7. Thin-film solar cell having an absorber made of a pentanary compound semiconductor Cu(In,Ga)(S,Se) 2 arranged on a body, wherein the compound semiconductor has a defined gallium depth profile from one surface of the compound semiconductor to an interface with the body, wherein the gallium depth profile is configured such that the gallium content has a first maximum value at the surface, decreases down to a minimum value toward the interface and then increases again, and has a second maximum value at the interface,

wherein the compound semiconductor has a defined sulfur depth profile from one surface ( 9 ) of the compound semiconductor to an interface with the body

wherein the sulfur depth profile is configured such that

the sulfur content has a minimum value at the surface, increases toward the interface, and has a maximum value at the interface; or

the sulfur content has a first maximum value at the surface, decreases down to a minimum value toward the interface, and then increases again, and has a second maximum value at the interface; or

the sulfur content has a first minimum value at the surface, increases up to a maximum value toward the interface, and has a second minimum value at the interface.

8. Method according to claim 1 , wherein for producing the pentanary compound semiconductor Cu(In,Ga)(S,Se) 2 ,

the second precursor layer is produced by depositing the chalcogens sulfur and selenium onto the first precursor layer.

9. Method according to claim 1 , wherein for producing the pentanary compound semiconductor Cu(In,Ga)(S,Se) 2 , at least selenium and/or at least one selenium-containing compound is contained in the process gas.

10. Method according to claim 2 , wherein the second precursor layer made of individual layers of the chalcogens selenium and sulfur is deposited.