Method for post-treating an absorber layer
A method for post-treating an absorber layer for photoelectric conversion of incident light into electric current. The method includes providing a chalcogen-containing absorber layer on a carrier, applying a post-treatment layer on a surface of the absorber layer, wherein the post-treatment material is not a buffer or component of a buffer, and thermally diffusing the post-treatment material into the absorber layer. A method for producing a layer system for the production of thin-film solar cells is also described.
1 . A method for post-treating an absorber layer for photoelectric conversion of incident light into electric current, comprising:
providing a chalcogen-containing absorber layer on a carrier;
applying a post-treatment layer on a surface of the absorber layer;
thermally diffusing the at least one post-treatment material into the absorber layer, during thermal diffusion, selectively increasing a surface termination of the absorber layer by controlling surface termination by chalcogen independently of passivation of the absorber layer by an alkali metal; and
measuring an increased surface S-correlated Raman signal of the absorber layer after the post-treatment to confirm a level of the surface S-correlated Raman signal of the absorber layer,
wherein the at least one post-treatment material has a dual function as 1) a supplier of the alkali metal for alkali passivation of the absorber layer and also as 2) a supplier of a sulfide for surface termination of the absorber layer with the increased surface S-correlated Raman signal after the post-treatment without or with additional surface cleaning, wherein the post-treatment layer contains exactly one post-treatment material selected from the group consisting of exactly one oxygen compound of an alkali chalcogenide and exactly one hydrogen-oxygen compound of an alkali chalcogenide, wherein only one single alkali element is chemically bound in the post-treatment material.
2 . The method according to claim 1 , wherein the thermally diffusing comprises heating the post-treatment layer.
3 . The method according to claim 2 , wherein the heating occurs in a temperature range from 70° C. to 700° C. with a heating time in a range from 1 min to 120 min.
4 . The method according to claim 3 , wherein the temperature range is from 150° C. to 700° C.
5 . The method according to claim 2 , wherein the heating occurs with an energy input in a range from 0.5 J/cm 2 to 15 J/cm 2 .
6 . The method of claim 5 , wherein the energy input is made of pulses with a pulse duration in a range from 0.2 msec to 20 msec.
7 . The method according to claim 1 , wherein the absorber layer has, after the thermally diffusing, a metal content in a range from 0.02 atomic % to 2.5 atomic %, based on a total amount of material of the absorber layer.
8 . The method according to claim 7 , wherein the range is from 0.1 atomic % to 1.3 atomic %.
9 . The method according to claim 1 , wherein the thermally diffusing the at least one post-treatment material into the absorber layer is performed in an atmosphere containing at least one chalcogen or in a chalcogen-free atmosphere.
10 . The method according to claim 9 , wherein the chalcogen-free atmosphere consists of inert gas.
11 . The method according to claim 1 , wherein the post-treatment material is selected from the group consisting of a hydrogen-oxygen compound of a metal chalcogenide with an oxidation state IV selected from NaHSO 3 , KHSO 3 , RbHSO 3 , and CsHSO 3 , an oxygen compound of a metal chalcogenide with the oxidation state IV selected from Na 2 SO 3 , K 2 SO 3 , Rb 2 SO 3 , and Cs 2 SO 3 , a hydrogen-oxygen compound of a metal chalcogenide with an oxidation state VI selected from NaHSO 3 , KHSO 3 , RbHSO 3 , and CsHSO 3 , and an oxygen compound of a metal chalcogenide with the oxidation state VI selected from Na 2 SO 4 , K 2 SO 4 , Rb 2 SO 4 , Cs 2 SO 4 ; and
the chalcogen-containing absorber layer is CIGSSe.
12 . The method according to claim 1 , wherein the at least one post-treatment material is applied on the surface of the absorber layer by a process selected from thermal evaporation, wet-chemical bath deposition, electron beam evaporation, sputtering, atomic layer deposition, and spray pyrolysis.
13 . The method according to claim 1 , wherein the absorber layer has a temperature in a range from 300° C. to 800° C. during application of the post-treatment layer.
14 . The method according to claim 1 , wherein the thermally diffusing the at least one post-treatment material into the absorber layer is performed in a vacuumed environment.
15 . The method according to claim 1 , further comprising
removing the at least one post-treatment material from the surface of the absorber layer after the thermally diffusing.
16 . A thin-film solar cell production method comprising producing a layer system for thin-film solar cells, wherein the producing comprises the method of claim 1 .
17 . A method for producing a layer system for production of thin-film solar cells, comprising:
providing a carrier,
producing a back electrode layer on the carrier,
producing a chalcogen-containing absorber layer on the back electrode layer, the chalcogen-containing absorber layer being treated according to the method of claim 1 , a surface termination of the absorber layer being selectively increased by controlling surface termination by chalcogen independently of passivation of the absorber layer by an alkali metal,
depositing at least one layer on the chalcogen-containing absorber layer,
producing a front electrode layer on the at least one buffer layer, and
measuring an increased surface S-correlated Raman signal of the absorber layer after the post-treatment to confirm a level of the surface S-correlated Raman signal of the absorber layer.
18 . The method according to claim 17 , wherein the at least one buffer layer is deposited in a vacuumed environment.
19 . The method according to claim 18 , wherein the at least one buffer layer is deposited by sputtering.
20 . The method according to claim 17 , wherein the at least one buffer layer comprises at least one of zinc oxysulfide, Zn(O,S) or zinc magnesium oxide, Zn1-xMgxO.