(DE4440878-C2)      In a thin film solar cell with a transparent conductive window layer (5'') on a buffer layer on top of an absorber layer (3a) of (pref. chalcopyrite-based) semiconductor material, the buffer layer contains a Cd-free metal component, oxygen and sulphur. Pref. the buffer layer comprises a ternary cpd. of In or Sn, O and S.    Also claimed are thin film solar cells, esp. as above, in which the absorber layer (3a) contains: (a) at least 5 at.% alkali metal; or (b) an alkali metal from a precursor layer of alkali metal-contg. cpd., on which the absorber layer is deposited by a process involving precursor layer heating.    Further claimed are processes for prodn. of the above thin film solar cells.    ADVANTAGE -   The solar cell has high efficiency and is produced by a relatively simple and environmentally compatible process.    (DE4447865-A1)      In a thin film solar cell with a transparent conductive window layer (5'') on a buffer layer on top of an absorber layer (3a) of (pref. chalcopyrite-based) semiconductor material, the buffer layer contains a Cd-free metal component, oxygen and sulphur. Pref. the buffer layer comprises a ternary cpd. of In or Sn, O and S.    Also claimed are thin film solar cells, esp. as above, in which the absorber layer (3a) contains: (a) at least 5 at.% alkali metal; or (b) an alkali metal from a precursor layer of alkali metal-contg. cpd., on which the absorber layer is deposited by a process involving precursor layer heating.    Further claimed are processes for prodn. of the above thin film solar cells.    ADVANTAGE -   The solar cell has high efficiency and is produced by a relatively simple and environmentally compatible process.    (DE4447866-A1)      In a thin film solar cell with a transparent conductive window layer (5'') on a buffer layer on top of an absorber layer (3a) of (pref. chalcopyrite-based) semiconductor material, the buffer layer contains a Cd-free metal component, oxygen and sulphur. Pref. the buffer layer comprises a ternary cpd. of In or Sn, O and S.    Also claimed are thin film solar cells, esp. as above, in which the absorber layer (3a) contains: (a) at least 5 at.% alkali metal; or (b) an alkali metal from a precursor layer of alkali metal-contg. cpd., on which the absorber layer is deposited by a process involving precursor layer heating.    Further claimed are processes for prodn. of the above thin film solar cells.    ADVANTAGE -   The solar cell has high efficiency and is produced by a relatively simple and environmentally compatible process.