Photoluminescence of AgGaS2 and CuGaS2 doped with rare-earth impurities

Photoluminescence (PL) related to rare-earth (RE) impurities (Ho, Er and Eu) in AgGaS2 and CuGaS2 crystals has been studied. In Ho-doped AgGaS2 and CuGaS2, two series of PL lines are observed in 1.86–1.92 eV region and 2.24 eV region, and they are assigned to 5F3–5I7 and 5S2–5I8 transitions of the Ho3+ ion, respectively. Similarly, in Er-doped AgGaS2 and CuGaS2, Er3+-related two PL series are observed: 1.83–1.88 eV region (4F9/2–4I15/2) and 2.22–2.26 eV region (4S3/2–4I15/2). For both Ho and Er impurities, the profile of the PL spectrum in AgGaS2 is complex, and PL exhibited large number of lines compared with that in CuGaS2. The differences in PL spectra between this two compounds are related to the crystal field at the cation site and the local atomic arrangement of the RE impurities. This work also refers to the PL band at 2.28 eV observed for the Eu-doped AgGaS2 crystal.