Optical and structural properties of orthorhombic and tetragonal polymorphs of Cu2CdGeSe4

The quaternary Cu2CdGeSe4 (CCGSe) is a potential absorber material for thin film solar cells. This study presents the results of photoluminescence (PL) and X-ray diffraction analysis of high-temperature and low-temperature CCGSe polycrystals with orthorhombic (space group Pmn21) and tetragonal (space group I4¯2 m) crystal structure, respectively. Detailed PL analysis revealed different dominating radiative recombination mechanisms for orthorhombic and tetragonal CCGSe.