Study of Cu2CdGeSe4 monograin powders synthesized by molten salt method for photovoltaic applications

Cu2CdGeSe4 monograin powders were synthesized by molten salt method for photovoltaic applications. The effects of salt material (CdI2 and KI), synthesis temperature and time on the structural, morphological, compositional and optoelectronic properties were investigated. Phase analysis by Raman spectroscopy and X-ray diffraction methods showed that the Cu2CdGeSe4 powder crystals synthesized at 500 °C had tetragonal structure and those synthesized at 600 °C and 700 °C had orthorhombic structure. The band gap values determined from external quantum efficiency measurements were 1.27 eV for orthorhombic Cu2CdGeSe4 and 1.14 eV for tetragonal Cu2CdGeSe4 powder crystals. The monograin layer solar cell on the base of orthorhombic Cu2CdGeSe4 powder showed the best conversion efficiency of 4.21% (active area), with an open-circuit voltage of 0.46 V, a short-circuit current density of 23.3 mA/cm2 and fill factor of 39%.