Journal of the Korean Solar Energy Society ISSN:1598-6411(Print) 2508-3562(Online) 한국태양에너지학회 논문집

The stoichiometric mixture of evaporating materials for the CaAl₂Se₄: Co single crystal thin film was prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal CaAl₂Se₄, it was found orthorhomic structure whose lattice constant a₀, b₀ and c₀ were 6.4818, 11.1310 Å and 11.2443 Å, respectively. To obtain the CaAl₂Se₄: Co single crystal thin film, CaAl₂Se₄: Co mixed crystal was deposited on throughly etched Si (100) by the HWE (Hot Wall Epitaxy) system. The source and substrate temperature were 600°C and 440°C respectively. The crystalline structure of CaAl₂Se₄: Co single crystal thin film was investigated by the double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of Van der Pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by impurity scattering in the temperature range 30 K to 100 K and by lattice scattering in the temperature range 100 K to 293 K. The temperature dependence of the energy band gap of the CaAl₂Se₄: Co obtained from the absorption spectra was well described by the Varshni's relation, Eg(T) = 3.8239 eV - (4.9823 × 10^-3 eV/K)T₂/(T + 559 K). The open-circuit voltage, short current density, fill factor ,and conversion efficiency of p-Si/ p- CaAl₂Se₄: Co heterojunction solar cells under 80 mW/cm² illumination were found to be 0.42 V, 25.3 mA/cm², 0.75 and 9.96%, respectively.