Influence of selenium evaporation temperature on the structure of Cu2ZnSnSe4 thin film deposited by a co-evaporation process

Cu2ZnSnSe4 (CZTSe) thin film solar cells have been fabricated using a one-step co-evaporation technique. The structural properties of polycrystalline CZTSe films deposited at different selenium evaporation temperatures (T-Se) have been investigated using X-ray diffraction spectra, scanning electron microscopy, and atomic force microscopy. A relationship between T-Se and the secondary phases deposited in the initial stage is established to explain the experimental observations. The Se flux is not necessarily increased too much to reduce Sn loss and the consumption of Se during fabrication could also be reduced. The best solar cell, with an efficiency of 2.32%, was obtained at a medium T-Se of 230 degrees C (active area 0.34 cm(2)).