Properties of Yb-added ZnO (Yb:ZnO) films as an energy-conversion layer on polycrystalline silicon solar cells

초록

Yb-added ZnO (Yb:ZnO) films, as an energy-conversion layer, were formed using a spin-coating technique. Asformed Yb:ZnO films mainly showed the wurtzite structural ZnO phase and a cubic structural Yb2O3 phase appeared at the annealing temperature of 750 ?C. The formation route of Yb:ZnO films was proposed as follows: Yb elements did not incorporate into the ZnO host, because of the large difference in ionic radii and the oxidation state of Zn2+ and Yb3+ ions. Thus, diffused Yb elements in the ZnO grains were crystallized independently in the grains during annealing process. The energy-transfer process from the ZnO host to the Yb2O3 nanocomposites occurred efficiently, and the mechanism was followed by a quantum cutting process. The improvement ratio of the power conversion efficiency for the Yb:ZnO-formed glass/pc-Si solar cell (11.7%) compared to that for the bare-glass/pc-Si cell (10.7%) was approximately 9%. Thus, the Yb:ZnO films could be used as an effective energy-conversion layer for Si-solar cells with the benefit of very simple and inexpensive processing.

키워드