Power conversion efficiency enhancement in silicon solar cell from solution processed transparent upconversion film

Transparent Er ^{3 +} doped NaYF ₄ upconversion films were formed on the glass substrate by a two-step process, ligand exchange and spin coating. Upconversion nanocrystals showed strong bonding ability with glass substrates and exhibited stronger emission intensity after silane ligand exchange. The spin coating rate and nano colloid concentration were varied and the resulting I-V curves of these films were measured and calculated under a standard AM0 non-concentrated condition. Immobilization of all these transparent upconversion films in the solar cell system yielded stable efficiency enhancements. Furthermore, control experiments demonstrated that upconversion was the only reason for the efficiency gains. The best improvement of the efficiency was measured to be relatively 8.6% under 100 mW/cm ² radiations.