High efficient antireflective down-conversion Y2O3:Bi,Yb films with pyramid preferred oriented nano-structure

Abstract

The high efficient antireflective down-conversion Y2O3:Bi,Yb films with nano-structure pyramids were grown successfully on Si (100) substrates using the pulsed laser deposition (PLD). The films microstructure can be controllably tuned only by changing the oxygen pressure in PLD process. With the increasing of the oxygen pressure, the surface morphology changes from smooth surface to pyramid nano-structure, and the preferential orientation of films changes from (222) to (400). Besides, the average reflectance of the films decreases first and then increases, giving a minimum value of 15.8% at 5 Pa as the oxygen pressure increases, which is comparable to that of uniform pyramidal micro-textured surfaces with an average reflectance of 13%–15% fabricated by the complicated chemical etching method. Moreover, upon excitation of ultraviolet photon varying from 300 to 400 nm, near infrared emission of Yb3+ due to transition of the 2F5/2→2F7/2 was observed for all samples, which can be efficiently absorbed by silicon solar cell. These pyramid nano-structure down-conversion Y2O3:Bi,Yb films possess promising applications in enhancement of energy efficiency for crystalline Si solar cells by light trapping and spectrum shifting.