Improvement of Light Trapping in a-Si:H-Based Solar Cells by Inserting a ZnO/LiF Double Interlayer

We develop a zinc oxide (ZnO)/lithium fluoride (LiF) double interlayer for effective light trapping in p-i-n-type hydrogenated amorphous silicon (a-Si:H)-based solar cells with a 200-nm-thick intrinsic a-Si:H absorber. The spectral response of the fabricated solar cell with an n-type a-Si:H (n-a-Si:H)/ZnO/LiF/aluminum back structure was significantly enhanced in the wide wavelength range of 500-750 nm because of the refractive index grading, reduced plasmonic absorption, and efficient tunneling of photogenerated electrons through the ultrathin LiF interlayer, resulting in the significant enhancement of the short-circuit current by 21.6%. Consequently, the conversion efficiency is improved by 13.3%.