Texturization of ZnO:Al surface by reactive ion etching in SF6/Ar, CHF3/Ar plasma for application in thin film silicon solar cells

Abstract

As-deposited sputtered ZnO:Al (AZO) thin films having high transparency (T ≥ 85% at 550 nm of wavelength) and good electrical properties (ρ = 2.59 × 10−04 Ω cm) are etched to get suitable light trapping in thin film solar cells, using reactive ion etching method in sulfur hexafluoride–argon (SF6/Ar) plasma and trifluoromethane–argon (CHF3/Ar) plasma to texture their surface. Though the electrical properties of the films are not affected much by the etching process but significant increment in the average haze values in the wave length range of 350–1100 nm in the etched AZO films (19.21% for SF6/Ar and 22.07% for CHF3/Ar plasma etched) are found compared to as-deposited AZO films (5.61%). Increment in haze value is due to more scattering of light from the textured surface. These textured substrates are used as front transparent conducting oxide electrode for the fabrication of amorphous silicon solar cells. Solar cells fabricated on etched AZO substrates show 7.76% increase in conversion efficiency compared to as-deposited AZO substrates.