The conversion efficiency of silicon heterojunction solar cells is limited by current losses mainly in the front layer stack. In order to minimize these losses, we implemented n-doped nanocrystalline silicon oxide (nc-SiOx:H) as front surface field to enhance both transparency and conductivity, thus improving the fill factor. Layers with refractive indexes (n) in the range 2.1-2.7 and conductivity of 10 -4 -10 -1 S/cm were applied. Both optical simulations and experimental results suggest different optimizing approaches for short-circuit current (JSC) enhancement depending on the surface morphology of the silicon wafer. While planar wafers benefit from an improved antireflection effect using less transparent (n ~ 2.7) and thicker films, textured wafers require thinner highly transparent layers (n <; 2.7) with less parasitic absorption, since the reflectance losses are already low due to the texture. Finally, a thickness optimization of the (n)nc-SiO x :H leads to a conversion efficiency of 21.6%, a fill factor of 80.0%, an open-circuit voltage of 729 mV, and J SC-EQE = 40.0 mA/cm 2 .