Improvement in quantum efficiency of thin film Si solar cells due to the suppression of optical reflectance at transparent conducting oxide/Si interface by TiO_2/ZnO antireflection coating

摘要

Through experiments and optical simulations the suppression of optical reflection at the transparent conducting oxide/Si interface of thin film Si p-i-n solar cells is shown by application of a TiO_2 antireflection (AR) coating. In addition, a deterioration in the transmittance of TiO_2 is shown to be due to its reduction by a H_2 plasma, which in turn deteriorates the quantum efficiency (QE) at long wavelength. Such a reduction is completely prevented by a ZnO overcoat of ～10 nm. Applying the TiO_2/ZnO AR coating realizes an improvement in QE at all wavelengths with an increase of up to ～10% at 550 nm.