Effect of Hydrogen Dilution on the Metastability of Hydrogenated Amorphous Silicon Oxide Solar Cells

Abstract

We investigated the effect of H2 dilution on the stability of hydrogenated amorphous silicon oxide (a-Si1-xOx:H) films and solar cells. a-Si1-xOx:H films were prepared by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) using a gas mixture of silane (SiH4), hydrogen (H2), and carbon dioxide (CO2). The degradation results after light soaking for 310 h under AM1.5, 125 mW/cm2 at 48 °C clearly showed that the film and device stabilities were improved substantially with increasing H2 dilution. Our best stable result with a high open-circuit voltage (Voc) of 1.03 V for a-Si1-xOx:H single-junction solar cells showed a degradation of 16.6%. This result indicates that the stability against the light soaking of the a-Si1-xOx:H material is not inferior to that of a conventional hydrogenated amorphous silicon (a-Si:H) material. The temperature dependences of current–voltage (I–V) characteristics observed before and after light soaking showed that a-Si1-xOx:H solar cells had a similar temperature dependence to conventional a-Si:H solar cells.