a-SiC:H films used as photoelectrodes in a hybrid, thin-film silicon photoelectrochemical (PEC) cell for progress toward 10 solar-to hydrogen efficiency

摘要

In this paper we describe the fabrication of amorphous SiC:H materials and using them as photoelectrodes in photoelectrochemical cells (PEC). With the increase of CH4 flow (in SiH4 gas mixture) during growth, the bandgap, Eg, increases from ~ 1.8eV to ~2.0eV, while the photoconductivity decreases from ~10-5 S/cm to ~10-8 S/cm. These high-quality a-SiC:H materials with Eg of 2.0eV included into a solar cell configuration led to a conversion efficiency,η~7% on textured Asahi U type SnO2 coated substrates, with the i-layer thickness of ~300nm. For a reduced i-layer thickness of ~100 nm, a current density, Jsc ~8.45mA/cm2 has been achieved, Immersing the a-SiC:H(p)/a-SiC:H(i) structure in 0.33M H3PO4 electrolytes, produced a photocurrent of ~7mA/cm2. With a further optimization we expect that the photocurrent could exceed 9mA/cm2. With the use of this configuration substrate/silicon tandem device (a-Si/a-Si or a-Si/nc-Si)/a-SiC:H(p)/a-SiC:H(i), it may therefore be possible to increase the solar-to-hydrogen (STH) efficiencies to beyond 10%.