Our efforts focus on developing a method to produce hydrogenated nanocrystalline silicon (nc-Si:H) with larger
crystallites to enhance carrier transport properties. A new PECVD methodology, called double pulsed PECVD (DPPECVD), employs alternating low frequency and high frequency discharge sub-cycles to sequentially grow and etch the evolving film, respectively. This confers enhanced process control compared to conventional methods, and provides a pathway to achieve our goal of enhanced carrier mobility. Preliminary results demonstrate nc-Si:H films possessing grains as large as 29 nm, with (220) preferred orientation, which is suitable for solar cell applications. Reactions between plasma species in a SiF4:H2:SiH4 glow discharge, which expectedly contribute to evolution of large grains, are also discussed. Our findings suggest the double pulse strategy is a valuable method for manipulating the microstructural evolution of PECVD grown thin film materials.
Photoelectrochemical (PEC) water dissociation into hydrogen and oxygen at a semiconductor-liquid interface offers an
environmentally benign approach to hydrogen production. We have developed an integrated PEC device using
hydrogenated amorphous silicon carbide (a-SiC or a-SiC:H) material as photoelectrode in conjunction with an
amorphous silicon (a-Si) tandem photovoltaic device. Such a "hybrid PV/a-SiC" PEC cell produces photocurrent of
about 1.3 mA/cm2 in a short-circuit configuration and is durable in a pH2 electrolyte. On the other hand, the
aforementioned structure finished with ITO contacts and measured as a solid-state device features a current density of 5
mA/cm2, indicating a potential solar-to-hydrogen (STH) conversion efficiency of about 6% in the hybrid PV/a-SiC PEC
cell. The much lower photocurrent measured in the hybrid PEC cell suggests that there exists an interfacial barrier
between the a-SiC and electrolyte, which hinders the photocurrent extraction. In order to mitigate against the interfacial
barrier and hence improve the photo-generated charge carrier transport through the a-SiC/electrolyte interface, we have
explored several surface modification techniques, namely the use of metallic nano-particles (such as platinum or
palladium) and the growth of an additional thin layer (a-SiNx, carbon-rich a-SiC, a-SiF, etc.) on the top of a-SiC by
PECVD. In the latter case, it is observed that the addition of a thin PECVD-fabricated layer does not significantly
improve the photocurrent, presumably due to a poor band alignment at the a-SiC/electrolyte interface. The use of lower
work function nanoparticles like titanium has led to promising results in terms of photocurrent enhancement and an
a nodic shift in the onset potential.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.