Spring 2014 IAB & Research Review
March 5 - 6
Carrier selective oxide contacts for photovoltaics and nanoelectronics.
Efficient carrier selective contacts and excellent surface passivation are key to solar cells with high power conversion efficiency. We explore substoichiometric molybdenum trioxide (MoOx, x<3) as a dopant-free, hole-selective contact for silicon. Using a hydrogenated amorphous silicon passivation layer between the oxide and the silicon absorber, we demonstrate a high open-circuit voltage of 711 mV and a power conversion efficiency of 18.8%. Due to the wide band gap of MoOx, we observe a substantial gain in photocurrent of 1.9 mA/cm2 in the ultraviolet and visible part of the solar spectrum, when compared to a p-type hydrogenated amorphous silicon emitter of a traditional silicon heterojunction cell. With a high workfunction exceeding those of elemental metals, MoOx presents an important opportunity to contact holes in inorganic semiconductor materials with low lying valence band maxima including III-V semiconductors such as InP or GaN, but also oxide- and carbon-based nanomaterials and layered transition metal dichalcogenide semiconductors.