High-Performance p-n Junction Transition Metal Dichalcogenide Photovoltaic Cells Enabled by MoO x Doping and Passivation.

Layered semiconducting transition metal dichalcogenides (TMDs) are promising materials for high-specific-power photovoltaics due to their excellent optoelectronic properties. However, in practice, contacts to TMDs have poor charge carrier selectivity, while imperfect surfaces cause recombination, leading to a low open-circuit voltage ( V _OC ) and therefore limited power conversion efficiency (PCE) in TMD photovoltaics. Here, we simultaneously address these fundamental issues with a simple MoO _x ( x ≈ 3) surface charge-transfer doping and passivation method, applying it to multilayer tungsten disulfide (WS ₂ ) Schottky-junction solar cells with initially near-zero V _OC . Doping and passivation turn these into lateral p-n junction photovoltaic cells with a record V _OC of 681 mV under AM 1.5G illumination, the highest among all p-n junction TMD solar cells with a practical design. The enhanced V _OC also leads to record PCE in ultrathin (<90 nm) WS ₂ photovoltaics. This easily scalable doping and passivation scheme is expected to enable further advances in TMD electronics and optoelectronics.