High-Performance p-n Junction Transition Metal Dichalcogenide Photovoltaic Cells Enabled by MoO<sub><i>x</i></sub> Doping and Passivation.

Nassiri Nazif, Koosha; Kumar, Aravindh; Hong, Jiho; Lee, Nayeun; Islam, Raisul; McClellan, Connor J; Karni, Ouri; van de Groep, Jorik et al. · Nano Lett · 2021

basic_science · Level V

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Abstract

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 (<i>V</i><sub>OC</sub>) and therefore limited power conversion efficiency (PCE) in TMD photovoltaics. Here, we simultaneously address these fundamental issues with a simple MoO<sub><i>x</i></sub> (<i>x</i> ≈ 3) surface charge-transfer doping and passivation method, applying it to multilayer tungsten disulfide (WS<sub>2</sub>) Schottky-junction solar cells with initially near-zero <i>V</i><sub>OC</sub>. Doping and passivation turn these into lateral p-n junction photovoltaic cells with a record <i>V</i><sub>OC</sub> of 681 mV under AM 1.5G illumination, the highest among all p-n junction TMD solar cells with a practical design. The enhanced <i>V</i><sub>OC</sub> also leads to record PCE in ultrathin (<90 nm) WS<sub>2</sub> photovoltaics. This easily scalable doping and passivation scheme is expected to enable further advances in TMD electronics and optoelectronics.