Toward Ultra-Efficient Solar Energy Regulation in WS₂ - MoSe₂ Heterojunction Photocells

Biologically inspired technologies may prove to be the key to increased efficiency in
next-generation solar energy harvesting devices. In conventional photovoltaic systems energy
fluctuations present a hurdle to high storage efficiency, since – without regulation – too much
power may overload electrical networks. A recent theoretical model [1] has demonstrated that
when two nondegenerate light absorbing states are coupled to a single lower state internal
energy fluctuations are passively reduced. Here we show that heterostructures of monolayer
transition metal dichalcogenides (TMDs) present a unique experimental space to realize this
model. We synthesize TMD photocells via exfoliation and deterministic transfer of monolayer
WS₂ and MoSe₂. Using supercontinuum photoresponse spectroscopy we are able to access
individual absorbing states and probe the resulting interlayer photocurrent. We compare this dual-
channel photocell to photosynthetic reaction centers, which act in tandem through chlorophyll a
and b, to efficiently convert solar energy into usable power for energy storage. [1] Nano Letters
16, 7461 (2016).