Principal Investigator Tomas Palacios
The group is interested in exploring the ultimate limits of microsystem scaling and functionality. The amount of energy available to the system is one of the key constraints, and solar cells based on transition metal dichalcogenides (TMDs) could be a key component of future highly-integrated microsystems.
Single atomic layer TMDs have been explored extensively for ultrathin optoelectronic applications due to their direct bandgap and strong light-matter interactions. However, optoelectronic applications of multi-layer TMD thin-films have not been as extensively studied despite their strong absorption characteristics and wide absorption frequency. Nevertheless, published work has shown that a p-n junction made with chemically doped multilayer MoS2 can achieve an efficiency of 2.8%, and a vertical Schottky junction WSe2 solar cell can achieve efficiencies as high as 6.7%. Most intriguingly, it has been shown that with careful design, a 15nm WSe2 solar cell can absorb 90% of 633nm incident light, demonstrating that TMDs can push the limit of thin film photovoltaics.
In this work, we study the electronic transport and photovoltaic characteristics of multilayer (~100 nm) WSe2 devices that can later be integrated as the energy harvester in a micro-scale sensing system. We have demonstrated a Schottky junction WSe2 solar cell using dissimilar metal contacts. The proof-of-concept dual- metal device showed an open-circuit voltage of ~ 0.2 V, short circuit current density ~ 4 mA/cm2 and power conversion efficiency ~ 2% under white light illumination with input power of 300W/m2.This study is extended to explore methods to better optimize the WSe2 based solar cell using experimental and modeling techniques. We are currently developing hole and electron transport layers to improve the device efficiency.