Transition Metal Dichalcogenide Solar Cells Enabling Widespread Solar Adoption

Reducing the cost per Watt of solar technologies would increase solar energy adoption and therefore decrease greenhouse gas emissions. Ultrathin transition metal dichalcogenides (TMDs) are promising candidates thanks to their ultrahigh absorption coefficients, desirable bandgap values and intrinsically passivated surfaces. However, challenges such as Fermi-level pinning at the metal contact-TMD interface and the inapplicability of traditional doping schemes have prevented most TMD solar cells from exceeding 2% power conversion efficiency (PCE). In addition, fabrication on flexible substrates tends to contaminate or damage TMD interfaces, further reducing performance. Using novel approaches in semiconductor device design, TMD materials growth, and photonic engineering we have obtained encouraging first results with TMD solar cells. These lead to record PCE of 5.1% and record specific power of 4.4 W g ^-1 for flexible TMD (WSe2) solar cells, the latter on par with established thin-film solar technologies cadmium telluride, copper indium gallium selenide, amorphous silicon and III-Vs. We further project that TMD solar cells could achieve specific power up to 46 W g ^-1 , creating unprecedented opportunities in a broad range of industries from aerospace to wearable and electronics.