A group of researchers led by Stanford University and Belgian research center Imec has made a significant breakthrough in the development of transition metal dichalcogenide (TMD) solar cells. The team has devised a new scalable manufacturing process that brings these advanced solar cells closer to commercial production.
TMDs are two-dimensional materials known for their exceptional semiconducting properties and high optical absorption coefficients, making them ideal for creating semi-transparent and flexible solar cells. These cells have potential applications in areas such as aerospace, architecture, electric vehicles, and wearable electronics, where lightweight, high power-per-weight ratio, and flexibility are crucial.
The research team developed a mass production-friendly method for creating wafer-scale tungsten diselenide (WSe2) films, a type of TMD. These films feature a layered van der Waals structure and exhibit superior characteristics, including charge carrier lifetimes of up to 144 nanoseconds—more than 14 times higher than any previously demonstrated large-area TMD films.
The WSe2 films, with thicknesses ranging from 15 to 30 nanometers, were produced on a 150 mm wafer using a selenization process. The process utilized either solid-source selenium (SS-Se) at 900°C or low-thermal-budget hydrogen selenide (H2Se) precursors at 650°C. The resulting films had an energy bandgap of 1.2 to 1.3 eV, which the researchers described as near-ideal for solar energy harvesting.
These films not only demonstrated superior characteristics compared to previous methods but also had smooth and uniform surfaces. With further optimization in contacts and doping, the researchers estimate that these cells could achieve efficiencies of up to 22.3%.
According to Koosha Nassiri Nazif, the study’s co-lead author, realistic models indicate that such carrier lifetimes could lead to around 22% power conversion efficiency and approximately 64 W g–1 specific power in a packaged solar cell. This corresponds to about 3 W g–1 in a fully packaged solar module. These advancements could pave the way for the mass production of high-efficiency WSe2 solar cells at low cost.
The research findings were detailed in a paper titled “Toward Mass Production of Transition Metal Dichalcogenide Solar Cells: Scalable Growth of Photovoltaic-Grade Multilayer WSe2 by Tungsten Selenization,” published in ACS Nano. The research team included experts from the University of Colorado Boulder, the US Department of Energy’s National Renewable Energy Laboratory (NREL), Hasselt University, and the University of Antwerp in Belgium. 
