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Researchers at Stanford University have studied the efficiency of a single junction solar cell that uses transition metal chalcogenides such as MoS2, MoSe2, WS2 and WSe2 as absorbers. The device has shown substantial light absorption capacity in 5 nanometer (nm) ultrathin films, achieving high levels of short circuit current.
Researchers at Stanford University have demonstrated a single-junction 50nm transition metal chalcogenide (TMDC) solar cell that could achieve 25% power conversion efficiency.
“We have developed a rigorous model of TMD solar cell performance that takes into account intrinsic and extrinsic factors, such as material quality, and therefore examines the true performance limits of TMD solar cells, achievable by optimizing the design, depending on the thickness and quality of the material,” researcher Koosha Nassiri Nazif told pv magazine .
They structured the device with a multilayer absorber based on molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2), tungsten disulfide (WS2), and tungsten diselenide (WSe2). The four materials have energy bands of 1.27 eV, 1.16 eV, 1.36 eV and 1.29 eV, respectively.
“Due to their large absorption coefficients and refractive indices, all of these TMDs exhibit significant light absorption even in 5 nm thick ultrathin films,” the researchers explain. “As expected from their exceptional light absorption characteristics, all TMDs can achieve high short-circuit current even at small thicknesses.”
The scientists also placed an anti-reflective coating on the front surface of the cell and a perfect retroreflector on the back surface. They also assumed that the surfaces had a non-specular texture and were created by etching, which they believed results in random light and angle-independent absorption.
Simulated under standard lighting conditions, the proposed cellular architecture was able to achieve efficiencies of up to 25%.
“We have shown that 50 nm thick ultra-thin TMD solar cells can achieve a power conversion efficiency of 25%, even with the current quality of materials,” says Nazif. “This corresponds to a specific power approximately ten times higher than that of current solar technologies in the form of fully packaged cells and about five times higher than the specific power in fully packaged modules.”
The academics presented their findings in “ Efficiency limit of transition metal dicholcogenide solar cells ,” recently published in Communication Physics .
In 2021, the same research group manufactured a flexible metal chalcogenide solar cell with an efficiency of 5.1%. The device achieved a power-to-weight ratio comparable to that of established thin film technologies, such as cadmium telluride (CdTe); copper, indium, gallium and selenium (CIGS); amorphous silicon (a-Si); and III-V solar cells.
Transition metaldicalkogenides (TMD) are two-dimensional materials with notable semiconducting properties and high optical absorption coefficients. This makes them suitable for the production of semi-transparent and flexible solar cells with potential applications in aerospace, architecture, electric vehicles and portable electronics, where light weight, a high power-to-weight ratio and flexibility are highly desirable. |
