In a significant stride towards enhancing solar cell efficiency, researchers from the University of Cambridge, led by Professor Manish Chhowalla, have developed high-efficiency photovoltaics using tungsten diselenide (WSe2), a type of layered transition metal dichalcogenide semiconductor. Their work, published in the journal Nature Communications, demonstrates a record-high power conversion efficiency (PCE) of approximately 11%, a notable improvement over the previously achieved 6%.
The team’s success is attributed to the use of ultra-clean indium/gold (In/Au) van der Waals (vdW) contacts. Van der Waals contacts are interfaces between two materials that are held together by weak van der Waals forces, rather than strong chemical bonds. These contacts are particularly useful in two-dimensional materials like WSe2, as they minimize defects and maintain the material’s properties.
The researchers employed grid-patterned top vdW electrodes, which resulted in near-ideal diodes with a record-high on/off ratio of 1.0×10^9. The solar cells exhibited an open-circuit voltage (VOC) of 571 ± 9 mV, a record-high short-circuit current density (JSC) of 27.19 ± 0.45 mA cm^-2—approaching the theoretical limit of 34.5 mA cm^-2—and a fill factor of 69.2 ± 0.7%. These impressive metrics culminated in a PCE of 10.8 ± 0.2% under 1-Sun illumination on large active area devices of approximately 0.13×0.13 mm^2.
The high efficiency of these solar cells is further evidenced by their external quantum efficiency, which reached up to approximately 93% across a broad spectral range of 500-830 nm. This means that a significant portion of the incident light is converted into electrical current, highlighting the potential of WSe2 for practical applications in the energy sector.
The findings of this research suggest that ultra-clean vdW contacts on WSe2 enable high-efficiency photovoltaics and lay the groundwork for further optimization. As solar energy continues to play a pivotal role in the global transition towards renewable energy sources, advancements in solar cell technology, such as those demonstrated by this study, are crucial. The practical applications of this research could lead to more efficient and cost-effective solar panels, contributing to the broader adoption of solar energy.
Source: Nature Communications
This article is based on research available at arXiv.