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arXiv · 2506.14733

High-efficiency WSe$_2$ photovoltaics enabled by ultra-clean van der Waals contacts

Kamal Kumar Paul·Cullen Chosy·Soumya Sarkar·Zhuangnan Li·Han Yan·Ye Wang·Leyi Loh·Lixin Liu·Hu Young Jeong·Samuel D. Stranks·Yan Wang·Manish Chhowalla
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Abstract

Layered transition metal dichalcogenide semiconductors are interesting for photovoltaics owing to their high solar absorbance and efficient carrier diffusion. Tungsten diselenide (WSe$_2$), in particular, has emerged as a promising solar cell absorber. However, defective metal-semiconductor interfaces have restricted the power conversion efficiency (PCE) to approximately 6%. Here we report WSe$_2$ photovoltaics with a record-high PCE of approximately 11% enabled by ultra-clean indium/gold (In/Au) van der Waals (vdW) contacts. Using grid-patterned top vdW electrodes, we demonstrate near-ideal diodes with a record-high on/off ratio of $1.0\times 10^9$. Open-circuit voltage (VOC) of 571 +/- 9 mV, record-high short-circuit current density (JSC) of 27.19 +/- 0.45 mA cm$^{-2}$ -- approaching the theoretical limit (34.5 mA cm$^{-2}$) -- and fill factor of 69.2 +/- 0.7% resulting in PCE of 10.8 +/- 0.2% under 1-Sun illumination on large active area (approximately 0.13x0.13 mm$^2$) devices have been realised. The excellent device performance is consistent with the high external quantum efficiency (up to approximately 93%) measured across a broad spectral range of 500-830 nm. Our results suggest that ultra-clean vdW contacts on WSe$_2$ enable high-efficiency photovoltaics and form the foundation for further optimisation.

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Kamal Kumar Paul, Cullen Chosy, Soumya Sarkar, Zhuangnan Li, Han Yan, Ye Wang, Leyi Loh, Lixin Liu, Hu Young Jeong, Samuel D. Stranks, Yan Wang, Manish Chhowalla. 2025-06-17. High-efficiency WSe$_2$ photovoltaics enabled by ultra-clean van der Waals contacts. https://arxiv.org/abs/2506.14733

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