Two-dimensional (2D) semiconductor devices hold great promise in specialized operating regimes including radio-frequency, high-temperature, and cryogenic conditions – yet their potential for power handling has received little emphasis, so far. Here we report a molybdenum disulphide (MoS₂) device design that strategically selects the channel width (W) and length (L) to distribute current density and mitigate self-heating, enabling operation at a source-drain bias V_ds of 10 V and a drain current I_ds of 0.1 A, while maintaining an on/off ratio of 10⁵. This corresponds to sustained dissipation P = I_dsV_ds~1 W, and highlights a pathway for watt-level switching in van der Waals electronics. We demonstrate a sensor circuit that uses our watt-level MoS₂ transistors to function as a step-down converter and a switching device. Further, a proof-of-concept on flexible substrates is presented. Our findings mark a step change in 2D power electronics, paving the way for higher-voltage devices compatible with flexible substrates and, ultimately, wearable and conformal power systems.

Perovskite solar cells (PSCs) have rapidly developed in the past few years, with a record efficiency exceeding 25%. However, the long-term stability of PSCs remains a challenge and limits their practical application. Many high-performance PSCs have an n-i-p device architecture employing 4-tert-butylpyridine (t-BP) and bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI) as bi-dopants for the hole-transporting layer (HTL). However, the hygroscopicity of Li-TFSI and low boiling point of t-BP negatively impact the moisture stability of these PSC devices. Herein, we report the use of the fluorine-containing hydrophobic compound tris(pentafluorophenyl)phosphine (35FP) as a dopant for poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA). With better hydrophobicity and stability than undoped PTAA, a PSC device containing 35FP-doped PTAA demonstrated improved charge transport properties and reduced trap density, leading to a significant enhancement in performance. In addition, the long-term stability of a 35FP-doped PTAA PSC under air exposure without encapsulation was demonstrated, with 80% of the initial device efficiency maintained for 1,000 h. This work provides a new approach for the fabrication of efficient and stable PSCs to explore hydrophobic dopants as a substitute for hydrophilic Li-TFSI/t-BP.