Laser-Induced Photothermal Conversion to Hemispherical MoS₂ Enabling Non-Contact Self-Powering Image Sensor

Molybdenum disulfide (MoS₂) has recently emerged as a promising material for the development of triboelectric nanogenerators (TENGs) owing to its inherently negative triboelectric properties when paired with polymeric layers, along with its notable transparency and mechanical flexibility. However, MoS₂-based TENGs operating in the contact-separation mode encounter critical limitations, including mechanical wear and limited triboelectric performance, particularly within the constraints of conventional 2D geometries. This paper reports the novel one-step laser-assisted synthesis of hemispherical MoS₂ through the controlled nucleation and growth of MoS₂ precursor seeds. The hemispherical structures synthesized at the optimized precursor concentration (0.32 m) exhibit a mean diameter of 234.4 nm with a standard deviation of 30.4 nm, uniformly distributed across a wafer-scale substrate. Hemispherical MoS₂ significantly increases the electric-field concentration, making it well-suited for integration into noncontact-mode TENG (NC-TENG) devices. Compared with a flat MoS₂-based NC-TENG, a hemispherical MoS₂-based NC-TENG demonstrates a 22-fold increase in average capacitance (≈112 pF, D_vertical = 2 mm) and a 37-fold increase in open-circuit voltage (≈2.25 V, D_vertical = 2 mm), while extending the operational distance to 10 mm. Furthermore, this advanced hemispherical MoS₂ architecture is employed to fabricate a self-powered image sensor array, underscoring its potential for broader applications.