High-Performance Broadband Mixed-Dimensional Phototransistors Based on the Boron Nitride Quantum Dots/MoSe₂ Heterostructure with Enhanced UV Sensitivity

Two-dimensional (2D) semiconductors have been of great interest in phototransistors in recent years due to their unique optoelectronic and electronic properties. However, their discernible spectral range and the efficiency of light absorption are usually restricted. Here, we present phototransistors based on mixed-dimensional heterostructures formed by zero-dimensional (0D) boron nitride quantum dots (BNQDs) and molybdenum diselenide (MoSe₂), which have high responsivity (<i>R</i>), specific detectivity (<i>D</i>*), and external quantum efficiency (EQE), especially in the ultraviolet (UV) spectral range. The heterostructure phototransistors showed a 440% increase in <i>R</i> at 375 nm (from 5.6 to 24.7 A/W) and a 260% increase in <i>D</i>* (from 3.3 to 8.7 × 10¹¹ Jones) compared to bare MoSe₂ at the wavelength of 375 nm and a bias of 1 V. A series of characterization and comparison experiments show that charge transfer on BNQDs/MoSe₂ results in the photogating effect and optical gain. Meanwhile, the high-performance BNQDs/MoSe₂ heterostructure phototransistors exhibit broadband imaging capabilities and thus hold great promise for ultrasensitive light detection, neuromorphic visual sensing, and in-sensor computing applications.