摘要： Few-layer Black phosphorus (BP) has recently emerged as a promising two-dimensional (2D) material for electronic and optoelectronic devices due to its high mobility and tunable bandgap. However, BP is known to have quick degradation and oxidize in ambient conditions by breaking of the P-P bonds. As a result, there is a growing need to encapsulate BP that avoids oxygen and water while retaining the high electric performance of the devices. Here we demonstrate a hydrophobic polymer encapsulation technique with improved thermal conductivity for high current density, which preserves the electrical properties of BP back-gate transistors compared to the commonly used Al2O3 encapsulation with improved mobility and minimal traps. The on-off ratio increases for more than an order of magnitude at room temperature and more than four orders of magnitude at cryogenic temperatures. High field transport shows the first systematic study on unprecedented breakdown characteristics up to -5.5 V for the 0.16 μm transistors with a high current of 1.2 mA/μm at 20 K. These discoveries open up a new way to achieve high-performance 2D semiconductors with significantly improved breakdown voltage, on-off ratios, and stability under ambient conditions for practical applications in electronic and optoelectronic devices.