Pronounced Photovoltaic Effect in Electrically Tunable Lateral Black-Phosphorus Heterojunction Diode

Recently, both lateral and vertical p-n junctions have been realized in 2D materials using various strategies, with a number of works on exploring the potential of lateral heterojunctions resulting from thickness-modulated bandgaps at the interface. Here, electrically tunable all-black-phosphorus (BP) lateral heterojunction diodes, without the need of split-gating or selective chemical doping or transfer-based vertical stacking, are experimentally demonstrated. The BP heterojunction diode, which exhibits an ultralow off-state current density of 8 pA mu m(-1) at a mere V-d of 100 mV and a significant gate-tunable current-rectifying behavior with the highest rectification ratio exceeding 600, is able to harvest solar energy at both visible and near-infrared wavelengths beyond the bandgap limitation of transition metal dichalcogenides. Specifically, at 660 nm, the device achieves an open-circuit voltage (V-oc) of 210 mV and a short-circuit current (I-sc) of 1.5 nA at 3.6 W cm(-2) power density, resulting in an external quantum efficiency of 7.4% which outperforms both split-gating and chemically doped homojunctions. This work paves the way for the exploitation of BP lateral heterojunction for broadband energy harvesting towards future optoelectronic applications.