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 µm−1 at a mere Vd 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 (Voc) of 210 mV and a short‐circuit current (Isc) 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.