High-Performance Photovoltaic Effect with Electrically Balanced Charge Carriers in Black Phosphorus and WS2 Heterojunction

2D van der Waals materials are promising for various electronic and optoelectronic devices because of their thickness-dependent mobility and tunable bandgap. Recently, heterojunction structures based on 2D van der Waals materials have exhibited their potential for photovoltaic applications as ultrathin p-n diodes. In this study, the photovoltaic effect of a multilayer black phosphorus (BP)/WS2 p-n heterojunction device is demonstrated under the 405 nm laser illumination and the AM 1.5 solar spectrum. The diode-like characteristics and photovoltaic effect rely on balance between charge carriers in the heterojunction device, by showing the highest performance at the balance position. The gate-tunable heterojunction device shows a high current rectification of 10(3) and an external quantum efficiency of 4.4% under the 405 nm laser illumination, and a photovoltaic efficiency of 4.6% under the AM 1.5 solar spectrum. This work suggests that the balancing of the charge carriers in the 2D heterojunction p-n diode is highly prioritized to fabricate high-performance photovoltaic device.