Two-dimensional (2D) heterostructures have garnered intense research interest owing to their advanced characteristics compared to 2D homostructures. Combining the best features of different ingredients in a single structure, 2D heterostructures enhance the performance of 2D material-based devices and enable the discovery of new physical effects at their interfaces. In the field of optoelectronics, different photocurrent mechanisms have been exploited in the heterojunctions, which play crucial roles in working principles of optoelectronic devices. Despite these advantages, achieving high-performance broadband phototransistors remains a challenge for 2D heterostructure-based devices. Furthermore, each heterostructure device typically operates using a single photocurrent mechanism. Hence, innovative strategies are required to combine 2D materials and explore adaptable photocurrent mechanisms, advancing high-performance phototransistors for a broad detection range.

This study introduces various methods and interpretations for understanding photocurrent generation mechanisms in a heterojunction. Using d.c. photocurrent measurement, a high-performance broadband photodetector based on ReS₂-2D Te heterojunction was successfully achieved by effectively controlling photoconductive and photogating effects. With the same structure, photovoltaic (PV) and photothermoelectric (PTE) effects were characterized in ReS₂-2D Te p-n junction through a.c. photocurrent mapping measurement. In addition, our observations reveal different photodetection mechanisms within the heterostructure. Even more, by controlling drain-source and gate biases, we can selectively choose a main detection mechanism of the structure. Thus, the adaptive sensing of the light is possible, which is unprecedented. Another study on the WTe₂-2D Te heterostructure noted distinct nature of photocurrent puddles within the structure. To homogenize the puddles, careful material selection based on thermal and electrical properties is essential because these puddles can interact counteractively. Otherwise, leveraging each photocurrent domain enables adaptive operation with both PV and PTE, enhancing device performance through the energy conversion from multiple sources (light and waste heat), and enabling the detection of long-wavelength light through light-induced heating. Our research reveals diverse photocurrent types coexisting in heterostructures. Distinguishing these mechanisms is crucial for precise control and selection in diverse design applications.