Materials constructed from the large number of 2D materials now identified offer enormous possibilities for fundamental research, promising improved or even novel electronic or optical technologies. Recently, there has been increased interest in the LEGO-like creation of fewlayer hybrid 2D heterostructures for photovoltaic and photonic applications. For example hybrid 2D heterostructures, in which the charge carriers move in the direction perpendicular to the plane of the 2D layers, have recently attracted attention as potential vertical p-n junctions. The 2D materials that have been investigated as p and n dopants include MoS 2 , MoSe 2 , WSe 2 . With the growing number of semiconducting vdW materials, the number of possible hybrid bilayers that achieve p-n band alignment is increasing, and the prediction of the band gap of these bilayers using ML models would greatly support the search for new atomically thin p-n junction materials for optoelectronics applications.