Organic heterojunctions with high mobility are typically desired in order to achieve high performance devices such as complementary circuits, organic light emitting diodes (OLEDs) and organic solar cells. Thus, organic single crystals are ideal candidates for the junctions as they have the potential to exhibit the superior charge transport properties among organic materials with ordered molecular packing compared with their amorphous or polycrystalline counterparts. Despite the great efforts that have been made to fabricate organic single crystalline heterojunctions, there are still difficulties in fabricating organic single crystalline heterojunctions via a convenient solution method. Here, we demonstrate a facile one-step solution method to grow several organic single crystalline heterojunctions from a droplet of mixed solutions containing two types of organic semiconductor molecules. One example of the obtained heterojunctions demonstrates multiple properties like charge transport as well as charge recombination and electronic devices based on the obtained heterojunction have been made as light-emitting field-effect transistors (LEFETs).