DPA-MoS2 van der Waals Heterostructures for Ambipolar Transistor and Wavelength-dependent Photodetection

Organic–inorganic van der Waals heterojunctions present unique opportunities to explore novel applications of optoelectronic devices. However, ambipolar and wavelength-dependent phototransistors based on organic–inorganic heterojunctions have rarely been reported. Here, we focus on an organic–inorganic heterojunction comprised of a single crystal of 2,6-diphenyl anthracene (DPA) and a monolayer MoS2 film. Such DPA/MoS2 bilayer heterojunctions are fabricated by a mechanical transfer method and show ambipolar charge transport characteristics with hole and electron mobilities of 0.13 and 1.1 cm2 V–1 s–1, respectively. More interestingly, an anomalous wavelength-dependent source–drain current (IDS) decrease is unexpectedly observed in the operation of heterojunction based phototransistors. Mechanism studies propose that a large interface in the bilayer structure and unique band alignment of the two components facilitate accumulation and recombination of the carriers. Due to the different optical absorption ranges of the two components, electrons (holes) inject in DPA (MoS2) under irradiation of 365 nm, while only electrons inject from MoS2 to DPA under 550 nm; thus, carriers quenched under different irradiations lead to the wavelength selected IDS decrease. Taken together, such organic–inorganic heterojunctions demonstrate potential applications for next-generation high-performance phototransistors, photodetectors, and complementary logic circuits.